An area approximately 1.5 millimeters in diameter within the macula lutea where the retina thins out greatly because of the oblique shifting of all layers except the pigment epithelium layer. It includes the sloping walls of the fovea (clivus) and contains a few rods in its periphery. In its center (foveola) are the cones most adapted to yield high visual acuity, each cone being connected to only one ganglion cell. (Cline et al., Dictionary of Visual Science, 4th ed)
The only family of the order SCANDENTIA, variously included in the order Insectivora or in the order Primates, and often in the order Microscelidea, consisting of five genera. They are TUPAIA, Ananthana (Indian tree shrew), Dendrogale (small smooth-tailed tree shrew), Urogale (Mindanao tree shrew), and Ptilocercus (pen-tailed tree shrew). The tree shrews inhabit the forest areas of eastern Asia from India and southwestern China to Borneo and the Philippines.
Clusters of neurons in the somatic peripheral nervous system which contain the cell bodies of sensory nerve axons. Sensory ganglia may also have intrinsic interneurons and non-neuronal supporting cells.
A family of the New World monkeys inhabiting the forests of South and Central America. There is a single genus and several species occurring in this family, including AOTUS TRIVIRGATUS (Northern night monkeys).
Photosensitive proteins expressed in the CONE PHOTORECEPTOR CELLS. They are the protein components of cone photopigments. Cone opsins are classified by their peak absorption wavelengths.
The domestic cat, Felis catus, of the carnivore family FELIDAE, comprising over 30 different breeds. The domestic cat is descended primarily from the wild cat of Africa and extreme southwestern Asia. Though probably present in towns in Palestine as long ago as 7000 years, actual domestication occurred in Egypt about 4000 years ago. (From Walker's Mammals of the World, 6th ed, p801)
Infection with flukes of the genus Dicrocoelium.
A genus of trematode liver flukes of the family Dicrocoeliidae which includes the species dendriticum and hospes. It occurs in the biliary passages or liver of many vertebrates including man. The intermediate hosts are mainly mollusks but occasionally ants.
The ten-layered nervous tissue membrane of the eye. It is continuous with the OPTIC NERVE and receives images of external objects and transmits visual impulses to the brain. Its outer surface is in contact with the CHOROID and the inner surface with the VITREOUS BODY. The outer-most layer is pigmented, whereas the inner nine layers are transparent.
An oval area in the retina, 3 to 5 mm in diameter, usually located temporal to the posterior pole of the eye and slightly below the level of the optic disk. It is characterized by the presence of a yellow pigment diffusely permeating the inner layers, contains the fovea centralis in its center, and provides the best phototropic visual acuity. It is devoid of retinal blood vessels, except in its periphery, and receives nourishment from the choriocapillaris of the choroid. (From Cline et al., Dictionary of Visual Science, 4th ed)
Neurons of the innermost layer of the retina, the internal plexiform layer. They are of variable sizes and shapes, and their axons project via the OPTIC NERVE to the brain. A small subset of these cells act as photoreceptors with projections to the SUPRACHIASMATIC NUCLEUS, the center for regulating CIRCADIAN RHYTHM.
Neurons which send impulses peripherally to activate muscles or secretory cells.
The total area or space visible in a person's peripheral vision with the eye looking straightforward.
The number of CELLS of a specific kind, usually measured per unit volume or area of sample.
Specialized cells that detect and transduce light. They are classified into two types based on their light reception structure, the ciliary photoreceptors and the rhabdomeric photoreceptors with MICROVILLI. Ciliary photoreceptor cells use OPSINS that activate a PHOSPHODIESTERASE phosphodiesterase cascade. Rhabdomeric photoreceptor cells use opsins that activate a PHOSPHOLIPASE C cascade.
Photosensitive afferent neurons located in the peripheral retina, with their density increases radially away from the FOVEA CENTRALIS. Being much more sensitive to light than the RETINAL CONE CELLS, the rod cells are responsible for twilight vision (at scotopic intensities) as well as peripheral vision, but provide no color discrimination.
The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM.
An imaging method using LASERS that is used for mapping subsurface structure. When a reflective site in the sample is at the same optical path length (coherence) as the reference mirror, the detector observes interference fringes.
The restriction of a characteristic behavior, anatomical structure or physical system, such as immune response; metabolic response, or gene or gene variant to the members of one species. It refers to that property which differentiates one species from another but it is also used for phylogenetic levels higher or lower than the species.
Photosensitive afferent neurons located primarily within the FOVEA CENTRALIS of the MACULA LUTEA. There are three major types of cone cells (red, blue, and green) whose photopigments have different spectral sensitivity curves. Retinal cone cells operate in daylight vision (at photopic intensities) providing color recognition and central visual acuity.
Clarity or sharpness of OCULAR VISION or the ability of the eye to see fine details. Visual acuity depends on the functions of RETINA, neuronal transmission, and the interpretative ability of the brain. Normal visual acuity is expressed as 20/20 indicating that one can see at 20 feet what should normally be seen at that distance. Visual acuity can also be influenced by brightness, color, and contrast.
The concave interior of the eye, consisting of the retina, the choroid, the sclera, the optic disk, and blood vessels, seen by means of the ophthalmoscope. (Cline et al., Dictionary of Visual Science, 4th ed)
Visualization of a vascular system after intravenous injection of a fluorescein solution. The images may be photographed or televised. It is used especially in studying the retinal and uveal vasculature.
The thin, highly vascular membrane covering most of the posterior of the eye between the RETINA and SCLERA.
Photosensitive protein complexes of varied light absorption properties which are expressed in the PHOTORECEPTOR CELLS. They are OPSINS conjugated with VITAMIN A-based chromophores. Chromophores capture photons of light, leading to the activation of opsins and a biochemical cascade that ultimately excites the photoreceptor cells.
Examination of the interior of the eye with an ophthalmoscope.
BIRDS that hunt and kill other animals, especially higher vertebrates, for food. They include the FALCONIFORMES order, or diurnal birds of prey, comprised of EAGLES, falcons, HAWKS, and others, as well as the STRIGIFORMES order, or nocturnal birds of prey, which includes OWLS.
Devices for examining the interior of the eye, permitting the clear visualization of the structures of the eye at any depth. (UMDNS, 1999)
A localized defect in the visual field bordered by an area of normal vision. This occurs with a variety of EYE DISEASES (e.g., RETINAL DISEASES and GLAUCOMA); OPTIC NERVE DISEASES, and other conditions.
The positioning and accommodation of eyes that allows the image to be brought into place on the FOVEA CENTRALIS of each eye.
The minimum amount of stimulus energy necessary to elicit a sensory response.
Large members of the FALCONIFORMES order of birds, family Accipitridae, most especially the genera Aquila, Haliaeetus, Harpia, and Circaetus. They are characterized by their powerful talons, which carry long, curved, pointed claws and by their opposable hindtoe.
An objective determination of the refractive state of the eye (NEARSIGHTEDNESS; FARSIGHTEDNESS; ASTIGMATISM). By using a RETINOSCOPE, the amount of correction and the power of lens needed can be determined.
Any of numerous burrowing mammals found in temperate regions and having minute eyes often covered with skin.
Perforations through the whole thickness of the retina including the macula as the result of inflammation, trauma, degeneration, etc. The concept includes retinal breaks, tears, dialyses, and holes.
The ability to detect sharp boundaries (stimuli) and to detect slight changes in luminance at regions without distinct contours. Psychophysical measurements of this visual function are used to evaluate visual acuity and to detect eye disease.
General disorders of the sclera or white of the eye. They may include anatomic, embryologic, degenerative, or pigmentation defects.
Investigative technique commonly used during ELECTROENCEPHALOGRAPHY in which a series of bright light flashes or visual patterns are used to elicit brain activity.
Method of making images on a sensitized surface by exposure to light or other radiant energy.
The process in which light signals are transformed by the PHOTORECEPTOR CELLS into electrical signals which can then be transmitted to the brain.
Defects of color vision are mainly hereditary traits but can be secondary to acquired or developmental abnormalities in the CONES (RETINA). Severity of hereditary defects of color vision depends on the degree of mutation of the ROD OPSINS genes (on X CHROMOSOME and CHROMOSOME 3) that code the photopigments for red, green and blue.
Degenerative changes in the RETINA usually of older adults which results in a loss of vision in the center of the visual field (the MACULA LUTEA) because of damage to the retina. It occurs in dry and wet forms.
The science dealing with the correlation of the physical characteristics of a stimulus, e.g., frequency or intensity, with the response to the stimulus, in order to assess the psychologic factors involved in the relationship.
Retinal diseases refer to a diverse group of vision-threatening disorders that affect the retina's structure and function, including age-related macular degeneration, diabetic retinopathy, retinal detachment, retinitis pigmentosa, and macular edema, among others.
Method of measuring and mapping the scope of vision, from central to peripheral of each eye.
Visual sensation derived from sensory stimulation by objects or shadows inside the eye itself, such as floating vitreous fibers, tissues, or blood.
Excessive axial myopia associated with complications (especially posterior staphyloma and CHOROIDAL NEOVASCULARIZATION) that can lead to BLINDNESS.
A membrane on the vitreal surface of the retina resulting from the proliferation of one or more of three retinal elements: (1) fibrous astrocytes; (2) fibrocytes; and (3) retinal pigment epithelial cells. Localized epiretinal membranes may occur at the posterior pole of the eye without clinical signs or may cause marked loss of vision as a result of covering, distorting, or detaching the fovea centralis. Epiretinal membranes may cause vascular leakage and secondary retinal edema. In younger individuals some membranes appear to be developmental in origin and occur in otherwise normal eyes. The majority occur in association with retinal holes, ocular concussions, retinal inflammation, or after ocular surgery. (Newell, Ophthalmology: Principles and Concepts, 7th ed, p291)
Fluid accumulation in the outer layer of the MACULA LUTEA that results from intraocular or systemic insults. It may develop in a diffuse pattern where the macula appears thickened or it may acquire the characteristic petaloid appearance referred to as cystoid macular edema. Although macular edema may be associated with various underlying conditions, it is most commonly seen following intraocular surgery, venous occlusive disease, DIABETIC RETINOPATHY, and posterior segment inflammatory disease. (From Survey of Ophthalmology 2004; 49(5) 470-90)
The blood vessels which supply and drain the RETINA.
The portion of the optic nerve seen in the fundus with the ophthalmoscope. It is formed by the meeting of all the retinal ganglion cell axons as they enter the optic nerve.
A series of tests used to assess various functions of the eyes.
Recording of electric potentials in the retina after stimulation by light.
Specialized PHOTOTRANSDUCTION neurons in the vertebrates, such as the RETINAL ROD CELLS and the RETINAL CONE CELLS. Non-visual photoreceptor neurons have been reported in the deep brain, the PINEAL GLAND and organs of the circadian system.
A naturally occurring lipid pigment with histochemical characteristics similar to ceroid. It accumulates in various normal tissues and apparently increases in quantity with age.
Methods and procedures for the diagnosis of diseases of the eye or of vision disorders.
Detachment of the corpus vitreum (VITREOUS BODY) from its normal attachments, especially the retina, due to shrinkage from degenerative or inflammatory conditions, trauma, myopia, or senility.
The inner portion of a retinal rod or a cone photoreceptor cell, situated between the PHOTORECEPTOR CONNECTING CILIUM and the synapse with the adjacent neurons (RETINAL BIPOLAR CELLS; RETINAL HORIZONTAL CELLS). The inner segment contains the cell body, the nucleus, the mitochondria, and apparatus for protein synthesis.

Optical, receptoral, and retinal constraints on foveal and peripheral vision in the human neonate. (1/692)

We examined the properties of the foveal, parafoveal, and near peripheral cone lattice in human neonates. To estimate the ability of these lattices to transmit the information used in contrast sensitivity and visual acuity tasks, we constructed ideal-observer models with the optics and photoreceptors of the neonatal eye at retinal eccentricities of 0, 5, and 10 degrees. For ideal-observer models limited by photon noise, the eye's optics, and cone properties, contrast sensitivity was higher in the parafovea and near periphery than in the fovea. However, receptor pooling probably occurs in the neonate's parafovea and near periphery as it does in mature eyes. When we add a receptor-pooling stage to the models of the parafovea and near periphery, ideal acuity is similar in the fovea, parafovea, and near periphery. Comparisons of ideal and real sensitivity indicate that optical and receptoral immaturities impose a significant constraint on neonatal contrast sensitivity and acuity, but that immaturities in later processing stages must also limit visual performance.  (+info)

Radiotherapy for isolated occult subfoveal neovascularisation in age related macular degeneration: a pilot study. (2/692)

BACKGROUND/AIMS: Teletherapy has been proposed as a possible treatment for choroidal neovascular membranes (CNV), secondary to age related macular degeneration (AMD) not amenable to laser photocoagulation. The aim of this prospective study has been to investigate the effect of teletherapy on isolated occult choroidal neovascular membranes of subfoveal location. METHODS: 28 AMD patients presenting with retrofoveal isolated occult CNV demonstrated by fluorescein angiography were treated by external beam radiation. A complete ophthalmological examination, fluorescein angiography, and indocyanine green angiography (ICG) were performed within 15 days before treatment and repeated at follow up. A total dose of 16 Gy was applied in four sessions of 4 Gy using a 4 MeV photon beam. Follow up ranged from 6 to 9 months (mean follow up 6.4 months). RESULTS: Visual acuity was found to be stable in 68% of the cases. The decrease in visual acuity was of 3-6 lines in 18% and of more than 6 lines in 10% of the eyes at last examination. On fluorescein angiography the size of the lesion area was found to be stable in 67%, decreased in 13%, and increased in 20% of the cases. On ICG angiography the size of the CNV was stable in 93% and increased in 7% of the cases. All the eyes experiencing a visual acuity decrease showed either no change or an increase in size of the membrane on fluorescein angiography and/or on ICG. CONCLUSION: According to this study with strict inclusion criteria, external beam radiotherapy seems to have a beneficial effect on the evolution of isolated occult subfoveal CNV.  (+info)

Contour integration in the peripheral field. (3/692)

Contour integration was measured in the normal peripheral field to determine if an explanation based solely on the known peripheral positional uncertainty was sufficient to explain performance. The task involved the detection of paths composed of micropatterns with correlated carrier orientations embedded in a field of similar micropatterns of random position and orientation (Field, D. J., Hayes A., & Hess, R. F. (1993). Vision Research, 33, 173-193). The intrinsic positional uncertainty for each eccentric locus was measured with the same stimulus and it did not account for levels of peripheral performance. We show that peripheral performance on this task does not get worse with eccentricity beyond about 10 degrees and that these results can be modeled by simple filtering without any subsequent cellular linking interactions.  (+info)

The effects of temporal noise and retinal illuminance on foveal flicker sensitivity. (4/692)

We measured foveal flicker sensitivity with and without external added temporal noise at various levels of retinal illuminance and described the data with our model of flicker sensitivity comprising: (i) low-pass filtering of the flickering signal plus external temporal and/or quantal noise by the modulation transfer function (MTF) of the retina (R): (ii) high-pass filtering in proportion to temporal frequency by the MTF of the postreceptoral neural pathways (P): (iii) addition of internal white neural noise; and (iv) detection by a temporal matched filter. Without temporal noise flicker sensitivity had a band-pass frequency-dependence at high and medium illuminances but changed towards a low-pass shape above 0.5 Hz at low luminances, in agreement with earlier studies. In strong external temporal noise, however, the flicker sensitivity function had a low-pass shape even at high and medium illuminances and flicker sensitivity was consistently lower with noise than without. At low luminances flicker sensitivity was similar with and without noise. An excellent fit of the model was obtained under the assumption that the only luminance-dependent changes were increases in the cut-off frequency (fc) and maximum contrast transfer of R with increasing luminance. The results imply the following: (i) performance is consistent with detection by a temporal matched filter, but not with a thresholding process based on signal amplitude; (ii) quantal fluctuations do not at any luminance level become a source of dominant noise present at the detector; (iii) the changes in the maximum contrast transfer reflect changes in retinal gain, which at low to moderate luminances implement less-than-Weber adaptation, with a 'square-root' law at the lowest levels; (iv) the changes of fc as function of mean luminance closely parallels time scale changes in cones, but the absolute values of fc are lower than expected from the kinetics of monkey cones at all luminances; (v) the constancy of the high-pass filtering function P indicates that surround antagonism does not weaken significantly with decreasing light level.  (+info)

Eye movements of rhesus monkeys directed towards imaginary targets. (5/692)

Is the presence of foveal stimulation a necessary prerequisite for rhesus monkeys to perform visually guided eye movements? To answer this question, we trained two rhesus monkeys to direct their eyes towards imaginary targets defined by extrafoveal cues. Independent of the type of target, real or imaginary, the trajectory of target movement determined the type of eye movement produced: steps in target position resulted in saccades and ramps in target position resulted in smooth pursuit eye movements. There was a tendency for the latency of saccades as well as pursuit onset latency to be delayed in the case of an imaginary target in comparison to the real target. The initial eye acceleration during smooth pursuit initiation elicited by an imaginary target decreased in comparison to the acceleration elicited by a real target. The steady-state pursuit gain was quite similar during pursuit of an imaginary or a real target. Our results strengthen the notion that pursuit is not exclusively a foveal function.  (+info)

Peripheral vision and oculomotor control during visual search. (6/692)

The present study concerns the dynamics of multiple fixation search. We tried to gain insight into: (1) how the peripheral and foveal stimulus affect fixation duration; and (2) how fixation duration affects the peripheral target selection for saccades. We replicated the non-corroborating results of Luria and Strauss (1975) ('Eye movements during search for coded and uncoded targets', Perception and Psychophysics 17, 303-308) (saccades were selective), and Zelinsky (1996) (Using eye movements to assess the selectivity of search movements. Vision research 36(14), 2177-2187) (saccades were not selective), by manipulating the critical features for peripheral selection and discrimination separately. We found search to be more selective and efficient when the selection task was easy or when fixations were long-lasting. Remarkably, subjects did not increase their fixation durations when the peripheral selection task was more difficult. Only the discrimination task affected the fixation duration. This implies that the time available for peripheral target selection is determined mainly by the discrimination task. The results of the present experiment suggest that, besides the difficulty of the peripheral selection task, fixation duration is an important factor determining the selection of potential targets for eye movements.  (+info)

Contrast dependency of foveal spatial functions: orientation, vernier, separation, blur and displacement discrimination and the tilt and Poggendorff illusions. (7/692)

To examine the effect of reducing luminance contrast in human foveal vision, discrimination thresholds were measured in four tasks and also a numerical measure of two visual illusions were obtained by a nulling technique. The patterns used for all tasks were made very similar to facilitate comparison between them--all featured luminance step edges whose contrast could be varied from near unity down to the detection threshold. Orientation, vernier and blur discrimination thresholds rise on average 5-6-fold when the contrast is reduced from near unity to a Michelson value of 0.03. Jump displacement thresholds are somewhat more robust to contrast reduction, and the curve of separation discrimination versus contrast is much shallower, rising by a factor of about 2. The magnitude of the Poggendorff and tilt illusions changes very little until the inducing contours are barely detectable.  (+info)

Temporal resolution deficits in the visual fields of MS patients. (8/692)

We assessed the relationship between temporal resolution and MS-induced neuropathy. A diagnostic strategy comprising assessments of temporal resolution at 16 points in the extra-foveal visual field up to 12 degrees from the fovea was first compared with foveal temporal resolution and with a standard VEP procedure in the same MS patients. At the group level, foveal temporal resolution was less sensitive to demyelination than the 16-point diagnostic strategy, the detection rate of which was comparable to that of the VEP procedure. Cross-sensitivity of the VEP and the 16-point diagnostic procedure was low. Subsequently, the average severity of MS-induced temporal resolution deficits was studied at three retinal loci of the same size but different eccentricities. Foveal deficits were not significantly greater than more peripheral deficits within the central 12 degrees.  (+info)

The fovea centralis, also known as the macula lutea, is a small pit or depression located in the center of the retina, an light-sensitive tissue at the back of the eye. It is responsible for sharp, detailed vision (central vision) and color perception. The fovea contains only cones, the photoreceptor cells that are responsible for color vision and high visual acuity. It has a higher concentration of cones than any other area in the retina, allowing it to provide the greatest detail and color discrimination. The center of the fovea is called the foveola, which contains the highest density of cones and is avascular, meaning it lacks blood vessels to avoid interfering with the light passing through to the photoreceptor cells.

Tupaiidae is a family of small mammals commonly known as treeshrews. They are not true shrews (Soricidae) but are included in the order Scandentia. There are about 20 species placed in this family, and they are found primarily in Southeast Asian forests. Treeshrews are small animals, typically weighing between 50 and 150 grams, with a body length of around 10-25 cm. They have pointed snouts, large eyes, and ears, and most species have a long, bushy tail.

Treeshrews are omnivorous, feeding on a variety of plant and animal matter, including fruits, insects, and small vertebrates. They are agile animals, well-adapted to life in the trees, with sharp claws for climbing and a keen sense of sight and smell.

Medically, treeshrews have been used as animal models in biomedical research, particularly in studies of infectious diseases such as malaria and HIV. They are susceptible to these infections and can provide valuable insights into the mechanisms of disease and potential treatments. However, they are not typically used in clinical medicine or patient care.

Sensory ganglia are clusters of nerve cell bodies located outside the central nervous system (the brain and spinal cord). They are primarily associated with sensory neurons, which are responsible for transmitting sensory information from various parts of the body to the central nervous system.

In humans, there are two main types of sensory ganglia: dorsal root ganglia and cranial nerve ganglia. Dorsal root ganglia are located along the spinal cord and contain the cell bodies of sensory neurons that innervate the skin, muscles, joints, and other tissues of the body. These neurons transmit information about touch, temperature, pain, and proprioception (the sense of the position and movement of the body).

Cranial nerve ganglia are associated with the cranial nerves, which are responsible for transmitting sensory information from the head and neck to the brain. For example, the trigeminal ganglion is a cranial nerve ganglion that contains the cell bodies of neurons that transmit sensory information from the face, mouth, and other structures of the head.

Overall, sensory ganglia play a critical role in our ability to perceive and interact with the world around us by transmitting important sensory information to the brain for processing.

Aotidae is a family of nocturnal primates also known as lorises or slow lorises. They are native to Southeast Asia and are characterized by their small size, round head, large eyes, and a wet-nosed face. Slow lorises have a toxic bite, which they use to defend themselves against predators. They are currently listed as vulnerable or endangered due to habitat loss and hunting.

Cone opsins are a type of photopigment protein found in the cone cells of the retina, which are responsible for color vision. There are three types of cone opsins in humans, each sensitive to different wavelengths of light: short-wavelength (S) sensitive cone opsin (also known as blue cone opsin), medium-wavelength (M) sensitive cone opsin (also known as green cone opsin), and long-wavelength (L) sensitive cone opsin (also known as red cone opsin).

These cone opsins are activated by light, which triggers a chemical reaction that sends signals to the brain and enables us to perceive color. Differences in the genes that code for these cone opsins can result in variations in color perception and can contribute to individual differences in color vision. Certain genetic mutations can also lead to various forms of color blindness, including red-green color blindness and blue-yellow color blindness.

"Cat" is a common name that refers to various species of small carnivorous mammals that belong to the family Felidae. The domestic cat, also known as Felis catus or Felis silvestris catus, is a popular pet and companion animal. It is a subspecies of the wildcat, which is found in Europe, Africa, and Asia.

Domestic cats are often kept as pets because of their companionship, playful behavior, and ability to hunt vermin. They are also valued for their ability to provide emotional support and therapy to people. Cats are obligate carnivores, which means that they require a diet that consists mainly of meat to meet their nutritional needs.

Cats are known for their agility, sharp senses, and predatory instincts. They have retractable claws, which they use for hunting and self-defense. Cats also have a keen sense of smell, hearing, and vision, which allow them to detect prey and navigate their environment.

In medical terms, cats can be hosts to various parasites and diseases that can affect humans and other animals. Some common feline diseases include rabies, feline leukemia virus (FeLV), feline immunodeficiency virus (FIV), and toxoplasmosis. It is important for cat owners to keep their pets healthy and up-to-date on vaccinations and preventative treatments to protect both the cats and their human companions.

Dicrocoeliasis is a parasitic infection caused by the fluke Dicrocoelium dendriticum, also known as the lancet liver fluke. This small flatworm infects the bile ducts of the liver in its definitive host, which are usually herbivorous animals such as sheep and cattle. Humans can become accidental hosts by ingesting contaminated vegetation or water that contains the encysted larval stage of the fluke.

The infection is typically asymptomatic or causes only mild symptoms, such as abdominal discomfort, diarrhea, and fatigue. However, in severe cases, it can lead to liver damage and other complications. The diagnosis of dicrocoeliasis is usually made by detecting the presence of the parasite's eggs in the stool or through imaging techniques such as ultrasound or CT scan. Treatment typically involves the use of anthelmintic medications that are effective against flukes, such as praziquantel or triclabendazole.

Dicrocoelium is a genus of digenean flatworms, also known as liver flukes. These parasites primarily infect the livers of herbivorous animals, such as sheep and cattle, but can also occasionally infect humans. The medical definition of Dicrocoelium refers to these parasitic worms that have a complex life cycle involving snails, ants, and definitive hosts (herbivores or humans).

The most common species is Dicrocoelium dendriticum, which causes dicrocoeliasis in its definitive host. Infection occurs when the herbivore ingests vegetation contaminated with metacercariae, the infective stage of the parasite, encysted on the surface of plants. Once inside the definitive host, the metacercariae excyst and migrate to the bile ducts in the liver, where they mature into adults and produce eggs that are excreted in the feces.

The life cycle continues when these eggs are consumed by a specific type of snail, which becomes infected after ingesting the eggs. Inside the snail, the parasites undergo asexual reproduction, producing cercariae, which then leave the snail and encyst on the surface of vegetation or in ants. When an ant accidentally ingests these encysted cercariae, they migrate to the brain of the ant and manipulate its behavior, causing it to climb up tall blades of grass or other vegetation during the daytime. This exposes the ant to being eaten by a grazing herbivore, which completes the life cycle when it ingests the infected ant.

In humans, Dicrocoelium infection is rare and usually occurs after consuming raw or undercooked vegetables contaminated with metacercariae. Symptoms of dicrocoeliasis can include abdominal pain, diarrhea, weight loss, and liver enlargement. Diagnosis is typically made by detecting eggs in the stool, and treatment involves administering anthelmintic medications to eliminate the parasites from the body.

The retina is the innermost, light-sensitive layer of tissue in the eye of many vertebrates and some cephalopods. It receives light that has been focused by the cornea and lens, converts it into neural signals, and sends these to the brain via the optic nerve. The retina contains several types of photoreceptor cells including rods (which handle vision in low light) and cones (which are active in bright light and are capable of color vision).

In medical terms, any pathological changes or diseases affecting the retinal structure and function can lead to visual impairment or blindness. Examples include age-related macular degeneration, diabetic retinopathy, retinal detachment, and retinitis pigmentosa among others.

The macula lutea, often simply referred to as the macula or fovea centralis, is a part of the eye that is responsible for central vision and color perception. It's located in the center of the retina, the light-sensitive tissue at the back of the eye. The macula contains a high concentration of pigments called xanthophylls, which give it a yellowish color and protect the photoreceptor cells in this area from damage by blue light.

The central part of the macula is called the fovea, which is a small depression that contains only cones, the photoreceptor cells responsible for color vision and high visual acuity. The fovea is surrounded by the parafovea and the perifovea, which contain both cones and rods, the photoreceptor cells responsible for low-light vision and peripheral vision.

Damage to the macula can result in a loss of central vision and color perception, a condition known as age-related macular degeneration (AMD), which is a leading cause of blindness in older adults. Other conditions that can affect the macula include macular edema, macular holes, and macular pucker.

Retinal Ganglion Cells (RGCs) are a type of neuron located in the innermost layer of the retina, the light-sensitive tissue at the back of the eye. These cells receive visual information from photoreceptors (rods and cones) via intermediate cells called bipolar cells. RGCs then send this visual information through their long axons to form the optic nerve, which transmits the signals to the brain for processing and interpretation as vision.

There are several types of RGCs, each with distinct morphological and functional characteristics. Some RGCs are specialized in detecting specific features of the visual scene, such as motion, contrast, color, or brightness. The diversity of RGCs allows for a rich and complex representation of the visual world in the brain.

Damage to RGCs can lead to various visual impairments, including loss of vision, reduced visual acuity, and altered visual fields. Conditions associated with RGC damage or degeneration include glaucoma, optic neuritis, ischemic optic neuropathy, and some inherited retinal diseases.

Efferent neurons are specialized nerve cells that transmit signals from the central nervous system (CNS), which includes the brain and spinal cord, to effector organs such as muscles or glands. These signals typically result in a response or action, hence the term "efferent," derived from the Latin word "efferre" meaning "to carry away."

Efferent neurons are part of the motor pathway and can be further classified into two types:

1. Somatic efferent neurons: These neurons transmit signals to skeletal muscles, enabling voluntary movements and posture maintenance. They have their cell bodies located in the ventral horn of the spinal cord and send their axons through the ventral roots to innervate specific muscle fibers.
2. Autonomic efferent neurons: These neurons are responsible for controlling involuntary functions, such as heart rate, digestion, respiration, and pupil dilation. They have a two-neuron chain arrangement, with the preganglionic neuron having its cell body in the CNS (brainstem or spinal cord) and synapsing with the postganglionic neuron in an autonomic ganglion near the effector organ. Autonomic efferent neurons can be further divided into sympathetic, parasympathetic, and enteric subdivisions based on their functions and innervation patterns.

In summary, efferent neurons are a critical component of the nervous system, responsible for transmitting signals from the CNS to various effector organs, ultimately controlling and coordinating numerous bodily functions and responses.

Visual fields refer to the total area in which objects can be seen while keeping the eyes focused on a central point. It is the entire area that can be observed using peripheral (side) vision while the eye gazes at a fixed point. A visual field test is used to detect blind spots or gaps (scotomas) in a person's vision, which could indicate various medical conditions such as glaucoma, retinal damage, optic nerve disease, brain tumors, or strokes. The test measures both the central and peripheral vision and maps the entire area that can be seen when focusing on a single point.

"Cell count" is a medical term that refers to the process of determining the number of cells present in a given volume or sample of fluid or tissue. This can be done through various laboratory methods, such as counting individual cells under a microscope using a specialized grid called a hemocytometer, or using automated cell counters that use light scattering and electrical impedance techniques to count and classify different types of cells.

Cell counts are used in a variety of medical contexts, including hematology (the study of blood and blood-forming tissues), microbiology (the study of microscopic organisms), and pathology (the study of diseases and their causes). For example, a complete blood count (CBC) is a routine laboratory test that includes a white blood cell (WBC) count, red blood cell (RBC) count, hemoglobin level, hematocrit value, and platelet count. Abnormal cell counts can indicate the presence of various medical conditions, such as infections, anemia, or leukemia.

Photoreceptor cells are specialized neurons in the retina of the eye that convert light into electrical signals. These cells consist of two types: rods and cones. Rods are responsible for vision at low light levels and provide black-and-white, peripheral, and motion sensitivity. Cones are active at higher light levels and are capable of color discrimination and fine detail vision. Both types of photoreceptor cells contain light-sensitive pigments that undergo chemical changes when exposed to light, triggering a series of electrical signals that ultimately reach the brain and contribute to visual perception.

Retinal rod photoreceptor cells are specialized neurons in the retina of the eye that are primarily responsible for vision in low light conditions. They contain a light-sensitive pigment called rhodopsin, which undergoes a chemical change when struck by a single photon of light. This triggers a cascade of biochemical reactions that ultimately leads to the generation of electrical signals, which are then transmitted to the brain via the optic nerve.

Rod cells do not provide color vision or fine detail, but they allow us to detect motion and see in dim light. They are more sensitive to light than cone cells, which are responsible for color vision and detailed sight in bright light conditions. Rod cells are concentrated at the outer edges of the retina, forming a crescent-shaped region called the peripheral retina, with fewer rod cells located in the central region of the retina known as the fovea.

Neurons, also known as nerve cells or neurocytes, are specialized cells that constitute the basic unit of the nervous system. They are responsible for receiving, processing, and transmitting information and signals within the body. Neurons have three main parts: the dendrites, the cell body (soma), and the axon. The dendrites receive signals from other neurons or sensory receptors, while the axon transmits these signals to other neurons, muscles, or glands. The junction between two neurons is called a synapse, where neurotransmitters are released to transmit the signal across the gap (synaptic cleft) to the next neuron. Neurons vary in size, shape, and structure depending on their function and location within the nervous system.

Optical coherence tomography (OCT) is a non-invasive imaging technique that uses low-coherence light to capture high-resolution cross-sectional images of biological tissues, particularly the retina and other ocular structures. OCT works by measuring the echo time delay of light scattered back from different depths within the tissue, creating a detailed map of the tissue's structure. This technique is widely used in ophthalmology to diagnose and monitor various eye conditions such as macular degeneration, diabetic retinopathy, and glaucoma.

Species specificity is a term used in the field of biology, including medicine, to refer to the characteristic of a biological entity (such as a virus, bacterium, or other microorganism) that allows it to interact exclusively or preferentially with a particular species. This means that the biological entity has a strong affinity for, or is only able to infect, a specific host species.

For example, HIV is specifically adapted to infect human cells and does not typically infect other animal species. Similarly, some bacterial toxins are species-specific and can only affect certain types of animals or humans. This concept is important in understanding the transmission dynamics and host range of various pathogens, as well as in developing targeted therapies and vaccines.

Retinal cone photoreceptor cells are specialized neurons located in the retina of the eye, responsible for visual phototransduction and color vision. They are one of the two types of photoreceptors, with the other being rods, which are more sensitive to low light levels. Cones are primarily responsible for high-acuity, color vision during daylight or bright-light conditions.

There are three types of cone cells, each containing different photopigments that absorb light at distinct wavelengths: short (S), medium (M), and long (L) wavelengths, which correspond to blue, green, and red light, respectively. The combination of signals from these three types of cones allows the human visual system to perceive a wide range of colors and discriminate between them. Cones are densely packed in the central region of the retina, known as the fovea, which provides the highest visual acuity.

Visual acuity is a measure of the sharpness or clarity of vision. It is usually tested by reading an eye chart from a specific distance, such as 20 feet (6 meters). The standard eye chart used for this purpose is called the Snellen chart, which contains rows of letters that decrease in size as you read down the chart.

Visual acuity is typically expressed as a fraction, with the numerator representing the testing distance and the denominator indicating the smallest line of type that can be read clearly. For example, if a person can read the line on the eye chart that corresponds to a visual acuity of 20/20, it means they have normal vision at 20 feet. If their visual acuity is 20/40, it means they must be as close as 20 feet to see what someone with normal vision can see at 40 feet.

It's important to note that visual acuity is just one aspect of overall vision and does not necessarily reflect other important factors such as peripheral vision, depth perception, color vision, or contrast sensitivity.

"Fundus Oculi" is a medical term that refers to the back part of the interior of the eye, including the optic disc, macula, fovea, retinal vasculature, and peripheral retina. It is the area where light is focused and then transmitted to the brain via the optic nerve, forming visual images. Examinations of the fundus oculi are crucial for detecting various eye conditions such as diabetic retinopathy, macular degeneration, glaucoma, and other retinal diseases. The examination is typically performed using an ophthalmoscope or a specialized camera called a retinal camera.

Fluorescein angiography is a medical diagnostic procedure used in ophthalmology to examine the blood flow in the retina and choroid, which are the inner layers of the eye. This test involves injecting a fluorescent dye, Fluorescein, into a patient's arm vein. As the dye reaches the blood vessels in the eye, a specialized camera takes rapid sequences of photographs to capture the dye's circulation through the retina and choroid.

The images produced by fluorescein angiography can help doctors identify any damage to the blood vessels, leakage, or abnormal growth of new blood vessels. This information is crucial in diagnosing and managing various eye conditions such as age-related macular degeneration, diabetic retinopathy, retinal vein occlusions, and inflammatory eye diseases.

It's important to note that while fluorescein angiography is a valuable diagnostic tool, it does carry some risks, including temporary side effects like nausea, vomiting, or allergic reactions to the dye. In rare cases, severe adverse reactions can occur, so patients should discuss these potential risks with their healthcare provider before undergoing the procedure.

The choroid is a layer of the eye that contains blood vessels that supply oxygen and nutrients to the outer layers of the retina. It lies between the sclera (the white, protective coat of the eye) and the retina (the light-sensitive tissue at the back of the eye). The choroid is essential for maintaining the health and function of the retina, particularly the photoreceptor cells that detect light and transmit visual signals to the brain. Damage to the choroid can lead to vision loss or impairment.

Retinal pigments refer to the light-sensitive chemicals found in the retina, specifically within the photoreceptor cells called rods and cones. The main types of retinal pigments are rhodopsin (also known as visual purple) in rods and iodopsins in cones. These pigments play a crucial role in the process of vision by absorbing light and initiating a series of chemical reactions that ultimately trigger nerve impulses, which are then transmitted to the brain and interpreted as visual images. Rhodopsin is more sensitive to lower light levels and is responsible for night vision, while iodopsins are sensitive to specific wavelengths of light and contribute to color vision.

Ophthalmoscopy is a medical examination technique used by healthcare professionals to observe the interior structures of the eye, including the retina, optic disc, and vitreous humor. This procedure typically involves using an ophthalmoscope, a handheld device that consists of a light and magnifying lenses. The healthcare provider looks through the ophthalmoscope and directly observes the internal structures of the eye by illuminating them.

There are several types of ophthalmoscopy, including direct ophthalmoscopy, indirect ophthalmoscopy, and slit-lamp biomicroscopy. Each type has its own advantages and disadvantages, and they may be used in different situations depending on the specific clinical situation and the information needed.

Ophthalmoscopy is an important diagnostic tool for detecting and monitoring a wide range of eye conditions, including diabetic retinopathy, glaucoma, age-related macular degeneration, and other retinal disorders. It can also provide valuable information about the overall health of the individual, as changes in the appearance of the retina or optic nerve may indicate the presence of systemic diseases such as hypertension or diabetes.

I believe there may be some confusion in your question. "Raptors" is a common name used to refer to a group of birds of prey, which include hawks, eagles, falcons, and owls, among others. However, the term "raptors" does not have a specific medical definition.

If you meant to ask for a medical definition of a different term, please let me know and I will be happy to help you with that.

An ophthalmoscope is a medical device used by healthcare professionals to examine the interior structures of the eye, including the retina, optic disc, and vitreous humor. It consists of a handle with a battery-powered light source and a head that contains lenses for focusing. When placed in contact with the patient's dilated pupil, the ophthalmoscope allows the examiner to visualize the internal structures of the eye and assess their health. Ophthalmoscopes are commonly used in routine eye examinations, as well as in the diagnosis and management of various eye conditions and diseases.

A scotoma is a blind spot or area of reduced vision within the visual field. It's often surrounded by an area of less distinct vision and can be caused by various conditions such as eye diseases, neurological disorders, or brain injuries. A scotoma may be temporary or permanent, depending on its underlying cause.

There are different types of scotomas, including:

1. Central scotoma - a blind spot in the center of the visual field, often associated with conditions like age-related macular degeneration and diabetic retinopathy.
2. Paracentral scotoma - a blind spot located slightly away from the center of the visual field, which can be caused by optic neuritis or other optic nerve disorders.
3. Peripheral scotoma - a blind spot in the peripheral vision, often associated with retinal diseases like retinitis pigmentosa.
4. Absolute scotoma - a complete loss of vision in a specific area of the visual field.
5. Relative scotoma - a partial loss of vision in which some details can still be perceived, but not as clearly or vividly as in normal vision.

It is essential to consult an eye care professional if you experience any changes in your vision or notice a scotoma, as early detection and treatment can help prevent further vision loss.

Ocular fixation is a term used in ophthalmology and optometry to refer to the ability of the eyes to maintain steady gaze or visual focus on an object. It involves the coordinated movement of the extraocular muscles that control eye movements, allowing for clear and stable vision.

In medical terminology, fixation specifically refers to the state in which the eyes are aligned and focused on a single point in space. This is important for maintaining visual perception and preventing blurring or double vision. Ocular fixation can be affected by various factors such as muscle weakness, nerve damage, or visual processing disorders.

Assessment of ocular fixation is often used in eye examinations to evaluate visual acuity, eye alignment, and muscle function. Abnormalities in fixation may indicate the presence of underlying eye conditions or developmental delays that require further investigation and treatment.

Sensory thresholds are the minimum levels of stimulation that are required to produce a sensation in an individual, as determined through psychophysical testing. These tests measure the point at which a person can just barely detect the presence of a stimulus, such as a sound, light, touch, or smell.

There are two types of sensory thresholds: absolute and difference. Absolute threshold is the minimum level of intensity required to detect a stimulus 50% of the time. Difference threshold, also known as just noticeable difference (JND), is the smallest change in intensity that can be detected between two stimuli.

Sensory thresholds can vary between individuals and are influenced by factors such as age, attention, motivation, and expectations. They are often used in clinical settings to assess sensory function and diagnose conditions such as hearing or vision loss.

I am not aware of a medical definition for the term "Eagles." It is possible that you may be referring to a condition called "aquilegia," which is a genus of flowering plants commonly known as columbines. There is also no widely recognized medical condition or pathology named after the bird species known as eagles. If you have more context or information about where you encountered this term, I'd be happy to help you further!

Retinoscopy is a diagnostic technique used in optometry and ophthalmology to estimate the refractive error of the eye, or in other words, to determine the prescription for eyeglasses or contact lenses. This procedure involves shining a light into the patient's pupil and observing the reflection off the retina while introducing different lenses in front of the patient's eye. The examiner then uses specific movements and observations to determine the amount and type of refractive error, such as myopia (nearsightedness), hyperopia (farsightedness), astigmatism, or presbyopia. Retinoscopy is a fundamental skill for eye care professionals and helps ensure that patients receive accurate prescriptions for corrective lenses.

A mole (nevus) is a benign growth on the skin that is usually brown or black. Moles can appear anywhere on the body, alone or in groups. Most adults have between 10 and 40 moles. They typically appear during childhood and adolescence. Some moles may change over time, possibly becoming raised and/or changing color. It's important to keep an eye on moles and see a healthcare provider if any changes are noticed, as melanoma, a type of skin cancer, can develop from moles.

It is also worth noting that there are different types of moles including congenital nevi (moles present at birth), dysplastic nevi (atypical moles) and acquired nevi (moles that appear after birth). Dysplastic nevi are larger than average and irregular in shape, with color variations. They are more likely to develop into melanoma than regular moles.

A retinal perforation is a full-thickness break or hole in the retina, which is the light-sensitive tissue that lines the inner surface of the eye. This condition can lead to a serious complication called retinal detachment, where the retina separates from the underlying tissue, potentially resulting in vision loss if not promptly treated. Retinal perforations may be caused by trauma, certain eye conditions, or invasive eye procedures. Immediate medical attention is required for retinal perforations to prevent further damage and preserve vision.

Contrast sensitivity is a measure of the ability to distinguish between an object and its background based on differences in contrast, rather than differences in luminance. Contrast refers to the difference in light intensity between an object and its immediate surroundings. Contrast sensitivity is typically measured using specially designed charts that have patterns of parallel lines with varying widths and contrast levels.

In clinical settings, contrast sensitivity is often assessed as part of a comprehensive visual examination. Poor contrast sensitivity can affect a person's ability to perform tasks such as reading, driving, or distinguishing objects from their background, especially in low-light conditions. Reduced contrast sensitivity is a common symptom of various eye conditions, including cataracts, glaucoma, and age-related macular degeneration.

Scleral diseases refer to conditions that affect the sclera, which is the tough, white outer coating of the eye. The sclera helps to maintain the shape of the eye and provides protection for the internal structures. Scleral diseases can cause inflammation, degeneration, or thinning of the sclera, leading to potential vision loss or other complications. Some examples of scleral diseases include:

1. Scleritis: an inflammatory condition that causes pain, redness, and sensitivity in the affected area of the sclera. It can be associated with autoimmune disorders, infections, or trauma.
2. Episcleritis: a less severe form of inflammation that affects only the episclera, a thin layer of tissue overlying the sclera. Symptoms include redness and mild discomfort but typically no pain.
3. Pinguecula: a yellowish, raised deposit of protein and fat that forms on the conjunctiva, the clear membrane covering the sclera. While not a disease itself, a pinguecula can cause irritation or discomfort and may progress to a more severe condition called a pterygium.
4. Pterygium: a fleshy growth that extends from the conjunctiva onto the cornea, potentially obstructing vision. It is often associated with prolonged sun exposure and can be removed surgically if it becomes problematic.
5. Scleral thinning or melting: a rare but serious condition where the sclera degenerates or liquefies, leading to potential perforation of the eye. This can occur due to autoimmune disorders, infections, or as a complication of certain surgical procedures.
6. Ocular histoplasmosis syndrome (OHS): a condition caused by the Histoplasma capsulatum fungus, which can lead to scarring and vision loss if it involves the macula, the central part of the retina responsible for sharp, detailed vision.

It is essential to consult an ophthalmologist or eye care professional if you experience any symptoms related to scleral diseases to receive proper diagnosis and treatment.

Photic stimulation is a medical term that refers to the exposure of the eyes to light, specifically repetitive pulses of light, which is used as a method in various research and clinical settings. In neuroscience, it's often used in studies related to vision, circadian rhythms, and brain function.

In a clinical context, photic stimulation is sometimes used in the diagnosis of certain medical conditions such as seizure disorders (like epilepsy). By observing the response of the brain to this light stimulus, doctors can gain valuable insights into the functioning of the brain and the presence of any neurological disorders.

However, it's important to note that photic stimulation should be conducted under the supervision of a trained healthcare professional, as improper use can potentially trigger seizures in individuals who are susceptible to them.

I'm sorry for any confusion, but "photography" is not a term typically used in medical definitions. Photography refers to the art, application, or process of creating images by recording light or other electromagnetic radiation, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film.

If you're looking for a medical term related to imaging, there are several terms that might be relevant, such as:

1. Radiography: This is a technique using X-rays to visualize the internal structures of the body.
2. Ultrasonography: Also known as ultrasound, this is a diagnostic imaging technique using high-frequency sound waves to create images of the inside of the body.
3. Computed Tomography (CT): A type of imaging that uses X-rays to create detailed cross-sectional images of the body.
4. Magnetic Resonance Imaging (MRI): A type of imaging that uses magnetic fields and radio waves to create detailed images of the organs and tissues within the body.
5. Nuclear Medicine: This is a branch of medical imaging that uses small amounts of radioactive material to diagnose and treat diseases.

If you have any questions related to medical definitions or topics, feel free to ask!

Ocular vision refers to the ability to process and interpret visual information that is received by the eyes. This includes the ability to see clearly and make sense of the shapes, colors, and movements of objects in the environment. The ocular system, which includes the eye and related structures such as the optic nerve and visual cortex of the brain, works together to enable vision.

There are several components of ocular vision, including:

* Visual acuity: the clarity or sharpness of vision
* Field of vision: the extent of the visual world that is visible at any given moment
* Color vision: the ability to distinguish different colors
* Depth perception: the ability to judge the distance of objects in three-dimensional space
* Contrast sensitivity: the ability to distinguish an object from its background based on differences in contrast

Disorders of ocular vision can include refractive errors such as nearsightedness or farsightedness, as well as more serious conditions such as cataracts, glaucoma, and macular degeneration. These conditions can affect one or more aspects of ocular vision and may require medical treatment to prevent further vision loss.

Color vision defects, also known as color blindness, are conditions in which a person has difficulty distinguishing between certain colors. The most common types of color vision defects involve the inability to distinguish between red and green or blue and yellow. These deficiencies result from an alteration or absence of one or more of the three types of cone cells in the retina that are responsible for normal color vision.

In red-green color vision defects, there is a problem with either the red or green cones, or both. This results in difficulty distinguishing between these two colors and their shades. Protanopia is a type of red-green color vision defect where there is an absence of red cone cells, making it difficult to distinguish between red and green as well as between red and black or green and black. Deuteranopia is another type of red-green color vision defect where there is an absence of green cone cells, resulting in similar difficulties distinguishing between red and green, as well as between blue and yellow.

Blue-yellow color vision defects are less common than red-green color vision defects. Tritanopia is a type of blue-yellow color vision defect where there is an absence of blue cone cells, making it difficult to distinguish between blue and yellow, as well as between blue and purple or yellow and pink.

Color vision defects are usually inherited and present from birth, but they can also result from eye diseases, chemical exposure, aging, or medication side effects. They affect both men and women, although red-green color vision defects are more common in men than in women. People with color vision defects may have difficulty with tasks that require color discrimination, such as matching clothes, selecting ripe fruit, reading colored maps, or identifying warning signals. However, most people with mild to moderate color vision defects can adapt and function well in daily life.

Macular degeneration, also known as age-related macular degeneration (AMD), is a medical condition that affects the central part of the retina, called the macula. The macula is responsible for sharp, detailed vision, which is necessary for activities such as reading, driving, and recognizing faces.

In AMD, there is a breakdown or deterioration of the macula, leading to gradual loss of central vision. There are two main types of AMD: dry (atrophic) and wet (exudative). Dry AMD is more common and progresses more slowly, while wet AMD is less common but can cause rapid and severe vision loss if left untreated.

The exact causes of AMD are not fully understood, but risk factors include age, smoking, family history, high blood pressure, obesity, and exposure to sunlight. While there is no cure for AMD, treatments such as vitamin supplements, laser therapy, and medication injections can help slow its progression and reduce the risk of vision loss.

Psychophysics is not a medical term per se, but rather a subfield of psychology and neuroscience that studies the relationship between physical stimuli and the sensations and perceptions they produce. It involves the quantitative investigation of psychological functions, such as how brightness or loudness is perceived relative to the physical intensity of light or sound.

In medical contexts, psychophysical methods may be used in research or clinical settings to understand how patients with neurological conditions or sensory impairments perceive and respond to different stimuli. This information can inform diagnostic assessments, treatment planning, and rehabilitation strategies.

Retinal diseases refer to a group of conditions that affect the retina, which is the light-sensitive tissue located at the back of the eye. The retina is responsible for converting light into electrical signals that are sent to the brain and interpreted as visual images. Retinal diseases can cause vision loss or even blindness, depending on their severity and location in the retina.

Some common retinal diseases include:

1. Age-related macular degeneration (AMD): A progressive disease that affects the central part of the retina called the macula, causing blurred or distorted vision.
2. Diabetic retinopathy: A complication of diabetes that can damage the blood vessels in the retina, leading to vision loss.
3. Retinal detachment: A serious condition where the retina becomes separated from its underlying tissue, requiring immediate medical attention.
4. Macular edema: Swelling or thickening of the macula due to fluid accumulation, which can cause blurred vision.
5. Retinitis pigmentosa: A group of inherited eye disorders that affect the retina's ability to respond to light, causing progressive vision loss.
6. Macular hole: A small break in the macula that can cause distorted or blurry vision.
7. Retinal vein occlusion: Blockage of the retinal veins that can lead to bleeding, swelling, and potential vision loss.

Treatment for retinal diseases varies depending on the specific condition and its severity. Some treatments include medication, laser therapy, surgery, or a combination of these options. Regular eye exams are essential for early detection and treatment of retinal diseases.

A visual field test is a method used to measure an individual's entire scope of vision, which includes what can be seen straight ahead and in peripheral (or side) vision. During the test, the person being tested is asked to focus on a central point while gradually identifying the appearance of objects moving into their peripheral vision. The visual field test helps detect blind spots (scotomas) or gaps in the visual field, which can be caused by various conditions such as glaucoma, brain injury, optic nerve damage, or retinal disorders. It's an essential tool for diagnosing and monitoring eye-related diseases and conditions.

Entoptic vision refers to the visual perception of internal structures or processes within the eye. These perceptions are not derived from external stimuli, but rather from the physiological responses of the eye itself. Examples of entoptic phenomena include floaters (small spots or strands that move across the visual field), blue field illusion (the appearance of white or dark dots in a blue field of view), and Purkinje trees (the pattern of light reflections from the cornea and lens). Entoptic phenomena are often used in scientific research to study the structure and function of the eye.

Degenerative Myopia is a progressive form of nearsightedness, characterized by excessive elongation of the eyeball, which results in a steep curvature of the cornea and an overly long axial length. This condition causes light to focus in front of the retina instead of directly on it, resulting in blurred distance vision.

In degenerative myopia, this elongation continues throughout adulthood and is often associated with various complications such as thinning of the retinal tissue, stretching of the layers beneath the retina, and abnormal blood vessel growth. These changes can lead to a higher risk of developing retinal detachment, macular holes, glaucoma, and cataracts.

Degenerative myopia is considered a more severe form of myopia than the common or simple myopia, which usually stabilizes in the teenage years. It is also sometimes referred to as pathological myopia or malignant myopia. Regular eye examinations are essential for individuals with degenerative myopia to monitor and manage any potential complications.

An epiretinal membrane, also known as a macular pucker or cellophane maculopathy, is a thin and transparent layer of tissue that forms over the macula (the central part of the retina responsible for sharp, detailed vision) in the eye. This membrane can contract and wrinkle the macula, distorting central vision.

Epiretinal membranes are typically caused by the migration and proliferation of glial cells or other cell types onto the surface of the retina following retinal injury, inflammation, or aging. In some cases, they may be associated with other eye conditions such as diabetic retinopathy, retinal vein occlusion, or age-related macular degeneration.

Mild epiretinal membranes may not require treatment, but if the distortion of vision is significant, a vitrectomy surgery may be recommended to remove the membrane and improve visual acuity.

Macular edema is a medical condition characterized by the accumulation of fluid in the macula, a small area in the center of the retina responsible for sharp, detailed vision. This buildup of fluid causes the macula to thicken and swell, which can distort central vision and lead to vision loss if not treated promptly. Macular edema is often a complication of other eye conditions such as diabetic retinopathy, age-related macular degeneration, retinal vein occlusion, or uveitis. It's important to note that while macular edema can affect anyone, it is more common in people with certain medical conditions like diabetes.

Retinal vessels refer to the blood vessels that are located in the retina, which is the light-sensitive tissue that lines the inner surface of the eye. The retina contains two types of blood vessels: arteries and veins.

The central retinal artery supplies oxygenated blood to the inner layers of the retina, while the central retinal vein drains deoxygenated blood from the retina. These vessels can be visualized during a routine eye examination using an ophthalmoscope, which allows healthcare professionals to assess their health and any potential abnormalities.

Retinal vessels are essential for maintaining the health and function of the retina, and any damage or changes to these vessels can affect vision and lead to various eye conditions such as diabetic retinopathy, retinal vein occlusion, and hypertensive retinopathy.

The optic disk, also known as the optic nerve head, is the point where the optic nerve fibers exit the eye and transmit visual information to the brain. It appears as a pale, circular area in the back of the eye, near the center of the retina. The optic disk has no photoreceptor cells (rods and cones), so it is insensitive to light. It is an important structure to observe during eye examinations because changes in its appearance can indicate various ocular diseases or conditions, such as glaucoma, optic neuritis, or papilledema.

Vision tests are a series of procedures used to assess various aspects of the visual system, including visual acuity, accommodation, convergence, divergence, stereopsis, color vision, and peripheral vision. These tests help healthcare professionals diagnose and manage vision disorders, such as nearsightedness, farsightedness, astigmatism, amblyopia, strabismus, and eye diseases like glaucoma, cataracts, and macular degeneration. Common vision tests include:

1. Visual acuity test (Snellen chart or letter chart): Measures the sharpness of a person's vision at different distances.
2. Refraction test: Determines the correct lens prescription for glasses or contact lenses by assessing how light is bent as it passes through the eye.
3. Color vision test: Evaluates the ability to distinguish between different colors and color combinations, often using pseudoisochromatic plates or Ishihara tests.
4. Stereopsis test: Assesses depth perception and binocular vision by presenting separate images to each eye that, when combined, create a three-dimensional effect.
5. Cover test: Examines eye alignment and the presence of strabismus (crossed eyes or turned eyes) by covering and uncovering each eye while observing eye movements.
6. Ocular motility test: Assesses the ability to move the eyes in various directions and coordinate both eyes during tracking and convergence/divergence movements.
7. Accommodation test: Evaluates the ability to focus on objects at different distances by using lenses, prisms, or dynamic retinoscopy.
8. Pupillary response test: Examines the size and reaction of the pupils to light and near objects.
9. Visual field test: Measures the peripheral (side) vision using automated perimetry or manual confrontation techniques.
10. Slit-lamp examination: Inspects the structures of the front part of the eye, such as the cornea, iris, lens, and anterior chamber, using a specialized microscope.

These tests are typically performed by optometrists, ophthalmologists, or other vision care professionals during routine eye examinations or when visual symptoms are present.

Electroretinography (ERG) is a medical test used to evaluate the functioning of the retina, which is the light-sensitive tissue located at the back of the eye. The test measures the electrical responses of the retina to light stimulation.

During the procedure, a special contact lens or electrode is placed on the surface of the eye to record the electrical activity generated by the retina's light-sensitive cells (rods and cones) and other cells in the retina. The test typically involves presenting different levels of flashes of light to the eye while the electrical responses are recorded.

The resulting ERG waveform provides information about the overall health and function of the retina, including the condition of the photoreceptors, the integrity of the inner retinal layers, and the health of the retinal ganglion cells. This test is often used to diagnose and monitor various retinal disorders, such as retinitis pigmentosa, macular degeneration, and diabetic retinopathy.

Photoreceptor cells in vertebrates are specialized types of neurons located in the retina of the eye that are responsible for converting light stimuli into electrical signals. These cells are primarily responsible for the initial process of vision and have two main types: rods and cones.

Rods are more numerous and are responsible for low-light vision or scotopic vision, enabling us to see in dimly lit conditions. They do not contribute to color vision but provide information about the shape and movement of objects.

Cones, on the other hand, are less numerous and are responsible for color vision and high-acuity vision or photopic vision. There are three types of cones, each sensitive to different wavelengths of light: short (S), medium (M), and long (L) wavelengths, which correspond to blue, green, and red, respectively. The combination of signals from these three types of cones allows us to perceive a wide range of colors.

Both rods and cones contain photopigments that consist of a protein called opsin and a light-sensitive chromophore called retinal. When light hits the photopigment, it triggers a series of chemical reactions that ultimately lead to the generation of an electrical signal that is transmitted to the brain via the optic nerve. This process enables us to see and perceive our visual world.

Lipofuscin is a type of pigment that accumulates in the lysosomes (membrane-bound organelles found inside cells) of various tissues, particularly in nerve cells and heart muscle cells. It consists of cross-linked proteins and lipids that are resistant to degradation by enzymes. The accumulation of lipofuscin is a normal part of aging but can also be associated with certain diseases such as neurodegenerative disorders.

It's often referred to as "age pigment" because it tends to increase in amount with age, and its presence in tissues has been linked to oxidative stress and cellular damage caused by free radicals. Lipofuscin is autofluorescent, meaning that it emits light when excited by certain wavelengths of light, which can be useful for its detection and quantification in research and diagnostic settings.

Diagnostic techniques in ophthalmology refer to the various methods and tests used by eye specialists (ophthalmologists) to examine, evaluate, and diagnose conditions related to the eyes and visual system. Here are some commonly used diagnostic techniques:

1. Visual Acuity Testing: This is a basic test to measure the sharpness of a person's vision. It typically involves reading letters or numbers from an eye chart at a specific distance.
2. Refraction Test: This test helps determine the correct lens prescription for glasses or contact lenses by measuring how light is bent as it passes through the cornea and lens.
3. Slit Lamp Examination: A slit lamp is a microscope that allows an ophthalmologist to examine the structures of the eye, including the cornea, iris, lens, and retina, in great detail.
4. Tonometry: This test measures the pressure inside the eye (intraocular pressure) to detect conditions like glaucoma. Common methods include applanation tonometry and non-contact tonometry.
5. Retinal Imaging: Several techniques are used to capture images of the retina, including fundus photography, fluorescein angiography, and optical coherence tomography (OCT). These tests help diagnose conditions like macular degeneration, diabetic retinopathy, and retinal detachments.
6. Color Vision Testing: This test evaluates a person's ability to distinguish between different colors, which can help detect color vision deficiencies or neurological disorders affecting the visual pathway.
7. Visual Field Testing: This test measures a person's peripheral (or side) vision and can help diagnose conditions like glaucoma, optic nerve damage, or brain injuries.
8. Pupillary Reactions Tests: These tests evaluate how the pupils respond to light and near objects, which can provide information about the condition of the eye's internal structures and the nervous system.
9. Ocular Motility Testing: This test assesses eye movements and alignment, helping diagnose conditions like strabismus (crossed eyes) or nystagmus (involuntary eye movement).
10. Corneal Topography: This non-invasive imaging technique maps the curvature of the cornea, which can help detect irregularities, assess the fit of contact lenses, and plan refractive surgery procedures.

Vitreous detachment, also known as posterior vitreous detachment (PVD), is a common age-related eye condition characterized by the separation of the vitreous gel from the retina. The vitreous is a clear, gel-like substance that fills the space between the lens and the retina in the eye. As we age, the vitreous may change in consistency, becoming more liquefied, leading to the formation of pockets of liquid within the gel.

In vitreous detachment, the posterior part of the vitreous closest to the retina begins to pull away from the retinal surface due to the shrinkage and liquefaction of the vitreous gel. This separation can cause symptoms such as floaters (spots or strands in the field of vision), flashes of light, or a decrease in vision sharpness. While vitreous detachment is typically not a serious condition on its own, it can sometimes lead to complications like retinal tears or retinal detachment, which require immediate medical attention.

The inner segment of a retinal photoreceptor cell, also known as the inner segment of a rod or cone cell, is the portion of the cell that contains the majority of its metabolic and energy-generating components. It is responsible for providing the energy needed for the outer segment, which is the part of the cell that contains the visual pigments and is responsible for phototransduction, or the conversion of light into electrical signals.

The inner segment is divided into two main parts: the ellipsoid and the myoid. The ellipsoid contains a high concentration of mitochondria, which provide energy to the cell through the process of oxidative phosphorylation. The myoid contains the endoplasmic reticulum and the Golgi apparatus, which are involved in protein synthesis and transport.

Damage to the inner segment of the retinal photoreceptor cells can lead to vision loss or impairment, as it can affect the ability of the outer segment to function properly and transmit visual signals to the brain.

... and the perifovea is found at a 2.75 mm radius from the fovea centralis. The term fovea comes from Latin fovea 'pit'. The fovea ... GCL has >5 layers of cells, and highest density of cones Anatomical fovea / fovea centralis (clinical: macula) Area of ... fovea) Diameter = 0.35mm (about 1 deg of VF) the central floor of depression of fovea centralis 50 cones / 100 um Highest ... The fovea centralis is a small, central pit composed of closely packed cones in the eye. It is located in the center of the ...
In the fovea centralis, cones predominate and are present at high density. The macula is thus responsible for the central, high ... The umbo is the center of the foveola which in turn is located at the center of the fovea. The fovea is located near the center ... Fovea - 1.55 mm (0.061 in) Foveal avascular zone (FAZ) - 0.5 to 0.6 mm (0.020 to 0.024 in) Foveola - 0.35 mm (0.014 in) Umbo - ... Within the macula are the fovea and foveola that both contain a high density of cones, which are nerve cells that are ...
Gass, J. Donald M (1999). "Müller Cell Cone, an Overlooked Part of the Anatomy of the Fovea Centralis". Archives of ... Approximately 0.35 mm in diameter, the foveola lies in the center of the fovea and contains only cone cells and a cone-shaped ... Schematic diagram of the macula lutea of the retina, showing perifovea, parafovea, fovea, and clinical macula Time-Domain OCT ...
It describes the appearance of a small circular choroid shape as seen through the fovea centralis. Its appearance is due to a ...
Frontal-eyed animals have a small area of the retina with very high visual acuity, the fovea centralis. It covers about 2 ... To get a clear view of the world, the brain must turn the eyes so that the image of the object of regard falls on the fovea. ...
There are two to three rods per cone in the fovea centralis but five to six near the optic papilla. Cattle can distinguish long ...
At the "center" of the retina (the point directly behind the lens) lies the fovea (or fovea centralis), which contains only ... The distribution of cone classes (L, M, S) are also nonhomogenous, with no S-cones in the fovea, and the ratio of L-cones to M- ...
This area, termed the fovea centralis, is avascular (does not have blood vessels), and has minimal neural tissue in front of ... that possess no fovea, but a central band known as the visual streak.[citation needed] Around the fovea extends the central ... of axons in the optic nerve are devoted to the fovea. The resolution limit of the fovea has been determined to be around 10,000 ... The fovea produces the most accurate information. Despite occupying about 0.01% of the visual field (less than 2° of visual ...
Cone photoreceptors are concentrated in a depression in the center of the retina known as the fovea centralis and decrease in ... The fovea is blind to dim light (due to its cone-only array) and the rods are more sensitive, so a dim star on a moonless night ... rod photoreceptors are present at high density throughout the most of the retina with a sharp decline in the fovea. Perception ...
The foveal avascular zone (FAZ) is a region within the fovea centralis at the centre of the retina of the human eye that is ...
... move their entire eyes to focus images of interest onto their fovea centralis. In jumping spiders with a translucent carapace, ...
... centralis of the retina Fovea buccalis or Dimple Fovea of the femoral head Trochlear fovea of the frontal bone Pterygoid ... Look up fovea in Wiktionary, the free dictionary. Fovea (/ˈfoʊviə/) (Latin for "pit"; plural foveae /ˈfoʊvii/) is a term in ... Fovea (spider), a depression in the centre of the carapace Hilum, another term associated with anatomic pits or depressions ... fovea of the mandible neck fovea ethmoidalis part of the frontal bone of skull that separates ethmoid sinuses from the anterior ...
An issue that Kühne encountered when attempting to produce an image from a human eye is that the size of the fovea centralis, ...
A Palaeozoic Geology of London, Ontario (1974), Coach House Press Fovea Centralis (1975), Coach House Press Alter Sublime (1980 ...
... body Ciliary processes Ciliary muscle Iris Pupil Inner layer of eyeball Retina Ora serrata Optic disc Macula Fovea centralis ... Mandibular foramen Mandibular canal Mylohyoid groove Coronoid process Mandibular notch Condylar process Pterygoid fovea Hyoid ...
... fovea centralis MeSH A09.371.729.690 - optic disk MeSH A09.371.729.727 - photoreceptors MeSH A09.371.729.727.660 - ...
... specifically the Fovea centralis. These reactions are then passed as electrical signals through the optic nerve into the ...
Angular diameter Dioptre Eye examination Fovea centralis Golovin-Sivtsev table, for testing visual acuity Hyperacuity Landolt C ... To resolve detail, the eye's optical system has to project a focused image on the fovea, a region inside the macula having the ... The smallest cone cells in the fovea have sizes corresponding to 0.4 minarc of the visual field, which also places a lower ... Light travels from the fixation object to the fovea through an imaginary path called the visual axis. The eye's tissues and ...
... s are densely packed in the fovea centralis, a 0.3 mm diameter rod-free area with very thin, densely packed cones ... being smallest and most tightly packed at the center of the eye at the fovea. The S cone spacing is slightly larger than the ... but greatly outnumber rods in the fovea. Structurally, cone cells have a cone-like shape at one end where a pigment filters ...
Bruch's membrane Drusen Fovea centralis Fundus (eye) Macula of retina This article incorporates text in the public domain from ...
MWS and LWS cones are most responsible for visual acuity as they are concentrated in the fovea centralis region of the retina, ...
... macula and fovea centralis) as patients with these pathologies are often unable to fixate reliably. By contrast, fundus ...
... with the fovea slightly procurved. Its labium possesses no cuspules. A serrula is present, as is a small patch of teeth. Its ... "Acanthogonatus centralis". Integrated Taxonomic Information System. ADW entry "Acanthogonatus centralis" at the Encyclopedia of ... Acanthogonatus centralis is a mygalomorph spider of Argentina, its name referring to its distribution, being one of the most ... 224." (1995). Ferretti, Nelson; Pompozzi, Gabriel; Pérez-Miles, Fernando (2011). "Sexual behavior of Acanthogonatus centralis ( ...
Towards the centre of the retina is the fovea (or the less specialised, area centralis) which has a greater density of ... Many raptors have foveas with far more rods and cones than the human fovea (65,000/mm2 in American kestrel, 38,000 in humans) ... Because the image can be centered on the deep fovea of only one eye at a time, most falcons when diving use a spiral path to ... The forward-facing eyes of a bird of prey give binocular vision, which is assisted by a double fovea. The raptor's adaptations ...
Although they lack a fovea, some diurnal lemurs have a cone-rich, although less clustered, area centralis. This area centralis ... allowing for the evolution of the fovea. With only a postorbital bar, lemurs have been unable to develop a fovea. Therefore, ... The fovea on the retina, which yields higher visual acuity, is not well-developed. The postorbital septum (or bony closure ... whereas diurnal anthropoids have no rod cells in their fovea. Once again, this suggests lower visual acuity in lemurs than in ...
... and it has a procurved fovea. Its labium possesses no cuspules. A serrula is present. Its sternal sigilla is as in A. Centralis ... Females are most similar to those of A. centralis, but are distinguished by the narrow fundus of the spermathecae. Female: ... fovea width 0.67 millimetres (0.026 in); medial ocular quadrangle length 0.67 millimetres (0.026 in), width 1.28 millimetres ( ...
... its fovea is sinuous, procurved and without a posterior notch. Its labium possesses 3 cuspules. A serrula is present and well ... centralis and A. parana, which have - unlike A. Confusus - no inferior tarsal claws on tarsus IV). Female: total length 24.6 ... fovea width 0.9 millimetres (0.035 in); labium length 1.12 millimetres (0.044 in), width 1.62 millimetres (0.064 in); sternum ...
... "area centralis": a central patch with up to three times the density of nerve endings as the visual streak, giving them detailed ... a high density of rods in the fovea, an increased flicker rate, and a tapetum lucidum. The tapetum is a reflective surface ...
1856 c g Empis fovea Saigusa, 1964 c g Empis frauscheri Strobl, 1901 c g Empis freidbergi Chvála, 1999 c g Empis freyi Yang, ... 1867 c g Empis centralis Brunetti, 1913 c g Empis cetywayoi Smith, 1969 c g Empis ceylonica Bezzi, 1904 c g Empis cherskii ...
Some areas have higher densities of cone cells, for example (see fovea). Fish may have two or three areas specialised for high ... Miyazaki, T; Iwamu, T; Meyer-Rochow, VB (2011). "The position of the retinal area centralis changes with age in Champsocephalus ...
... and the perifovea is found at a 2.75 mm radius from the fovea centralis. The term fovea comes from Latin fovea pit. The fovea ... GCL has >5 layers of cells, and highest density of cones Anatomical fovea / fovea centralis (clinical: macula) Area of ... fovea) Diameter = 0.35mm (about 1 deg of VF) the central floor of depression of fovea centralis 50 cones / 100 um Highest ... The fovea centralis is a small, central pit composed of closely packed cones in the eye. It is located in the center of the ...
10 Fun Facts about Fovea Centralis. The fovea centralis is a small, specialized area located in the retina of the eye, and it ... Fovea in the human eye (Wikimedia). Here are 10 fun facts about fovea centralis to know more about it. ... The fovea centralis, with its densely packed cone cells and unique anatomical design, remains a testament to the remarkable ... Microscopic Marvel: Despite its small size, the fovea centralis contains an incredibly high concentration of cone cells-up to ...
Fovea Centralis. The fovea centralis, a small avascular depression at the center of the inner retinal surface filled with ... What Cajal did not realize was that, in order to maintain such visual acuity, each cone cell in the fovea is actually connected ... Signals from the fovea constitute half of all input to the visual cortex. ... In addition, information transmitted from the fovea to the visual cortex also contributes to color vision. ...
chūshinka): fovea centralis. *. 中心街. (. ちゅうしんがい. ). (chūshingai): town center ...
Fovea Centralis * Humans * Male * Optics and Photonics * Photometry * Photoreceptor Cells * Retinal Pigments / physiology* ...
Fovea Centralis / surgery* * Fundus Oculi * Histoplasmosis / complications * Humans * Macular Degeneration / complications * ...
Categories: Fovea Centralis Image Types: Photo, Illustrations, Video, Color, Black&White, PublicDomain, CopyrightRestricted 5 ...
The fovea centralis is part of the retina. There are only cone cells in the fovea centralis. It is the site for maximal visual ...
fovea centralis 743.55. *. gallbladder 751.69. *. Gartners duct 752.89. *. gastrointestinal tract 751.8. *. genitalia, genital ...
FOVEA (FOVEA CENTRALIS) [5] A small ellipse-shaped depression in the central region of the RETINA which measures somewhat less ... at the FOVEA CENTRALIS there are no rods, farther out they are more numerous than the cones. Sight or vision in which only RODS ... FOVEA CENTRALIS, which is nearly 100% CONES and is thus where color perception and discrimination are optimal. VISION, INDIRECT ... The FOVEA is found in the Macula. A container for rolled film or photographic plates attached to the camera body and usually ...
Gass, J.D.M., Müller Cell Cone, an Overlooked Part of the Anatomy of the Fovea Centralis, Arch Ophthalmol. 117:821-823, 1999. ... the fovea (Latin: pit) at the centre of the macula (Figures 2 & 5). Away from the fovea the VA diminishes progressively towards ... Schein, S.J., Anatomy of macaque fovea and spatial densities of neurons in foveal representation, J. Comp. Neurol. 269:479, ... And consistent with these functions, there is a low ratio of receptors to ganglion cells27 (1:1.2 or more) at the fovea where ...
In the center of the macula is the foveola (also termed fovea centralis), an area of 1.5 mm in diameter. It comprises a high ...
... s differentiable spatial fovea mechanism are both inspired by the fovea centralis of many vertebrate eyes, for example. With ... and there is even an anatomical basis for visual attention in the fovea centralis, a pit region in the center of the retina ...
This area, termed the fovea centralis, is avascular (does not have blood vessels), and has minimal neural tissue in front of ... that possess no fovea, but a central band known as the visual streak.[citation needed] Around the fovea extends the central ... of axons in the optic nerve are devoted to the fovea. The resolution limit of the fovea has been determined to be around 10,000 ... Distribution of rods and cones along a line passing through the fovea and the blind spot of a human eye[14]. The vertebrate ...
In the center of the macula is an area known as the fovea centralis. The fovea only contain cones that are tightly packed ... The shape of your eyes lens and its ability to change shape, allows us to focus the light entering the eye, on the fovea. ... This helps the lens focus the light appropriately on the fovea.. In the end, if you forget all the medical terminology or finer ... its ability to focus light on the fovea is reduced. By squinting, we change the shape of our eye, ever-so-slightly. ...
The cones on the other hand are mainly concentrated in the focal point of the lens (fovea centralis). They enable crisp, ...
På lysets rejse gennem øjet brydes det for at ramme fovea centralis og skabe et skarpt billede på nethinden. Alle elementer, ... Da øjenlængden påvirker lysets brydning - og om lyset rammer fovea centralis til dannelse af skarpt syn - er det vigtigt at ...
TAGS: gaze, heterogeneity of variance, perimetry, visual fields, fovea centralis Invest. Ophthalmol. Vis. Sci.. 2016; 57(13): ... TAGS: age-related macular degeneration, scotoma, blindness, fovea centralis Invest. Ophthalmol. Vis. Sci.. 2017; 58(5):2652- ...
The Wiki article Fovea centralis tells me "50 per 100 micrometres in the most central fovea". This is approximately 12,700 per ... Title text - Our retina display features hundreds of pixels per inch in the central fovea region.. There is so much language in ... And then the human eye isnt large as an inch, and the "most central fovea" is much smaller. Maybe Randall will correct the " ... Additionally, the central fovea region is a portion of your eyes retina containing the most densely packed photosensitive ...
Lipid-laden ganglion cells appear as a gray-white area around the retinal fovea centralis (a central cherry-red spot with a ... The cherry-red central spot or perifoveal white patch seen in the retinal fovea centralis of the retinal macula of those ...
The central region of the macula, termed the fovea centralis, is only about 150 micrometers in diameter and provides detailed ... Consequently, damage to the fovea, even though the structure comprises only 3 to 4 percent of the retinal area, can result in ...
Many people have observed that the human eye is high resolution on in the center of attention, known as the fovea centralis. If ...
Fovea centralis: central depressed area in macula; area of most acute vision ... trochlear fovea for pulley of superior oblique muscle 4. Laterally: under roof, lacrimal fossa for lacrimal gland 5. Superior ...
fovea centralis + foveola of retina frontal nerve (branch of ophthalmic) fundus of gallbladder ...
When the eye focuses, a cluster of eye cells - the fovea centralis - reduces the intensity of the signal from the rest of the ...
fovea centralis + foveola of retina frontal nerve (branch of ophthalmic) future hindbrain meninx + ...
Fovea, Also known as the fovea centralis, is a part of the eye, located in the center of the macula region of the retina. The ... called fovea) called drusen between the retinal pigment epithelium and the underlying choroid. ... fovea is responsible for sharp central vision, which is necessary for humans for reading, watching television or movies, ...
... fovea centralis and the blind spot were charted in μm. By combining information from fundus photography and b-scan, the exact ...
The blind spot (Fovea centralis)The blind spot (Fovea centralis) The blind spot, or scotoma, is the place in our eyes where the ... This small, central pit - the fovea centralis - is located right in the middle of the macula and is responsible for sharp, ... The blind spot is located about 15 degrees on the nasal side of the fovea. Healthy humans do not generally notice this lack of ...
fovea centralis.. optic disc.. macula lutea.. iris.. *The clear jellylike substance behind the lens of the eye is the. aqueous ...
  • citation needed] Approximately half the nerve fibers in the optic nerve carry information from the fovea, while the remaining half carry information from the rest of the retina. (wikipedia.org)
  • The size of the fovea is relatively small with regard to the rest of the retina. (wikipedia.org)
  • The fovea centralis is part of the retina. (histology-world.com)
  • A number of mechanisms contribute to this effect, and there is even an anatomical basis for visual attention in the fovea centralis , a pit region in the center of the retina with an increased density of photosensitive cone cells responsible for facilitating detailed visual tasks. (kdnuggets.com)
  • therefore, the optic nerve must cross through the retina en route to the brain. (wikipedia.org)
  • Our retina display features hundreds of pixels per inch in the central fovea region. (explainxkcd.com)
  • Age-Related Macular Degeneration , Age-related macular degeneration begins with characteristic yellow deposits in the macula (central area of the retina which provides detailed central vision, called fovea) called drusen between the retinal pigment epithelium and the underlying choroid. (fortworth2020.com)
  • The central point for image focus (the visual axis) in the human retina is the fovea. (utah.edu)
  • Some vertebrate retinas have instead of a fovea, another specialization of the central retina, known as an area centralis or a visual streak. (utah.edu)
  • These muscles, named extraocular muscles rotate the eyeball in the orbits and allow the image to be focussed at all times on the fovea of central retina. (utah.edu)
  • Light continues through the vitreous humor and the light converges on the retina, specifically the fovea centralis of the macula. (medscape.com)
  • Anatomical macula / macula lutea / area centralis (clinical: posterior pole): Diameter = 5.5mm (~3.5 disc-diameters) (about 18 deg of VF) Demarcated by the superior and inferior temporal arterial arcades. (wikipedia.org)
  • GCL has >5 layers of cells, and highest density of cones Anatomical fovea / fovea centralis (clinical: macula) Area of depression in the centre of the macula lutea. (wikipedia.org)
  • In the center of the macula is an area known as the fovea centralis. (todayifoundout.com)
  • This small, central pit - the fovea centralis - is located right in the middle of the macula and is responsible for sharp, central vision. (zeiss.co.za)
  • Fovea centralis is the central depressed part of the macula. (optography.org)
  • The fovea centralis is a small, central pit composed of closely packed cones in the eye. (wikipedia.org)
  • The perifovea contains an even more diminished density of cones, having 12 per 100 micrometres versus 50 per 100 micrometres in the most central fovea. (wikipedia.org)
  • The fovea is a depression in the inner retinal surface, about 1.5 mm wide, the photoreceptor layer of which is entirely cones and which is specialized for maximum visual acuity. (wikipedia.org)
  • The high spatial density of cones along with the absence of blood vessels at the fovea accounts for the high visual acuity capability at the fovea. (wikipedia.org)
  • The central fovea consists of very compact cones, thinner and more rod-like in appearance than cones elsewhere. (wikipedia.org)
  • Cones in the central fovea express opsins that are sensitive to green and red light. (wikipedia.org)
  • The fovea only contain cones that are tightly packed together. (todayifoundout.com)
  • The cones on the other hand are mainly concentrated in the focal point of the lens (fovea centralis). (erco.com)
  • When the eye focuses, a cluster of eye cells - the fovea centralis - reduces the intensity of the signal from the rest of the vision cones, boosting their own and producing a detailed image. (usacarry.com)
  • The "blue" cones have the highest sensitivity and are mostly found outside the fovea , leading to some distinctions in the eye's blue perception. (theomegafoundation.org)
  • That is the business of the cones, which are most concentrated at the fovea centralis. (emergentpublications.com)
  • There is a small pit called the fovea where almost all the light sensing cells are cones. (flight-study.com)
  • There are so many cones in the fovea that are at the very center of the visual field but virtually has no rods at all. (flight-study.com)
  • The cones concentrated in the fovea centralis of the eye are primarily responsible for vision in bright light. (flight-study.com)
  • The fovea is responsible for sharp central vision (also called foveal vision), which is necessary in humans for activities for which visual detail is of primary importance, such as reading and driving. (wikipedia.org)
  • The fovea is located in a small avascular zone and receives most of its oxygen from the vessels in the choroid, which is across the retinal pigment epithelium and Bruch's membrane. (wikipedia.org)
  • Within the fovea is a region of 0.5mm diameter called the foveal avascular zone (an area without any blood vessels). (wikipedia.org)
  • This area, termed the fovea centralis , is avascular (does not have blood vessels), and has minimal neural tissue in front of the photoreceptors, thereby minimizing light scattering. (wikipedia.org)
  • The center of the fovea is the foveola - about 0.35 mm in diameter - or central pit where only cone photoreceptors are present and there are virtually no rods. (wikipedia.org)
  • Starting at the outskirts of the fovea, however, rods gradually appear, and the absolute density of cone receptors progressively decreases. (wikipedia.org)
  • So in low light, the middle of the visual field is not very sensitive, but farther from the fovea, the rods are more numerous and provide the major portion of night vision. (flight-study.com)
  • The blind spot is located about 15 degrees on the nasal side of the fovea. (zeiss.co.za)
  • It is placed 3.4 mm nasal to the fovea. (optography.org)
  • The fovea centralis is the area of sharpest visual acuity. (msdmanuals.com)
  • Therefore, the acuity of foveal vision is limited only by the density of the cone mosaic, and the fovea is the area of the eye with the highest sensitivity to fine details. (wikipedia.org)
  • There are only cone cells in the fovea centralis. (histology-world.com)
  • In two eyes, the temporal ICC extended beyond the central fovea.ConclusionsPeripapillary ICC can develop temporal to the optic disc without involving the area inferior to optic disc in highly myopic eyes. (elsevierpure.com)
  • As we focus our vision on something specific, like the words you're reading now, the eye continually moves so it refracts the light coming from those words, directly on the fovea, leaving you with a detailed image. (todayifoundout.com)
  • The fovea is surrounded by the parafovea belt and the perifovea outer region. (wikipedia.org)
  • This anatomy is responsible for the depression in the center of the fovea. (wikipedia.org)
  • Methods Consecutive patients with vascular disorder patients underwent FA with 55-degree lens (Spectralis Heidelberg Engineering, Heidelberg, Germany) and OCTA with the prototype PlexElite (Carl Zeiss Meditec, Dublin, CA) using a 12 mm x 12 mm volume scan pattern centered on the fovea and a prototype of + 20.00-diopter designed specifically by Zeiss. (unimi.it)
  • The parafovea extends to a radius of 1.25 mm from the central fovea, and the perifovea is found at a 2.75 mm radius from the fovea centralis. (wikipedia.org)
  • To achieve a high visual resolution, visual stimuli from the fovea are processed with a comparably high number of neurons in the brain. (bernstein-network.de)
  • Anatomical macula / macula lutea / area centralis (clinical: posterior pole): Diameter = 5.5mm (~3.5 disc-diameters) (about 18 deg of VF) Demarcated by the superior and inferior temporal arterial arcades. (wikipedia.org)
  • GCL has >5 layers of cells, and highest density of cones Anatomical fovea / fovea centralis (clinical: macula) Area of depression in the centre of the macula lutea. (wikipedia.org)
  • In the fovea centralis or macula lutea or simple yellow spot, cones predominate and are present at high density. (ichacha.net)
  • The fovea is surrounded by the parafovea belt and the perifovea outer region. (wikipedia.org)
  • The parafovea extends to a radius of 1.25 mm from the central fovea, and the perifovea is found at a 2.75 mm radius from the fovea centralis. (wikipedia.org)
  • Within the fovea is a region of 0.5mm diameter called the foveal avascular zone (an area without any blood vessels). (wikipedia.org)
  • This anatomy is responsible for the depression in the center of the fovea. (wikipedia.org)
  • Fluorescein angiography of the left eye showed a hypofluorescent fovea surrounded by irregular hyperfluorescent defects, suggestive of acute macular neuroretinopathy. (amjcaserep.com)
  • The results suggest that supplementation with L or Z increases MPOD at the fovea and at 2.5 degrees , and that supplementation can improve CATs at high mesopic levels and hence visual performance at low illumination. (nih.gov)
  • The fovea centralis is the area of sharpest visual acuity. (msdmanuals.com)
  • En su centro (foveola) están los conos más adaptados para dar elevada agudeza visual, cada cono está conectado sólo a una célula ganglionar. (bvsalud.org)
  • If we want to see an object in sharp focus then we have to fixate on it - because eyesight is sharp in only a very small area of our visual field, the so-called central field of vision (fovea centralis) which deviates from our central axis of vision by +/- 1 degree. (viewpointsystem.com)
  • This is the fovea centralis and this area is why you can see colors during the day. (savannahboater.com)
  • The exact cellular types that form the human fovea remain a subject of debate, and few studies have been conducted on human macula to solve this question. (molvis.org)
  • The purpose of this study was to perform immunohistochemistry on fresh human samples to characterize the glial cells that form the human fovea. (molvis.org)
  • To improve the interpretation of OCT imaging, a better understanding of the cells that form the macula and the fovea is needed. (molvis.org)