• The pupillary light reflex (PLR) or photopupillary reflex is a reflex that controls the diameter of the pupil, in response to the intensity (luminance) of light that falls on the retinal ganglion cells of the retina in the back of the eye, thereby assisting in adaptation of vision to various levels of lightness/darkness. (wikipedia.org)
  • The cornea serves as a protective covering for the front of the eye and also helps focus light on the retina at the back of the eye. (msdmanuals.com)
  • The middle portion of the iris has an opening, called the pupil, that helps regulate the amount of light that passes through the retina. (scopeheal.com)
  • The pupil changes in size so that the retina receives the optimal light level. (scopeheal.com)
  • In its centre is an aperture of about 4 mm diameter called pupil which regulates the amount of light reaching the retina. (opthametry.com)
  • [1] In most vertebrates and some molluscs , the eye allows light to enter and project onto a light-sensitive layer of cells known as the retina . (knowpia.com)
  • Some arthropods, including many Strepsiptera , have compound eyes of only a few facets, each with a retina capable of creating an image. (knowpia.com)
  • The ophthalmoscope is a handheld, battery-powered device containing illumination and viewing optics intended to examine the media (cornea, aqueous, lens, and vitreous) and the retina of the eye. (mfimedical.com)
  • The size of the pupil is controlled by the action of the pupillary sphincter muscle and dilator muscle. (msdmanuals.com)
  • The iris is a 12mm diameter structure that regulates the amount of light that enters the eye and separates it into the anterior and posterior chambers. (scopeheal.com)
  • Dilator pupillae muscle lies in the posterior part of stroma of the ciliary zone of iris. (opthametry.com)
  • Pupil-involving third nerve palsy is considered a neurological as it is most often due to a posterior communicating artery aneurysm compressing the nerve. (nih.gov)
  • Thus, the pupil dilates and constricts like the aperture of a camera lens as the amount of light in the immediate surroundings changes. (msdmanuals.com)
  • It is supplied by cervical sympathetic nerves and dilates the pupil. (opthametry.com)
  • It may be helpful to consider the Pupillary reflex as an 'Iris' reflex, as the iris sphincter and dilator muscles are what can be seen responding to ambient light. (wikipedia.org)
  • Pupillary reflex is conceptually linked to the side (left or right) of the reacting pupil, and not to the side from which light stimulation originates. (wikipedia.org)
  • Left pupillary reflex refers to the response of the left pupil to light, regardless of which eye is exposed to a light source. (wikipedia.org)
  • Right pupillary reflex means reaction of the right pupil, whether light is shone into the left eye, right eye, or both eyes. (wikipedia.org)
  • A direct pupillary reflex is pupillary response to light that enters the ipsilateral (same) eye. (wikipedia.org)
  • A consensual pupillary reflex is response of a pupil to light that enters the contralateral (opposite) eye. (wikipedia.org)
  • Thus there are four types of pupillary light reflexes, based on this terminology of absolute laterality (left versus right) and relative laterality (same side versus opposite side, ipsilateral versus contralateral, direct versus consensual): Left direct pupillary reflex is the left pupil's response to light entering the left eye, the ipsilateral eye. (wikipedia.org)
  • Left consensual pupillary reflex is the left pupil's indirect response to light entering the right eye, the contralateral eye. (wikipedia.org)
  • Photons within the visible spectrum (ie, light) enters the eye first by passing through the cornea, a clear, dome-shaped structure at the anterior post portion of the globe. (medscape.com)
  • Light passing through the cornea is converged (bent) where it passes through the anterior chamber and the pupil, a circular opening regulating the amount of light entering the eye. (medscape.com)
  • After passing through the cornea, light travels through the pupil (the black dot in the middle of the eye). (msdmanuals.com)
  • Provided is a dilator capable of increasing the diameter of a hole formed on the wall of a digestive tract and the like while ensuring distal-end flexibility and maintaining pushability and torquability even when a shaft is longer and curved. (justia.com)
  • A dilator includes a hollow shaft having an outer diameter that is smaller at a distal end than at a proximal end, and a grip portion connected to the proximal end of the shaft. (justia.com)
  • The superior miniaturised optics facilitate entry in to even the very small diameter pupils. (hiberniamedical.ie)
  • the former, supplied by branches from the oculomotorius nerve, is under control of the will, whilst the dilator fibres belong to the sympathetic system. (yourdictionary.com)
  • The pupil is the dark circular opening in the center of the iris and is where light enters the eye. (wikipedia.org)
  • By analogy with a camera, the pupil is equivalent to aperture, whereas the iris is equivalent to the diaphragm. (wikipedia.org)
  • Whereas, the pupil is the passive opening formed by the active iris. (wikipedia.org)
  • Light enters the eye through the cornea , the clear, curved layer in front of the iris and pupil. (msdmanuals.com)
  • The iris -the circular, colored area of the eye that surrounds the pupil-controls the amount of light that enters the eye. (msdmanuals.com)
  • The iris allows more light into the eye (enlarging or dilating the pupil) when the environment is dark and allows less light into the eye (shrinking or constricting the pupil) when the environment is bright. (msdmanuals.com)
  • The iris makes a small circular opening in front of the lens, called the pupil. (scopeheal.com)
  • The iris is located behind the cornea and is commonly described as the colored part of the eye. (scopeheal.com)
  • It is a hereditary malformation of the iris that is characterized by an aperture due to the lack of development of the iris. (scopeheal.com)
  • This vibration or agitated movement of the iris with the direction of the eye can be due to a subluxation of the lens, the incomplete or partial dislocation of the lens, or by aphakia, the absence of a lens. (scopeheal.com)
  • Such eyes are typically spheroid, filled with the transparent gel-like vitreous humour , possess a focusing lens , and often an iris . (knowpia.com)
  • Muscles around the iris change the size of the pupil , regulating the amount of light that enters the eye [4] and reducing aberrations when there is enough light. (knowpia.com)
  • The ipsilateral efferent limb transmits nerve signals for direct light reflex of the ipsilateral pupil. (wikipedia.org)
  • Throughout the years, in the absence of ancillary or diagnostic tools, many descriptive phrases, clichés, or analogies have been used to describe the eye, such as "the eye is the window to the soul," the "eye works like a camera," and "the eye is the only structure that allows us to physically see blood vessels and nerve fibers. (medscape.com)
  • The optic disk, the first part of the optic nerve, is at the back of the eye. (msdmanuals.com)
  • Pupil-sparing third nerve palsy is most often due to an ischemic vascular cause and usually resolves spontaneously in 3 months. (nih.gov)
  • [1] From more complex eyes, retinal photosensitive ganglion cells send signals along the retinohypothalamic tract to the suprachiasmatic nuclei to effect circadian adjustment and to the pretectal area to control the pupillary light reflex . (knowpia.com)
  • It is the eyes' way of ensuring that only the proper amount of light enters the eye. (scopeheal.com)
  • The most simple eyes, pit eyes, are eye-spots which may be set into a pit to reduce the angle of light that enters and affects the eye-spot, to allow the organism to deduce the angle of incoming light. (knowpia.com)
  • In some instances, they are pretty pronounced and follow a dislocation of the lens, wounds, and contusions of the eye , or a considerable softening of the vitreous body. (scopeheal.com)
  • This attachment is crucial in changing the eye focus by changing the shape of the lens, a process known as accommodation. (opthametry.com)
  • [5] The eyes of most cephalopods , fish , amphibians and snakes have fixed lens shapes, and focusing is achieved by telescoping the lens in a similar manner to that of a camera . (knowpia.com)
  • In contrast to compound eyes, simple eyes have a single lens. (knowpia.com)
  • The extraocular muscles control the movements of the eye (see Table 2, below). (medscape.com)
  • An outside observer makes the vibrations visible to the naked eye and is evaluated by slit-lamp examination. (scopeheal.com)
  • The L28 delivers superb illumination for pupil examination. (hiberniamedical.ie)
  • The levator palpebrae superioris is the other extraocular muscle that, although not directly involved in eye movement, is primarily responsible for elevating the upper eyelid. (medscape.com)
  • Blepharoptosis is upper eyelid drooping with the eyes in the primary position of gaze. (nih.gov)
  • The outer covering of the eyeball consists of a relatively tough, white layer called the sclera (or white of the eye). (msdmanuals.com)
  • Some insect larvae , like caterpillars , have a type of simple eye ( stemmata ) which usually provides only a rough image, but (as in sawfly larvae) can possess resolving powers of 4 degrees of arc, be polarization-sensitive, and capable of increasing its absolute sensitivity at night by a factor of 1,000 or more. (knowpia.com)
  • non-mydriatic and small-pupil capable, the RetinaVue 700 Imager enables comfortable exams without chemical dilation. (medicaldevicedepot.com)
  • Light shone into one eye will cause both pupils to constrict. (wikipedia.org)
  • When light is shone into only one eye and not the other, it is normal for both pupils to constrict simultaneously. (wikipedia.org)
  • The terms direct and consensual refers to the side where the light source comes from, relative to the side of the reacting pupil. (wikipedia.org)
  • The contralateral efferent limb causes consensual light reflex of the contralateral pupil. (wikipedia.org)
  • Each eye constantly adjusts the amount of light it lets in, focuses on objects near and far, and produces continuous images that are instantly transmitted to the brain. (msdmanuals.com)
  • However, in low-light environments, the pupils will appear much more prominent (or dilated). (scopeheal.com)
  • Eyes detect light and convert it into electro-chemical impulses in neurons (neurones). (knowpia.com)
  • The structures and functions of the eyes are complex. (msdmanuals.com)
  • Eyes with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system. (knowpia.com)
  • Complex eyes distinguish shapes and colours . (knowpia.com)
  • The eyes of mantis shrimps (here Odontodactylus scyllarus ) are considered the most complex in the whole animal kingdom. (knowpia.com)
  • With large, brown eyes and dark hair, she was toned and tall, a model's body with an extra layer of muscle . (yourdictionary.com)
  • Near the front of the eye, in the area protected by the eyelids, the sclera is covered by a thin, transparent membrane ( conjunctiva ), which runs to the edge of the cornea. (msdmanuals.com)
  • The shape of one's eyes along with the position of the eyelids, shape, and position of the eyebrow determines one's identity. (nih.gov)
  • For the purpose of this article on eye globe anatomy, the eye will be divided into 2 sections: extraocular (ie, structures outside of the globe) and the ocular (ie, the globe and intraocular structures). (medscape.com)
  • A fast, more complete exam is here with little to no chemical dilation needed for small pupils. (medicaldevicedepot.com)
  • This is why, on a bright day, you will notice that the pupils are more constricted. (scopeheal.com)
  • This layer gives rise to the dilator pupillae muscle. (opthametry.com)
  • The image below depicts a sagittal section of the eye. (medscape.com)
  • [1] Image-resolving eyes are present in molluscs , chordates and arthropods . (knowpia.com)
  • The compound eyes of the arthropods are composed of many simple facets which, depending on anatomical detail, may give either a single pixelated image or multiple images per eye. (knowpia.com)
  • With each eye producing a different image, a fused, high-resolution image is produced in the brain. (knowpia.com)
  • The primary function of the orbit is to protect the eye from physical injuries. (medscape.com)
  • It consists of loosely arranged collagenous network in which are embedded the sphincter pupillae muscle, dilator pupillae muscle, vessels, nerves, pigment cells and other cells which include lymphocytes, fibroblasts, macrophages and mast cells. (opthametry.com)
  • And one reason why they can be used as a means of security is through eye scanners. (scopeheal.com)
  • Jumping spiders have one pair of large simple eyes with a narrow field of view , augmented by an array of smaller eyes for peripheral vision . (knowpia.com)
  • In other organisms, particularly prey animals, eyes are located to maximise the field of view, such as in rabbits and horses , which have monocular vision . (knowpia.com)
  • [3] The last common ancestor of animals possessed the biochemical toolkit necessary for vision, and more advanced eyes have evolved in 96% of animal species in six of the ~35 [a] main phyla . (knowpia.com)
  • Some eyes have up to 28,000 such sensors arranged hexagonally, which can give a full 360° field of vision. (knowpia.com)