• retinal
  • Visual acuity is dependent on optical and neural factors, i.e., (i) the sharpness of the retinal focus within the eye, (ii) the health and functioning of the retina, and (iii) the sensitivity of the interpretative faculty of the brain. (wikipedia.org)
  • The results of a measurement of the retinal visual acuity of more than two hundred patients with various types of cataract before extraction of the crystalline lens and after replacement and the determination of the corresponding correction coefficient, reaching 0.7-0.9, make it possible to use the laser retinometer for pre-operative diagnosis. (osapublishing.org)
  • Several important features of visual perception can be traced to the retinal encoding and processing of light. (wikipedia.org)
  • Snellen
  • For example, using the Snellen fraction with English units, 20/20 or 20/100 indicates that the person being evaluated can see at 20 ft what a person with "normal visual acuity" can see at 20 ft or at 100 ft, respectively. (amamanualofstyle.com)
  • For 6/6 = 1.0 acuity, the size of a letter on the Snellen chart or Landolt C chart is a visual angle of 5 arc minutes (1 arc min = 1/60 of a degree). (wikipedia.org)
  • For the purposes of this study, amblyopia was defined quantitatively as a difference of two Snellen acuity lines between eyes or if unilateral central steady maintained (CSM) vision and a clear fixation preference was observed. (bmj.com)
  • These children underwent a visual screening examination which included best corrected, full line near and distance acuities tested with Snellen letters, numbers, or Allen pictures. (bmj.com)
  • stimuli
  • The current study investigates a new method to objectively assess visual acuity in infants, which is uses a video gaze tracker (GT) and computer-generated stimuli, developed in the lab of M. Eizenman at the University of Toronto. (uwaterloo.ca)
  • Objective GT VA was compared with VA measured with subjective responses using the same stimuli and with Teller Acuity Cards (TACs). (uwaterloo.ca)
  • In these stimuli, spatial frequency is expressed as the number of cycles per degree of visual angle. (wikipedia.org)
  • functional
  • The theory (for which empirical support has yet to be developed) states that in each functional module of the visual cortex, Fourier analysis is performed on the receptive field and the neurons in each module are thought to respond selectively to various orientations and frequencies of sine wave gratings. (wikipedia.org)
  • significantly
  • RESULTS: Patients with MA30/60 acrylic IOLs were significantly older, had a worse preoperative best corrected visual acuity (BCVA), and had more concomitant ocular diseases than those with SI-30/40 silicone IOLs. (rti.org)
  • Improvement in best corrected visual acuity after treatment was significantly associated with the presence of vasculitis on fluroangiography (p=0.005), neurosyphilis, according to lumbar puncture findings (p=0.037) and marginally with anterior uveitis (p=0.070). (bmj.com)
  • vision
  • Visual acuity (VA) commonly refers to the clarity of vision. (wikipedia.org)
  • Visual acuity is typically measured while fixating, i.e. as a measure of central (or foveal) vision, for the reason that it is highest there. (wikipedia.org)
  • However, acuity in peripheral vision can be of equal (or sometimes higher) importance in everyday life. (wikipedia.org)
  • A reference value above which visual acuity is considered normal is called 6/6 vision, the USC equivalent of which is 20/20 vision: At 6 meters or 20 feet, a human eye with that performance is able to separate contours that are approximately 1.75 mm apart. (wikipedia.org)
  • In the expression 6/x vision, the numerator (6) is the distance in meters between the subject and the chart and the denominator (x) the distance at which a person with 6/6 acuity would discern the same optotype. (wikipedia.org)
  • The latter is the value used in the international definition of visual acuity: Acuity = 1/gap size [arc min] Acuity is a measure of visual performance and does not relate to the eyeglass prescription required to correct vision. (wikipedia.org)
  • Indeed, a subject diagnosed as having 6/6 vision will often actually have higher visual acuity because, once this standard is attained, the subject is considered to have normal (in the sense of undisturbed) vision and smaller optotypes are not tested. (wikipedia.org)
  • Loss of visual acuity in one eye refers to the loss of sharp, clear vision in one eye. (rightdiagnosis.com)
  • Any further reduction in vision acuity is not observed until the individual is between the ages thirty to forty. (wikipedia.org)
  • The spatial-frequency theory of vision is based on two physical principles: Any visual stimulus can be represented by plotting the intensity of the light along lines running through it. (wikipedia.org)
  • They provide organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. (wikipedia.org)
  • Subsequently
  • Subsequently, we obtained information of best corrected, full line visual acuity, cycloplegic refractions, and a complete list of ophthalmological diagnoses from previous ocular examinations for the children in the study group. (bmj.com)
  • retina
  • MacuLogix Inc) can aid in the diagnosis of early-stage, or subclinical, age-related macular degeneration before visual loss occurs and even before structural changes are observed, and adds to the information obtained from retina cameras and OCT imaging. (modernmedicine.com)
  • The precise distance at which acuity is measured is not important as long as it is sufficiently far away and the size of the optotype on the retina is the same. (wikipedia.org)
  • Visual acuity is measured by the smallest letters that can be distinguished on a chart and is governed by the anatomical spacing of the mosaic of sensory elements on the retina. (wikipedia.org)
  • spatial
  • Visual Acuity' sets the bar with dynamic spatial rendering applied to starbursting synths and rogue Garage patterns, while 'You Could Be Forgiven For Thinking That' casts of into sparser, more emotive deep space electronics. (boomkat.com)
  • Visual acuity is a measure of the spatial resolution of the visual processing system. (wikipedia.org)
  • Yet spatial distinctions can be made on a finer scale still: misalignment of borders can be detected with a precision up to 10 times better than visual acuity. (wikipedia.org)
  • The spatial-frequency theory refers to the theory that the visual cortex operates on a code of spatial frequency, not on the code of straight edges and lines hypothesised by Hubel and Wiesel on the basis of early experiments on V1 neurons in the cat. (wikipedia.org)
  • Research on spatial frequency detection by visual neurons complements and extends previous research using straight edges rather than refuting it. (wikipedia.org)
  • clinical
  • Currently, the Teller Acuity Cards (TACs) are considered the gold standard for clinical testing and are effective in obtaining a quick estimate of an infant's VA, but they have certain drawbacks. (uwaterloo.ca)
  • observer
  • The experimenter controlled the staircase method and an observer used the objective information of visual fixations using the software to judge if the grating was seen or not. (uwaterloo.ca)
  • normal
  • Representation of the normal visual acuity in a healthy eye. (sciencephoto.com)
  • Normal individuals have an acuity of 6/4 or better (depending on age and other factors). (wikipedia.org)
  • Assuming normal visible acuity and clear skies, it is possible to approximately convert Globe at Night naked eye limiting maximum estimates into other units: The Globe at Night project was launched as a NASA program in the United States. (wikipedia.org)
  • the visual acuity of one species has been measured at 2.6 times that of a normal human. (wikipedia.org)
  • Another problem is that minute visual aberrations can be normal and therefore should be distinguished from genuine visual abnormalities. (wikipedia.org)
  • respectively
  • The equivalent metric measurements for visual acuity are 6/6 and 6/30, respectively. (amamanualofstyle.com)
  • Infant GT VA acuity estimates were within 1 octave of the TACs 90% and 79% of the time for the first and second visit respectively, while GT VA estimates were within half octave of the TACs 63.2% and 47% of the time for the first and second visit respectively. (uwaterloo.ca)
  • We measured static, kinetic, and dynamic visual acuity (SVA, KVA, and DVA, respectively) of Japanese professional baseball players to ascertain whether there would be any difference in SVA, KVA, and DVA among player groups stratified according to their performance level. (dovepress.com)
  • patients
  • Decrements in visual acuity during head movement in patients with vestibular hypofunction are potentially serious problems. (clinicaltrials.gov)
  • The purpose of this study was to examine the effect of an exercise intervention on visual acuity during head movement in patients with unilateral and bilateral vestibular hypofunction. (clinicaltrials.gov)
  • AIM: To assess foveal cone photoreceptor function in patients with unexplained loss of central visual acuity. (bmj.com)
  • CONCLUSION: Testing of foveal cone photoreceptor function using scanning laser densitometry may determine the location of pathological changes in certain patients with unexplained visual loss. (bmj.com)
  • cortex
  • In support of this theory is the experimental observation that the visual cortex neurons respond even more robustly to sine-wave gratings that are placed at specific angles in their receptive fields than they do to edges or bars. (wikipedia.org)
  • When all of the visual cortex neurons that are influenced by a specific scene respond together, the perception of the scene is created by the summation of the various sine-wave gratings. (wikipedia.org)
  • lens
  • The distance between the person's eyes and the testing chart is set so as to approximate "optical infinity" in the way the lens attempts to focus (far acuity), or at a defined reading distance (near acuity). (wikipedia.org)
  • optic nerve
  • These are sent to various visual centres of the brain through the fibres of the optic nerve. (wikipedia.org)
  • The optic nerve is a central tract of many axons of ganglion cells connecting primarily to the lateral geniculate body, a visual relay station in the diencephalon (the rear of the forebrain). (wikipedia.org)
  • The visual signals are then transmitted to the brain via the optic nerve. (wikipedia.org)
  • changes
  • Analyzed were the changes in visual acuity and development of PCO 1 month postoperatively and at the last available ophthalmologist visit or the visit before neodymium:YAG (Nd:YAG) capsulotomy. (rti.org)
  • ability
  • The distinction between resolving power or acuity, literally sharpness, which depends on the spacing of the individual receptors through which the outside world is sampled, and the ability to identify individual locations in the sensory space is universal among modalities. (wikipedia.org)
  • tests
  • That aperture, which can be measured by visual field tests, varies widely among different human subjects. (wikipedia.org)
  • field
  • The examinee's task is to perceive these artificial distortions and mark their locations on the visual field. (wikipedia.org)
  • system
  • Visual scanning patterns were measured by the GT system that requires minimal subject cooperation in adult and infant populations. (uwaterloo.ca)
  • visual acuity is measured using a computerized system first with the head stationary and then with the head moving in yaw plane. (clinicaltrials.gov)
  • size
  • That size is specified as a visual angle, which is the angle, at the eye, under which the optotype appears. (wikipedia.org)
  • difference
  • There was no obvious difference among the mean acuities obtained by 6 objective GT protocols, the subjective GT protocol and the TACs. (uwaterloo.ca)
  • There was no significant difference in the examined visual functions among player groups with different performance levels. (dovepress.com)
  • treatment
  • Prompt treatment enables a good visual prognosis, while any delay in therapy increases the risk of subsequent relapse. (bmj.com)
  • brain
  • In some cases, low visual acuity is caused by brain damage, such as from traumatic brain injury or stroke. (wikipedia.org)
  • A sophisticated circuitry in the brain identifies the location of a visual feature by assessing the "center of gravity" of the light over several receptors, a task that can be accomplished with much higher precision than the resolution limit set by the receptor spacing. (wikipedia.org)
  • study
  • Results Experiment 1: The mean age of participants in the adult study was 28.47±7.93 yrs and their mean uncorrected logMAR acuity was 0.9±0.2. (uwaterloo.ca)