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The visual field index (VFI) reflects retinal ganglion cell loss and function, as a percentage, with central points weighted more. [21] It is expressed as a percentage of visual function; with 100% being a perfect age-adjusted visual field and 0% represents a perimetrically blind field.
The Goldmann perimeter is a hollow white spherical bowl positioned a set distance in front of the patient. [3] An examiner presents a test light of variable size and intensity. The light may move towards the center from the perimeter (kinetic perimetry), or it may remain in one location (static perimetry).
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The value D, indicated to the left of each row, gives the distance in meters from which a person with a visual acuity of 1.0 can read the corresponding row. The value V, indicated to the right, gives the minimum visual acuity needed to read the row from a distance of 5 meters. The first row contains symbols 70 mm in size (V = 0.1); the second ...
Visual hyperacuity is at least 10 times more sensitive than visual acuity, the ability to separate between distinct objects. [4] Therefore, in retinal diseases such as macular degeneration responses to hyperacuity stimuli may be abnormal long before any changes in visual acuity are observed.
In addition to this, the LEA symbols test has been experimentally verified to be both a valid and reliable measure of visual acuity. As is desirable of a good vision test, each of the four optotypes used in the symbols test has been proven to measure visual acuity similarly and blur equally as well, supporting the test's internal consistency. [3]
An example of the Landolt C eye chart (also known as the Japanese eye chart). Numerous types of eye charts exist and are used in various situations. For example, the Snellen chart is designed for use at 6 meters or 20 feet, and is thus appropriate for testing distance vision, while the ETDRS chart is designed for use at 4 meters. [16]
Snellen chart is used to estimate visual acuity (last three rows are 20/15, 20/13 and 20/10) A Snellen chart is an eye chart that can be used to measure visual acuity . Snellen charts are named after the Dutch ophthalmologist Herman Snellen who developed the chart in 1862 as a measurement tool for the acuity formula developed by his professor ...
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