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A person taking the test covers one eye from 6 metres or 20 feet away, and reads aloud the letters of each row, beginning at the top. The smallest row that can be read accurately indicates the visual acuity in that specific eye. The symbols on an acuity chart are formally known as "optotypes". Variation of Snellen chart with another letter ...
Another test, including Visual acuity (EVTS/OptimEyes), uses targets which change in size, contrast, and viewing time. This test was developed by Daniel M. Laby with colleagues and uses item response theory to calculate a vision performance score (core score). This specific test of visual function has been shown to correlate to professional ...
An eye examination, commonly known as an eye test, [1] is a series of tests performed to assess vision and ability to focus on and discern objects. [2] It also includes other tests and examinations of the eyes. [2] Eye examinations are primarily performed by an optometrist, ophthalmologist, or an orthoptist.
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]
The Jaeger chart is an eye chart used in testing near visual acuity.It is a card on which paragraphs of text are printed, with the text sizes increasing from 0.37 mm to 2.5 mm. [1] This card is to be held by a patient at a fixed distance from the eye dependent on the J size being read.
An occluder is placed over the eye that is not being tested (e.g.: over the left eye, to test the right eye's vision). A pinhole occluder is then placed before the patient's eye, and their vision is then tested again (each eye separately) to determine if the patient's poor visual acuity is a result of optical irregularities, or pathological issues.
A visual field test is an eye examination that can detect dysfunction in central and peripheral vision which may be caused by various medical conditions such as glaucoma, stroke, pituitary disease, brain tumours or other neurological deficits.
The unilateral cover test is performed by having the patient focus on an object then covering the fixating eye and observing the movement of the other eye. If the eye was exotropic , covering the fixating eye will cause an inwards movement; and if esotropic , covering the fixating eye will cause an outwards movement.