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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 ...
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]
10-2: Measures 10 degrees temporally and nasally and tests 68 points. Used for macula , retinal and neuro-ophthalmic conditions and advanced glaucoma [ 4 ] 24-2: Measures 24 degrees temporally and 30 degrees nasally and tests 54 points.
Visual acuity with Near chart without correctors Visual acuity with eye chart at Near 15.7 inches (400 mm) and without (sc: Latin sine correctore) correctors (spectacles); Ncc is with (cc: Latin cum correctore) correctors. See Visual_acuity#Legal_definitions: VA OS Left visual acuity VA OD Right visual acuity VDU Visual display unit VF Visual field
Amsler grid, Chart 1. There are 7 types of Amsler grid charts. All charts measure 10 cm × 10 cm (3.9 in × 3.9 in), which when viewed at a distance of 33 cm (13 in) from the eye can be used to measure defects in the central 20 degrees of the visual field. [3]
In order to determine if the patient has astigmatism at a particular meridian, the -0.50 JCC is presented at the following axes: 90°, 180° and then check the oblique axes at 35° and 145°. [ 6 ] As the JCC is a combination of two cylindrical lenses, any cylindrical power that is added must be accompanied by a spherical lens equivalent, to ...
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Developed by Australian ophthalmologist Noel Alpins and introduced in 1993, the Alpins Method provides a coherent basis for reporting astigmatism results, and on this basis became the standard in the major ophthalmology journals, [9] [10] [11] and was accepted worldwide for studies that include refraction and corneal astigmatism measurements.