optotypes

op·to·types

(op'tō-tīps),
Test letters. See: test types.
[opto- + G. typos, type]
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I lots - optotypes projector; Lot II - slit lamp; Lot III - SchiE[micro]tz type tonometer; Lot IV - cystoscopes.
b The spaces between optotypes are equal to the width of the optotypes
3-5 years: Matching optotypes (use the illiterate E chart, Landolt's C test, Sheridan-Gardener's test, Lea charts).
The 4-m chart used had high contrast Sloan letters and optotypes were in LogMAR increments.
They presented optotypes in progressively smaller sizes, five at each acuity level, until the subject incorrectly identified five optotypes at a single line of acuity.
Grating acuity was measured with persons with severe disabilities only if it was not possible to use optotypes.
3) This is perhaps because Snellen VA is measured with high contrast static optotypes, very unlike natural conditions of the "number plate test", making Snellen VA a poor predictor of a person's ability to meet the legal driving standard.
BCVA with Early Treatment Diabetic Retinopathy Study optotypes (Precision Vision; La Salle, Illinois) ranged from 20/10 to 20/125; 82 percent were 20/20 or better.
One or more sessions with an occupational therapist were devoted to training in reading skills with suprathreshold optotypes (larger than critical print size) or continuous print materials.
a) The spacing of the optotypes and the lines follows a geometric progression
Indeed, logMAR charts such as the Bailey-Lovie chart are advantageous in that task difficulty remains consistent across all levels of acuity, with equal number of optotypes presented per line, and there is a regular logarithmic progression of acuity such that each line is a scaled version of the preceding line, allowing each individual letter to contribute to the VA measure, increasing the accuracy.
The computerised Test Chart 2000 is extremely useful for this because a variety of optotypes can be presented, including lower case letters, numbers, Lea symbols, and Kay pictures.