The letters can be interchanged for different languages, while it also allows the user to change the optotypes
to the universal language of numbers.
A functional scale seems essential for preschool children with visual impairments whose visual acuity cannot be recorded using optotypes
Children less than 2 years with good co-operation and response Lea paddles, 2-4 years Lea symbols or single optotypes
such as Landolt C or HOTV (Simson 1983) was used and above 5 years Snellen's chart was used.
Definitions and Characteristics of the Visual Tests Test Brief Definition Measuring Device Static visual acuity The ability to recognize Electronic English alphabets and chart spatial localization of the visual system with a 100% contrast (black optotypes
on white background).
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.
The best known optotypes
for the assessment of SVA, the Snellen letters and the Landolt-C targets, are now well over 100 years old (see Riggs, 1972).
However, it has been shown that in diseased foveas or under non-foveal viewing conditions, such as in patients with AMD, the detection and recognition thresholds for these optotypes
can be quite different; this is because the eye still possesses sufficient cells to detect contrast in the stimulus but no longer has enough to properly resolve the target (termed 'under-sampling').
Most of the visual acuities in our study were measured in the clinic operated by NSUOCO, where the Early Treatment of Diabetic Retinopathy Study (ETDRS) chart was used and visual acuity was interpolated from the total number of optotypes
correctly identified (Ferris, Kassoff, Bresnick, & Bailey, 1982).
I lots - optotypes
projector; Lot II - slit lamp; Lot III - SchiE[micro]tz type tonometer; Lot IV - cystoscopes.
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.