Indian numeral test chart for partially sighted patients

ABSTRACT

A test chart was designed for precise evaluation of central visual acuity [VA] in patients with a VA below 20/70 who are familiar with the Indian numerals widely used in the Middle East. The chart consists of 14 pages, each about 42 by 45 cm; the test distance is 20 feet; the test objects are selected pairs of Indian numerals. The chart design is similar to that described by Mahmoud Al-Salem and is based on Snellen's principle. Two-digit numbers were constructed on a 5x5 frame, each test frame subtending 5 minutes of arc on the patient's retina at the distance specified in the numerator of the connotation. Object sizes represent a range of VA from 20/700 to 20/70 in 16 steps, with individual symbols ranging in height from 30.94 to 3.10 cm. There are between one and nine two-digit numerals on each page of the chart, arranged in one to three rows. Where a page contains multiple two-digit units, spaces between them are equal to the total size of each unit; where there is more than one horizontal row, spaces between the rows are approximately equal to the height of the digits in the bottom row