Vision Eye Chart 3M Snellen
$26.00 Excl. GST
A Snellen chart is an eye chart used by eye care professionals and others to measure visual acuity. Rows of letters, numbers and symbols in standardized graded sizes, with a designated distance at which each row should be legible to a normal eye.
In the most common acuity test, a Snellen chart is placed at a standard 3 or 6 metre distance, where the symbols on the line representing “normal” acuity subtend an angle of five minutes of arc, and the thickness of the lines and of the spaces between the lines subtends one minute of arc. This line is designated 20/20 (US) or 6/6 (non-US), and is the smallest line that a person with normal acuity can read.
The contrast between letters and background provided by this chart satisfies all relevant clinical standards, including BS4274-1:1968, which dictates that (a) The luminance of the presentation shall be uniform and not less than 120 cd/m2m, and (b) Any variation across the test chart shall not exceed 20%.
The chart’s Optotype (letter / symbol) geometry meets relevant clinical requirements for line thickness and white space dimensions.
|Dimensions||29 × 11.5 × 1 cm|