Reduced logMAR visual acuity test chart
AssigneesUniversity College London, Moorfields Eye Hospital NHS Trust
InventorsIan E. Murdoch, D. Allstair H. Laidlaw, Dan A. Rosser, Fred W. Fitzke
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Abstract
An improved visual acuity chart is disclosed. The ratio of the size of the optotypes of neighbouring lines on the chart is a constant and preferably the size decrement between lines is 0.1 logMAR. Each line of optotypes has two, three or four optotypes, preferably three. Crowding bars for visual acuity charts are also disclosed. These bars are spaced from the ends of row and/or above and below the top and bottom lines. The individual bars may be joined together with linking sections. The spacing form the optotypes is preferably one half the width or height of the optotypes and their breadth is preferably that of the strokes of the optotypes.
Claims20
A visual acuity chart having a plurality of lines of optotypes, wherein the ratio of the size of optotypes of each line of the plurality to the size of the optotypes of the preceding line is a constant, wherein the number of optotypes on each line of the plurality is three, and wherein said ratio is such that the difference between the logarithm to base 10 of the size of the optotypes of each line of the plurality and logarithm to base 10 of the size of the optotypes of each line of the plurality and the logarithm to base 10 of the size of those of the next is 0.1.
A visual acuity chart having a plurality of optotypes, the size of the optotypes of the lines of the plurality decreasing line by line, said acuity chart having at least two crowding bars spaced from the ends of one of said lines of optotypes, said two crowding bars being joined by a linking section at an angle to a line perpendicular to the lines of optotypes.
Dependencies are inferred from the claim text.