Low vision rehabilitation: visual acuity measurement in the low vision range

1. To predict function and prescribe low vision aids, accurate measurements are needed. The routine measurement range can be extended by moving test charts normally used at 20 ft to a closer distance; 1 m is recommended, which gains a factor of 6. 2. Some practitioners recommend testing all reading at a standard distance, but they differ in the distances they recommend. Using a variable distance and recording the distance with every measurement allows for patients' preferred distances. 3. If the distance and letter size are properly recorded, the same visual acuity score should be calculated for all distances. Inches and J numbers, the most prevalent measurements, make visual acuity calculations impossible, but by adopting metric measurements, calculations are far easier.