Designed by: Dr. August Colenbrander
Conventional, high-contrast letter chart acuity captures only one aspect of visual performance. Low contrast acuity is equally important for activities of daily living, since most everyday objects have less than black-on-white contrast, are larger than the smallest letters seen on a letter chart and are seen at various intermediate distances.
All tests provide HC targets on the left and LC targets (10% contrast) on the right. The left-hand margin indicates the letter size in M-units. Three of the four sides provide letter tests, calibrated for use at 40 cm (16”), 63 cm (25”) and 100 cm (40”). A cord on each card ensures that the viewing distance is maintained accurately. These distances cover the range that is most important for manual activities of daily living. They require a reading add of 2.5 D, 1.5 D and 1.0 D. The fourth side provides lines of text, calibrated for 40 cm. The print sizes follow the standard logarithmic sequence. Each line of text has the same number of characters. Basic reading assessment is important, since it may show the effect of para-central scotomata that do not yet interfere with central letter acuity. Each set comes with complete instructions, background and recording sheet for scoring.