AN EVALUATION OF ACUITY CARD PROCEDURES

1. Acuity cards are now commonly used to assess the grating acuity of infants, but the procedures vary across clinical settings. To evaluate differences between various acuity card procedures and a more objecti ve preferential looking test of acuity, we compared each of three acui ty card procedures with a preferential looking (PL) staircase procedur e in toddlers with ocular disorders. 2. In Expt 1, we used PL and two or three variations of the acuity card procedure to measure grating ac uity in one eye of 30 toddlers aged 15-30 months expected to have redu ced acuity because of structural ocular abnormalities. For the acuity card procedures, observers knew either the stripes' location (random p rocedure), their relative size (Dobson procedure), or their location a nd absolute size (informed procedure). For comparison, we tested 38 ad ditional children, aged 16-32 months, with two tests of PL. 3. All thr ee acuity card procedures yielded results which agreed moderately well with PL, with Dobson's procedure agreeing best overall. However, the acuity card procedures agreed with PL within 1/2 octave only 44-67% of the time, whereas two tests of PL agreed within 1/2 octave 79% of the time. A comparison of the results from the different acuity card proc edures did not correspond to those that would be predicted by observer bias. 4. In Expt 2, we tested interocular acuity differences using PL and the Dobson acuity card procedure in 30 children aged 4-35 months who were suspected to be amblyopic. 5. PL and acuity cards agreed for only half the patients on whether or not there was an interocular diff erence of at least 1 octave. A comparison of the results from each pro cedure to the expected interocular acuity differences based on medical history indicated that the acuity card procedure was either (a) influ enced by an observer's expectation of interocular differences or (b) m ore sensitive for detecting expected interocular differences than is P L. 6. We conclude that acuity cards, used with these procedures. canno t substitute for PL, but can yield moderately similar results in much less time.