The effect of colored crowding bars on the HOTV visual acuity test in amblyopic patients.

Background: Colored versus black crowding bars surrounding a black optotype may induce a greater level of interest in visual acuity testing in young children. To evaluate the adequacy of colored bars for a satisfactory crowding effect in children with amblyopia, we compared visual acuity measurements using black versus red, green, or yellow bars.

Methods: To choose the best color to compare with black, 53 patients with amblyopia were randomly assigned to 1 of 3 crowding bar colors. Subjects had the visual acuity of each eye measured with black HOTV optotypes and bars and then with black optotypes and either red, green, or yellow bars. In a second phase of the study red crowding bars were compared with black in a group of 48 different patients with amblyopia.

Results: The difference in logMAR visual acuity between amblyopic eyes tested with red versus black crowding bars was not statistically significant (mean visual acuities of -0.24 and -0.26, respectively; p = 0.315), but the difference was significant with either green (-0.30 and -0.34; p = 0.047) or yellow (-0.14 and -0.24; p = 0.0003). In the nonamblyopic eyes none of the colored crowding bars yielded significantly different visual acuity measurements compared with black. In the second phase of the study red crowding bars yielded an average of one letter worse visual acuity than black bars, but the difference was not statistically significant.

Conclusions: Red crowding bars surrounding black optotypes are an acceptable alternative to black crowding bars for the measurement of visual acuity in amblyopic eyes.