A comparison of behavioural procedures for measuring Vernier acuity and grating acuity

Abstract

I evaluated a novel 4/4 vision testing procedure recently implemented by our laboratory in a larger study to estimate the maturation ages of three visual functions. This rigorous procedure requires participants to locate a stimulus on four consecutive presentations before progressing to more difficult stimuli. I determined the time-efficiency of the procedure and whether children are affected differently than adults by the procedure, which would suggest that maturation age estimates from the larger study are inaccurate. Fifty-five adults and 52 children were tested on grating acuity and vernier acuity using the Teller acuity cards (TAC) and vernier acuity cards, respectively. I hypothesized that the 4/4 procedure would agree with the widely-used staircase and TAC procedures for both visual functions and across age groups, and that the 4/4 procedure would be more time-efficient than the staircase procedure. The 4/4 procedure showed strong to acceptable agreement with the staircase and TAC procedures for grating acuity, while levels of agreement for vernier acuity were poorer due to the misalignment step sizes. For both visual functions, levels of agreement were stable across age indicating that the measurement of children’s acuity was not affected differently than the measurement of adults’ acuity when tested with the 4/4 procedure. Although for both visual functions, the 4/4 procedure had longer completion times than the TAC procedure, it was more time-efficient than the staircase procedure. Thus, this procedure is sufficiently accurate and practical to measure visual maturation.