Objective measurement of distance visual acuity determined by computerized optokinetic nystagmus test.

PURPOSE To investigate the efficacy of a computerized optokinetic nystagmus (OKN) test in evaluating the objective distance visual acuity and to determine the correlation between subjective and objective visual acuities. METHODS This prospective, noninterventional study included 83 eyes of 83 volunteers. Objective visual acuity was defined as the smallest size stripe that evoked the OKN response (induction method) or as the smallest dot size that suppressed the OKN response (suppression method). Distance visual acuity was measured by computerized OKN and infrared oculography at distance. The reproducibility of the test was evaluated by intraclass correlation coefficient (ICC). The correlation between measured objective and subjective visual acuity was then evaluated with linear regression analysis. Subjects were grouped according to their objective visual acuity, and the mean subjective visual acuities were compared with those of the objective visual acuity groups. RESULTS There was a significant correlation between distance objective and subjective visual acuity (correlation coefficient R(2), induction method:suppression method = 0.566:0.832, P < 0.05). The mean subjective visual acuity was significantly different in the objective visual acuity groups (Welch's ANOVA, P = 0.000 for induction and suppression methods). The objective visual acuity test showed good reproducibility (ICC; induction method:suppression method = 0.945:0.988, P < 0.05). CONCLUSIONS The computerized OKN test could serve as an objective and reliable tool for assessing distance visual acuity.