Objective measurement of visual acuity by optokinetic nystagmus suppression in children and adult patients.

PURPOSE: To investigate the correlation between subjective and objective visual acuity as elicited with a new computerized optokinetic nystagmus (OKN) suppression test ("SpeedWheel") in adults and school-aged children.

METHODS

Fifteen children (6-12 years) and 27 adults with refractive errors, amblyopia, cataract, age-related macular degeneration, and thyroid-associated orbitopathy underwent testing of subjective visual acuity with E- and Landolt-C symbols (Freiburg Acuity and Contrast Test [FrACT]) and visual acuity as estimated with the SpeedWheel on an LCD screen.

STATISTICAL ANALYSIS: linear regression, Spearman correlation, and Bland-Altman plots.

RESULTS

Mean difference against the mean was -0.01 when SpeedWheel was compared to Landolt C, but -0.15 when compared to E-symbols. Overall, SpeedWheel correlated very strongly to FrACT ("E": r = 0.85; P < 0.001; Landolt-C: r = 0.81; P < 0.001). This also held true in children ("E": r = 0.74; P < 0.003; Landolt-C: r = 0.69; P < 0.005).

CONCLUSIONS

SpeedWheel enables estimation of visual acuity in a variety of conditions in both adults and school-aged children.