Aniseikonia Detection May Not Be Achieved Through Visual Acuity Screening

Insignificant visual acuity changes in individuals with aniseikonia may not allow aniseikonia detection during a clinical examination, according to a study published in Clinical and Experimental Optometry. This finding indicates that visual acuity cannot be used as a marker for aniseikonia, according to the report.

Researchers included 10 individuals (age range, 18-21 years; women, 6) in the investigation and introduced aniseikonia up to 20% using 2 different methods, which included lenses to minify the field of view and polaroid filters that allowed vectographic viewing of optotypes on a 3 dimensional computer monitor. The team measured best corrected visual acuity (BCVA) on conventional logarithmic progression format vision charts and isolated optotypes in both induced aniseikonic conditions.

There was a small, but statistically significant increase in the binocular visual acuity thresholds with induced aniseikonia, with 0.06 logarithm of the minimum angle of resolution (logMAR) being the largest deficit for 20% size differences between the eyes, according to the report. For aniseikonia of 9% or greater, binocular visual acuity was worse than monocular visual acuity. Slightly higher thresholds (0.01 logMAR) were observed for acuity measured with the vectographic presentation compared with those viewed with the lenses. The research team also noted slightly higher thresholds (0.02 logMAR) for visual acuity measured with charts compared with isolated letters.

The study authors highlight the practical applications of these findings and stress that visual acuity examinations cannot allow aniseikonia detection.

“[V]isual acuity cannot be used as a marker of aniseikonia in clinical settings,” the investigators explain. “Even with very marked induced aniseikonia, binocular visual acuity remained well within standards for [licensing] of drivers.”

This study is limited by the inclusion of optometry students as participants and a failure to perform assessments that included individuals with pathological or physiological aniseikonia.