Effect of Spherical Lens Induced Aniseikonia on Binocular Function

ABSTRACT

PURPOSE: To study the effect of spherical lens induced aniseikonia on stereopsis and fusion. METHODS: One hundred subjects, with normal binocular function without any ophthalmic disease or surgery history, were examined. The aniseikonia was induced with spherical lenses in 1 diopter (D) stepwise manner from -2 D to +2 D. The amount of aniseikonia was measured by Awaya's New Aniseikonia Test. Stereopsis and fusion were determined with Titmus Stereo Test and fusion card of major amblyoscope respectively. RESULTS: As the amount of aniseikonia was increased, the stereopsis and fusion were decreased. The change was statistically significant (ANOVA, p<0.001). Aniseikonia was more correlated to fusion than stereopsis. A significant decline in the stereopsis was detected when the size of aniseikonia changed from 1% to 2%. A significant decline in fusion was noticed when aniseikonia changed from 2% to 3% (Independent t-test, p<0.01). CONCLUSIONS: Our study suggests that binocular function can be disturbed by experimentally induced aniseikonia in normal subjects and that stereoacuities and fusional amplitude can be decreased as the degree of aniseikonia becomes larger.