Case Report: When Two Is Worse Than One-Stereo Imbalance in a Case of Wavefront-guided Scleral Lenses

Wavefront-guided scleral lenses (WGSLs) reduce visually debilitating residual higher-order aberrations. Although reduced higher-order aberrations lead to improvement in monocular high-contrast visual acuity (VA), the success of the lenses in everyday life depends on additional factors such as retinal contrast, binocular balance, and stereoacuity.

This report describes a case where WGSLs provided improved monocular vision compared with scleral lenses (SLs) but reduced binocularity and stereoacuity.

A 48-year-old woman with moderate keratoconus right eye (OD) and severe left eye (OS) was fitted with SLs and WGSLs. Visual acuity with best SLs was 20/20 -2 OD and 20/25 -2 OS. Residual higher-order root-mean-square (HORMS) wavefront error (6 mm pupil) was 0.56 μm OD and 1.38 μm OS. Visual acuity with WGSLs was 20/16 -2 OD and 20/25 +2 OS, and residual HORMS was 0.41 μm OD and 0.98 μm OS. Monocularly, WGSLs were reported to provide better VA. However, binocularly, the patient reported an "imbalanced feeling" and preferred the SLs over WGSLs. Binocular VA at distance was 20/25 with SLs and 20/25 -2 with WGSL. To investigate, the Worth Four-Dot test was performed, and the outcomes reported fusion with SLs but suppression OS at distance with WGSLs. Stereoacuity was 160 arc seconds at near and 120 arc seconds at distance with SLs and 400 arc seconds at near and >1200 arc seconds at distance with WGSLs. Dichoptic contrast balancing showed a balance point of 0.48 with SLs and 0.17 with WGSLs, indicating a strong preference toward OD. Simulation of the patient's retinal image revealed a greater difference in image contrast between the two eyes with WGSLs.

Wavefront-guided scleral lenses reduced HORMS and improved VA compared with SLs. However, in this case, it inadvertently caused binocular imbalance. As WGSLs become more widely available, future work should include methods to optimize binocular balance to maximize overall patient satisfaction.