Dual focus contact lenses modulate central retinal function

Abstract

Introduction: Dual-focus contact lenses create two focal planes, one providing a clear retinal image while the other imposes myopic defocus on the retina to slow myopia progression. This study used global-flash multifocal electroretinograms (gmfERG) direct (DC) and indirect components (IC) to compare central versus peripheral retinal responses under different dual-focus conditions, and to assess the optimal degree of myopic defocus compared to a single vision control lens. Methods: Twenty participants each underwent three gmfERG trials, wearing a spectacle correction over dual-focus contact lenses with plano central power and peripheral secondary focal powers of either +2.00DS, +4.00DS or a plano single-vision lens. We compared amplitudes and latencies of the gmfERG direct and induced components (DC and IC) within participants, between the three different contact lens powers, and at different retinal eccentricities (gmfERG ring). Results: We observed significant differences in the gmfERG responses between the single-vision and dual-focus contact lenses. Overall, DC amplitudes peaked between zero and +2.00D secondary power, while IC amplitudes were maximal between +2.00D and +4.00D. Compared to the single-vision control, the greatest increase in DC and IC amplitudes while wearing dual-focus lenses occurred within the central 10 degrees of the retina. There was no interaction effect between gmfERG ring (eccentricity) and secondary power, and no difference in the latency of the gmfERG responses between different powers. Conclusion: We found that dual-focus contact lenses with +2.00D secondary power are close to that expected to induce the greatest increase in gmfERG responses relative to a single-vision lens. Dual-focus lenses produce the highest DC and IC response amplitudes relative to a single-vision lens in the central 10 degrees of the retina. This suggests that dual-focus contact lenses slow myopia progression by modifying central rather than peripheral retinal activity.