Optically Induced Peripheral Contrast Reduction Restores ON/OFF Pathway Balance in Myopic Eyes

The aim of this study was to investigate ON/OFF pathway responses and the impact of contrast reduction in myopes and emmetropes.

This was a cross-sectional study.

Thirty-eight young adult participants aged 20 to 29 years were included. Their spherical equivalent refraction ranged from +0.75 to -5.75 diopters (D).

All participants (20 myopes, 18 emmetropes) underwent multifocal electroretinogram recording after 90 minutes of exposure to monocular diffuse (contrast reduction) conditions. The 5 experimental conditions were assessed in random order on separate days for each participant: control (no diffuse), slight peripheral diffuse (0.8 Bangerter foil, 5 mm clear center), medium peripheral diffuse (MPD) (0.4 Bangerter foil, 9 mm clear center), MPD (0.4 Bangerter foil, 5 mm clear center), and medium full-field diffuse (0.4 Bangerter foil).

P1- and P2-wave amplitudes, as well as the P2/P1 amplitude ratio at varying retinal eccentricities were analyzed.

Compared with those of emmetropic eyes, both P1- and P2-wave amplitudes were significantly lower in myopic eyes (P1-wave: 8.25 ± 1.42 vs 10.29 ± deg/deg², P < 0.05; P2-wave: 2.52 ± 0.79 vs 3.89 ± 1.57 nV/de g², P < 0.01). However, the decline in P2-wave amplitude (35%) was more pronounced than the reduction in P1-wave amplitude (20%), resulting in a decrease in the P2/P1 ratio (0.30 ± 0.07 vs 0.41 ± 0.19, P < 0.05). Compared with the control condition, all the peripheral diffuse conditions increased the P2-wave amplitude and significantly increased the P2/P1 ratio (0.38∼0.41 vs 0.30, all P < 0.05) in the entire analyzed field, whereas no change was observed in the full-field diffuse condition (P > 0.05). No significant differences between the slight and medium diffuse conditions were observed (P > 0.05).

Peripheral contrast reduction significantly strengthened OFF-pathway responses, contributing to the restoration of ON/OFF pathway balance in myopic eyes.

The author has no/the authors have no proprietary or commercial interest in any materials discussed in this article.