S-Cone Retinal Pathway Dysfunction in Myopia.

Purpose: To compare S-cone retinal pathway activity in participants with and without myopia and investigate its association with refractive error and axial length. Methods: Forty-eight healthy young adults, including 23 myopes and 25 non-myopes, underwent fullfield electroretinogram (ERG) testing in the dilated right eye. S-cone ERGs were recorded twice with blue flashes on an amber background after a 10-minute adaptation-first to broadband white light and second to limited-bandwidth amber light. Responses were compared between refractive error groups and wavelength conditions and correlated with refractive error and axial length. Results: In the amplitude domain, the S-cone ERG response was significantly smaller in the myopic group than in the non-myopic group (mean ± SEM, 12.42 ± 0.95 µV vs. 16.45 ± 1.08 µV; P = 0.008). Although a similar reduction was observed for the a-wave amplitude in myopes (P = 0.016), no difference was found in the L-/M-cone amplitude (P = 0.11). The S-cone ERG amplitudes correlated positively with refractive error (r = 0.49, P = 0.0005) and negatively with axial length (r = -0.49, P = 0.0005). A 10-minute adaptation to amber light produced a reduction in S-cone ERG amplitudes in the non-myopic group (P = 0.004) but not in the myopic group (P = 0.97). In the time domain, no differences were observed between refractive error groups and wavelength conditions (P > 0.05). Conclusions: S-cone ERG amplitudes were reduced by approximately 25% in myopic participants, with greater reductions associated with increasing myopia and axial length. A 10-minute adaptation to amber light failed to produce the expected decrease in S-cone amplitudes in the myopic group. These findings suggest functional deficits in the S-cone retinal pathway in individuals with myopia.