Kinetics of foveal cone photopigment in myopia without chorioretinal degeneration.

PURPOSE To study the early changes in the outer retina of myopic eyes, we performed fundus reflection foveal cone densitometry in 45 subjects with normal visual acuity and no chorioretinal degeneration (ages: 18-47 years, refraction; +2.00-(-14.50) diopters). METHODS After full bleaching, the density of the photopigment was measured for 7 minutes by using a test spot, 562 nm in wavelength and 1 degrees in diameter, focused on the fovea. We calculated the density difference (DD) and the time constant (TC) of photopigment regeneration. RESULTS Although we found no correlation between the DD and the refractive error, there was a significant increase in TC as the refractive error increased (r = 0.50, P < 0.01). CONCLUSIONS These findings indicated that the kinetics of cone pigments become abnormal preceding the loss of cone cells or chorioretinal degeneration in high myopia.