To evaluate for which range of refractive error the optic disk size depends on, or is independent of, the refractive error. Clinical observational study. The study included 1999 eyes of 1011 subjects with a mean refractive error of -0.97 +/- 2.72 diopters (range, -24.25 to +9.4 diopters). Optic disk photographs were morphometrically evaluated. The relation between optic disk area and refractive error showed a curvilinear shape, with a steep increase toward high myopia starting at -8 diopters, and a decrease toward high hyperopia starting at +4 diopters. The optic disk size depends on the refractive error with an increase in highly myopic eyes beyond -8 diopters and a decrease in highly hyperopic eyes beyond +4 diopters. Confirming histomorphometric studies, the limits of -8 diopters and +4 diopters may be discussed to refine the definitions of high hyperopia and high myopia.