Prevalence of refractive errors in students with and without color vision deficiency

To evaluate refractive errors in school age children with color vision deficiency (CVD) and those with normal color vision (NCV) in order to make a better understanding of the emmetropization process. A total of 4,400 primary school students aged 7–12 years were screened for color vision using Ishihara pseudoisochromatic color vision plate sets. Of these, 160 (3.6%) students had CVD. A total of 400 age‑ and sex‑matched students with NCV were selected as controls. Refractive status was evaluated using objective cyclorefraction. The CVD group included 136 male (85%) and 24 female (15%) subjects with mean age of 10.1 ± 1.8 years. The NCV group comprised of 336 male (84%) and 64 female (16%) subjects with mean age of 10.5 ± 1.2 years. The prevalence of myopia (7.7% vs. 13.9%, P < 0.001) and hyperopia (41% vs. 57.4%, P = 0.03) was significantly lower in the CVD group. Furthermore, subjects with CVD subjects demonstrated a lower magnitude of refractive errors as compared to the CVD group (mean refractive error: +0.54 ± 0.19 D versus + 0.74 ± 1.12 D, P < 0.001). Although the lower prevalence of myopia in subjects with CVD group supports the role of longitudinal chromatic aberration in the development of refractive errors; the lower prevalence of hyperopia in this group is an opposing finding. Myopia is a multifactorial disorder and longitudinal chromatic aberration is not the only factor influencing the emmetropization process.