Effects of hemiretinal form deprivation on central refractive development and posterior eye shape in chicks

► The effects of covering half retina on refractive error and eye shape were studied. ► Spherical-equivalent refractive error and astigmatism were measured along pupillary axis. ► Axial length and equatorial diameter were measured by imaging enucleated eyeballs. ► Covering superior retina produced the highest central myopia and AL/ED ratio. ► Subtle differences in J0 and J45 were noted across the treatment groups. We determined effects of hemiretinal form deprivation (i.e., form-depriving half of the retina) on central refractive development and posterior eye shape in chicks. Seventy-seven White Leghorn chicks were randomly assigned to receive superior (SRD, “Superior Retinal Deprivation” or inferior visual field deprivation, same principle applies for the following abbreviations, n=17), inferior (IRD, n=14), temporal (TRD, n=23) or nasal hemiretinal (NRD, n=23) form deprivation monocularly from day 5 to day 26. Central refractive errors, expressed as interocular difference in spherical equivalent (M), J0 and J45 astigmatic components, were measured using Hartinger refractometer at the beginning and weekly after treatment for 3weeks. At the end of the treatment period, eyes of a subset of birds were enucleated and eye shape profile was photographed along four different meridians. These digital images were later processed to extract axial length (AL), equatorial diameter (ED), and AL/ED. For comparison purposes, the eye shape profile was also acquired from a separate group of birds reared with monocular full-retinal form deprivation (FRD, n=10). The four hemiretinal form deprivations altered central ametropia and posterior eye shape to different degrees. The biggest contrast in M was found between SRD and IRD groups (mean±SE after 3weeks: SRD=−4.14±0.71 D vs. IRD=+1.24±0.36 D; p