Change in the land vertebrate community under new conditions in nature]

PURPOSE: To report bilateral congenital optic nerve head pits in monozygotic siblings. METHOD: Case reports. RESULTS: Pits were found in abnormally large optic disks in both eyes of two otherwise healthy female monozygotic siblings aged 15 years. Pit size increased and visual acuity decreased with increased optic disk area. In one eye, nonrhegmatogenous retinal detachment developed that eventually necessitated pars plana vitrectomy. The siblings' parents were unremarkable. CONCLUSIONS: Congenital optic nerve head pits can occur bilaterally in otherwise healthy monozygotic siblings with ophthalmologically unremarkable parents. Associated nonrhegmatogenous retinal detachment may be treated by pars plana vitrectomy. Pit size is positively correlated with disk area.