An analysis of 54 cases of ARD, and a PRD control group, revealed that retraction of the posterior vitreous hyaloid was more severe in the aphakic eyes. On the basis of retinal break morphology, the ARD cases could be divided into two groups: (1) detachments that had resulted from small tears situated along the posterior slope of a peripheral retinal traction ridge and (2) detachments that had resulted from breaks that resembled those encountered in the PRD group. The yearly incidence of retinal detachment, in the 38 and over age group, was calculated to be 12 times greater for an aphakic eye. That increase in risk was thought to be due to the changes in vitreous morphology which follow cataract extraction.