Distribution of myopia in aphakic retinal detachments.

The aetiology of retinal detachment after lens extraction requires analysis to determine common factors. According to Treister (I972) an increased incidence is due to the use of chymotrypsin. Shapland (I934) quotes an overall incidence of 2z2 per cent using the extracapsular technique. He thought it to be higher in myopic aphakia but he gave no figures. Hyams, Bialik, and Neumann (I975) give an incidence of 6X7 per cent for myopia above -6-oo. The factors that may be considered statistically are age, sex, surgical technique, type of anaesthesia, and precataract refractive error. Details of surgical technique are difficult to analyse, but the essential procedures may be grouped easily into extraand intracapsular removal of the lens, cryoextraction, and use of enzyme. Complications such as vitreous loss may also be clearly indicated. Results may be analysed by using corrected acuity as the yardstick, though the incidence of poor acuity after extraction is likely to be high in degenerative myopia, complicated cataracts, traumatic cataracts, and infantile cataracts. The results analysed in this paper exclude infantile cataracts, in which the incidence of detachment is high (Shapland, I96I) and the acuity poor (Ruben, I 969). By analysing the results of almost iooo cataract extractions for the incidence of detachment and for visual acuity and a random group of them for refractive error power corrections we hoped to show the role of myopia in the incidence of aphakic retinal detachment. In order to obtain these results a schematic aphakic eye was introduced so that the precataract refractive state could be easily calculated.