Experimental eye enlargement in mature animals changes the retinal pigmentepithelium

Form deprivation has been shown to result in myopia in a number of species such that the eye enlarges if one eye is permanently closed at the time of eye opening. In the quokka wallaby, the eye grows slowly throughout life. A fter form deprivation, the eye enlarges by 1-1.5 years of age to the size o f that in a 4-6-year-old animal and the number of multinucleated retinal pi gment epithelial (RPE) cells in the enlarged retina remains much lower than would be expected in eyes of comparable size. Here we have repeated the ex periment but examined animals at 4 years of age. The sutured eye grew signi ficantly larger than did its partner. Numbers of RPE cells were comparable between sutured and partner eyes but were lower than in normal animals of s imilar age. Reductions in RPE cell density were greater in nasal than in do rsal or ventral retina and were not seen in temporal retina. The distributi on of multinucleated cells was quite different in the sutured and open eyes . As in normal eyes, partner eyes had most multinucleated cells in ventral retina, while in the sutured eyes such cells were located mainly in the far periphery. In conclusion, the RPE is significantly changed by the eye enla rgement process. However, it is not known whether this change results from an active part played by the RPE in the retinal expansion process or whethe r the changes are simply a result of a passive increase in area of the RPE.