Morphological recovery in the reattached retina.

After experimental retinal detachment in the cat, a number of morphological changes take place in retinal and RPE cells. Following reattachment, the ultrastructural relationship between the photoreceptors and the RPE is re-established, but it does not return to the predetachment state even after short detachment episodes coupled with prolonged recovery periods. All of the reattached retinae show some degree of abnormality, ranging from subtle changes in photoreceptor ultrastructure to dramatic degenerative effects in the outer retina. Abrupt transitions in morphology from one reattached area to an adjacent area are not unusual. Photoreceptor recovery varies widely between animals, and between adjacent regions within the same retina. Ensheathment of outer segments by RPE apical processes is abnormal. In some reattached areas rod outer segment dimensions and disc structure are near normal as is the displacement rate of rod outer segment discs. In others, especially in areas of RPE or Müller cell proliferation and hypertrophy, the outer segments are shortened or absent completely, and there is a reduction of cell bodies in the outer nuclear layer. In some retinae, recovery in cones is inferior to that in rods. At short detachment durations (less than 1 wk) morphological recovery in the reattached retina is optimal while at long intervals (greater than 1 month) recovery is poor. The changes at the photoreceptor-RPE interface identified in the reattached cat retina probably have adverse effects on visual recovery when they occur within the human macula.