Morphologic findings in the rabbit retina following irradiation with the free-running neodymium-YAG laser. Disruption of Bruch's membrane and its effect on the scarring process in the retina and choroid.

The scarring process induced within the retina and choroid of pigmented rabbits' eyes following irradiation with the neodymium-YAG laser (working in the free-running mode) was examined at the ultrastructural level. Scarring of the sensory retina proceeded rapidly and was well advanced two weeks after irradiation, whereas in the choroid, signs of repair were apparent only after six weeks. This difference in the rate of repair between the two tissues has a bearing on the scarring pattern in the retinochoroid as a whole. The severity of damage to the elastic component of Bruch's membrane also has important consequences in relation to the repair processes in the retina and choroid. Microfractures within this layer, while enabling migrating cells of various kinds to penetrate into the inner collagenous zone, did not prevent complete regeneration of the retinal pigment epithelium (RPE). In instances of greater rupture, however, RPE regeneration was found to stop at the border of the break, and the discontinuity produced within Bruch's membrane and the RPE allowed the glial scar to expand into the choroid. In this region, new formation of vessels was not found.