Vitreous morphology after carbon dioxide laser irradiation.

The immediate vitreous changes produced by a continuous-wave carbon-dioxide laser beam in freshly enucleated bovine and pig eyes were studied by gross examination with a dissecting microscope, and histopathologically by light microscopy and transmission electron microscopy. The lesions produced by the laser beam on the vitreous in an air tissue interface technique were remarkable for their ring-shaped vitreous condensations. The diameter and density of these condensations increased with irradiance. With the same irradiation parameters the lesions at the anterior hyaloid membranes showed greater size and density than those in the central area of the vitreous. These vitreous condensations were demonstrated to consist of heat-denatured collagen fibrils. For light microscopic evaluation of the vitreous a modified method of tissue processing according to Szent Györgi has proven optimal in reducing vitreous shrinkage from dehydration. This method of fixation and tissue processing appeared to be useful in evaluating lesions of the vitreous and their relationship to their surroundings.