COMPARISON OF RETINAL LESIONS PRODUCED BY TRANSSCLERAL KRYPTON LASER PHOTOCOAGULATION, TRANSPUPILLARY KRYPTON LASER PHOTOCOAGULATION AND CRYOCOAGULATION

We compared the retinal lesions produced by transscleral and transpupi llar krypton lasers and cryocoagulation. Transscleral laser photocoagu lation was applied under indirect ophthalmoscope visual control with i ndentation of the sclera by the laser probe. Transpupillar laser was p erformed with a Volk 90 D lens. The power and the spot size were adjus ted to create lesions of similar size and intensity as in transscleral photocoagulation. The output power needed for transscleral photocoagu lation was 0.2 W with exposure time of 3-5 sec. In the transpupillar p hotocoagulation the output power was 0.3 W and the exposure time 2-3 s ec, respectively. The lesions were studied histologically 1 h, 1, 3, 7 , 30 and 60 days after treatment. Histopathological studies of the kry pton laser lesions revealed destruction and scarring of the outer laye rs of the retina and the choroid. The lesions produced by transpupilla r and transscleral laser appeared to be rather similar. These results indicate that, in the rabbit eye, there is no difference between the l esions produced by the transpupillar or transscleral route of laser ap plication. Transscleral laser application may have clinical advantages over transpupillary laser in the eyes with hazy media or in other cas es when transpupillar laser is not possible.