Development of laser-induced retinal damage in the rabbit

Background: Laser lesions may induce retinal damage that is larger than exp ected from the size of the coagulated area. This study was designed to foll ow the development of laser-induced reduction in retinal function and to co rrelate it with structural changes. Methods: Pigmented rabbits were treated in one eye with 225 argon laser les ions. The ERG responses were recorded at different times after treatment. T he effect of the laser treatment upon the functional integrity of the retin a was assessed from the ERG responses. Structural damage was examined by li ght microscopy. Results: Shortly (1-2 h) after laser treatment, the ERG responses were redu ced by about 50%. ERG deficit continued to develop and reached a maximal le vel about 24 h after treatment. Thereafter, slow recovery was observed but permanent deficit, relative to the initial laser effect, was seen even 30 d ays after treatment. Histological observations indicated extensive serous r etinal detachment between laser lesions that developed within 24 h after tr eatment. At 30 days post-treatment, lesioned areas were completely destroye d and heavily pigmented. The retina between lesions was attached to the pig ment epithelium but exhibited different degrees of structural damage. Conclusions: The immediate laser damage is confined to the coagulated areas while secondary functional damage develops within 24 h and probably reflec ts serous retinal detachment between lesions. The serous retinal detachment completely resolves with time but may induce permanent structural abnormal ities in non-coagulated retinal areas that is reflected in a functional def icit larger than the initial laser effect.