[Ultrastructure study on the RPE, Bruch's membrane and choroid after laser photocoagulation of the retina].

OBJECTIVE

To observe ultrastructural changes and repair process of retina after laser photocoagulation of the retina, in order to provide histopathologic findings of laser treatment for RPE and choroidal diseases.

METHODS

In seven patients with orbital malignant tumor needed exenteration, the normal retina was coagulated (using I, II, or III grade photic spot) 1, 3, or 7 days before the exenteration after signing consent by the patients. The retina and the choroid from these enucleated eyeballs were observed by electron microscope.

RESULTS

One day after photocoagulation (I grade photic spot), some RPE cells were swollen and necrotic, with partial disappearance of microvilli. The number or RPE was reduced. Bruch's membrane was intact. Endothelial cells of choroidal capillaries were swelled with occlusion in a few of the lumens. In III grade photic spot, many RPE cells were lysed. Vacuoles were found in Bruch's membrane. Many choroid capillaries were occluded. In III grade photic spot, numerous RPE cells were disappeared and Bruch's membrane was destroyed partially. Middle size vessels in the choroid were damaged. Three days after photocoagulation, edema of RPE cells and choroid was relieved. Phagocytes appeared in the damaged area RPE cells and fibrous tissue in choroid started to proliferate. Seven days after photocoagulation, damage area was covered by proliferative RPE. Choroid vessels were decreased in number and fibrosis was appeared in the stroma.

CONCLUSIONS

Photocoagulation causes edema and necrosis of RPE and various degrees destruction of Bruch's membrane and choroidallvessels. Subsequently, the damaged area is covered by proliferative RPE cells and fibrous tissue. Diseases of the RPE and choroid can be treated by laser at various degrees of energy.