Studies on the blood-retinal barrier after cryoretinopexy with vitreous fluorophotometry.

The extent of damage to the blood-retinal barrier, induced by cryoapplication on the sclera, was measured in adult pigmented rabbits by using a vitreous fluorophotometer. In eight isolated cryopexies. the intensity of each was equalized by stopping freez.ing exactly when a white spot started to appear in the fundus. and the blood-retinal barrier damage was repaired 7-10 days after the operation. On the other hand, in the eyes treated with double cryoapplication refreezing being initiated just after the initial ice ball in the fundus disappeared, fluorescein concentration was reduced below the control value in 3-5 days but histopathological reparation of the retinal pigment epithelium was incomplete in these cases. The eyes treated with 20 scattered applications showed more profuse leaking of the fluorescein dye and required 35-42 days before the concentration of fluorescein was reduced below the control value; however, when the leaking ceased, the regenerated retinal pigment epithelium covered the Bruch's membrane. The above findings indicate that to prevent protraction of blood-retinal barrier damage associated with the retinal pigment epithelium, cryoretinopexy twice or more to the same area or extremely extensive cryoapplications at one time are prohibitive.