Cryotherapy causes extensive breakdown of the blood-retinal barrier. A comparison with argon laser photocoagulation

Using computerized vitreous fluorophotometry (VFP) in pigmented rabbits, we examined two modalities frequently used in retinal reattachment surgery, cryotherapy and argon laser photocoagulation, for their effect on the blood-retinal barrier. The VFP readings were taken 2 mm posterior to the lens one hour after intravenous injection of 14 mg/kg of fluorescein sodium. After baseline fluorophotometry readings, rabbits were treated with confluent cryotherapy over the inferior 180 degrees in one eye and with confluent laser over an equivalent area of retina in the other eye. The VFP readings were taken 2, 4, 6, and 15 days after treatment. By day 6, the VFP reading had risen from a pretreatment value of 6.4 +/- 0.4 ng/mL to 41.8 +/- 7.9 ng/mL in the cryotherapy-treated eyes as opposed to 15.5 +/- 3.1 ng/mL in the laser-treated eyes. By day 15, the readings were almost back to baseline, and there was no significant difference between the two treatment groups. These data suggest that there is a significant breakdown of the blood-retinal barrier with both modalities, but that it is considerably more severe with cryotherapy.