Laser-induced experimental vascular occlusion using liposome-encapsulated ADP.

The therapeutic occlusion of retinal vessels is often helpful in treating various pathological conditions. We compared the combined effects of argon laser photocoagulation and adenosine diphosphate (ADP) released from temperature-sensitive liposomes with argon laser photocoagulation alone on occlusion of retinal vessels in pigmented rats. In Group A, 8 eyes were treated with liposome-encapsulated ADP and laser photocoagulation. In Group B, 8 eyes were treated with laser photocoagulation alone. The laser parameters (power, spot size, exposure time) were maintained at the same levels for both groups. The laser was focused on the retinal vessels at the optic nerve head. The treated retinal vessels were observed at time zero, day 1, day 4, and weekly for a period of 3 months. At time zero, 6 of 8 eyes were totally occluded in Group A, with best results obtained at 80 mW. Only 1 of 8 eyes in Group B achieved total occlusion. After 3 months, 4 of 8 eyes in Group A remained totally occluded; no eyes in Group B were occluded. Complete and permanent occlusion of retinal vessels can be achieved by using ADP and laser photocoagulation of lower power density than traditional laser photocoagulation alone.