HISTOLOGICAL-EVALUATION OF PHTHALOCYANINE MEDIATED PHOTODYNAMIC OCCLUSION OF CORNEAL NEOVASCULARIZATION ENHANCED BY HYPERBARIC OXYGENATION

PURPOSE: We evaluated the effective irradiation parameters for photody namic thrombosis of experimental corneal neovascularization enhanced b y simultaneous hyperbaric oxygenation. METHODS: Neovascularization was provoked in both eyes of each of 35 albino rabbit corneas using the i ntracorneal suture technique. The lasered animals were divided in 3 gr oups. Group 1 (10 rabbits) was treated under hyperbaric conditions (28 atm for 25 min.); group 2 (5 rabbits) was treated breathing pure oxyg en delivered by a face mask; group 3 (10 rabbits) was treated breathin g room air. The fourth group (10 rabbits) was used for control. Animal s were anaesthetized, and irradiation of new corneal vessels was carri ed out 30 minutes after the injection of 5 mg/kg chloroaluminum sulfon ated phthalocyanine. A 670 nm diode laser with a power 4 mW and a spot diameter 350 mm was used. Exposure times necessary for vascular occlu sion were registered. Histological examination was carried out at the end of the follow-up time. RESULTS: Exposure times were significantly lower in groups 1 and 2 as compared to group 3 (1.75 +/- 0.15 min., 3. 1 +/- 0.4 min., and 4.75 +/- 0.15 min. respectively). Total light dose averaged 490 J/cm,(2) 870 J/cm,(2) and 1330 J/cm,(2) respectively. Hi stological examination revealed thrombus formation in the targeted ves sels of all three investigated groups. CONCLUSION: Combination of PDT with hyperbaric oxygenation results in an acceleration of the photodyn amic process and provides for a possibility of significant reduction o f photodynamic dose.