Abstract
Abstract: :
Purpose: To analyze the choroidal and retinal cellular events following laser photocoagulation of the mouse eye. Methods: Wild type C57BL mice, six to eight weeks old underwent a standard photocoagulation protocol. After pupil dilatation and ketamine anesthesia, krypton laser (50um spot size, 0.05'', 400mW) fundal lesions were created. Thirty-three mice (66 eyes) received one single lesion located one to two disc diameters nasal to the optic nerve in both eyes. One to three mice were sacrificed every day during the first week after photocoagulation and every 3 to 4 days thereafter during the next three weeks. At random, one eye of each mouse was snap frozen, cryopreserved in OCT and processed for immunohistochemical analysis of GFAP, Lectin and von-Willebrand factor receptors. TUNEL reaction was also carried out along with DAPI staining for the amplification of nuclear material. The second eye was preserved in 4% PAF and processed for conventional histology or used for flat mount preparations. Results: Little to negligible inflammatory cellular infiltrates were observed during the entire period of follow up. The TUNEL reaction demonstrated the presence of positive cells within the lesion and its immediate vicinity 24 to 48 hours after treatment. These were mostly located within the retinal nuclear and ganglion cell layers with a few positive cells also observed within the choroid. A burst of GFAP expression (Muller's and glial cells) was detected 48 to 72 hours after treatment, persisting during the entire follow up period. Extension of the GFAP positive staining was observed within the lased choroidal space. DAPI, Lectin and vW stainings demonstrated that reorganization of the retinal cellular layers and vessels is taking place very rapidly. 12 to16 days post laser, organized well-formed blood vessels lectin and vW positive are observed deep within the lesion. Careful analysis of the cellular components in the vicinity of these vessels shows unequivocally that these are "original" retinal vessels accompanying the reorganizing retinal cell layers which have invaginated within the "choroidal void" created by the laser spot. Conclusion: Invagination of the retinal cells and vessels occurs as part of the healing process without any hard evidence for chorio-retinal neovascularization taking place during the first month following Krypton laser photocoagulation.
Keywords: 346 choroid: neovascularization