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W.W. Dawson, D.E. Brooks, S. Vanech; Structural Changes in the Choroid and Retina of the Living Eye After Argon Laser Exposures . Invest. Ophthalmol. Vis. Sci. 2003;44(13):3058.
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Purpose: Vascular structural response to disease, aging or trauma is poorly understood in regions proximal to the retina and pigment epithelium unless there is fluorescein leakage. The living pigment epithelium transmits some infrared. We have identified a safe IR illumination and used it to search for measurable changes in the choroid of the living monkey eye after peripapillary laser lesions. Methods: To produce total eye immobility an "anesthetized paralysis" support procedure was developed for two normal adult rhesus monkeys. To test for damage/change by the IR illumination, 2 mm diameter areas of the choroidal circulatory tree (CCT) were sequentially exposed to increasing (850 nm) energy densities up to 520 J/cm2 in 10 min. Later, four Argon laser treatments were delivered (0.5 - 0.7 watts, 0.1 sec., 50 um spots) to two or four 1.5 mm diameter peripapillary areas. After laser treatment, reflected IR (850 nm) flash images* were recorded (2, 14, 30 days) on a silicon chip and analyzed off-line for CCT changes around the lesion area. Fluorescein angiogram records followed 0.5 cc Na fluorescein injected into the saphenous vein. Results: No change in local CCT element diameter, visualized by IR, (typical "before" mean diameter = 113um; SD = 9.5 "after" mean = 103um, SD=9) was detected (N= 150). There was no fluorescein leakage. The Argon laser treatment area visible-light images showed "cotton ball" overlapping edema at +2 days. The edema cleared and IR images showed (14 and 30 days) one treatment site with new "knotted" CCT elements and one site of distortion of and "rerouting" of CCT elements. Very early high- resolution angiography showed small new membrane-like objects in the depigmented areas and obliteration of one capillary bed in the retinal circulatory tree. There was no evidence of dye leakage. Conclusions: Infrared reflectance images show quantitative details of normal and new choroidal elements. Argon laser exposure can obliterate and remodel microvascular portions of the retinal and choroidal systems.
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