Transmission electron (TEM) and Light Microscopic (LM) analysis of hyperopic and myopic corrections induced by a photosensitizing dye and the argon laser in a rabbit model
Purpose: To study the histopathologic effects and possible collagen fiber alterations in rabbits previously shown to exhibit refractive change by treatment with a photoactivated chromophore and the argon laser while maintaining clear corneas. Methods: Two New Zealand white rabbits at least 4 months postoperative were selected for analysis. One rabbit had undergone 4D hyperopic refractive treatment which regressed, while the other maintained 2.3D of myopic refractive change. The rabbits were anesthetized, and corneas excised prior to euthanasia. The treated and untreated corneas of each rabbit were promptly bisected with a cryostat blade through the treatment zone, and half of each cornea immediately fixed in 2% glutaraldehyde for TEM and the other half in a formaldehyde/glutaraldehyde mixture for LM stains (H&E, Masson-trichrome, colloidal iron). Results: TEM on treated and untreated eyes showed no obvious differences when examined by a masked corneal pathologist. Masked LM analysis disclosed only a slightly thicker acellular zone beneath the epithelium with a very subtle increase in collagen irregularity in the myopic treated cornea. TEM findings from deepithelialized, dye-treated control corneas are in progress. Conclusions: 1. TEM and LM analysis of refractive corrections induced by a photosensitizing dye and the argon laser did not reveal evidence of corneal denaturation or obvious differences to explain the refractive changes. 2. Although not identified on these histopathologic specimens, collagen crosslinking is speculated to be the responsible keratorefractive mechanism; further studies on this possible mechanism are in progress.
Rose, JG; Fowler, WC; Proia, AD; Iacobucci, MJ; Vietorisz, EC; Straub, KD; Ross, JR; Barletta, JP; Plunkett, MA
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