ABSTRACT
Phototherapeutic keratectomy(PTK)has been employed as a surgical tool to treat corneal disease for about 20 years.PTK made it possible to remove superficial corneal opacities and thereby restore vision by splitting molecules of biological tissue with 193 nm ultraviolet light.Recently,the development of the excimer laser technique is more rapid.It has principally focused on refractive surgery but has also benefited PTK.Anterior corneal pathology,such as elevated lesions,stromal opacities,corneal scars,corneal dystrophies and corneal degenerations etc,can be visually devastating.Over the past decade,there was a shift in the treatment of these conditions from corneal transplantation to PTK for visual restoration.PTK is a powerful tool for the management of anterior corneal pathology.In a properly selected and well-counseled patient,PTK can significantly improve vision and quality of life.This article reviews the recent literature of techniques for performing and refining PTK and also of various pathologic conditions that can be treated with PTK.
ABSTRACT
Background Intracameral or intracorneal administration of amphotericin B (AMB) can achieve significant therapeutic efficacy in the treatment of recalcitrant fungal keratitis in cases that do not respond to conventional antifungal therapy. However, the ocular pharmacokinetics of the two routes of administration is unclear.Objective The goal of this study was to investigate the level of amphotericin B in cornea and aqueous humor of rabbits after administration of AMB via three different routes. Methods Forty-five healthy domestic rabbits were randomly divided into three groups. 1% amphotericin B of 10 μg was intrastromally or intracamerally injected into 15 rabbits, respectively,in group A and group B. Topical 0. 25% amphotericin B was topically administered to the eyes with corneal epithelial debridement (group C). Experimental animals were sacrificed and the corneas and aqueous humor samples were obtained for the detection of levels of amphotericin B at 30 minutes,6 hours, 1 day,3 and 7 days by high-performance liquid chromatography (HPLC). Results Calibration curves were linear over the range of 0. 10-100. 00 mg/L. The concentration of 0. 10 mg/L was the lowest quantifiable limit. The recovery of amphotericin B ranged from 89. 1% -95.7% from aqueous humor samples and 81.4% -83.6% from the cornea samples. After a single injection,effective drug levels were achieved and maintained for 7 days in cornea in group A, exceeding the minimum inhibitory concentration at which 90% of isolates are inhibited (MIC90) for a wide spectrum of fungi and molds with significant differences in comparison with group B and group C ( P＜0. 05 ). Effective drug levels were achieved in the aqueous humor in group B at 30 minutes after a single injection, but drug levels decreased dramatically within 6 hours. The evident differences were found between group B and group A or group C (P＜ 0.05). A considerable amount of amphotericin B was detected in the cornea and aqueous humor in group C within 1 day.Conclusion Effective high drug levels can be reached in rabbit cornea and aqueous humor after intrastromal and intracameral injection, respectively. Penetration of topical amphotericin B was greatly elevated after epithelial debridement.