Hyo-Myung Kim

Concentrations of mitomycin C in rabbit corneal tissue and aqueous humor after topical administration

Purpose: To study the aqueous and corneal pharmacokinetics of mitomycin C (MMC) after single topical administration to the central cornea and to evaluate the effects of different concentrations and different application times on the aqueous concentration of MMC. Methods: Mechanical epithelium debridement of the central 7.5 mm of the cornea was performed in New Zealand white rabbits, and a sponge soaked in 0.02% MMC solution was placed on the denuded corneal stroma for 2 minutes. Aqueous fluid and central corneal tissues samples were taken at 0.5, 1, 2, and 3 hours thereafter. MMC concentration of the samples was analyzed by high-performance liquid chromatography and evaluated at different exposure times (range: 15-120 seconds) and concentrations of applied MMC (range: 0.005%-0.04%). Results: Peak corneal concentration was 3.728 ± 2.547 μg/g at 30 minutes after topical administration. Maximum aqueous concentration was 0.380 ± 0.038 μg/mL at 1 hour after topical application. The aqueous concentration of MMC increased in a dose-dependent manner with increasing exposure time and application concentration. Aqueous MMC concentration increased at a higher rate with change of applied concentration than with exposure time. Conclusion: Good penetration of MMC through central bare cornea may be noxious to endothelial cells. Reducing concentration or decreasing exposure time seems a good modality to reduce potential MMC toxicity.

Effects of topical tranilast on corneal haze after photorefractive keratectomy

Purpose: To determine whether topical tranilast might reduce corneal haze through suppression of transforming growth factor (TGF)‐β1 synthesis in keratocyte after photorefractive keratectomy. Setting: Department of Ophthalmology, Korea University College of Medicine, Seoul, Republic of Korea. Methods: Photorefractive keratectomy was performed on 48 eyes of 28 white rabbits and 24 eyes in a tranilast group were treated with tranilast solution, and the other 24 eyes in control group were treated with saline after laser ablation. The grades of corneal haze at 1, 2, 4, and 8 weeks after surgery were evaluated in 10 eyes of each group for comparison. Immunohistochemistry was performed on 10 eyes of each group, and Western blot analysis was done on 4 eyes of each group for studying TGF‐β1 expression at postoperative day 7. Results: There was no statistically significant difference in corneal haze between 2 groups from week 1 to week 4 after surgery, but a significant difference was found at week 8 after photorefractive keratectomy (P = .02). The mean number of keratocytes that expressed TGF‐β1 in the tranilast group was 58.3 (±17.2), which showed significant difference, compared with that of the control group, 104.5 (±23.0) (P<.01). Western blot analysis also revealed that the amount of TGF‐β1 in tranilast group was slightly less than the control group. Conclusions: Topical tranilast could reduce corneal haze by suppressing TGF‐β1 expression in keratocytes after photorefractive keratectomy.