Mitomyucin C augmented trabeculectomy for post-keratoplasty glaucoma
We read with interest the article by Ishioka and coworkers, in which the authors studied the effect of trabeculectomy with and without mitomycin C in post-keratoplasty glaucoma. The authors conclude that trabeculectomy with mitomycin C showed better results for glaucoma following penetrating keratoplasty. We congratulate the authors for an excellent study. We have published similar observations on trabeculectomy with mitomycin C for post- keratoplasty in 1997. The salient features of this study are worth mentioning as literature on mitomycin C augmented trabeculectomy in post-keratoplasty glaucoma is limited.
In the study by Sharma and coworkers trabeculectomy with mitomycin C (0.2 mg/ml for 2.5 minutes) was performed in 16 eyes of 16 patients for medically uncontrolled glaucoma following penetrating keratoplasty. The mean pre-trabeculectomy IOP with maximal medical therapy was 34.6 mm Hg (range 24 to 45 mm Hg). The mean IOP following trabeculectomy with mitomycin C was 14.2 mm Hg (range 8 to 36 mm Hg) by the end of follow-up of 14.2 months (range 8 to 32 months). Fourteen eyes (87.5%) had complete success, one eye (6.25%) had qualified success and one eye (6.25%) had failure. All the patients had either better than or maintained pre-operative visual acuity. None of the patients developed postoperative complications such as shallow anterior chamber, epithelial defect of hypotony. Earlier Khatana et al presented in ARVO showed reduction of IOP following trabeculectomy with mitomycin C in most of their patients. In addition to the efficacy, safety of trabeculectomy with mitomycin C for post-keratoplasty glaucoma reported is a major concern. Mitomycin C as an adjunct to trabeculectomy has been safe for corneal endothelium. In an experimental study on rabbit eyes, the peak aqueous level of mitomycin C after topical application (0.4 mg/ml) was 0.03 ± 0.02 mg/ml. This aqueous concentration was considered above the therapeutic level for inhibition of subconjunctival fibroblast proliferation but below the level known to cause endothelial toxicity. In studies by Sharma et al and Khatana et al, mitomycin augmented trabeculectomy caused no damage to the clear penetrating grafts.
Our observations were in accordance with those by Ishioka, et al that in medically uncontrolled glaucoma following penetrating keratoplasty, trabeculectomy with mitomycin C may be considered unless there is a contraindication to the use of adjuvant. However, the authors may have inadvertently missed our earlier report.
1. Sharma A, Kumar S, Ram J, et al. Trabeculectomy with mitomycin C for post-keratoplasty glaucoma: A preliminary study. Ophthal Surg Lasers 1997;28:891-5.
2. Khatana AK, Olivier M, Shin DH, et al. Safety and efficacy of adjunctive mitomycin-C in filtration surgery in eyes with corneal grafts. Invest Ophthalmol Vis Sci 1993;34(Suppl):1099.
3. Anglade E and Dreyer E. The effect of mitomycin-C and 5-fluorouracil on corneal endothelium in trabeculectomy surgery. Invest Ophthalmol Vis Sci 1993;34(Suppl):730A.
4. Eezuduemboi RD, Sarraf D, Wilson MR, et al. Aqueous and vitreous concentration of mitomycin following topical administration. Invest Ophthalmol Vis Sci 1993;34(Suppl):726.