Specialty News and Views: Cornea/External Disease - April 2006
The Specialty News and Views section represents the opinions of the contributing authors and does not imply endorsement by the American Academy of Ophthalmology. The Cornea/External Disease team members are: Donald Stone, MD; Surendra Basti, MD; Thomas Harvey, MD; Saiyid Hasan MD; and Ivan Schwab, MD.
Mitomycin C in the Aqueous Following Corneal Application
A recent animal study showed that mitomycin C (MMC) was consistently detected in the aqueous following a 2 minute application of the solution to corneas with and without an intact epithelium.1 The primary intent of Torres and colleagues was to study eyes where MMC had been applied following photorefractive keratectomy (PRK).
After applying MMC 0.02% for 2 minutes to 2 groups of hen eyes?those that had PRK and those with intact corneal epithelia?the researchers sampled aqueous humor at different time points (10, 30, 60, 360, and 720 minutes). High performance liquid chromatography detected significant quantities of MMC in both groups up to 60 minutes after application. Eyes with PRK had higher levels and could be seen up to 360 minutes later. No drug was undetectable in any eye at 12 hours.
While the presence of MMC in the aqueous following application during glaucoma filtration procedures has been documented, there has been a paucity of literature regarding aqueous levels in eyes following application to the ocular surface. This study unequivocally demonstrates that MMC remains in the aqueous in all eyes following topical application.
MMC is a potent wound healing modulator used by glaucoma, refractive, and corneal surgeons. Advocates of its use have extrapolated success of this agent in decreasing failure of filtration blebs to areas of refractive and corneal surgery. Its efficacy has led to a progressive widening of its applications in recent years. However, this antineoplastic agent can have potential long-term consequences on intraocular structures, because it blocks DNA-RNA replication and protein synthesis.
Previous studies involving topical application of MMC 0.04% at 3-4 times a day have demonstrated ocular surface toxicity on impression cytology and suggested a radiomimetic effect for at least 8 months following therapy.2,3 It is also believed that the toxic effects of MMC can be delayed and cumulative. In light of these facts, it is evident that more investigations of the pharmacokinetic and cytotoxic effects of MMC are needed, particularly with regard to aqueous levels. In the interim, it may be prudent to limit the use of this agent as well as to provide informed consent about the lack of knowledge regarding the long-term effects of MMC.
1. Torres RM, Merayo-Lloves J, Daya SM, et al. Presence of Mitomycin-C in the Anterior Chamber After Photorefractive Keratectomy. J Cataract Refract Surg. 2006;32: 67-71.
2. McKelvie PA, Daniell M. Impression cytology following mitomycin C therapy for ocular surface squamous neoplasia. Br J Ophthalmol. 2001;85:1115-1119.
3. Dogru M, Erturk H, Shimazaki J, Tsubota K, Gul M. Tear function and ocular surface changes with topical mitomycin (MMC) treatment for primary corneal intraepithelial neoplasia. Cornea. 2003;22:622-639.