LASEK (PRK) Haze and MMC

 

Haze

Surface ablation such as PRK and LASEK are associated with risk of visually significant haze formation. Enhancement of previous LASIK with PRK (PRK on top of a LASIK flap) carries an increased risk of haze. This has led many surgeons to incorporate prophylactic use of Mitomycin C (MMC) during surface ablation to prevent haze.

MMC was originally used as a systemic chemotherapeutic agent. It is now commonly used topically in several fields of ophthalmic surgery.

MMC has potential long-term consequences on the ocular surface and intraocular structures, because it blocks DNA-RNA replication and protein synthesis.

Potential side effects of MMC following corneal application include long-term loss of corneal keratocytes, biomechanical instability, iatrogenic ectasia, corneal melting, scleral melting, corneal edema, decrease of endothelial cells leading to vision loss and need for corneal transplant, dry eye, and long-term presence in aqueous humor with unknown consequences.

“I encourage you to use the same technology to look at patients who are having mitomycin prophylactic treatment for prevention of haze; probably 90 percent of refractive surgeons are using mitomycin without any long-term data as to the effect. It is clear the reason mitomycin works so well is that it eliminates 100 percent of all corneal cells in about 20 percent of the anterior cornea. Similar to your concerns, I think they are even magnified in those patients because data after six months in the animal model shows that none of those cells have returned. What happens in the future since we have limited experience with these types of patients? In 10 to 20 years, are we going to see anterior corneal necrosis or other problems? Your type of study could give us more data about that in humans.”
– Dr. Steven E. Wilson

Source

Source: Erie JC, McLaren JW, Hodge DO, Bourne WM. Long-term corneal keratoctye deficits after photorefractive keratectomy and laser in situ keratomileusis. Trans Am Ophthalmol Soc. 2005;103:56-66; discussion 67-8. Accessed 4/1/2013 at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1447559/