Insights on microbial keratitis risk post-LVC

Portland, OR-Results of a retrospective analysis of more than 432,000 eyes that underwent LASIK or photorefractive keratectomy (PRK) as a primary procedure show a very low rate of postoperative microbial keratitis, said Julie Schallhorn, MD, MS.

“Microbial keratitis is a potentially devastating complication of laser vision refractive surgery,” said Dr. Schallhorn, cornea fellow, Casey Eye Institute, Oregon Health and Science University, Portland.

The eyes included in the study were operated on between January 2008 and December 2012 at the 25 Optical Express centers in the United Kingdom. All of the patients received standard antibiotic prophylaxis that consisted of four times daily topical fluoroquinolone (ofloxacin), which was continued for 1 week after LASIK and until complete re-epithelialization and bandage contact lens removal following PRK.

Suspected microbial keratitis based on slit lamp appearance was diagnosed in 57 eyes (0.013%) of 54 patients. About three-fourths of the eyes with microbial keratitis had a final best-corrected visual acuity (BCVA) of 20/20 or better, and BCVA was 20/40 or better in about 88%.

Analyses to determine variables associated with development of microbial keratitis showed the risk of infection was significantly higher among hyperopes compared with myopes, with PRK compared with LASIK, and when using a mechanical keratome for LASIK flap creation versus a femtosecond laser.

Hyperopes undergoing PRK had a 6-fold greater risk of suspected microbial keratitis compared to a myope undergoing LASIK with femtosecond laser flap creation.

All eyes with suspected microbial keratitis were cultured, although not all culture data could be obtained because of United Kingdom privacy laws. Among 12 culture-positive cases that could be reviewed, methicillin-resistant Staphylococcus aureus was the most common isolate (33%). There were two cases each of methicillin-susceptible S. aureus and Mycobacterium chelonae infection and a fungal pathogen was isolated in four eyes.

“The results of our study representing a large refractive surgery population are consistent with previous reports and reassuring in showing that the risk appears to be low,” Dr. Schallhorn explained. “In addition, we believe this is the first study to provide information comparing the rate of microbial keratitis after LASIK versus PRK and to analyze potential risk factors.

“This information may be useful when counseling potential refractive surgery candidates,” she said.

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