Lasik Eye Surgery

Fourth-generation fluoroquinolone use in LASIK patients

by Daniel S. Durrie, M.D.

"We concluded that moxifloxacin in commercial Vigamox penetrates into the aqueous humor with four times daily dosing to therapeutic effective kill levels, where gatifloxacin in Zymar does not." James P. McCulley, M.D.

The ideal antibiotic for refractive surgery would be safe, effective, non-toxic, well tolerated, and well accepted as the standard in refractive surgery. Fourth-generation fluoroquinolones have all but possibly the last criterion.

New antibiotics are normally evaluated based on kill rates, penetration into the cornea and anterior chamber, and the sensitivity of certain bacteria to these antibiotics. However, no clinical studies for fourthgeneration fluoroquinolones were conducted on LASIK patients, so there were no data to assure me of the safety of the use of fourthgeneration fluoroquinolones in LASIK patients.

LASIK presents a unique risk because it creates a space for potential microorganism sequestration and proliferation deep within stroma. Additionally, there is the uncoupling of natural defense mechanisms with temporary denervation and alteration of tear film dynamics. Because the fourth-generation fluoroquinolones fit the profile of the ideal antibiotic, my colleagues and I wanted to determine whether they would be safe to use in LASIK patients. We also wanted to determine whether there was a difference between the two fourthgeneration fluoroquinolones: Vigamox and Zymar.

Our goal was to see if there was anything unusual with the healing profile compared to what had been seen previously in the clinical trial that used TobraDex (Alcon). I had used all three of the third-generation fluoroquinolones for the past three or four years and had never had an infection. All three of these fluoroquinolones were very well tolerated.

However, resistance to these fluoroquinolones was starting to develop. Between 1993 and 2001, the number of resistant strains increased, especially in endophthalmitis. (Figure 1) LASIK surgeons needed to consider moving to the fourth-generation fluoroquinolones. We needed an antibiotic that would be well tolerated by patients and that would provide the broadest spectrum of coverage.

Assessing safety

Our research center conducted a clinical trial designed to assess the overall safety of Vigamox and Zymar in humans undergoing LASIK. This prospective, randomized, doublemasked, single-center clinical trial included 60 eyes in 30 patients. One eye of each patient received Vigamox and the other received Zymar. Subjective and objective outcome measures were analyzed for comparisons.

Our study evaluated the following measures:

• Pupil size
• Visual acuity
• SPK
• Edema
• Glare
• Haze
• Halos
• Sharpness and clarity
• Overall vision

We found no significant differences between Vigamox and Zymar in outcome measures or patient responses. Both were found to be safe and well tolerated in the LASIK setting. We found no difference compared to third-generation fluoroquinolones, and we found no difference between Vigamox and Zymar.

This was great news for LASIK surgeons because they could now make the decision to use fourth-generation fluoroquinolones in LASIK patients. Since LASIK is an elective procedure you want patients to be comfortable. If one fluoroquinolone had been better tolerated than the other, it would have been an important consideration when choosing an antibiotic.

Other considerations

Although our study found no differences between Vigamox and Zymar, there are inherent differences. Moxifloxacin has a more natural pH of 6.8, compared to Zymar's pH of 6.0. The theory is that moxifloxacin may feel better when it is instilled in the eye, and it may penetrate better. (Figure 2) Additionally, Vigamox is self-preserved. It does not contain BAK, and BAK and other preservatives have been found to be toxic to epithelial cells.

Personally, I have made the decision to use Vigamox because I like not having an added preservative, and I like the pH closer to 7. I use Vigamox in my LASIK patients, and I've also started using it for PRK, LASEK, CK, and refractive lensectomy patients.

For LASIK patients, I use Vigamox 30 minutes prior to surgery, followed by Alphagan P (Allergan) and proparacaine, one drop before the prep. During surgery, I use tetracaine after inserting the speculum. I also use Vigamox immediately following surgery and in conjunction with a steroid four times a day for a week.

Daniel S. Durrie, M.D., is director of refractive surgery at Durrie Vision in Kansas City, and clinical associate professor of ophthalmology at the University of Kansas School of Medicine. Article posted on Copyright © 1997-2005 EyeWorld News Service. accessed from http://www.eyeworld.org/ewweeksupplementarticle.php?id=14 September 08, 2005.

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