Collagen Shields
A discussion of the use of collagen shields in conjunction with anti-infectives.
BY RANDALL OLSON, M.D.

Collagen shields are an ophthalmic contact lens, made up of animal collagen. These shields slowly dissolve on the surface of the eye due to naturally occurring enzymes in tears, allowing for effective delivery of the presoaked medication.

Svyatoslav Fyodorov, M.D., the pioneer of the research behind collagen shields, was able to shape collagen in the form of a contact lens to then be placed on the surface of the eye. From these early stages, surgeons have been soaking collagen shields with a variety of drugs for prophylactic treatment in advance of, and following, cataract and refractive surgery.

This drug delivery system has been making a comeback. Recent studies have shown that collagen shields, when presoaked with fourth-generation fluoroquinolones — Zymar (gatifloxacin ophthalmic solution, Allergan) or Vigamox (moxifloxacin, Alcon Labs, Inc.) — have been shown to enhance antibiotic penetration into the eye, as well as potentially mechanically reinforce the wound site, obviate wound leakage and reduce the incidence of endophthalmitis.

Similar to applying a band-aid with a healing agent on a wound, collagen shields act in the same manner when used in conjunction with anti-infectives. The shields act to keep the wound reinforced, as well as disinfect and promote the healing process.

Wound Leakage

As a part of reinforcing the wound, collagen shields may inhibit wound leakage. In a recent study of endophthalmitis, we found that antibiotic soaked collagen shields in a multivariate regression analysis decreased the risk of endophthalmitis about 3-fold, which was independent of all other factors associated with endophthalmitis.1Therefore, we surmise that there are mechanical factors, as well as antibiosis, that are operative to explain these results.

   Introducing microorganisms into the eye is always a top concern of surgeons performing ocular surgery. This occurrence could result in postoperative endophthalmitis. With collagen shields properly in place, they act as an effective barrier to wound integrity and a partial barrier to gross contamination of the anterior chamber should there be a micro-leak of the wound. Deterring bacteria from entering the wound plus powerful antibiosis should decrease the endophthalmitis risk.

Study Results

Several studies my colleagues and I have conducted, and are in the process of conducting, appear to illustrate the significance of collagen shields used in conjunction with gatifloxacin. The first was presented at ASCRS, where we evaluated the penetration of gatifloxacin and moxifloxacin into the anterior chamber using collagen shields presoaked in both anti-infectives. One of our findings showed the concentration of gatifloxacin in the aqueous humor overall was higher than moxifloxacin. The difference was statistically significant at the 6-hour sample. Furthermore, the concentrations were over 2 mg/mL for gatifloxacin, and still high at
6 hours. Our results suggest that collagen shields can be effective as a drug-delivery system for the fourth-
generation fluoroquinolones with a longer effect for gatifloxacin.

Following the results of this study, my colleagues and I thought it beneficial to repeat the study, though this time with commercial preparations — Tequin (Zymar and Vigamox). The Tequin was used at half-strength (acidic) to equal Vigamox (neutral), maintaining consistency with both products at 0.5%. Our results remained consistent with the first study, showing much higher levels of both drugs in the eye than that achieved with topical instillation. Consistent with the first study, we found again that there was statistically more gatifloxacin than moxifloxacin in the eye at 6 hours. In talking to our infectious disease colleagues they have found that moxifloxacin is more likely to be protein bound, and higher systemic levels are achieved with gatifloxacin. We surmise that the same thing is happening here with moxifloxacin binding to the collagen in the shield and not being released for corneal and intraocular absorption.

The results of these studies drive home three main points:

► Collagen shields may be important in preventing endophthalmitis.

► Collagen shields promote excellent intraocular levels of antibiotics, especially gatifloxacin.

► Beyond antibiosis, collagen shields may have a mechanical protective effect in relation to wound integrity.

Some surgeons are already soaking shields in gatifloxacin and moxifloxacin, which makes sense. With our studies successfully completed we should have even better evidence either supporting or refuting this approach; however, we know enough now to suspect the results will be supportive.

In the age-old battle with microorganisms any successful tool must aggressively be pursued especially in our quest to decrease the incidence of postoperative endophthalmitis. OM

Reference

1. Heatley CJ, Spalton DJ, Kumar A, Jose A, Boyce J, Bender LE. Cohort study of 27 cases of endophthalmitis at a single institution. JCRS. 2005;31:735-741

Randall Olson, M.D., is the John A. Moran Presidential Professor and Department Chair of the Department of Ophthalmology and Visual Sciences at the John A. Moran Eye Center at the University of Utah School of Medicine. Dr. Olson is a consultant for Allergan. He can be reached by e-mail at randall.olson@hsc.utah.edu.