PRK vs. Contact Lenses:
The Risk is Relative

GUEST EDITORIAL

BY KARLA ZADNIK, O.D. Ph.D. & DONALD O. MUTTI, O.D., Ph.D.
JAN. 1996

As optometrists, we watch the FDA's approval of photorefractive keratectomy from an interesting vantage point. We watch the process as members of a profession that experienced unbridled enthusiasm at the prospect and then the reality of a new method for correcting refractive error that made patients forget they were ever myopes: extended wear contact lenses. Then we watched as the incidence of contact lens-related corneal ulceration was quantified and as extended wear was identified as the primary risk factor in contact lens-related bacterial keratitis. We acknowledged that the risk that an individual patient -- even one in extended wear -- would develop a corneal ulcer was low (20.9 in 10,000 annually). And we watched as our patients occasionally experienced these devastating infections and emerged with moderate to severe acuity loss.

Now, we watch again, but this time the FDA and the ophthalmic laser industry have made the judgement that a much higher rate of loss of best corrected visual acuity is acceptable. If the risk that a patient in extended wear will develop a corneal ulcer is 21 in 10,000, this translates to 6,500 of the approximately 3.2 million patients in extended wear. Data from FDA-supervised laser refractive surgery trials indicate that 1 percent to 3 percent of patients undergoing PRK lose two or more Snellen lines of best corrected acuity. If as few as 5 percent of the 60 million U.S. myopes undergo PRK, we can expect significant acuity loss (as defined above by the FDA) in 30,000 to 90,000 patients after PRK.

With extended wear, 21 patients in 10,000 run the risk of losing best corrected vision. With PRK, that same risk is up to 100 to 300 patients in 10,000. As clinicians, we lost our initial enthusiasm for extended wear contact lenses, and rightly so, because of an increase in the risk of sight-threatening infection by a factor of 5 to 15 times compared to daily wear. Of course, corneal infections are certainly more unpredictable and potentially more devastating than vision losses after PRK. However, hopefully our experience with extended wear and our responsibility to preserve our patients' best corrected acuity will temper our enthusiasm over PRK. We wonder if a patient's perspective will change after being informed of the increase in risk of 5 to 15 times for vision loss after PRK compared to extended wear. Are patients' decisions being driven by true informed consent and regard for their welfare or as suggested by the Wall Street Journal, "an increasingly common medical reality: It is often entrepreneurial zeal that drives new technology," and possibly new referrals.

No one would prescribe extended wear contact lenses for overnight wear to a patient without informing him or her of the increased risk of infection. By a conservative estimate, this risk may be increased by a factor of five times compared to daily wear contact lenses. Do patients deserve to know that they could face a 25 to 75 times increased risk of losing two lines of best corrected acuity after PRK compared to daily wear contact lenses? We believe they do. CLS

References are available upon written request to Contact Lens Spectrum; to receive references via fax, call 1-800-239-4684 and enter Document #10. (Be sure to have a fax number ready.)

Drs. Zadnik and Mutti are Senior Optometrists engaged in patient-based, optometric research at the UC-Berkeley School of Optometry.