I began to explore PRK 9 years ago as one of the principal investigators involved in the FDA clinical trials. Because of PRK's simplicity, safety and accuracy, it held the most promise as a universally adopted refractive procedure for ophthalmic surgeons. Yet in recent years, most ophthalmologists have abandoned PRK in favor of LASIK.

I believe, however, that PRK should remain the procedure of choice for fulfilling the needs and goals of our patients. My experience with the procedure -- I've performed it more than 3,000 times -- illustrates why. Consider the following points, and the advice that follows on maximizing PRK outcomes.

When compared with older refractive procedures, such as keratophakia, keratomileusis, epikeratophakia and radial, hexagonal and astigmatic keratotomy, PRK involves a simpler refractive excimer laser technique to reshape the cornea. Minimal contact with the eye by the surgeon reduces surgery time to a minute or less.

Newer adaptive surgical techniques are more complex than PRK. For example, LASIK requires the surgeon to cut a corneal flap. Several companies make microkeratomes, and each requires some assembly and cleaning for proper maintenance. Technical support staff must take the time to play an important role in keeping microkeratomes clean, properly assembled and maintained. Surgeon training and techniques for LASIK are also much more complex, so the learning curve is higher than for PRK.

Intrastromal corneal ring insertion to correct myopia is more technically tedious than PRK, and the procedure is limited to a small segment of the population with refractive disorders. Phakic implant surgery requires considerably more surgeon skill than does PRK. All of these procedures involve factors that complicate refractive surgery. I don't think the visual end results compared with PRK results justify such complicated means.

As mentioned previously, I've performed more than 3,000 PRK procedures, and my complications have always been non-sight threatening and manageable. Furthermore, only 2% to 3% of my patients have needed a second PRK laser procedure. Complications from all other procedures have been much greater, necessitating higher enhancement or retreatment rates. Average retreatment rates reported for LASIK range from 10% to 30%, depending on the surgeon's skills or the microkeratome used.

Microkeratomes for LASIK vary, but essentially the mechanical devices available today require that high intraocular pressure be established by some means. The pressures needed are dangerous if maintained too long. Cases of blindness from acute vascular occlusion can and have occurred.

Total corneal thickness is another consideration critical to LASIK. To ensure safety, the surgeon must avoid cutting the cornea too thin. Each pre-op workup must include pachymetry. And because the laser ablation must be applied starting deeper in the cornea, potential harm could occur to the endothelium during treatment of high myopia.

Overall, reports on LASIK indicate a small but significant resulting visual acuity loss as well as a few cases of blindness. Late complications, such as flap loss or epithelial ingrowth, after LASIK can also create serious problems.

Post-PRK patients can experience central haze or central islands, but these complications can be prevented or resolved with increased central corneal hydration or retreatment, as I'll discuss shortly. The bottom line: PRK results in fewer complications than LASIK -- and they're more manageable.

For the past 4 years, I've monitored our PRK results using the outcomes analysis program designed at the Ottawa Eye Institute in Ontario, Canada. Monitoring spherical equivalent over time, intended vs. achieved results and other important factors is the only way to ensure a high level of accuracy.

This scrutinization of our outcomes, along with careful preoperative preparation, a well calibrated laser and attentive postoperative care (See "Ensuring Post-op Compliance," on page 52.), has helped us maintain our very favorable results. More than 70% of our PRK patients achieve at least 20/20 uncorrected visual acuity 2 weeks after surgery. Approximately 2% of our patients achieve 20/10 vision. The refractive error of these patients ranges from -1.00D to -22.60D of myopia and myopic astigmatism. I've performed PRK on -1.00D to -27.0D eyes as single-stage laser procedures.

None of the other refractive procedures available today have been able to maintain that kind of accuracy for such a wide range of refractive errors. In my practice, I've been able to achieve better visual outcomes with PRK than with LASIK by following these guidelines:

• Contact lens wear.
Patients should not wear lenses for a minimum of 2 weeks prior to the evaluation and prior to surgery. The surgeon should perform critical refractions the day of surgery and use that data as the primary basis for the PRK procedure. Perform topography the day of surgery to detect corneal dry spots or shifts in astigmatism. Cancel surgery if significant discrepancies exist between initial exams and those done the day of surgery.
• Dry eye.
Tear-film management is the most important factor other than steroid use in post PRK wound-healing care. Assess the ocular tear film for any signs of dry eye syndrome. Aggressively manage it before and after PRK with frequent use of low or non-preserved tears, punctal occlusion and nocturnal moisture retention goggles. To detect dry eye syndrome, we prefer to non-invasively measure tear break-up time with the TearScope Plus.
Since 1997, my results have indicated more rapid visual recovery, clarity and stability when ocular moisture levels are high. Prior to aggressive dry eye syndrome management in our refractive surgery patients, 60% of the PRK eyes achieved 20/20 or better visual acuity. But now, with aggressive dry eye control, 80% of the PRK patients achieve vision of 20/20 or better by 1 month
We presented study results in 1998 at the American Academy of Ophthalmology Scientific Video Exhibit in New Orleans, which illustrated that counseling PRK patients about the dangers of dry environments, improper blinking and medications that dry the ocular surface is crucial for reducing visual fluctuations and aberrations. Our findings also included:

• 53% of the PRK candidates with a mean age of 40 had dry eye syndrome
• 40% of the eyes, which showed stable tear film preoperatively, had inadequate tear stability post-PRK
• 55% to 75% of our PRK candidates were noted to have mild to moderate acne rosacea, a skin disorder associated with dry eye. These patients showed marked improvement in postoperative visual outcome when we inserted punctal plugs prior to surgery.
• 30% to 50% of PRK candidates who had worn contact lenses had incomplete blinking and or nocturnal lagophthalmos leading to evaporative dry eye syndrome. Moisture retention goggles at bedtime improved results.

Although technological advances in refractive surgery will allow for improved consistency and reduced complications, PRK is not dead. Refractive surgeons should strongly consider reviving PRK as their primary refractive procedure to avoid additional complications and achieve the highest visual outcomes, which is what patients truly desire.

As ophthalmic surgeons, we should get back to the basics of surgery: simplicity, safety and accuracy, which is best for all concerned. When performed properly, PRK affords the best visual results for the widest range of refractive disorders, whether the surgeon performs only a few refractive surgeries or many.

Typically, refractive surgery patients are active people between the ages of 30 and 40. Because of their active lifestyles, they tend to not be as compliant with postoperative recommendations as we'd like. For example, they're likely to prematurely stop using drops, which are critical to healing.

In my practice, clearly written instructions of drops and dosage schedules have improved patient compliance; however, many refractive patients require support and constant reassurance to avoid non-compliance, misunderstandings and litigation. And I've found that the pre- and post-op counseling is best done by the surgeon.

Our center receives about one phone call per week from distraught or nervous LASIK patients concerned about lost or abnormal flaps or poor postoperative vision. Most revealing about these callers is that most of them aren't under the care of the surgeon who performed the LASIK procedure, but are being followed by someone else, who is either unaware of or unable to manage adequate post-op care. The cornea is a unique tissue that requires careful medical monitoring during wound healing to avoid potential problems after PRK or LASIK.

Patients do more of what they're supposed to do during the post-op healing phase when direct surgeon contact is maintained, especially in the first 3 months after surgery. Such contact reinforces the importance of our recommendations, which include 48 hours of ocular rest away from work to reduce pain and anxiety and improve the rate of epithelial healing.

Dr. Norton is director of the Jerva Eye Laser Center in Syracuse, N.Y. She's also an adjunct professor at the University of Ottawa Eye Institute and was an FDA principal investigator for PRK from 1991 to 1996.