I recommend that surgeons perform custom ablations in as many of their cases as possible. I treat every eye that falls within the Food and Drug Administration-approved guidelines for CustomVue (Visx) with a custom ablation. My enhancement rate over the past year has been very low, despite an unusual practice mix that includes many "problem" referrals. My patients" average age is 47. Sixteen percent have had previous corneal surgery and 5 percent have had more than one previous corneal surgery. More than 25 percent were high myopes or hyperopes (≥D or > +3 D); 3 percent had more than 3 D of preop cylinder; 14 percent needed Restasis therapy pre- or postop for severe dry eye; and 6 percent were on one or more glaucoma medications at the time of surgery. Despite this patient base, which would seem to predispose me to higher rates of retreatment, my enhancement rate with 100-percent surface ablation in the past year has been much lower than in the previous years.
My recommendations for achieving a low enhancement rate are: consistency in your surgical technique and environment; strict attention to detail, both in capturing wavefront data and in planning treatments; and considering surface ablation.
In my practice, I do all surface ablation, primarily epi-LASIK. I ensure that I have removed all basal epithelial cells, even those in the periphery. My surgical routine is consistent. Once I have removed the epithelium, either as an epi-LASIK flap or in a modified PRK procedure, I pass a very wet Merocel PVA sponge over the cornea, swing the laser arm into place, get into focus at the microscope, and begin the ablation within 10 to 15 seconds. If I am interrupted, I repeat the wet Merocel pass again, so that I know the moisture level on the cornea is always the same. I also try to keep the laser room at almost exactly the same temperature and humidity for every procedure.
Whether you perform LASIK or surface ablation, or use a wet or dry technique, it is critical to do exactly the same thing during every procedure so that your technique and your results are standardized.
Attention to Detail
Ironically, good wavefront outcomes depend not just on the quality of the equipment and the skill of the surgeon, but on the refractive technicians" skill and attention to detail. Because the wavefront map drives the ablation, it is absolutely essential to get good data on the front end to avoid retreatments on the back end.
I have a superb refractionist who also takes all the wavefront exams. That technician then sits down with me as I plan the treatments so I have the benefit of any observations she might have made during the exam that aren"t noted in the chart.
In larger practices, it may not be possible for one person do all of this. In any case, the technicians performing wavefront exams must be well-trained and experienced. They must know how to help a patient relax accommodation and be deft enough to quickly obtain well-focused, high-quality images. They have to understand enough about refractions and aberrometry to recognize unusual or poor quality results.
There"s a big safety factor in doing wavefront surgery. The wavefront map itself will not be confused or transposed, but someone must still enter the manifest refraction, corneal curvature, and other basic information. It"s still important to be accurate with the simple things. For this reason, my technician and I plan treatments together and always double check each other"s numbers.
I am a strong proponent of surface ablation and recommend that refractive surgeons consider a return to the surface, especially now that we have very good control of postoperative pain. In addition to the safety and tissue-preserving benefits of eliminating the lamellar flap, I think surface ablation also results in better visual outcomes, something recent research by the U.S. military supports.
Consider that patients start with a complex higher-order aberration map. As soon as you cut and lift a flap you have changed that wavefront pattern in a way that is impossible to predict in advance. When we try to correct fine detail, we want predictability to be as high as possible.
I perform epi-LASIK on everyone I possibly can, recognizing that our use of this new technique is still evolving. In patients with keratometry steeper than 46 D or who have more than 2 D of cylinder, I do a hybrid of PRK and LASEK, without any alcohol, until we have worked out the suction and oscillation/advancement settings for patients with steeper corneas and higher degrees of astigmatism.
Surface ablation, in my opinion, is one step closer to the ideal, but with consistency and rigorous attention to detail by both the surgeon and staff, I believe any practice can improve its wavefront results and reduce its enhancement rate.
Dr. McDonald is the medical director for the Southern Vision Institute and a clinical professor of ophthalmology at Tulane University, Health Sciences Center.