Therapeutic Wavefront

A broad spectrum of patients may benefit from therapeutic applications of customized corneal correction, including those with refractive errors after previous RK, automated lamellar keratoplasty, or penetrating keratoplasty; individuals whose LASIK procedures failed, involving those who have had multiple enhancements; and people who suffered traumatic injury after an uneventful surgery.

It is difficult to generalize about such a diverse group of patients, but, in our experience, approximately two-thirds of these complicated retreatment cases can benefit from customized ablations. However, identifying which two-thirds, as well as finding a solution for the remaining one-third, continues to challenge refractive surgeons. Fortunately, although Customcornea surgery with the Ladarvision system (Alcon Laboratories, Inc., Fort Worth, TX) cannot help every therapeutic case, we find that it very rarely worsens the problem. Typically, a poor outcome primarily happens due to improper patient selection criteria.

PATIENT SELECTION
Before considering performing a wavefront-guided therapeutic treatment, it is important to rule out potential sources of the visual symptoms or reduction in best-corrected vision that are not related to higher-order aberrations and will not be affected by a customized correction.

The examination should include a refraction and an attempted correction with glasses. The physician should evaluate the eye's corneal topography and ocular surface, including corneal staining, to rule out dry eye-related problems, ocular surface disease, or other pathology. An over-refraction with a hard gas permeable contact lens can help distinguish between corneal surface irregularities and opaque transmission defects. Finally, the surgeon should consider whether pupil size is contributing to the patient's symptoms and whether Alphagan (Allergan Inc., Irvine, CA) will provide any relief. It is surprising how often other conditions can cause or contribute to a patient's complaints.

SURGICAL TIPS
Several factors contribute to the success of a therapeutic ablation. The eye should not be excessively dry during wavefront capture. Additionally, it is essential to lift the previous LASIK flap, if possible. Careful relifting, rather than recutting, is preferred because it reduces the likelihood of induced astigmatism. When recutting is necessary, creating the new flap with the Intralase femtosecond laser (Intralase Corp., Irvine, CA) seems not to introduce the trefoil that a microkeratome does.

Although formal studies for the FDA approval of Customcornea for retreatments are ongoing, sharing anecdotal information from complicated cases helps all of us better understand the results we can expect from customized therapeutic ablations. Some of our recent therapeutic cases indicate what this technology can accomplish.

DR. SLADE: MIXED ASTIGMATISM My colleagues and I treated a 37-year-old white male with mixed astigmatism. Following conventional LASIK, the patient had 2.00D of against-the-rule cylinder. Nevertheless, his visual symptoms of glare and halos were significantly worse than would be expected from his postoperative refraction. Six months after undergoing therapeutic Customcornea surgery, he had gained two lines of BSCVA, and his photopic and mesopic contrast sensitivity had improved significantly. Furthermore, we were able to reduce the amount of his total higher-order aberrations by 32%, with spherical aberrations being the most notably affected. The patient is very happy with his surgical results.

In general, I would say we are able to correct coma, spherical aberration, secondary astigmatism, and tetrafoil quite well. Trefoil has proven more difficult to address, but, fortunately, it also seems to cause less visual distortion than some of the other aberrations.

DR. SOLOMON: SYMPTOM RESOLUTION IN AN EMMETROPE
A 35-year-old white male underwent a conventional procedure with the Visx Star (Visx Inc., Santa Clara, CA) laser in February 2002 for the correction of fairly typical myopic astigmatism. Postoperatively, his UCVA was 20/20, but he was very unhappy. The patient complained of double vision, ghosting, and glare in his left eye, especially at night but also sometimes during the day. Topography revealed a well-centered ablation and no irregular astigmatism. His ocular surface was healthy.

After a Customcornea enhancement in March 2003, the patient's UCVA improved from 20/25 to 20/15. Total higher-order aberrations were reduced from an RMS of 0.27 to 0.17, and spherical aberration was almost completely eliminated (Figures 1 through 3). Most importantly, his quality-of-vision problems were resolved, and the patient claims to have better vision than he has ever experienced.

NO PATIENT LEFT BEHIND
We believe that wavefront-guided treatments like Customcornea represent a paradigm shift in laser vision correction. We have moved from improving Snellen acuity to improving quality of vision. The ultimate effect of this change has been to raise the bar in terms of our surgical expectations. We now look not only for good Snellen acuity, but also a flatter wavefront, good contrast sensitivity, and other quality-of-vision improvements.

Even more exciting is that, for the first time, we can begin to address the patients who were “left behind” after previous refractive surgery.

Therapeutic customized retreatments have a great deal of potential. As clinicians, we should be selective about which patients should receive the procedure and should first certainly rule out simpler contributors such as ocular surface disease. However, in the right patients, the technology can achieve the quality of vision patients desire from refractive surgery.

Stephen G. Slade, MD, FACS, is in private practice in Houston. He is a consultant for Alcon Laboratories, Inc. Dr. Slade may be reached at (713) 626-5544; sgs@visiontexas.com.
Kerry Solomon, MD, is Professor of Ophthalmology and Medical Director, Magill Laser Center, Medical University of South Carolina in Charleston. He is a consultant for Alcon Laboratories, Inc. Dr. Solomon may be reached at (843) 792-8854; solomonk@musc.edu.