Treatment of substantial levels of coma and trefoil using wavefront-guided excimer surface ablation resulted in very good visual outcomes. These patients fared well when compared with patients who underwent LASIK early after the introduction of the procedure and compared with those with atypical topographies who underwent LASIK in the late 1990s. The results still fell slightly short of the outcomes achieved in patients with normal corneal topographies.
"LASIK is characterized by the advantages of faster healing and less haze postoperatively, while PRK, because the depth of the surgery is shallower than that of LASIK, provides greater mechanical stability. In our practice, the choice of LASIK or PRK is typically based on corneal thickness, age, topography, and other disease conditions like anterior basement membrane dystrophy," Dr. Hardten said.
After 3 or more months of follow-up, the mean spherical equivalent was 0.02 D in 110 eyes. Dr. Hardten reported, however, "The mean standard deviation was greater compared with results in normal eyes, i.e., 0.4 D. The mean astigmatism was 0.3 D. Uncorrected visual acuity (UCVA) of 20/20 or better was achieved in 80% of cases at the 3-month (the last) follow-up visit. UCVA of 20/40 or better was achieved in all eyes.
When the investigators analyzed patients who had at least 1 year of follow-up, they found that slight improvement in the visual outcome occurred, with 20/25 or better vision being achieved in 95% of this subgroup. All patients still had 20/40 or better uncorrected vision.
Dr. Hardten compared the results from this series of patients with groups of patients that had been analyzed previously in this practice. "When we looked at normal patients who underwent wavefront-guided LASIK after the nomogram was adjusted, slightly more than 90% of patients achieved 20/20 or better vision. Before the nomogram was adjusted, about 80% of patients achieved 20/20 or better vision. The results from non-wavefront-guided LASIK indicated that about 60% of patients achieved 20/20 or better. Finally, about 55% of patients with atypical topography from the late 1990s who underwent LASIK achieved 20/20 vision. In the current series of patients with atypical topography, about 80% achieved 20/20 or better," Dr. Hardten commented.
"Obviously, our results have continued to improve in patients with normal and atypical corneal topographies over time. In this group of patients in which the surgeon chose to perform PRK instead of LASIK because of atypical corneal topography, the results were quite good, but they fell slightly short of the results achieved by patients with normal eyes. These patients received special counseling about the fact that their results were not going to be as accurate because there was something unusual about their eyes," he said.
In a subgroup of these patients in whom iris registration was used, the results were better compared with the entire cohort of patients. The results with iris registration, however, still did not match those of normal patients without substantial levels of higher-order aberrations.
"Obviously the long-term outcome in these patients is the real concern. If they were chosen because they were atypical and were early keratoconus patients, that condition will progress at some point. This is something that is unknown right now. In the patients with irregular topography that may not have been due to progressive keratoconus, there should be little or no change over time," Dr. Hardten said.