Ablation techniques distinguished mainly by discomfort profiles

October 15, 2009

Results from early follow-up in a eye study of advanced surface ablation techniques show that whether epithelium is lifted as a flap in an epi-LASIK technique or removed using the phototherapeutic keratectomy mode of an excimer laser, good visual acuity results and patients are satisfied with their outcomes.

Speaking on behalf of Daniela Jardim, MD, and colleagues in the Rio de Janeiro Corneal Tomography and Biomechanics Study Group, Dr. Bonfadini presented the findings from a study comparing the two advanced surface ablation techniques in 11 patients with low to high myopia.

Outcomes assessed included pain/discomfort ratings during and after surgery, rate of epithelial healing, uncorrected visual acuity (UCVA), wavefront analysis, and patient preferences.

Epithelial ablation with the PTK mode was associated with less discomfort and higher patient preferences intraoperatively compared with epi-LASIK, whereas in the early postoperative period, patients noted better comfort and indicated a greater preference for the epi-LASIK eye. By day five, epithelial healing was achieved in all eyes, and UCVA was 20/40 or better.

Results from seven patients who were evaluated beyond 3 months showed no differences between eyes in UCVA outcomes, visual quality, higher-order aberrations, or patient ratings of satisfaction.

"Of the various techniques that are now available for surface ablation, we believe epi-LASIK and epithelial ablation with PTK are preferred, and the results from this study so far do not favor either of those procedures over the other," Dr. Bonfadini said. "However, longer follow-up with data from a larger number of patients is important to see if any differences emerge, particularly with respect to haze formation and visual quality."

For the patients enrolled in the contralateral eye study, preoperative spherical equivalent ranged from –1.75 to –8.0 D. Epithelial cleavage for the epi-LASIK procedure was performed using proprietary microkeratomes (EpiK, Moria, six eyes; Amadeus II, Abbott Medical Optics, five eyes). All flaps were removed. All of the ablations, including PTK, were performed with an excimer laser (Allegretto Wave Eye-Q, Alcon Laboratories).

Patient responses

Results from the patient questionnaires showed that when asked which eye they preferred during the procedure, 10 of 11 patients favored the PTK eye, whereas during the first 4 to 72 hours after surgery, more patients preferred their epi-LASIK eye (eight of 11).

These results were consistent with the subjective ratings of discomfort level, he said. With a scale ranging from 0 (none) to 5 (worst), the mean discomfort score during surgery was about 4 for the epi-LASIK eyes and about 2.3 for eyes where the epithelium was removed by PTK. On the first day after surgery, the mean score was about 4.4 in the PTK eyes and about 2.3 for the EpiLASIK eyes.

"However, by the second postoperative day, the mean discomfort rating had decreased to about 1 for both procedures, and it continued to improve through day five, when the bandage contact lens was removed," Dr. Bonfadini said.

Surface ablation advantages

Although LASIK has several advantages as a method for laser vision correction surgery, surface ablation procedures offer benefits as well because they avoid flap-related complications, have less biomechanical impact on the cornea, and may be a better platform for customized treatments. Advances in surface ablation techniques addressing wound healing issues and haze risk have contributed to increasing interest in surface ablation, but limitations of delayed visual recovery and postoperative discomfort persisting for up to 1 week remain limitations, he said.

Although a surface ablation procedure also can be performed using alcohol to remove the epithelium, concerns about alcohol-related keratocyte toxicity, particularly when it is used in combination with mitomycin C, support his group's preference for using a separator to cleave the epithelial layer or the excimer laser to ablate it, Dr. Bonfadini concluded.