Finding the best technique for wavefront-guided LASIK

July 15, 2005

Washington, DC—Early outcomes after wavefront-guided LASIK may be better when using the femtosecond laser microkeratome (IntraLase Corp.) for flap creation compared with mechanical microkeratomes, but show no difference whether the procedure is performed in a single session or with a staged approach regardless of the microkeratome used.

David J. Tanzer, MD, reported on the initial results from a prospective, parallel group comparison trial during the annual meeting of the American Society of Cataract and Refractive Surgery.

"Currently, excimer laser refractive surgery in Navy aviators can only be done with PRK," Dr. Tanzer explained. "With consideration being given to the possibility of performing LASIK, this study was undertaken to evaluate the best technology for flap creation and whether better outcomes can be achieved with a staged approach that takes into account flap creation-induced higher-order aberrations.

Dr. Tanzer, surgical director, refractive surgery center, department of ophthalmology, Naval Medical Center, San Diego, received the "Best Paper of Session" award for his presentation.

The study was conducted at the Naval Medical Center, San Diego. Patients underwent bilateral wavefront-guided LASIK using the VISX STAR S4 CustomVue (version 3.07) excimer laser after flap creation with the Amadeus (AMO), Hansatome (Bausch & Lomb), or IntraLase microkeratomes. Fifty patients in each microkeratome arm were randomly assigned to undergo standard treatment with flap creation followed by immediate ablation. Another 50 patients received a staged procedure in which the flap was cut, lifted, and laid back down followed 4 weeks later by wavefront measurement and ablation. Two surgeons, Dr. Tanzer and Capt. Steven C. Schallhorn, MD, director of cornea and refractive surgery, Naval Medical Center, San Diego, performed all of the surgeries.

At 1 day after surgery, there were significant differences favoring the femtosecond laser procedure compared with each of the mechanical microkeratome groups. With respect to uncorrected visual acuity, (UCVA) outcomes with rates of 20/16 or better were achieved by 68% of eyes treated with the femtosecond laser, 49% treated with the Amadeus, and 42% treated with the Hansatome. Significant differences favoring the femtosecond laser group persisted at 1 week and 1 month as well.

Mean MSE at 1 week was also significantly better in the femtosecond laser group (–0.03 D) compared with the Hansatome (–0.16 D) and Amadeus (–0.24 D) groups, as well as after 1 month and 3 months. A predictability difference favoring the femtosecond laser group was seen only at week 1 compared with the Amadeus group, and by 3 months, UCVA outcomes were also comparable in all three groups with the rates of UCVA 20/16 or better ranging from 78% to 88%.

Results at 3 months However, at 3 months, mean UCVA was better than mean preoperative best-corrected visual acuity (BCVA) only in the IntraLase group, and comparisons of the mean difference between the 3-month postoperative UCVA and preoperative BCVA showed a statistically significant difference favoring the IntraLase over the Amadeus, but no other significant differences.

At 3 months all groups had a slight gain in BCVA. However, the proportion of eyes gaining one or more lines of BCVA was significantly higher in the femtosecond laser group (45%) relative to the mechanical microkeratome groups (33% for both).

Analyses of change in photopic (5%) contrast acuity showed no differences between the femtosecond laser and Hansatome groups, each of which were associated with a slight improvement (–0.02 and –0.01 logMAR units, respectively) from their preoperative levels. However, there was a slight worsening in the Amadeus group (+0.03 logMAR units) and pairwise comparisons favored both the Hansatome and femtosecond laser over the Amadeus.