After the femtosecond laser was introduced, there was some skepticism about how beneficial all-laser LASIK would be in a high-volume laser vision clinic. Numerous clinical studies have shown that LASIK with a femtosecond laser allows more predictable flap thickness, better astigmatic neutrality, and decreased epithelial injury compared with mechanical microkeratomes for LASIK.1-3 But the femtosecond-laser-versus-mechanical-microkeratome-technology debate is ongoing; it has scarcely been discussed in conjunction with performing LASIK in high-volume laser vision clinics.
Ultralase (Leeds, UK) is a 16-clinic chain providing a range of vision correction solutions. Herein, I present a 6-month analysis of all-laser LASIK outcomes. Ultralase delivered all treatments between October 2006 and January 2007, and we concluded that LASIK with the femtosecond laser was effective and popular in our high-volume chain clinic setting. Results are presented as mean ± standard deviation.
PATIENTS and METHODS
Our study included 457 eyes (226 right, 231 left) of 234 patients (112 male, 122 female) who underwent primary LASIK with a target refraction of plano. In every case, we used the IntraLase femtosecond laser (Advanced Medical Optics, Inc., Santa Ana, California). In our sample, 395 eyes were myopic, and 62 were hyperopic. Criteria for inclusion was as follows: at least 6 months of follow-up data available. Exclusion criteria were as follows: degrees of amblyopia that would preclude the patient from a visual acuity of 6/6; residual, recurrent, or active disease or inflammation of the eye/adnexa; previous refractive surgery; history of herpetic eye disease; or topographic signs indicative of keratoconus or forme fruste keratoconus. Treatments were performed by one of 14 surgeons; follow-up consultations were carried out at clinics nationwide.
The mean age of patients was 40.58 ±10.67 years (range, 21–66). Mean preoperative spherical refractive error was -2.87 ±3.02 diopters of sphere (DS) (range, -10.50 to 6.00 DS). Mean myopic sphere was -3.75 ±2.15 DS, and mean hyperopic sphere was 2.75 ±1.11 DS. Preoperative mean cylinder was -0.89 ±0.880 diopters of cylinder (DC), (range, 0 to -5.75 DC). The mean preoperative spherical equivalent was -3.31 ±3.00 D.
All eyes were categorized into five groups according to the degree of preoperative spherical equivalent (SE). A total of 138 eyes with low myopia (SE up to and including -3.00 D), 179 eyes with medium myopia (SE more than -3.00 D, up to and including -6.00 D), and 78 eyes with high myopia (SE in excess of -6.00 D) were included in our analysis. There were 62 hyperopic eyes, 49 of which were classified with low hyperopia (SE up to 3.00 D) and 13 with medium hyperopia (SE hyperopia above 3.00 D) (Figure 1). Five eyes were treated with standard noncustomized PlanoScan treatment (Bausch & Lomb, Rochester, New York), 20 eyes were treated with a tissue-sparing algorithm customized to keratometry, and 432 eyes were treated with Zyoptix 217z100 (Bausch & Lomb) wavefront-guided LASIK (Figure 1).
Clinical examination and scheduling. At least 24 hours prior to treatment, patients received a preoperative workup from an optometrist at an Ultralase clinic. This examination included refraction, topography analysis, undilated and dilated aberrometry, pachymetry, anterior segment examination with a slit lamp, posterior segment examination with a Volk lens (Volk Optical, Inc., Mentor, Ohio), and patient counseling. Charges for all follow-up care were inclusive in the patient's treatment fee. The typical attendance rate for 6-month follow-up care was approximately 45%, despite reminders being issued.
Equipment and treatment modes. All eyes underwent all-laser LASIK using the IntraLase FS60 femtosecond and Zyoptix lasers. Fourteen surgeons treated between two and 134 of the eyes (median, 45). Postoperative examination took place on day 1 and at 1 week, 1 month, and 6 months. One component of inclusion criteria was attendance at a follow-up visit at least 180 days postoperatively (mean, 195 ±9 days). Postoperative medication regimen was topical chloramphenicol 0.1% and topical Pred Forte 0.1% (Allergan, Inc., Irvine, California) two times per hour for the first 48 hours and subsequently four times daily for 2 weeks.
Predictability and postoperative complications
The R2 value in a linear regression denotes the degree of correlation; perfect correlation has a coefficient of 1.0. The overall sample R2 value was 0.979 (Figure 2). There was no recorded postoperative complication in 450 eyes (98.5%). Diffuse lamellar keratitis was reported in three eyes (0.7%), which was resolved by increasing the frequency of postoperative steroids in the first 2 weeks. One eye (0.2%) suffered a minor postoperative infection; however, no permanent effects on visual outcome were observed. There was one case of a flap displaced by a patient (0.2%) and one case (0.2%) of dry eye persisting beyond 1 month, which resolved by 6 months. There was no recorded case of transient light sensitivity syndrome in this sample.
Efficacy: Postoperative UCVA
Mean UCVA (logMAR) was 0.037 at 1 week, 0.025 at 1 month, and 0.028 at 6 months (Figures 3A and B). Assuming that the criterion for a 6/12 vision is set at 6/12-2 and that 6/6 vision is set at 6/6-2, then 99.6% of eyes achieved postoperative visual acuity of 6/12 at 6 months, with 64.3% of eyes achieving 6/6 UCVA. In the myopic subgroup, 99.5% reached 6/12, and 68.3% achieved 6/6. Of the hyperopic subgroup, 100% reached 6/12, and 38.7% attained 6/6. LogMAR UCVA is found in Figure 4, postoperative refraction is depicted in Figure 5, and the evolution of postoperative spherical equivalent is found in Figure 6.
Safety: Change in visual acuity
At 6 months, no eye had lost more than two lines of BCVA. Two eyes (0.4%) gained more than two lines of BCVA, and 86.7% of eyes showed no change (± one line) in BCVA. Figure 7 shows the distribution of change in lines of BCVA for the entire population (Figure 7A), myopic eyes (Figure 7B), and hyperopic eyes (Figure 7C).
During postoperative care, all patients were asked about their satisfaction with the outcome of their treatment. Answers were broken down into five categories: (1) couldn't be better, (2) pleased with results, (3) satisfactory outcome, (4) had hoped for better, and (5) regret having had it. Results (182 patients) were recorded at 1 month (Figure 8).
The demanding setting for delivering LASIK within a high-volume chain of clinics requires the highest degree of reliability from the equipment, repeatability, predictability, and safety. Flap creation with the IntraLase femtosecond laser allows thinner flaps, which in turn leads to more patients being suitable for treatment thanks to the tissue-saving profile. We found no intraprocedural complications. Among Ultralase clinics, our experience has been that the overall complication rate with the IntraLase femtosecond is greatly reduced (ie, 1 in 600 with microkeratome flap creation vs 1 in 4,000 with femtosecond laser flap creation).
There appears to be a conceptual discrepancy between the figures for postoperative refraction within ±0.50 (81.2%) and the finding for UCVA of at least 6/6 (64.3%). Conventional wisdom would hold that these two parameters should be closely related, but here they are more remote than might be expected. This fact may be explained with reference to the high-volume setting of a chain clinic. Follow-up appointments are scheduled at intervals, meaning that patients are frequently not encouraged to settle down and give their best visual performance. However, the refraction result has a defined endpoint with the duochrome refraction test used as a check. This means that the refraction is likely to be accurate, which correlates to the high subjective satisfaction rating obtained, and approximately 92% of patients are either pleased, delighted, or satisfied with the outcome.
In this large-sample, medium-term study encompassing a wide range of preoperative prescriptions (ie, from high myopia to medium hyperopia), all-laser LASIK seemed to be a safe and predictable technique. UCVA and SE settled to their postoperative levels rapidly, and a high degree of stability was demonstrated. Patients revealed an extent of satisfaction with the outcome of treatment, indicating that all-laser LASIK is an effective and popular technique that is well-suited for a high-volume chain clinic setting.
Jay Dermott, DOpt, is Training and Clinical Research Manager at Ultralase, Chelmsford, United Kingdom. Mr. Dermott states that he has no financial interest in the products or companies mentioned. He may be reached at email@example.com.