To see the figures related to this article please refer to the prnt version of our September issue, page 28.
Results from trials involving the STAR S4 excimer laser (VISX, Inc., Santa Clara, CA) and the treatment of presbyopia have provided evidence of the safety and efficacy of wavefront-guided laser vision correction. Through investigations conducted at the University of Ottawa over the past 2 years, my colleagues and I have shown that the multifocal ablation pattern under evaluation works best for hyperopes, but we have also recently achieved encouraging results in myopes.1
What Is a Multifocal Ablation?
A multifocal ablation pattern on the cornea is designed as an alternative to dynamic accommodation of the lens. Optical multifocality requires a simpler and less invasive procedure than does recreating dynamic accommodation using foldable IOLs, ciliary sclerotomy, or scleral expansion bands. Unlike multifocal IOLs, multifocal ablations do not attempt to create multiple concentric zones on the cornea for distance, intermediate, and near vision. The Array lens (Advanced Medical Optics, Inc., Santa Ana, CA) is a zonal progressive IOL with five concentric zones on its anterior surface. Zones one, three, and five are distance-dominant zones, whereas zones two and four are near-dominant.
When treating presbyopia with the excimer laser, some investigators have steepened the peripheral cornea for near vision and used the central cornea for distance vision. VISX, Inc., has patented a multifocal ablation pattern that can be created using the company's Variable Spot Scanning technology (Figure 1). With this system, surgeons can customize ablation patterns to ablate a central, steepened zone for near correction and a peripheral zone targeted for distance. Currently, we are gathering data from an enlarged cohort on the higher-order aberrations induced by this multifocal ablation pattern.
Results
Our multifocal laser vision correction study was designed to determine the safety and efficacy of the ablation profile for the correction of presbyopia. The study population consisted of eight eyes from five patients who underwent bilateral treatment. The mean patient age was 54, ±2.8 years. Preoperatively, this group had an MRSE of +1.17 ±0.31 D. The mean add requirement was +2.13 ±0.13 D (n = 8).
We measured subjects' near UCVA at 16 inches under photopic and mesopic conditions and measured their add at 16 inches as well. We evaluated subjects' distance-corrected near vision under photopic and mesopic conditions and their best-corrected near vision. Additionally, we used the MN Read Acuity Chart to determine critical print size, speed, the number of sentences, and the number of errors.
For both distance and near visual acuity results, my colleagues and I observed simultaneous gains in uncorrected near and uncorrected distance acuities (Figure 2). Mean MRSE at 1 month was -0.14 ±0.24 D. The mean add at 1 month was 1.69 ±0.18 D, and the mean change in add power was approximately 0.44 D. Because the number of eyes was small, we did not examine the significance of this change.
For UCVA distance at 1 month, 100% of the patients achieved 20/20 or better (J1). For near UCVA, 88% were 20/40 or better (J3), 38% achieved 20/25 or better (J2), and no eyes were 20/20 or better (J1). For near BCVA, 100% of the patients maintained 20/20 or better. No eyes lost more than one line of distance BSCVA.
Case Examples
Patients in the study group who underwent multifocal ablation for presbyopia showed dramatic visual improvement at their last follow-up visit. A 55-year-old male who had 20/25 UCVA distance vision preoperatively in both eyes reached a distance UCVA of 20/16 +1 OD and 20/12.5 OS. His near UCVA was 20/125 in both eyes preoperatively and 20/40 (J3) OD and 20/25 (J1) OS postoperatively. His preoperative manifest refraction was +1.25 +0.50 X 10 OD and +1.25 +0.50 X 170 OS. At his last reading, the subject had +0.25 D sphere in his right eye, and his left eye was plano. His BSCVA was 20/10 at near preoperatively in both eyes. At the last follow-up visit, he was 20/12.5 +1 in the right eye and 20/10 in the left eye (Figure 3). The patient reported improved vision over spectacles. We cannot currently be sure how much of this gain in near vision is attributable to the multifocal portion of the ablation, because we have not conducted comparative studies with hyperopic treatments alone. Nevertheless, none of our hyperopic patients corrected with LASIK who has low refractive errors can read as comfortably without spectacles as these few study subjects can.
A 48-year-old male, one of the first patients treated with WaveScan-guided multifocal ablation for the correction of myopia, also achieved excellent results. Preoperatively, his MRSE was -3.50 +0.25 X 75 OD. His UCVA was 20/125, and he was J1. At 1 month postoperatively, he was -0.75 D OD with 20/20 UCVA and J1+. His left eye was -4.50 +0.25 X 110 with 20/200 +1 UCVA, and he was J6. One month after surgery, he was -0.75 D with 20/20 UCVA and J1++.
Conclusion
In addition to refining our presbyopic multifocal ablation pattern, my colleagues and I are now treating presbyopic, myopic, and hyperopic eyes with wavefront-guided multifocal ablations. Although additional research is necessary, the data from our ongoing study demonstrate the viability of using laser vision correction for the treatment of presbyopia with a multifocal corneal ablation. Many surgeons are skeptical about multifocal ablations owing to their experience with multifocal IOLs and associated induced optical aberrations, and we have not yet analyzed related data for patients undergoing multifocal ablations. Thus far, none of the patients in the latter group has complained of significant optical aberrations. We have since transitioned to performing wavefront-guided presbyopic ablations and are presenting more data this month at the ESCRS meeting in Munich, Germany.
Laser vision correction can specifically address the refractive error in the cornea without the need for incisional surgery. The multifocal laser vision correction study demonstrates the safety of using the Variable Spot Scanning ablation technology for developing a refined ablation that will improve near vision correction without compromising distance vision. Efforts toward optimizing the multifocal patterns with the use of computer models, along with additional patient trials and analysis of longer-term follow-up data, will help to improve the effectiveness of the STAR S4 for the treatment of presbyopia.
W. Bruce Jackson, MD, FRCSC, is Professor and Chairman of the Department of Ophthalmology at the University of Ottawa Eye Institute and Director General of the University of Ottawa Eye Institute at The Ottawa Hospital, General Campus in Canada. Dr. Jackson is a consultant to VISX, Inc., and receives research funding for this project. He holds no financial interest in any company or product mentioned herein. Dr. Jackson may be reached at (613) 737-8759 or (613) 737-8374; bjackson@ottawahospital.on.ca.
1. Jackson WB. Preliminary results of the treatment of presbyopic eyes with multifocal ablations using the Star S3 excimer laser system. Paper presented at: The ASCRS/ASOA Symposium on Cataract, IOL, and Refractive Surgery; April 13, 2003; San Francisco, CA.
