The LADARVision CustomCornea System (Alcon Laboratories, Inc., Fort Worth, TX) is FDA-approved to treat up to -7.00 D of sphere and up to -0.50 D of cylinder in myopes. A difference of 1.00 D between phoropter and wavefront refraction measurements, however, permits the treatment of up to -8.00 D of sphere and up to -1.50 D of cylinder. Brian S. Boxer Wachler, MD, of Beverly Hills, California, adds that the CustomCornea System (Figure 1) is also capable of correcting up to +0.90 D of hyperopia, because the wavefront manifest refraction and dry manifest refraction from the phoropter may be within 1.00 D of the approved limits. He and Stephen S. Lane, MD, of St. Paul, Minnesota, comment upon their experiences with this system and share some insights into what the next several years may hold.
DILATION AND TOPOGRAPHY
CustomCornea procedures require pupil dilation, which both physicians believe offers several benefits. According to Dr. Lane, dilation allows the surgeon to be sure that all wavefront information obtained is for a true pupil size of 6.5 mm or more. He adds that dilation maximizes eye-tracking precision by ensuring the accurate identification of landmarks (eg, the pupillary edge) and an absolute reference that does not change or move during surgery. Finally, he finds that dilation allows him to easily identify postoperative striae against the red reflex of the pupil. Dr. Boxer Wachler, meanwhile, states that dilation permits the surgeon to capture data from the entire periphery, where many spherical aberrations exist that are responsible for halos and glare at nighttime.
Dr. Lane acknowledges that dilation takes additional time, can increase patients' light sensitivity intraoperatively, and results in an occasional inability to treat patients who either do not dilate adequately or who are pseudophakic, both of which can make eye tracking more difficult. The CustomCornea platform does not include a topography unit, and the company has no plans to incorporate one directly into the system.
CLINICAL EXPERIENCETime and Pricing
Incorporating wavefront-guided treatments into practice ?does require a few extra steps such as capturing the wavefront data and uploading it into the laser. We allocate an additional 15 minutes for this process,? comments Dr. Boxer Wachler. Performing wavefront-guided ablations has not limited the number of cases Dr. Lane can complete per session. To maintain patient flow, his practice has hired a technician who is responsible for obtaining the wavefront measurements. Two more technicians assist during the surgical procedure; one works with the microkeratome, and the other helps operate the excimer laser.
Candidacy
Dr. Lane says he has rarely treated patients with customized ablation who were poor candidates for conventional LASIK. Nevertheless, the former procedure has attracted many patients to his practice who had been waiting for the new technology. Moreover, Dr. Lane has found that the availability of customized ablation has prompted several patients who were previously unsure about undergoing refractive surgery to proceed. Rarely do individuals who visit his practice for a LASIK evaluation and know nothing of customized ablation fail to choose this procedure if they are eligible for it.
Expectations
Dr. Boxer Wachler anticipates improvements in UCVA and overall quality of vision by means of advanced nomogram accuracy for sphere and cylinder aberrations.
Dr. Lane also anticipates an improvement in surgical outcomes in terms of enhanced UCVA and decreases in the amount of higher-order aberrations, as well as a coincidental decline in patients' postoperative symptoms of glare and halos. Three-month data from early results with customized ablation bear out these expectations, he says. Of 19 patients studied, nine (47%) averaged a 66% decrease in higher-order aberrations compared with baseline at a pupil size of 6.5 mm. Six patients (30%) experienced no change, and four (21%) averaged a 63% increase in higher-order aberrations. Dr. Lane fully expects patients' postoperative expectations to rise for customized ablation, just as they have with other technologies.
TIPS
To ensure optimal surgical outcomes, Dr. Boxer Wachler suggests that surgeons obtain centration photos before dilating the eye. Next, he recommends marking two areas of the conjunctiva, approximately 3 mm outside the limbus. He finds that drying the surface with a cotton swab allows the subsequently placed marks to last longer. Next, Dr. Boxer Wachler suggests adjusting the target offset based on nomogram variables (Table 1).
Additionally, before commencing the procedure on the first eye, Dr. Boxer Wachler recommends taping the fellow eye once the patient is beneath the laser. Anesthetizing the eye for limbal marking prior to taking wavefront measurements diminishes the eye's natural blink reflex, he says, and the eye remains open far longer between blinks. Dr. Boxer Wachler finds that taping the second eye shut prevents corneal dehydration and reduces the risk of overcorrection.
After verifying eye tracking under the laser, Dr. Boxer Wachler says surgeons should (1) create and lift the flap, (2) track and align the conjunctival marks with reticles, (3) place the LADARVision hinge protector, and (4) perform customized treatment.
THE FUTURE
Dr. Lane foresees limits on the range of treatments possible with customized ablation: ?Increases in higher-order aberrations after LASIK (more so in conventional procedures) are probably due to a combination of biological, optical, and mechanical effects that will alter the corneal shape, regardless of whether a perfect ablation can be performed.? Nonetheless, both physicians anticipate continuing improvements to the LADARVision System and CustomCornea platform. Dr. Lane believes that, within
1 year, the system will become easier to operate, thanks to planned system enhancements and the pending release of more accurate treatment algorithms. He comments that the company will be incorporating CustomCornea Surgical Planning software into the LADARWave that will allow surgeons to refine individual treatment plans and make nomogram adjustments. Dr. Lane adds that the system will soon include autocentration, which will enable it to automatically locate the pupillary center more quickly and accurately. In addition, he says that the company is working on methods for cyclotorsional tracking.
In the future, Dr. Lane anticipates achieving better postoperative UCVAs while further decreasing higher-order aberrations, and he expects to be able to treat a full range of refractive errors as well as provide monovision. He expects that engineers will enhance the system's beam profiling and improve the physical integratation of the wavefront analyzer and excimer laser such that treatment data may be transmitted from the aberrometer to the laser. He imagines that analyzers will be more compact and faster, and, as a result of these improvements, physicians will be able to successfully treat large numbers of patients' surgically induced visual problems. Dr. Lane also hopes the near future holds better microscope optics and a means of accurately registering a patient's eye without dilation, which, he says, does not currently exist on any laser.
Both surgeons expect the FDA to approve the LADARVision System for CustomCornea to treat the full range of myopia, hyperopia, and astigmatism currently possible with conventional LASIK. Dr. Boxer Wachler envisions the future approval of as much as -10.00 D of sphere and -3.00 D of cylinder for myopia. Once the FDA approves a broader range of treatment parameters, Dr. Lane believes that customized ablation will supplant conventional LASIK, which will then disappear.
Stephen S. Lane, MD, is a clinical professor at the University of Minnesota in St. Paul and is the president of the ASCRS. He is a member of the Refractive Medical Advisory Board of Alcon Surgical, Inc., but has no proprietary interest in any of the technology described herein. Dr. Lane may be reached at (651) 275-3000; sslane@associatedeyecare.com.Brian S. Boxer Wachler, MD, is Director of the Boxer Wachler Vision Institute in Beverly Hills, California, and a faculty member at the University of California, Los Angeles. He is a consultant for Alcon Laboratories, Inc. Dr. Boxer Wachler may be reached at (310) 860-1900; bbw@boxerwachler.com.
