Not since the introduction of the excimer laser has there been so much hype, secrecy, and so much on the line for ophthalmic companies in the refractive surgery arena. Is wavefront technology an inflection point in the history of eye surgery? Is wavefront just marketing hype, or is it the future of refractive surgery? Is it a useful technology that will create ?super vision?? And why are companies such as Alcon, Bausch & Lomb, Nidek, and VISX, spending millions of dollars to turn technology originally developed for use in astronomy into the cornerstone of refractive surgery?
Has a technology so firmly backed by so many companies ever failed?The following is an overview of each company's technology currently involved in US custom ablation clinical trials.
Alcon—LADARWave™ CUSTOMCORNEA® Wavefront System
The LADARVision® platform includes the LADAR4000 Excimer Laser System and the LADARWave™ CUSTOMCORNEA® Wavefront System. The overall system offers several features. The LADAR4000 is the only laser with an FDA claim that has proven tracker efficacy. The LADAR4000 tracker offers the only laser radar tracker, as well as the only closed-loop tracker in the industry. According to Stephen Brint, MD, closed-loop means continuous transmission and response of the eye's position, such that the measured error is driven to zero, allowing LADARVision® to lock on to the eye and remain locked for the duration of the surgery. The FDA claim states the LADARVision® “improves the accuracy of corneal shaping.”1 The LADAR4000 delivers a true Gaussian flying small-spot, 0.8-mm beam and sophisticated ablation algorithms that produce smooth corneal surfaces. Furthermore, the LADAR4000 scanning enables the beam to be placed at any desired location, in order to perform the intricate, precise ablations required for complex treatments, such as mixed astigmatism. These two features, says Dr. Brint, closed-loop tracking and true Gaussian small-spot scanning, complement the strengths of the LADARWave.™
The LADARWave™ CUSTOMCORNEA® Wavefront System offers sophisticated registration capabilities that ensure accurate wavefront ablation placement on the patient's “line of sight,” and a wavefront measurement map precisely matched to the participant's eye. It also includes an automatic “fogging” system that eliminates patient accommodation to ensure an accurate reading. LADARWave™ features direct measurement of the optical system, and is able to capture multiple individual measurements. It offers a sizable dynamic range in order to measure a wide range of refractive errors. LADARWave™ will operate over a range of +15 to -15 D of maximum curvature in any meridian for pupil sizes up to 7 mm. Dr. Brint explains that LADARWave™ can measure even the highest refractive errors just as quickly as those that are low (the instantaneous range is the same as the total range). A large instantaneous range is important for ease of use, speed of use, stability of the device, accuracy, and calibration. Finally, LADARWave™ performs accurately, specifically within 0.04 (RMS µm) for a large (8-mm) pupil.
Bausch & Lomb—Zyoptix™
Zyoptix™ is Bausch & Lomb's new system for Personalized Vision Solutions, which incorporates its Zywave™ Hartmann-Shack aberrometer coupled with its Orbscan™IIz multidimensional corneal measurement device. The data captured by the integrated diagnostic workstation generate the individual ablation profile for use with the Bausch & Lomb Technolas® 217z Excimer Laser system to perform the customized treatment.
The Technolas® 217z Excimer Laser uses a combination of 2-mm and 1-mm diameter flying spots. First, a 2-mm spot is used to correct most of the refractive error by ablating approximately 90% of the corneal tissue. Finally, the spot size is reduced to 1 mm to correct the fine structures, such as higher-order aberrations, and create an optimized transition zone. The company claims that this, combined with a truncated Gaussian beam, which the company claims, results in maximum smoothness of the corneal bed, minimal thermal effects, less tissue removal, and a wider fully corrected optical zone in an efficient treatment time. The laser also incorporates an active 120 Hz eye tracker with its active scanner feedback control for exact spot placement during the ablation sequence in reference to the pupil location.
Bausch & Lomb believes that not only wavefront, but corneal shape and architecture, are key components to obtaining the best possible results from custom ablation in the future, and it is why they incorporate the utilization of both devices in their approach. To date, there have been more than 2,500 custom ablation procedures performed worldwide using Zyoptix™.
LaserSight® Technologies— CustomEyesCE Custom Ablation Platform The CustomEyes Custom Ablation platform consists of the following components: the AstraMax Stereo Topographer, the CIPTACE Custom Vision Planning Software, and the AstraScan Custom Laser System.The AstraMax is a three-camera stereo topographer that provides a stereopsis of the anterior segment of the eye. The device performs six complex measurements in one exam, including posterior and anterior corneal topography, optical pachymetry, limbus-to-limbus coverage, and scotopic and photopic pupillometry. The system's patented polar grids target yields critical measurements (35,000 measuring points in under 0.2 seconds) independent of adjoining points, providing robust anterior data that are not dependent on the arc step method.
CIPTACE, an acronym for Corneal Interactive Programmed Topographic Ablation, is a custom corneal ablation planning and programming software developed in conjunction with Ligi Medicali by ORBTEK, INC. (now part of Bausch & Lomb). CIPTACE was originally created to allow the Orbscan™ system to create a shot pattern to drive a flying spot excimer laser system, such as the LaserScan LSX®. CIPTACE uses actual height data, K readings, pupil size, and Q values to determine the treatment necessary for the best possible outcome, and removes the prescribed amount of tissue at the prescribed location.
The AstraScan Custom Laser System, introduced to the international market at the recent AAO meeting in New Orleans, LA, offers many features of the LaserScan LSX®, which combines the efficiency of a 200 Hz laser repetition rate, the precision of a small microspot, and optimized low laser fluence. New features include an advanced video-based intelligent eye tracker, a redesigned optical delivery system, and an interface to the CIPTACE custom ablation planning software.
The focus of the CustomEyes Platform when combined with LaserSight's laser system is to treat patients with irregular astigmatism and retreat patients with decentered ablations from previously performed laser refractive procedures. Currently available internationally, LaserSight® will make CustomEyes available to US customers once all regulatory requirements are fulfilled.
NIDEK Incorporated—NAVEXNAVEX consists of the following components: the OPD-Scan, Final Fit Software, and the EC-5000 Excimer Laser with Multipoint Ablation.
The OPD-SCAN performs aberrometry, topography, and autorefractions. Designed specifically for ophthalmology, it uses dynamic skiascopy (opposed to Shack-Hartmann aberrometry) to determine the aberrations of the eye. It has a relatively wide measuring range (-20 to +22 D of sphere and + 12 D of cylinder), and all measurements are performed on the same unit, so that data registration and axis of alignment are not an issue.
The Final Fit Software is the interface software that communicates between the OPD and the EC-5000, and calculates the ablation algorithm for the ideal refractive correction. The algorithm maintains the prolate shape of the cornea postoperatively, utilizing both topography and aberrometry to calculate the ablation profile for the laser.
The EC-5000 Excimer Laser with Multipoint Ablation uses both slit and spot ablation. The bulk of the correction is performed using slit scanning, and the irregularity components are treated using Multipoint Ablation that can deliver up to six spots onto the cornea simultaneously. This combination minimizes ablation time. The eyetracker can compensate for cyclotorsion, and it takes a direct real-time measurement of the eye without requiring dilation.
Nidek says that they are focusing on using this technology to help patients with higher-order aberrations who might not normally be candidates for LASIK surgery. The company intends that this technology, which is currently in clinical trial stages, will eventually be used for all LASIK candidates to determine patients' refractive maps prior to refractive surgery, in order to treat those unique aberrations. In addition to the regular refractive surgery patient, NAVEX technology has been used to successfully treat patients with irregular astigmatism and decentered ablations.
VISX®—WavePrint
The VISX® WavePrint system incorporates both subjective and objective patient information into the platform. The WavePrint system uses diagnostic information taken from an initial WaveScan measurement to plan a treatment table for the ablation. This planned treatment is then ablated onto a plastic disk, termed the PreVue lens, and tested in trial lenses with the patient. Once a satisfactory result is achieved, the ablation is performed using the Star S3 laser, which features a three-dimensional tracker.
VISX® is currently developing technology to replace the PreVue lens with adaptive optics, which is a new technology that uses a deformable mirror that is shifted to a pattern inverse to the patient's wavefront. When an eye chart is displayed on this mirror, the patient sees the quality of their aberration-free vision, and is able to preview the postoperative results of the pending surgery. At this stage, the surgeon will be able to modify various Zernike terms to optimize the patient's vision in the WaveScan unit, as well as in the final result.
WaveFront Sciences—Complete ophthalmic analysis system The Complete Ophthalmic Analysis System (COAS) from WaveFront Sciences is the highest resolution wavefront analyzer available, according to the company. This resolution, and the associated precision optical design, is critical to accurately measuring the higher-order aberrations of the eye. The system provides comprehensive diagnostic capabilities by allowing doctors to “see through their patients' eyes” to determine whether patient complaints are the result of distortions in the optical path. COAS can be used for pre- and postprocedure diagnostics, as well as to track surgical performance results.
Wavefront Sciences states that the unique features of COAS enable it to acquire and display the ocular wavefront in real-time. By acquiring data in a continuous, free-running mode, instantaneous changes in the wavefront can be followed, recorded, and played back as a movie, allowing clinicians to examine wavefront changes dynamically. Dynamic wavefront testing is a unique and completely objective way of assessing accommodative changes in the eye, and is proving to be of intense interest in presbyopia surgery as well as in accommodative IOL technology.
Wavefront Sciences also offers the COAS aberrometer for excimer laser refractive surgery through their partner, Asclepion-Meditech, and under the trade name WASCA in international markets. Asclepion is currently seeking FDA approval in the US.1. FDA labeling, LADARVision System Operation Binder, Physician's Booklet.
