As the waves of technological change roll over our practices with increasing frequency, we have less and less time to recover in between. And, as you might expect, the next wave is about to hit. Clinical trials to assess how wavefront-guided custom ablation can improve laser refractive surgery have begun. Therefore, now is the time for refractive surgeons to make their own assessments of what's to come.

Begin your assessment with the articles on the following pages. They contain insights on how custom ablation might change the LASIK
procedure, how to interpret wavefront acuity maps, and why delivering reliable results is such a complex endeavor. You'll also want to read why these pending advances, which could do so much for refractive surgery, could also stir a backlash against it -- if the possibilities and limitations aren't properly communicated to your patients.

Your level of preparedness will ultimately determine whether this next technology wave takes you off guard or refreshes you, your patients and your practice.

Preparing for the Future

By Marguerite B. McDonald, M.D., F.A.C.S.,
New Orleans, La.

Optical customization, often referred to as custom ablation, holds great promise for refractive surgeons and their patients. This new approach to refractive surgery will vastly increase the chance that our patients will see 20/20 or better uncorrected after undergoing laser-assisted in situ keratomileusis (LASIK). It will decrease the chance that they'll lose best-corrected visual acuity, experience additional night glare postoperatively, or suffer a loss of contrast sensitivity.

Another, often overlooked, use for customized ablations is treating patients with irregular astigmatism following previous refractive surgery, corneal transplant surgery, cataract surgery, trauma or corneal infection, who may be functionally blind in one or both eyes but are contact lens intolerant. Ophthalmologists are eager to use customized ablations to fix these problem cases in their practices.

The latest thinking

Actually, two types of customized ablations are already used. The first is functional customization, which is based on patient characteristics and needs. For years, as laser surgeons planned individual ablations, they've considered age, the presence or absence of presbyopia, occupation, refraction, and psychological tolerance.

Laser surgeons have also been using anatomical customization for some time. This surgical plan takes into account pupil size and corneal diameter and thickness. In some cases, anterior chamber depth, anterior and posterior lens shape, and axial length are considered as well.

The current excitement surrounding customization stems from the new opportunities we now have to perform optical customization based on wavefront measurements. Light travels in a series of flat sheets known as wavefronts. The sheets are wrinkled, or distorted, as they pass through imperfections in the refractive medium (i.e., the cornea or the lens). These errors can be displayed on a color map.

We can accomplish clinical wavefront sensing in many ways. But most methods trace the paths of multiple light rays through an individual eye. When combined, these paths simulate the propagation of a complete wavefront through that eye, providing a wavefront map that is as unique to that individual as a fingerprint.

Obtaining the optical "fingerprint"

Several of the current wavefront sensors are built upon the Hartmann-Shack method, in which a single, thin laser beam is passed into the eye and reflects off the retina from a single point. As the reflected light passes out of the eye, it reaches an array of small lenslets, which focus the rays into spots used to define the eye's wavefront pattern. The VISX, Alcon Summit Autonomous and Chiron wavefront sensors all use the Hartmann-Shack method.

The Wavelight/Technomed team has based its wavefront sensor on the Tscherning method. The Tscherning aberroscope involves an incoming optics pattern. It projects an entire grid of laser spots into the eye through various optical elements, which are then imaged on the retina by an indirect ophthalmoscope. Analysis of the light rays on the back of the eye and the deviation and distortion of these spots from the ideal grid pattern is then used to compute the wavefront map.

The Tracey system, used by Dr. Ioannis Pallikaris, is similar to the Tscherning system, except that only one light ray at a time is projected onto the back of the eye. The light ray moves rapidly from one spot to the next, tracing a grid pattern.

In its OPD Scan unit (formerly known as the ARK 10,000), Nidek uses a skiascopy/autofractor system. And other companies are using different types of aberrometry to build their wavefront sensors.

A wavefront map represents two categories of optical aberrations: second-order and higher-order. Second-order aberrations include basic spherocylindrical errors. These aberrations have the largest impact on visual acuity. Higher-order aberrations are smaller irregularities in the optical system. They represent approximately 17% of the total aberration error.

Until recently, we've had no way to correct the higher-order aberrations. They prevent us from seeing better than 20/20; they block the utilization of full visual potential.

Clinical trial results are encouraging

Retinal physiologists and neurobiologists claim that humans have the potential, based on the spacing of the retinal photoreceptors, to see between 20/5 and 20/8. This level of acuity approaches that of other visually gifted animals: Eagles see 20/4 and hawks see 20/6.

The early data from all the customized ablation clinical trials are very encouraging. As of this writing, both the Alcon Summit Autonomous and Wavelight teams have measured 20/8 uncorrected visual acuities in some post-op patients, and results continue to get better as the algorithms are improved.

Now that the technological capability to both measure and treat higher-order aberrations is available, interest in "super vision" has exploded among military personnel, professional athletes, commercial pilots, and amateur and professional marksmen. Many surgeons wonder whether their patients want super vision at all. The answer is an emphatic yes. It seems that even individuals who don't have an occupational need for extremely good acuity are also interested in seeing the world as clearly as possible.

Many have even asked whether it would be wise to postpone undergoing conventional surgery until the FDA approves customized ablations, but this isn't necessary because current outcomes are so good. Furthermore, patients who undergo procedures now can have a "touch-up" in the future.

How the procedure might change

Even though custom ablation will have such an impact on outcomes, the surgical technique will change very little. However, surgeons will have a small learning curve to overcome as they learn to read wavefront maps. (For a primer, see "The Meaning of Wavefront Maps," below) Also, the process of obtaining a wavefront map and using it in combination with the laser will lengthen the preoperative exam and the surgical procedure somewhat, but results are incredibly precise. Instead of a treatment based on one number (such as -2.00 in the case of a spherical ablation) or, at most, three numbers (such as -2.00 +0.50 x 90 in the case of a myopic astigmat) the ablation is now based on 14 or more numbers.

We can get an idea of what a customized procedure will be like by describing the Alcon Summit Autonomous experience. The patient arrives at the laser center and is dilated. Twenty minutes after dilation, four marks are placed near the limbus with an inked marker, which has four long blades. Small cautery burns are added to the marks at the limbus because the gentian violet or methylene blue ink last only a few minutes. These marks are necessary for ensuring that the treatment pattern and the wavefront map are superimposed perfectly over the treatment area.

After another twenty minutes passes (to allow for the cautery-induced mucus to subside), a series of five wavefront maps is generated. This process takes approximately 5 minutes. The surgeon selects the three best maps to generate the final wavefront map that will be used to drive the ablation. The wavefront information is then saved on a floppy disc and placed into the computer that drives the laser.

At first it will be a bit strange to pop a disc containing patient wavefront information into the computer that drives the laser, as opposed to manually entering the refraction. But some wavefront sensors generate an autorefractor-type printout that can be used as a check prior to initiating the ablation.

Unless we find some way to replace the tiny limbal cautery burns with a less invasive permanent registration mark, patients will need several drops of topical NSAID postoperatively to reduce or eliminate discomfort. The level of corneal pain is much less than that created by PRK, but LASIK surgeons should be aware of it and be prepared to treat it.

In the Alcon Summit Autonomous clinical trials, we've recently had success using two rather than four limbal marks without cautery. The marks remained for nearly 2 hours because the eye had been "dried" (holding the lids apart) before marking the limbus firmly for 5 seconds. This, of course, reduced postoperative discomfort for the patient.

How to prepare

Even though custom ablations can't be performed now outside of clinical trials, surgeons should be preparing themselves for when the technology is widely available.

First, as we mentioned earlier, they should familiarize themselves with both two-and three-dimensional wavefront maps. Next, they should carefully research and compare the different wavefront-measuring devices. Many of these instruments will be introduced for the first time at this month's American Academy of Ophthalmology conference. Surgeons should attend sessions on wavefront imaging at the Academy and ASCRS meetings, as well as at any regional meetings where the topic is being covered. The first textbook covering wavefront sensing, Customized Corneal Ablations: The Quest for Super Vision, edited by Scott M. MacRae, Ronald R. Krueger, and Raymond A. Applegate, will be published early next year.

Surgeons can also attend the 2nd International Congress on Wavefront Sensing & Aberration Free Refractive Correction to be held Feb. 10, 2001 in Monterey, Calif. (For more information on this ISRS co-sponsored event, call (801) 943-5549 or e-mail corcommun@aol.com.)

Doctors should also locate the laser centers near them that are participating in custom ablation clinical trials, so their interested and/or needy patients can participate in protocols for both virgin and non-virgin eyes. It's also a good idea to be aware of which LASIK centers in Canada and Mexico will offer the technology. These centers can help patients who decide not to enter a clinical trial but want to access the technology before FDA approval in the United States. When centers are chosen, Alcon Summit Autonomous, and most likely other laser manufacturers, will make the information public.

And finally, keeping abreast of the latest custom ablation developments is crucial. What we know today about this dynamic area of ophthalmology could change by tomorrow.

Dr. McDonald, a clinical investigator of Alcon Summit Autonomous's custom ablation technology, is a clinical professor of ophthalmology at Tulane University in New Orleans and the director of the Southern Vision Institute.

The Meaning of Wavefront Maps

By John F. Doane, M.D.
Kansas City, Mo.

Just as you may (or may not) have become accustomed to understanding corneal topography maps, the next evolution of refractive ocular imaging -- wavefront analysis -- has come onto the visual science scene. This technology is rooted in astrophysics, where astronomers have worked to perfect the images impinging on their telescopes.

It's important to understand that wavefront technology isn't a newer form of corneal topography, but a measurement of visual acuity that takes into consideration all elements of the optical train, including tear film, anterior corneal surface, corneal stroma, posterior corneal surface, anterior crystalline lens surface, crystalline lens substance, posterior crystalline lens surface, vitreous and retina.

In this article, using the VISX 20/10 Perfect Vision Wavefront System as the model, I'll explain the meaning of wavefront measurement and what it can and can't tell us about a patient's refractive status.

What the acuity map shows us

This system, which has been brought to market as a stand-alone, desktop-sized unit, describes the refraction of the eye within 0.05 microns. This is five times more accurate than the excimer laser beam and 25-50 times more accurate than phoropter, autorefractor and topography-based systems. A 785- nm nominal wavelength light is projected into the eye onto the macula. The light is projected as flat sheets, or wavefronts. The wavefronts are projected through the entire optical system, reflected back and collected by a CCD video camera. If the optical system is without aberration, the wavefronts exit the eye as parallel flat sheets, just as they entered. If the optical system has aberrations, the flat sheets will exit as irregular, curved sheets.

The returning wavefront captured by the CCD video camera is converted to a color-coded acuity map (some prefer the terms phase map or spatially resolved refractometer map) for points over the pupil area. The map is a translation of 100,000 data point numbers for a 6-mm pupil. Measurements are taken every 20 microns over a 6-mm pupil area and thus describe the refractive properties of the eye from tear film to retina.

Acuity maps are color coded and separated into 20 shades of color, which are autoformated in micron scale for the given eye.� The total interval of measurement is determined by the actual microns of difference in the most advanced (maximum) and most latent (minimum) of the wavefronts for the individual eye.

After the scale range in microns is taken into account, widely spaced contours indicate an eye relatively free of optical aberrations. Tightly spaced contours indicate a greater degree of aberration.

In addition to the acuity map, the clinician should evaluate the Shack-Hartmann data map. This is the raw light image impinging on the CCD camera, which appears as a grid of light dots. If the eye is without aberration, the pattern will be uniform with the dots perfectly aligned horizontally and vertically. Also, the image of each dot will be precise, without blurring or comet-like trailing of the edges. If the eye has significant aberration, the image will show a distorted pattern with individual qualitative abnormalities of the dots and overall irregularity of the group pattern.

Driving the ablation

Once the surgeon has obtained the wavefront data, he would compare it to and integrate it with preoperative corneal topography to compute an ablation profile. This profile would be fed into the excimer laser. The inverse of the wavefront would be ablated onto the front surface of the cornea to effectively neutralize the primary, secondary and possibly higher-order aberrations.

Shortcomings

It's important to remember that wavefront data can detect abnormalities within the ocular system, as depicted on the acuity map, but can't tell us whether an abnormality is located at the cornea, lens, vitreous or retina. Complete ocular examination, data from keratometry and corneal topography, and sound clinical judgment will all be needed to locate the source of the refractive problem.

Furthermore, investigation of current wavefront technology has shown that tear film abnormalities, media opacities and pupil size can dramatically affect findings. An irregular tear film will result in data suggesting significant wavefront aberration. Opacities are poorly defined by the current devices, probably because of light scatter. It may be impossible to obtain a measurement on eyes with marked aberrations, such as scars or keratoconus. And eyes with relatively miotic pupils may require pharmaceutical dilation to be measured.

While current devices work extremely well with normal eyes and eyes with mild to marked aberrations, we do have room for improvement before this wave reaches its crest.

Dr. Doane practices at Discover Vision Centers in St. Louis, Mo. He's performed more than 10,000 LASIK procedures.

Custom Ablation: When Can We Deliver?

By Brian R. Will, M.D.
Vancouver, Wash.

Without question, custom ablations, calculated specifically for individual patients, have become the "brass ring" for laser vision correction. Despite the compelling desire of refractive surgeons to deliver this technologic advance, the clinical results of attempts in previous years have been disappointing. Why has this goal been so elusive? It appears that our failure as clinicians to understand the complexity of the endeavor and to deliver a comprehensive approach to refractive surgery is primarily at fault.

What we need

To consistently provide high-quality visual outcomes using customized corneal techniques, we must arm ourselves with a complement of highly specialized technical tools. Just as a three-legged stool requires all three legs to function, delivering consistent and reproducible results with customized corneal technique requires attention to the following three broad areas:

�        a comprehensive technique for precisely measuring and/or mapping all of the clinically significant optical aberrations present within the individual patient's visual pathway

�        accurately communicating this precise aberration data to the laser with perfect point-to-point synchronization

�        a laser delivery device that possess the pinpoint accuracy and the precise beam contour to create the proper ablation profile on the patient's cornea in real time, while the patient's cornea acts as a dynamic, often erratic, complex moving target.

Like a chain, the weakest link in this technologic tool set will ultimately determine the success or failure of our attempts to provide our patients with the potential benefits of truly customized corneal ablations.

Measuring optical aberrations

Current wisdom suggests that wavefront analysis or corneal topography (or some combination thereof) will provide the necessary information for accurately defining each of the visually significant optical aberrations present in an individual eye.

Placido-based corneal topography has been an essential element of refractive surgery. With these devices we're able to accurately map and image the anterior surface of the cornea --by far the most important refractive structure in the visual system. However, despite its importance, corneal topography is unable to provide information on the other optical elements of the eye (including the posterior corneal surface, the crystalline lens and the macula) or define their contribution to the entire optical system. In addition, each commercially available topographer appears to provide slightly different data for the same eye, indicating that the measurement apparatus and mathematical assumptions of each manufacturer limit "absolute truth" regarding corneal topography.

In recent months, wavefront measurement devices have become recognized as tools that can simultaneously measure all of the optical aberrations present in an individual eye. Commercially available systems at present capture the wavefront data using either a modified Hartmann-Shack sensing device, are based on the concept of a Tscherning's aberrometer, or utilize the methodology of ray tracing. Additional approaches and devices are no doubt currently being conceived and developed in the back rooms of excimer laser companies or in the "garages" of ophthalmologists and optical engineers.

No approach seems superior now

Wavefront technology is in its infancy, and now no device or approach appears superior to another. In fact, on a purely theoretical basis, devices based on Hartmann-Shack, Tscherning's or ray tracing technologies should, for any given optical system, provide equivalent data. However, in the eye, all such devices must effectively contend with ocular accommodation, ocular movement during the measurement, opacities in the optical pathway and the effect of pupil size.

Practically speaking, Hartmann-Shack and Tscherning's wavefront measuring devices are more limited in their dynamic range and therefore, to be more user friendly, are most often mated to an autorefractor. At present, the autorefractor component appears to be the most difficult element to develop and incorporate, particularly for eyes whose corneas have been previously distorted by refractive surgery procedures. Ray tracing generally appears to have a superior dynamic range. However, at present the apparatus in development is a "stand-alone" measurement, lacking the ability to communicate with the laser delivery system -- an essential part of custom cornea.

Irrespective of the type of measurement device used by the excimer laser manufacturer, it's imperative that clinicians recognize that the final visual outcome for custom ablations will never be any better than the quality of the information that is captured by the measurement device and ultimately programmed into the laser delivery system.

Accurate point-to-point synchronization

Once the optical aberrations of the eye have been measured, imaged and mapped, the second essential stage of custom ablations must be fulfilled. Success in custom refractive surgery requires that we accurately communicate the precise aberration data set generated by the wavefront sensor to the laser corrective device with perfect point-to-point synchronization. In simple terms, the map generated by the wavefront sensing device and the map used by the laser delivery system must line up perfectly or all bets are off on the results.

Perfect point-to-point registration requires that the imaging device and the laser delivery device be synchronized to:

�        identify reproducible landmarks or benchmarks on the corneal/ocular surface that can be used for the synchronization of the measurement and delivery maps

�        use these benchmarks to control X and Y axis map alignment as well as intraoperative cyclorotational axis change.

In laser-assisted in situ keratomileusis (LASIK), determination of the perfect ocular landmark, identifiable by the wavefront sensing device and the laser, is particularly difficult. For the control of X and Y axis alignment, either the corneal limbus or the pupillary margin could be used. However, after the flap is created, the edge of the corneal limbus is challenging to identify. Elevating the flap reduces the optical clarity of the cornea, producing a poorly demarcated pupillary image and reducing pupillary edge definition.

Moreover, the state of the patient's entrance pupil during LASIK is anything but natural. This can be affected by a number of things, including:

�        patient anxiety (creating a highly charged adrenaline state, which contributes to pupillary dilation)

�        patient accommodative effort

�        transient ischemia and the effects of prostaglandin release during application of the LASIK suction

�        scleral expansion caused by the LASIK suction ring

�        the pharmacologic and neurophysiologic effects of benzodiazepines and other sedatives routinely used during LASIK to calm patients.

Each of these factors contributes to a potential distortion of the patient's true entrance pupil that could translate into map registration and synchronization error in the X and Y axes.

Many refractive surgeons who intend to use wavefront-guided custom ablations are also concerned about the issue of intraoperative compensation for ocular cyclorotation. Cyclo-rotational eye movements could be a significant source of error, even in purported spherical corrections. In fact, studies that we've conducted indicate that this can be more of a problem than many surgeons realize.

We recently evaluated both the magnitude and frequency of ocular cyclorotation that occurred when patients moved from the sitting to the supine position (pre-laser cyclorotation) and the ocular cyclorotation that occurred during the laser ablation (intra-laser cyclorotation). Intra-laser cyclorotation occurred in only 4 out of 2,092 consecutive eyes, and the maximum observed rotation was only 2�.

However, we found pre-laser cyclorotation to be a far more serious problem. In a series of 159 eyes, 64.7% demonstrated pre-laser ocular cyclorotation, some as great as 12�. (2.5% of them rotated more than 10�.) Clearly, for accurate customized corneal ablations, the point-to-point synchronization system used must correct for intraoperative pre-laser cyclorotation.

It's our responsibility to understand the synchronization process used by the various laser systems and to make an informed decision regarding their levels of sophistication.

Precise application of the custom pattern

The third fundamental requirement for precise customized ablations is a laser delivery device that possesses both the pinpoint accuracy and the precise beam contour to create the proper ablation profile on the cornea in accordance with the data set provided by the measurement device.

Broad beam laser systems are highly successful when treating regular and symmetrical ablation patterns. However, their ability to create beam ablation patterns that incorporate irregular and asymmetrical corneal contours, as required by customized cornea, is much more limited. As a result, we're seeing an unmistakable trend in excimer laser refractive surgery toward small spot scanning technology.

Because the margin of error for beam placement with a small scanning beam is minute, accuracy in laser application is critical to obtaining consistent results. (This is of particular concern when the typical 1-degree saccade during fixation occurs at 100� per second.) For that reason, it's essential that the laser system incorporate an accurate eye tracking system.

To maintain an acceptable peak spot placement offset error when using a < 1 mm beam spot size, the sampling rate of the tracking system must be extremely fast. The rule of thumb is: The smaller the laser beam spot size, the faster the tracker must be to attain accurate and reliable beam placement.

Many surgeons become understandably confused when comparing eye tracker speeds among the various laser manufacturers. We must consider many significant variables when selecting an eye tracking system, including:

�        reliability and accuracy of the eye
position acquisition hardware

�        tracker speed and precision

�        mirror translation speed

�        signal-to-noise compensation
algorithms.

Discussion of each of these parameters is beyond the scope of this article. However, the fundamental requirement for a small spot tracker-guided scanning excimer laser system is having sufficient "closed loop bandwidth." This isn't the same as tracker sampling speed. Rather, it's a measure of the actual speed or frequency at which the laser system acquires the eye's position, filters the tracker signal to eliminate tracker noise, directs the beam delivery mirrors to the new eye position and delivers the actual laser pulse.

To effectively track intraoperative eye movement, while delivering a < 1 mm beam spot size, the closed loop bandwidth should be in excess of 100 Hz. This is the true measurement of the time it takes to complete each of the steps from the acquisition of the eye's position to delivery of the laser beam.

At this time, many excimer laser manufacturers don't publicly discuss their laser system's closed loop bandwidth. That makes it even more important for us to thoroughly understand how each laser system handles these complex challenges.

We're getting closer

The imminent arrival of laser systems equipped to accomplish consistent custom ablations makes it imperative that each of us thoroughly understands the three essential steps we've reviewed here. It's the only way we'll be able to successfully navigate the future of refractive surgery and deliver what that future promises.

Brian R. Will, M.D., is president and chief executive officer of Will Vision & Laser Centers in Vancouver, Wash. He has also served as project director for the International Institute for Advanced Laser Surgery.

Manage Patient Expectations to Prevent a Backlash

By Glenn Hagele
Sacramento, Calif.

There's the promise, and then there's the reality. It's when the promise and the reality don't match that refractive surgeons find themselves sitting across from angry, frustrated -- and possibly litigious -- patients. The terms "custom ablation" and "newest technology" present an opportunity to increase this potential hazard exponentially.

The public's expectation of refractive surgery is already very high. And in many cases, expectations are unreasonable. In a recent informal survey of potential refractive surgery candidates, most felt that laser-assisted in situ keratomileusis (LASIK) would produce uncorrected Snellen visual acuity of 20/20 more than 90% of the time. Most also thought that the possibility of complications of all types would be less than a fraction of 1%.

To be certified by the Council for Refractive Surgery Quality Assurance (CRSQA), a surgeon must maintain outcomes of 20/40 or better 90% of the time and 20/20 or better 50% of the time, with a complication rate of not more than 3%. These figures more accurately represent the national norms, but they're inconsistent with the public's perception.

The danger is in minimizing your role

Advertisements that present the illusion of throwing away your glasses forever and counselor affirmations of being the perfect candidate often have the public thinking they need only sign a check, look into a machine, and voila, perfect vision. This perception does little to signify the importance of the skill and experience of the surgeon.

Marketing by the industry shares only part of the blame for unreasonable expectations. Add patients who hear what they want to hear with informed consents that are dismissed as a formality and you have a recipe for a serious backlash against refractive surgery. Recent regional and national news articles about the "victims" of refractive surgery are indicative of this backlash. Most of the people interviewed aren't victims of poor medical care, but are victims of not receiving what they had expected.

Emphasis on the tools of the trade de-emphasizes the master of those tools. This may be fine for manufacturers, but it does little to help a candidate identify the better surgeon. Most refractive surgery candidates have little or no experience in selecting a surgeon. The general public better understands how to select a toaster than how to assess the abilities of a surgeon.

Teach your patients what's important

When candidates are faced with the prospect of evaluating something as nebulous as the skill of a doctor, they fall back on what they know and "choose the toaster" by seeking a particular brand of technology or an affordable price. It's much easier for a layperson to understand the parameters of a piece of equipment than the abilities of a surgeon. It's even easier to understand a lower price.

Even perfect reshaping of the cornea does nothing to ensure that a patient won't experience post-surgery complications, such as dry eye, fluctuation in visual acuity, and low-light problems like haloes around light sources. A piece of equipment won't evaluate medical and personal history, such as pregnancy or the presence of autoimmune disease, but this is easily lost by the public's clamor for the newest technology.

The technological idea behind true custom ablation appears ideal. The ability to reshape the cornea within a tenth of a diopter of optical perfection not only could provide refractive surgery candidates with excellent postoperative vision, but also may be able to help those patients who received less than optimal vision from previous refractive surgery techniques and technologies. Unfortunately, it will take years of clinical trials, FDA evaluations and practical experience before the promise of custom ablation will be in the hands of the majority of refractive surgeons and become a reality for the average patient.

Technology can't stand alone

Refractive surgery candidates and surgeons alike need to remember that no amount of technology will compensate for an inferior surgeon, and only a skilled surgeon knows how to maximize the technology.

Glenn Hagele is the executive director of the Council for Refractive Surgery Quality Assurance, 8543 Everglade Dr., Sacramento CA, 95826-3616. You can reach him by
calling (916) 381-0769, e-mailing glenn.hagele@usaeyes.org or visiting

Industry Update

�        Alcon Summit Autonomous. Feasibility studies of the patented CustomCornea measurement device and the LADARVision laser system are under way. Twenty LASIK and 13 PRK patients, whose pre-op refractive error ranged from
-5.75D to +4.25D sphere with up to -3.25D of cylinder, have been treated. Closely matched eyes of the same patients were randomly selected for treatment using the new technology or conventional LADARVision surgery.
Algorithm modifications in the first 33 eyes resulted in significant improvement in wavefront error profiles. Postoperative uncorrected visual acuities (UCVAs) correlated with the amount of residual wavefront distortions, with better UCVAs corresponding to smaller wavefront errors.
Overall, the results were similar between the LASIK and PRK groups, with some potential biomechanical effects noted. Trends related to positioning of the LASIK flap were observed, which resulted in induced comatic aberrations in the direction of the hinge. New ablation algorithms applied after the first 33 patients resulted in improved patient outcomes and even lower levels of higher-order aberrations.

�        VISX. The WaveScan Wavefront System will be commercially available this fall, making it the first commercially sold wavefront system in the world. In the meantime, the company is continuing its work in the area of custom ablation. It will report on those efforts at the meeting of the International Society of Refractive Surgery this month.
Right now, the WaveScan Wavefront System can be used diagnostically to measure standard spherocylindrical refractive error, assess opacities in the lens, diagnose irregular astigmatism and measure other higher order-aberrations. It will be used to obtain a more complete objective refraction than can be obtained by the traditional means available today.

�        Bausch & Lomb. The Zywave Aberrometer is currently in feasibility testing outside the United States. The Zywave is an integral component of what will be B&L's personalized vision solution, Zyoptix. In addition to the Zywave, Zyoptix includes the Orbscan IIZ corneal measurement device for use with the Technolas 217Z laser's Zylink software. The laser uses a dual-diameter flying-spot approach.

�        Nidek. The OPD-Scan (formerly known as the ARK 10,000) is currently in pre-clinical testing in preparation for application for U.S. regulatory approval. The OPD-Scan combines autorefraction, corneal topography and spatial refractive power-mapping to generate customized corneal maps. This data is fed into the Final Fit software, which calculates the proper ablation. At this time, the diagnostic data is transferred to the laser on a floppy disk. Eventually it will be directly transferred.
Nidek is also awaiting final approval of its patent application to use its excimer laser technology to correct monogenic myopic astigmatism and compound astigmatism. This would allow varied tissue ablation for astigmatic corneas.
Nidek has taken a somewhat different approach to custom ablation. The EC-5000 laser produces a scanning slit beam for most of the ablation, but then the segmental ablation module divides the rectangular-shaped beam into six equal segments, which can be individually or simultaneously projected onto the cornea. (This approach is similar to the VISX and B&L approach in that more than one spot size is used during the ablation.)

�        LaserSight Inc. The FDA recently granted approval for LaserSight to advance the laser pulse repitition rate of its LaserScan LSX excimer laser to 200 Hz. The company had said previously that once that approval was secured, it would file a PMA supplement for its eye tracker technology.
Treatments using LaserSight's CustomEyes system and its ASTRA family of custom ablation products continue in international clinical studies, and clinical research involving the AstraPro custom ablation planning software was expanded during the third quarter. Results will be presented at this month's American Academy of Ophthalmology annual meeting.
In addition, LaserSight has received a notice of allowance from the U.S. Patent & Trademark Office for a method of corneal analysis using a checkered placido apparatus. The company sees this method as being valuable in custom corneal ablations, because it more accurately determines the shape of the cornea, particularly in cases involving irregular surface topographies.

�        WaveLight Laser Technologies. The current FDA clinical trial of the Allegretto laser system for correction of myopia with LASIK will be expanded soon to include customized ablations using a wavefront device based on the Dresden Analyzer.
More than 60 patients have been treated in WaveLight customized ablation trials in Europe. In a series of 25 eyes, LASIK was performed to correct myopic astigmatism (sphere: -1.5D to -8.5D; cylinder: up to -2.5D) using the Allegretto scanning spot laser. Optical aberrations were determined preoperatively and postoperatively by means of a Tscherning aberrometer.
The average best-corrected visual acuity increased from 20/16 to 20/12 at 3 months after surgery. The increase in wavefront error ranged from 0.6 to 2.3. None of the patients lost one line or more in low contrast and glare visual acuity.