Building a Wavefront-Driven Refractive Practice: Optimizing Results, Expanding Indications, and Applying the Latest Technology

WASHINGTON, DC 2005 SHOW DAILY SUPPLEMENT www.eyeworld.org Great service and leading wavefront technology are the key tools for building a successful refractive practice. May 2005 The News Magazine of the American Society of Cataract and Refractive Surgery Robert K. Maloney M.D. Moderator Building a Wavefront-Driven Refractive Practice: Optimizing Results, Expanding Indications, and Applying the Latest Technology Leading clinicians report on exciting advancements in US clinical trials and share their personal experience with recently approved wavefront technologies such as Fourier Analysis and Iris Registration. Inside: The Cosine Effect: Compensating for Unique Corneal Geometry with Peripheral Ablations US Presbyopia Clinical Trial: The First Report Report from the U.S. Clinical Trials: High Myopia and Mixed Astigmatism Can Iris Registration Improve a High Volume Practice? The Impact of Iris Registration on Cylinder, Acuity and Visual Quality Optimized vs. Wavefront-Guided Ablations: Is There a Difference? CONTRIBUTORS Stephen Coleman, M.D. Colman R. Kraff, M.D. Jeffery Machat, M.D. Eric Mandel, M.D. Terrence P. O Brien, M.D. Louis E. Probst, M.D. Julian D. Stevens, F.R.C.S. Steven C. Schallhorn, M.D. Supported by an unrestricted grant from VISX, Inc.

2 ASCRS Washington, DC Show Daily Supplement Building a Wavefront-Driven Refractive Practice Compensating for the Cosine Effect Using actual patient K values versus the default K value is an important factor in reducing induced spherical aberrations By Louis E. Probst, M.D. Using actual patient K values versus the default K value is an important factor in reducing induced spherical aberrations. Louis E. Probst, M.D. The shape of the anterior cornea has a significant effect on laser-tissue interaction and must be taken into consideration to achieve the desired wavefront-guided LASIK ablation. The Cosine Effect, which is the loss of laser energy as a result of both reflection and area expansion, occurs as the laser moves from the corneal center to the periphery. To compensate for this energy loss, additional laser energy (pulses) is placed in the corneal periphery. Using actual patient K values versus the default K value is an important factor in reducing induced spherical aberrations. Energy Loss Understanding what happens to laser energy at the center of the cornea versus the periphery is key to achieving the As the laser moves from the corneal center to the periphery, laser energy is reflected and the beam becomes ovalized. most accurate ablation. Corneal power, reflection, and area expansion are the major factors involved in laser energy loss at corneal periphery. Corneal power is a measure (in diopters) of the capability of a lens to converge (plus lens) or diverge (minus lens) light rays. Reflection involves the bouncing back of light rays by a mirror-like surface. Area Expansion is the ovalization of the laser beam. For example, for typical corneas (K = 44 D), at a distance of 3 mm from the vertex, the fluence loss is 2.5% for reflection, and 8.1% for area expansion. The VISX laser uses algorithms to compensate for reflection and area expansion by increasing the number of pulses fired in the periphery. VISX has compensated for the Cosine Effect since 1986. However, if no K value is entered into the laser, the system uses a default K value of 44 D. The default K value was determined by analyzing a population of patients. Using actual patient K values versus the default K value is very important because the amount of the compensation of the cosine effect is dependent on the K values. The Cosine Effect is due to the relative steepness in the cornea. Therefore, a steeper cornea requires more compensation than a flatter cornea. If the patient has a steep cornea and the actual K s are not entered, the laser will use the default. Therefore, full compensation will not be used and the patient will not get the full benefit of the treatment. Case Studies For a -5D myopic treatment case study in which no K s were compared to actual K s, the patient had a 6 mm pupil, and a 6mm OZ, 8mm AZ. The actual K was 44D. Figure 2 shows the treatment profile difference if no K values are used. In a case such as this when no K value is used compared to the actual K value, as much as 0.14 microns of spherical aberration can be induced in this -5D myopic treatment. For a +5D hyperopic treatment case study in which the default K was compared to the actual K, the patient had a 6 mm pupil, a 6mm OZ and a 9.5mm AZ. The actual K reading was 30D and the default K was 44D. Figure 3 shows the treatment profile difference. In a case such as this one, using the default K value compared to the actual K values as much as 0.38 microns of spherical aberration can be induced in a +5D hyperopic treatment. Using actual patient K values, versus the default K value, is an important factor in reducing induced aberrations

Better Wavefront Results With Fourier By following key guidelines, surgeons can optimize custom LASIK outcomes By Eric Mandel, M.D. Building a Wavefront-Driven Refractive Practice ASCRS Washington, DC Show Daily Supplement 3 Results from a three-month, wavefront-guided LASIK study using the CustomVue procedure with the Fourier algorithm showed superior results, when compared with treatments using CustomVue with the Zernike algorithm. Surgeons can optimize their wavefrontguided results by following several key guidelines culled from my wavefrontguided LASIK clinical experience, as well as from my teaching and consultation with many LASIK surgeons. Of the first 51 eyes treated, 100% were 20/20 or better, and 100% of patients did not complain of any significant or problematic glare or halo. Eric Mandel, M.D. The Study The prospective study included our first 51 eyes that underwent Fourier CustomVue treatment at their first point of stability 10 to 16 weeks post-op. These patients were the first eyes to have Fourier analysis and treatment in our practice. There was no learning or transitional period. Of the first 51 eyes treated, 100% were 20/20 or better, and 100% of patients did not complain of any significant or problematic glare or halo. The vast majority of patients met or exceeded their expectations. In our CustomVue Zernike study presented several years ago, we first achieved 95% of eyes with 20/20 or better in the same group. Getting Better Results Some surgeons have remarked that when they switched from conventional LASIK to wavefront-guided LASIK with Zernike, or from Zernike to Fourier wavefront-guided LASIK, their results were improved, but not as high as their expectations. Some surgeons even felt that conventional surgery achieved more consistent results. This study proves that using the Fourier algorithms and treatments yield excellent results. Surgeons who follow these guidelines can help optimize their best possible outcomes: 1) Acquire Wavefront Information the Day of Surgery. High volume surgeons often contend that this step takes too much time and hinders patient flow on the day of surgery. Instead, they often use wavefront data that is days or weeks old. However, in my experience, I find that it is best to do the wavefront acquisition the same day as the surgery. 2) Remove Contact Lenses Earlier. Patients who have their contacts out the longest period of time prior to surgery have better results. Surgery Fourier-driven ablations provide a higher level of precision and improve resolution compared to Zernike-driven ablations. is then performed on the eyes in their most natural and non-iatrogenic state. This is more important today than ever before because we have learned that not only hard lenses, but also soft and toric lenses can warp the corneal surface. Therefore, we require patients to remove soft lenses a minimum of two weeks pre-op, and toric and gas permeable lenses a minimum of three weeks. 3) Lubricate, Lubricate, Lubricate. Aggressive pre-operative lubrication is essential. We treat pre-operatively with tears, ointments at night (like Refresh PM, Allergan, Irvine, Calif.), and, often, with silicone or hydrogel plugs. We also use Restasis (Allergan) extensively both pre- and post-operatively. 4) Acquire Wavefront Information Carefully. It is very important to employ an experienced technician with exquisite attention to detail. The technician must make sure patients do not accommodate while acquiring wavefronts. Accommodation can significantly affect lower and higherorder aberrations. This technician should also ensure that each patient's head is in the correct position while the wavefront data is being acquired. This helps reduce the potential for registration mismatch during ablation. Iris Registration, which was just approved in the United States, will further optimize this aspect of the procedure. 5) Intra-operative Tips and Technique. During surgery, surgeons can prevent a slightly offaxis ablation (Cosine Effect) and avoid suboptimal results by making sure the patient's actual K values are used, that the chin does not tilt up or down, and their eyes do not slightly roll up (Bells reflex). Also, it is very important that the surgeon check to make sure that fluid from the tear film does not egress onto the stromal bed creating an irregular ablation. 6) Keep Humidity and Temperature Tightly Controlled. Consistent humidity and temperature in the operating room are very important. Keep extra equipment such as backup humidifiers, dehumidifiers, and portable air conditioner units on hand in the OR to make sure the proper conditions can be maintained at all times. 7) Less Illumination, More Dim Lighting. Dim lighting during surgery is better for patient comfort, and it also helps avoid a shifting pupil centroid. With dim lighting on a non-dilated pupil, the laser system will keep the pupil centroid in the best location. 8) Optimize Healing. Adequately preparing the patient's surface preoperatively and quickly repositioning the flap with minimal handling will minimize the amount of postoperative healing and remodeling.

4 ASCRS Washington, DC Show Daily Supplement Building a Wavefront-Driven Refractive Practice U.S. Presbyopia Clinical Trial: The First Report Early results are promising for wavefront-guided laser vision correction of hyperopic presbyopia By Colman R. Kraff, M.D. Corrections have been accurate and predictable, and patient satisfaction with both near and distance uncorrected acuity has been high. Colman R. Kraff, M.D. Results have been very promising from a U.S. study to determine the preliminary safety and effectiveness of CustomVue WaveScan-guided LASIK for the treatment of presbyopic patients with hyperopic refractive errors. VISX has developed a patented, multifocal ablation profile designed to give patients good uncorrected near and distance vision in the same eye. Using Variable Spot Scanning, the laser creates a subtle change in the ablation shape derived from the subject's wavefront map. The goal is to provide near vision in the steepened central zone, and distance vision in the peripheral zone. The combination of the pupilsize-dependent central zone, the peripheral zone, and the LASIK flap produces an aspheric curve that expands the depth of focus beyond what monovision can offer. Ultimately, I would expect that the patients who respond best to this treatment will be low hyperopes in the presbyopic age group. Study design The criteria for enrollment in the preliminary trial are quite strict. We are enrolling 20 subjects, each of whom will have their non-dominant eye treated with the wavefront-guided presbyopic procedure. The dominant eyes will receive a wavefront-guided CustomVue hyperopic treatment. Both eyes will be targeted for emmetropia. Iris Registration technology was utilized in this clinical trial. This is a critically important component of the presbyopia treatment because it ensures proper registration of the ablation and proper placement of the pupil-size dependent central zone relative to the pupil centroid. Patients must be at least 40 years old with best-corrected vision of 20/20 in both eyes, and uncorrected vision worse than 20/40. Pre-operatively, they must be hyperopes with up to +4.0 D sphere and up to 1.5 D astigmatism for a manifest refraction spherical equivalent up to +4.5 D. They must be presbyopic with a near add requirement of at least 1.25 D. And, of course, patients must be otherwise qualified for a CustomVue LASIK procedure, with adequate corneal thickness, visual stability over one year, and no pathology. Finally, before having the surgery, the patients have to go through a bifocal contact lens trial to determine whether they like multifocal correction. To date, eight of the 20 subjects have been enrolled, with three-month follow-up on two. A larger, multi-site study will be undertaken prior to seeking approval for the procedure from the Food and Drug Administration. Case results The preliminary results have been outstanding. Corrections have been accurate and predictable, and patient satisfaction with both near and distance uncorrected acuity has been high. To offer one example, we treated a 54-year-old female whose pre-operative refraction in the multifocal eye was +1.00 +0.25 x 96. Pre-operatively, she had uncorrected distance, intermediate, and near vision of 20/40, 20/50, and 20/63 respectively. Three months following the multifocal ablation, her refraction in that eye was -1.00 D sphere with 20/20 uncorrected distance acuity, 20/16 intermediate vision, and 20/20 near vision. This patient gained five lines of near acuity in her multifocal eye compared to a two-line gain in the monofocal eye. Binocular near acuity also increased five lines to 20/20. Both eyes achieved 20/20 or better distance UCVA with no loss of best-corrected acuity. In a second case, a 52-year-old male was treated with multifocal ablation in his left eye. The pre-operative manifest refraction was +2.00 +0.25 x 175 with uncorrected distance vision of 20/50, intermediate vision of 20/125, and near vision of 20/160. Three months after treatment, his manifest refraction in that eye was - 0.25 +0.50 x 125. He has 20/20 uncorrected distance vision and 20/32 intermediate vision. Uncorrected near vision improved six lines from 20/160 to 20/40, compared to a two-line gain in the monofocal eye. Binocular near acuity increased five lines to 20/32. Both eyes achieved 20/20 distance UCVA. There was no significant loss of best-corrected acuity although the multifocal eye lost one line of distance BSCVA, from 20/16 to 20/20. The distance vision obtained by patients in this trial is at least as good, and possibly better than we would expect from hyperopic CustomVue. The use of Iris Registration in this trial may be a factor in the outcomes due to better cyclotorsional alignment. If the results continue in this vein, a multifocal wavefront-guided treatment could become my treatment of choice for presbyopic patients. This patient is able to see 20/20 or better uncorrected at distance, intermediate,and near measures at 3 months compared to 20/63 or better at pre-op. At 3 months, 100% of patients are very satisfied/satisfied with their distance vision without correction compared to 50% at pre-op with correction.

Report from U.S. Clinical Trial: High Myopia Wavefront-guided laser vision correction offers excellent quantity as well as quality of vision By Terrence P. O Brien, M.D. Building a Wavefront-Driven Refractive Practice ASCRS Washington, DC Show Daily Supplement 5 Not surprisingly, these patients many of whom had been wearing glasses since kindergarten or earlier are ecstatic with the dramatic change in their visual performance. Terrence P. O'Brien, M.D. Like others who participated in the VISX CustomVue for high myopia clinical trial, I was excited about the opportunity to provide customized laser vision correction to patients with, arguably, the most to gain from the treatment. However, we also had some very specific concerns going into this trial. In patients with high refractive error, one must already remove a lot of tissue. A custom treatment removes slightly more tissue than a conventional one, so there were concerns about the At 6 months, 65% of patients are 20/16 or better, while 84% are 20/20 or better uncorrected. potential for creation of iatrogenic keratectasia. Because of this, we were very careful with pre-operative and intraoperative monitoring to leave at least 250 microns of tissue remaining in the stromal bed after the ablation. Study design Ninety-two patients were treated in the clinical trial. All were treated bilaterally (184 eyes), and all of the eyes were targeted for emmetropia. We were able to make use of the new Fourier wavefront reconstruction algorithm for more precise wavefront maps, and Variable Repetition Rate for faster treatment times. Both of these are now standard for all CustomVue procedures. Pre-operative refractive error was quite high, with average sphere of -8.0 (±1.4 D, range -5.5 to -11.3 D). Average cylinder was -1.0 D (±1.0, range 0.0 to -5.3 D). Manifest refraction spherical equivalent was -8.5 D (±1.3, range -6.4 to -11.8 D). Results At six months, 98% of the eyes were seeing 20/40 or better uncorrected, 84% were 20/20 or better, and 65% were 20/16 or better. Three-quarters had the same or better post-op UCVA compared to their pre-op BSCVA. Among the spherical myopes, 99% were 20/20 or better uncorrected, with 84% 20/16 or better at six months. Not surprisingly, these patients - many of whom had been wearing glasses since kindergarten or earlier - are ecstatic with the dramatic change in their visual performance. As a surgeon, it has been very gratifying to see a -10 D myope seeing 20/16 uncorrected on just the first day or week post-op. Initially, we were concerned that such high treatments might lead to a loss of quality of vision or disturbances in night vision due to changes in the corneal curvature that are more dramatic than we typically see in lower myopes. However, that has certainly not proven to be the case. No eye in the study lost more than one line of vision at the six-month visit, and patient satisfaction with the quality of vision postoperatively has been very high. There are several other options for high myopic corrections, but at this VISX CustomVue mixed astigmatism receives FDA approval Patients in the clinical trial report sharper, better, and clearer vision with this custom procedure By Stephen Coleman, MD The CustomVue treatment for mixed astigmatism is demonstrating positive results at nine months, with 74% of eyes achieving 20/20 or better uncorrected visual acuity (UCVA), and 99% achieving 20/40 or better UCVA. The FDA recently approved the VISX CustomVue LASIK procedure for the reduction or elimination of naturally occurring mixed astigmatism when the magnitude of cylinder (from 1 D to 5 D) is greater than the magnitude of sphere, and the cylinder and sphere have opposite signs. Coleman Vision is one of six centers who participated in this U.S. clinical trial evaluating Wavefront-Guided LASIK treatment of mixed astigmatism. Study results For the U.S. clinical trial for mixed astigmatism, all patients received bilateral LASIK treatment using the VISX Star S4 Active Trak with Variable Repetition Rate (up to 20 Hz). No nomogram adjustments were made. All eyes were targeted for emmetropia, and follow-up is available to nine months for the majority of patients. Environmental conditions included 40% to 45% relative humidity and an operating room temperature of 68 to 72 Fahrenheit. The study included 86 eyes of 44 mixed astigmatism patients. The mean age was 41±11 years. Sphere was -2.09 ± 1.12 D (-5.16 to -0.66), and cylinder ranged from + 2.98 ± 1.20 D (1.25 to 5.0). The MRSE was -0.60 ± 0.89 D (-2.66 to 1.72). At nine months, UCVA was excellent, with 74% of eyes 20/20 or better, 87% 20/25 or better, and 99% 20/40 or better. Stability was achieved at three months post-op. One hundred percent of eyes changed < 1 D between all visits. The accuracy of the sphere was also impressive. At nine months, 77% of eyes were within ± 0.5 D of intended MRSE. In a survey of patients regarding vision at night at six months, 53% said they were satisfied or very satisfied pre-op (with glasses), and this improved to 89% post-op (without glasses). For vision at night with glare, 38% of patients were unsatisfied pre-op, and this number decreased to 8% post-op. Patients also reported that their frequency of halos around lights decreased, as did their post-op frequency of glare. For best spectacle corrected visual acuity (BSCVA), no eye lost more than two lines of BSCVA. At nine months, UCVA was excellent, with 74% of eyes 20/20 or better, 87% 20/25 or better, and 99% 20/40 or better. point I would say that none of them surpasses a custom wavefront correction in patients for whom a corneal procedure is appropriate. As this trial demonstrates, a customized approach offers excellent quantity as well as quality of vision. Most importantly, it provides an alternative to intraocular refractive surgery that may portend an increased potential of retinal detachment in this already high risk group. With a careful pre-operative exam and close attention to residual bed limits, I am now quite comfortable treating high myopes up to -11 or -12 D with a custom LASIK procedure.

6 ASCRS Washington, DC Show Daily Supplement Building a Wavefront-Driven Refractive Practice Iris Registration a Far Greater Advance than Anticipated This new technology is able to identify and compensate for small amounts of cyclorotation that can have a large impact on post-op results By Jeffery J. Machat, M.D. In order to maximize custom ablation outcomes, it is important to position the ablation pattern onto the cornea in a manner that corresponds directly to the measurements taken by the wavefront device. In the past, some surgeons have marked the cornea while others have relied on careful positioning and observation to ensure that the cornea was properly aligned and the treatment well centered. VISX has recently introduced automated Iris Registration (IR) for its CustomVue system. IR relies on matching reference points in the natural iris pattern to compensate for cyclotorsion and pupil centroid shift between the time of wavefront capture and the ablation. I expected this new process to be of incremental value and, to be honest, doubted that I actually needed it. But now that I ve used IR for several months, I find myself increasingly reliant on it. Moreover, I ve been humbled to realize how flawed my own judgment of centration and alignment really is. Whereas I was once quite confident that I could recognize significant cyclotorsion when it happened, I now know that it is entirely possible for an eye to be 4-5 degrees excyclotorted without my being aware of it in the least. A couple of my recent cases illustrate what might have happened had I not been using Iris Registration. In one, a 55-year- Iris Registration is likely to quickly become standard of old male with high cylinder preop (+0.25 - care. Jeffery J. Machat, M.D. IR Results in Less Cylinder, Better UCVA Postop Multi-center study finds significant differences between treatments with and without IR In a retrospective analysis of data from four international centers, Iris Registration has made a significant difference in outcomes. In 270 primary laser vision correction patients with preop BCVA of 20/20 or better, the mean cyclotorsional movement was 2.4 ± 2.0 degrees. A comparative analysis was conducted on a subgroup of eyes with 1.5 D or greater preoperative cylinder. Cohort A (n=57) was treated without IR; Cohort B (n=59) was treated with IR. The two groups had similar levels of cylinder preop. Postop, the IR cohort had 50% less cylinder (0.2 D, compared to 0.4 D for the non-ir cohort). Additionally, there was a statistically significant difference between the two groups in the percentage of eyes achieving 20/20 or better UCVA postop. Ninety-two percent of the IR cohort, versus 82% of the non-ir cohort, was 20/20 or better at the last postop visit. At one of the centers, Dr. David Chaokai Chang, of Taipei, Taiwan, performed a contralateral eye study in which 26 patients received CustomVue with IR in one eye and CustomVue without IR in the other. At one week postop, nearly half the patients (46%) had better uncorrected vision in the eye treated with IR. Not a single patient had better UCVA in the non-ir eye. 4.50 x 164 OS) cyclotorted 5.8 degrees during surgery. With IR, he had an excellent outcome and maintained his preop BCVA of 20/20. Without it, he would have had induced sphere and cylinder and poor quality of vision. IR Pearls Iris Registration compares iris markings in two images one taken at the WaveScan during the wavefront exam and the other at The IR cohort has 50% less post-op cylinder than the Non-IR cohort Ninety-two percent of the IR cohort, versus 82% of the non-ir cohort was 20/20 or better. This difference is statistically significant. Case Study Without IR, this patient would have had induced sphere and cylinder, and poor quality of vision. the laser just prior to ablation. If there is any problem getting IR to work, it s going to happen when the second image is captured. Our rate of successful IR capture rate is approximately 80% with IntraLase flaps and about 97% with mechanical microkeratome flaps. Dark irides, especially green eyes with brown flecks, are the easiest to capture. The most difficult eyes are those with pale gray irides or velvety iris patterns. Nearly featureless irides may always be among the small percentage that we have to treat without IR. But for most others, there are several steps that can be taken to minimize IR failures. The first is positioning. The eye must be in a plane perpendicular to the laser beam. Chin position should be neutral so that shadows from the nose don t affect the image. Metal or reflective items around the eye can also cause unwanted shadows. The second important factor is lighting. If the iris image is at all difficult to capture at the laser, I typically reduce the indirect, side illumination (which seems to cause more reflection off the cornea), keeping the direct microscope lighting. This works about 80% of the time. In other cases, the iris pattern actually becomes more evident with the lights turned up moderately or in rare instances, very brightly. VISX recommends an operative pupil of 4-6 mm, and it is probably true that IR is most successful when the pupil size at the laser is closer to what it was during the WaveScan exam. IR is going to make a small difference for most patients and a huge difference for a few patients. The problem is, we have no idea which patients are in the latter category. As I noted earlier, I ve been very poorly predictive of who has significant cyclotorsion and who does not. For this reason, I am most comfortable now using it on every case, and believe that Iris Registration is likely to quickly become standard of care.

Building a Wavefront-Driven Refractive Practice ASCRS Washington, DC Show Daily Supplement 7 The Impact of Iris Registration on Cylinder, Acuity, and Visual Quality Proper alignment of wavefront-guided ablations is key to reducing post-operative visual complaints By Julian Stevens F.R.C.S. This technology provides instant feedback. For the first time, surgeons and staff receive feedback as to how well we re aligning our patients. Julian Stevens, F.R.C.S. Arecent study of 69 eyes that received wavefront-guided LASIK using VISX Iris Registration demonstrated that the technology had more precise alignment, prevented angle errors, and helped improve outcomes, according to Julian Stevens, of Moorfields Eye Hospital, London. Angle and Rotation Dr. Stevens notes that Iris Registration is extremely helpful for therapeutic treatments, which are often highly complex shapes. When you have such highly complex shapes, as in therapeutic treatments, precise alignment is needed, he explains. As such, angle is very important. When patients are scanned sitting up, one particular angle is achieved. Once the eye is covered over in a monocular situation, particularly under the laser, then there is the potential for an excyclotorsion. Also, when the patient lies in the supine position there is an angle error as well, Dr. Stevens says. Another issue is the degree to which the eye rotates when the LASIK flap is cut. In the study, Dr. Stevens found that eyes could potentially have a significant undercorrection due to rotational error when Iris Registration is not employed. About 10% would have had a 20% undercorrection of astigmatism if I had not used Iris Registration in the treatment, because this registration was done at the point of firing the laser, he says. Research has shown that angle change produces about a 2-4 error is common. Dr. Stevens points out that he has found that 2.8 counterclockwise error was the norm for the 69 eyes in the study and 4% had more than 7 of angle error. Twenty-seven percent of patients had greater than or equal to more than a 5 difference in rotational angle error between eyes. More than a 5 difference was quite remarkable. No matter how well the patient is aligned at the start, when bilateral treatment is done there will be a considerable difference between eyes, he explains. If you take a look at the absolute angle error, it doesn t matter which direction, the mean was 2.8, he explains. He also found that the eye rotates a relatively small amount when the flap is cut. One or two patients had a big change, but the overall absolute angle change after the LASIK flap was cut was a 1.2 change clockwise. When a classic LASEK epithelial flap is created the degree of absolute angle change is about 1.3 counter clockwise, he says. Dr. Stevens re-registered three patients throughout the procedure from the beginning to the end, and two patients were essentially neutral. They didn t move at all. One patient who was less cooperative made a considerable change of position. There was a jump from a counterclockwise position to a clockwise rotational error, says Dr. Stevens, who notes that with the Iris Registration technology a change in position becomes quite clear. For example, the surgeon can see the patient move their eye or move their head, and then re-register. IR Technology Iris image registration, which is now available in the US, permits compensation for cyclorotational errors as well WaveScan image verification and re-registration for intra-operative cyclotorsional movement. Over the past several hundred patients I have treated with Iris Registration my iris capture rate has been 100%, said Stevens. Using the IR technology, the torsional angles are calculated from multiple measurements. Then, the system identifies the prominent landmarks of the iris, and provides WaveScan reference marks. There also is cyclotorsion rotation indicator. Sophisticated algorithms calculate the ablation torsional angle. The algorithms compensate for pupil distortion, axial misalignments, changes in pupil size, and reflections, he said. The iris registration technique is flexible for both PRK and LASIK. In addition to compensating for cyclotorsional error, this upgrade also compensates for any pupil centroid shift from the WaveScan pupil to the pupil image under the laser. Future Outcomes The Iris Registration technology is an important advancement in wavefront-guided LASIK, according to Dr. Stevens. This technology provides instant feedback. For the first time, surgeons and staff receive feedback as to how well we re aligning our patients. Therefore, the staff is already learning to get better at actually putting people on the table, he says. The technology also is improving outcomes. For example, a patient with 4.5 D of cylinder pretreatment was 20/15 unaided in each eye the next day. There is more happiness all around and the technology is very easy to use, he concludes. Analysis of pre-operative cyclotorsional rotation shows that 14% sign of patients cyclorotate more than 5 degrees. Without Iris Registration, the astigmatism in 32% of patients in this cohort would have been undercorrected by 10 to 20%.

8 ASCRS Washington, DC Show Daily Supplement Building a Wavefront-Driven Refractive Practice Optimized vs. Wavefront-Guided Ablations: Is There a Difference? Regardless of pre-operative aberration structure, wavefront-guided ablations provide a better result than both conventional and wavefront-optimized ablation By Steven C. Schallhorn, M.D. The greater the pre-operative HOA, the greater is the benefit from a wavefront-guided procedure in addressing those aberrations. Steven C. Schallhorn, M.D. Wavefront-optimized refractive surgery is a technique in which extra laser pulses are added in the periphery of the cornea in an attempt to reduce the induction of spherical aberration commonly associated with conventional LASIK. The correction is not customized in the sense that we typically think of a wavefront procedure being customized. Rather, it is based on the patient's sphere and cylinder prescription, just as in conventional LASIK. And as with conventional LASIK, a wavefront-optimized procedure aims to correct only lower-order aberrations; namely, sphere and cylinder. To the extent that it can do this without inducing as much spherical aberration as LASIK typically induces, wavefront-optimized surgery is certainly better than conventional surgery. But that doesn't necessarily make it as good as wavefront-guided surgery. A Wavefront-Guided (WFG) refractive surgery procedure enables the surgeon to measure all of the eye's aberrations - both lower- and higherorder aberrations - and then designs a customized treatment profile based on those aberrations. The visual improvement from a WFG treatment would be very apparent in a patient with significant pre-op, higher-order aberrations (HOA). The greater the pre-op HOA, the greater is the benefit from a wavefront-guided procedure in addressing those aberrations. Offering wavefront-optimized surgery only to those with very low HOA would require wavefront aberrometry on all patients, and then selection criteria based on the aberrations. However, the visual advantages of WFG over optimized should also be apparent in patients without significant pre-operative higher aberrations. An optimized procedure is designed to reduce the induction of spherical aberration. However, other higher-order aberrations, such as coma and trefoil, are also induced by conventional LASIK. The optimized procedure will likely induce these same aberrations. Of note, WFG surgery also reduces the induction of these other aberrations. The net effect is an improved quality of vision with a WFG procedure. We tested this theory by creating a model of the visual effect of aberrations induced by the procedures. Three real patients were analyzed. The first had a normal level of HOA, the second had an elevated level of HOA (representing a therapeutic treatment of a post-conventional LASIK patient), and the third had negative spherical aberration. Each patient was theoretically treated with three LASIK ablations: conventional, optimized, and WFG. All three treatments were assumed to perfectly correct sphere and cylinder. The induction of higher-order aberrations was patterned after our large population studies of both conventional and WFG LASIK. The mean and standard deviation of each higher-order term was calculated. Using these standard deviations, a random wavefront map was created for each treatment modality, which had the appropriate RMS value for the induced HOA. For the optimized procedure, no post-op change in spherical aberration was assumed, while other higher-order terms were induced similar to a conventional procedure. Comparison was done with maps, point-spread functions, and a convolved letter E. In the first two patients, the optimized procedure resulted in improved visual quality over conventional. However, the WFG procedure was superior to both conventional and optimized, primarily due to less induction of higher-order aberrations, not just the spherical term. In the third patient, who had negative spherical aberration, the visual result of conventional was actually better than optimized. This is significant as 5-10% of the population has negative spherical aberration. This is because conventional LASIK induces positive spherical aberration, hence reducing the amount of this aberration in this patient. Even in this patient, the WFG procedure was still superior to both other treatments because it was able to measure and treat the negative spherical aberration. No wavefront-guided platform has fully achieved the goal of inducing zero aberrations and/or completely eliminating all pre-existing aberrations. But as we learn more about higher-order aberrations, how to correct them, and what they mean for vision, the value of platforms that can adjust corrections based on this information will become greater and greater. Wavefront-optimized treatments may be better than conventional for most patients because they induce less spherical aberration. However, the future lies not in simply optimizing corrections for a population mean, but in further perfecting individually customized corrections. Treatment Outcome Comparison Modeling of 3 real patients with 3 differents LASIK ablations. All 3 treatments were assumed to perfectly correct sphere and cylinder. Using induced HOA standard deviations from our large data sets, a random wavefront map was created for each treatment modalily.