September 15, 2004

Sponsored as an educational service by Alcon Laboratories, Inc.

Eric D. Donnenfeld, MD,is the medical director at the TLC LaserCenter in Long Island and a partner withOphthalmic Consultants of Long Islandand Connecticut. Dr. Donnenfeld is alsoa member of the OCULAR SURGERY NEWS

editorial board.

Marc A. Mullie, MD,is an ophthalmic surgeon specializing inLASIK at the LaservueRefractive SurgeryClinic in Montreal, Quebec.

Roger F. Steinert, MD, is professor of ophthalmology and vice-chair of clinical ophthalmology at theUniversity of California, Irvine.

Daniel S. Durrie, MD,is the director and head of the refractivesurgical team at Durrie Vision inOverland Park, Kan. Dr. Durrie is also amember of the OCULAR SURGERY NEWS

editorial board.

Introduction

Customized wavefront ablation technology has allowedfor more precise surgical outcomes in LASIK proceduresand several clinical trials have shown the technology to

be superior for correcting higher-order aberrations. The purpose of this discussion was to compare wavefront sys-

tems with each other and conventional LASIK systems in termsof treating aberrations and reducing induced aberrations duringthe surgical procedure. Additionally, the faculty compared thedifferent features that are available on the approved customizedwavefront platforms and how these differences translate to capa-bility for precision in surgical outcomes. I would like to thankOCULAR SURGERY NEWS for organizing this roundtable symposiumand Alcon for its support.

Richard L. Lindstrom, MDChief Medical EditorOCULAR SURGERY NEWS

Stephen F. Brint, MD, is an associate clinical professor ofophthalmology at Tulane UniversitySchool of Medicine in New Orleans,and is in private practice inMetairie, Louisiana. Dr. Brint is alsoa member of the OCULAR SURGERY

NEWS editorial board.

Moderator

Copyright 2004, SLACK Incorporated. All rights reserved. No part of this publi-cation may be reproduced without written permission. The ideas and opinionsexpressed in this OCULAR SURGERY NEWS monograph do not necessarily reflectthose of the editor, the editorial board, or the publisher, and in no way implyendorsement by the editor, the editorial board, or the publisher.

Mark G. Speaker, MD, is the medical director of TLC LaserCenter in Manhattan and is the founderof Laser and Corneal Surgery Associates,which has offices in New York, NewJersey and Connecticut.

Centration with wavefrontStephen F. Brint, MD: When Alcon (Fort Worth,Texas) first acquired the LADARVision fromAutonomous in 2001, this system was the onlylaser for wavefront ablations that had the capabil-ity for registration. Currently, manymore laser manufacturers are realiz-ing the importance of registrationand, as a result, are making attemptsto incorporate registration into theirplatforms.

Dr. Steinert, you have used theLADARVision system for severalyears and have also used other wave-front systems. First, can you explainthe importance of registration and,second, can you compare this fea-ture on the systems that you haveused?

Roger F. Steinert, MD: Registra-tion has come to symbolize the con-cept that wavefront optical measure-ment is taken on a system differentthan that on which the laser treat-ment is performed. Thus, the wavefront measure-ment data must be transferred to the patient whois lying under the laser in a different location,which is registration.

The LADARVision system has always had aversion of registration, so when wavefront tech-nology became available, it was an easy matchfor this system. Additionally, the LADARVisionsystem has always considered astigmatism andthe true horizontal axis, so applying limbus align-ment for a patient in a supine position is a natur-al transition, allowing surgeons to match thewavefront information to the patient to treat thecorrect area.

Our early studies with the basicLADARVision system without the wavefrontcomponent showed that at least one-quarter ofpatients treated had potential for misalignmentfrom basic astigmatism, which is a lower-order

aberration. When wavefront technology becameavailable, I found that the higher-order aberrationerrors were magnified considerably. A small mis-alignment in terms of axis can have a majorimpact on undercorrection and, in some cases,

can actually cause new higher-orderaberrations due to misalignment ofthe pattern of treatment to the actu-al wavefront error on the eye.

I am not aware of any systemother than the LADARVision thatcurrently has an effective means ofregistering the information cap-tured on the wavefront device tothe patients’ eyes when under thelaser. With other systems, centeringon the pupil may result in shifts ofalignment because the pupil doesnot expand concentrically, evenwith natural dilation on differentillumination.

Several companies have recog-nized that this is an issue and arenow trying to find a means ofanatomical landmark registration

such as with iris recognition software.

Marc A. Mullie, MD: The Zyoptix (Bausch &Lomb, Rochester, N.Y.) system’s iris recognitionsoftware uses a type of limbal retical similar toCustomCornea’s (Alcon). However, it appearsthat because centration is not computer-driven,the surgeon is required to manually set the lightonto the apparent center of the pupil, which canresult in a 200-µm to 300-µm error.

Eric D. Donnenfeld, MD: The biggest differencebetween conventional and customized ablation isthat the concept of centration has shifted from thecenter of the pupil to the center of the wavefrontmap. Therefore, the wavefront must be measuredaccurately and registered to the same area of thecornea at which it was originally measured at thetime of surgery.

Clinical Results with Customized Ablation Technology

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3

The wavefront must

be measured

accurately and

registered to the

same area of the

cornea at which it

was originally

measured at the

time of surgery.

— Eric D.

Donnenfeld, MD

4

To say that a pupil-tracking system canaccomplish this is ludicrous — because thepupil is a moving target, it will continuallymove with illumination level. Thus, with pupiltracking, the surgeon may apply wavefronts toareas of the cornea that do not correspond to theareas of the cornea that were measured (Figure1) and, in doing so, induce significant aberra-tions. The LADARVision is the only systemavailable that allows the surgeon to directlyapply wavefront to the areas from which theywere taken.

Brint: It seems fairly straightforward that whentracking the pupil relative to the limbus, a fastvideo-tracking system should, theoretically, besufficient. However, it seems that even though themovement of the eye may be tracked, the move-ment of the pupil within the eye is a differentmatter and results in an inferior landmark.

Donnenfeld: It is important for surgeons tounderstand that the pupil cannot be classified asa landmark because it moves. Rather, the limbusis a landmark. In our study, we found that therewas a mean 177-µm movement in pupil posi-tions between dim and bright illumination; 10%of patients measured in our study had a 300-µmmovement. [AU: Please provide reference.] Ifthe intent is to treat a patient for spherical aber-ration with measurements that are off by 300 µm, the surgeon will actually be treatingcoma and will induce significant aberrations.

Daniel S. Durrie, MD: I often use wavefronttechnology to provide custom upgrades forpatients who have had previous surgery, some-times to correct 1 µm or more of spherical aber-ration. The ablation pattern of the laser when it isset for higher-order aberrations is dramatic in thatthe hot and cold spots are in close proximity toone another, especially with coma. There are 5º to7º of rotation, so a few microns of deviation canhave a significant effect.

The CustomCornea system has a sophisticatedregistration system, which starts at theLADARWave (Alcon) (Figure 2). TheLADARWave locates the center of the undilatedpupil and the limbus. Then, two small ink dotsare placed on the conjunctiva outside the limbus.The eye is then dilated to capture the largestamount of data and a wavefront measurement istaken. This measurement records the location ofthe pupil center, the ink marks and the wavefront.After these data are loaded into theLADARVision system, registration of the wave-front to the exact position on the patient’s eye issimple and laser correction is delivered to thecorrect location.

I perform a large number of custom upgradesfor patients who have had previous surgery. TheLADARVision’s registration system allows me tofeel comfortable that I am delivering the appro-priate correction to these eyes in complicatedcases.

With the LADARVision system, two dots aremarked on the eye to align the eye to the laser,

OCULAR SURGERY NEWS

Figure 1. No fixed reference results in a decenteredablation due to difference in lighting conditionsbetween when the wavefront was taken and theablation was performed. Figures 1 and 2 courtesy of Eric D. Donnenfeld, MD.

Figure 2. The fixed reference with CustomCornea reg-istration does not cause any wavefront shift becausethe registration is fixed on the limbus for both thewavefront measurement and the ablation, not thepupil.

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which is a slight adjustment from simply usinglimbal registration. This system of taking a dilat-ed wavefront on the LADARWave, registering itto the limbus and the two small dots and visuallyrealigning to the points in the operating room, isa vast step beyond what other platforms offer.

Steinert: Surgeons have labored over the ideathat the ideal treatment is centered on the pupil.Based on the literature from the 1980s, surgeonswere using the corneal light, or apical, reflex forcentration, which was less reliable than the pupilcenter. However, prior to wavefront technology,ophthalmologists were, in theory, looking for thetrue visual axis as it intercepted with the cornea,which is an indeterminable point.

With the proper registration technology, suchas is used by the LADARWave, this all becomesa non-issue. I predict that the impact will be evengreater when hyperopic wavefront technology isavailable, because many patients with hyperopiahave angle kappa deviations. My results treatinghyperopia improve dramatically when I recog-nize these deviations. That said, there is also asignificant number of patients with myopia andsome degree of angle kappa deviation for whomcentering on their pupil will bring poor results.

The pupil issue fades away with the use ofwavefront technology, and the improved resultsthat I have achieved corroborate this. The regis-tration on the LADARWave ensures that allpatients are well centered.

Brint: It will be interesting to see the results ofthe study comparing Bausch & Lomb’s pupiltracking system compared to Alcon’s registrationsystem.

Mullie: In my opinion, three potentially signifi-cant sources of error exist with the Technolas 217system (Bausch & Lomb). First, the wavefrontmeasurements are taken on a dilated pupil and thetreatment is performed on an undilated pupil,which may result in a large error in treatment.Second, the surgeon must manually set themachine to what he or she perceives to be thepupil center. Third, there is no registration withrespect to a fixed reference such as the limbus onthe present system.

Brint: Dr. Speaker, how do your results in dilat-ed situations compare with those in non-dilated

situations, relative to the systems that you haveused?

Mark G. Speaker, MD: With CustomVue (Visx,Santa Clara, Calif.) technology, I must use mydri-atic agents often because undilated pupils are notlarge enough to capture an adequatewavefront. Dilating the pupil even amodest amount can dramaticallychange the wavefront that is cap-tured. I have looked at the differ-ence in a patient for whom I cap-tured the wavefront from the pupilat both 5.5 mm and dilated to 6.5 mm. The wavefront that Ireceived from the dilated pupil wastruer, both numerically and qualita-tively. Being able to capture awavefront through a dilated pupil isa significant advantage.

Mullie: With the LADARVisionsystem, the cornea stays clear dur-ing the treatment in comparison toTechnolas 217. We are performinga contralateral eye study usingLADARVision and Technolas 217,and have seen a tremendous differ-ence.1 With the Technolas 217, a 2-mm beam hammers away at thecornea and, as a result, the corneatends to become gray during long treatments andpatients lose the fixation light. WithLADARVision, the cornea is perfectly clearthroughout the procedure.

In the study, after the patients had been treat-ed with LADARVision for one eye and Technolas217 for the other, we asked patients with whicheye was is easiest to the see the light and proper-ly fixate. Thirty-five out of 40 patients reportedthis to be the LADARVision eye.

Speaker: The LADARVision system has a particu-larly good fixation light, making it easier for patientsto fixate during treatment than on other systems.

New algorithms for minimizing aberrationsBrint: Are all of the refractive laser platformsmaking algorithm changes to minimize inducedspherical aberration?

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The pupil issue

fades away with the

use of wavefront

technology, and the

improved results that

I have achieved

corroborate this.

— Roger F.

Steinert, MD

(Roundtable continues on page 8)

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OCULAR SURGERY NEWS

Stephen G. Slade, MD

With or without a nomogram adjustment tothe laser system, the LADARVision (Alcon, FortWorth, Texas) system for performing aCustomCornea (Alcon) procedure provides mea-surements and results that are more accurate andthat induce fewer higher-order aberrations thanCustomVue (Visx, Santa Clara, Calif.) technology.

Apples to applesWe performed a contralateral eye study com-

paring the LADARVision system laser toCustomVue technology. As it is inherently difficultto compare separate studies, we treated one eyeof each patient with the LADARVision laser andthe other eye with the Star S4 (Visx) laser to seewhich provided the best results. The preoperativedata for eye were similar (Table). Ablations wereperformed on the first group of patients with noadjustments to either laser to provide an “apples-to-apples” comparison. We found that theCustomCornea procedure provided better resultsthan CustomVue, both in terms of traditional met-rics and higher-order aberrations. The eyes treatedwith CustomVue were consistently undercorrectedand the accuracy was better at 3 months withCustomCornea (Figure 1). The manifest refractive

spherical equivalent (MRSE) difference was approximately0.33 D between theCustomCornea eyes and theCustomVue eyes over 3 months(Figure 2).

The subjective responses ofpatients when asked which eyethey preferred at 1 month, 15of 22 patients (68%) preferred the CustomCorneaeye to the CustomVue eye. Furthermore, whenpatients were asked at 3 months which eye hadbetter quality of vision, 17 of 23 patients (74%)responded that the quality of vision in theirCustomCornea eye was better than that of theirCustomVue eye. Overall satisfaction with theCustomCornea procedure was better than withCustomVue.

Visual acuity not the entire storyInterestingly, one patient who had better visual

acuity in the CustomVue-treated eye reported thatthey were happier with the quality of vision thatthey achieved in the LADARVision-treated eye.However, no patients reported that they were hap-pier with the quality of vision they received fromCustomVue when their visual acuity was better inthe LADARVision-treated eye.

LADARVision system vs.CustomVue technology

Stephen G. Slade

Preoperative Patient Demographics

Mean Sphere Mean Cylinder Mean MRSE(Range) (Range) (Range)

CustomCornea -3.15 D 0.52 D -3.41 D(-0.75 D to -7 D) (0 D to -1.25 D) (0.88 D to -7.13 D)

CustomVue -3.08 D -.052 D -3.34 D(-0.75 D to -5.75 D) (0 D to 1 D) (-0.88 D to -6.25 D)

Table information courtesy of Stephen Slade, MD.

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OCULAR SURGERY NEWS

Nomogram adjustmentsFor a group of 10 patients, we made nomo-

gram adjustments to CustomVue to achieveresults matching the LADARVision system and,with no nomogram adjustment to theLADARVision system, we performed contralater-al surgery. Even with the nomogram change forCustomVue, the higher-order aberration databecame more skewed in favor of theLADARVision system because, as ablationsbecome larger, so do the amount of higher-order aberrations that are induced. SinceCustomVue technology was undercorrectingpatients, we increased the ablation sizes for thegroup treated with the nomogram onCustomVue, which results in more inducedaberrations.

With no nomogram adjustments toCustomCornea procedure vs. the nomogram-adjusted CustomVue procedure, patients reportedoverall better visual results at 1 month (Figure 3).Additionally, contrast sensitivity was significantlybetter for patients treated with CustomCorneathan with CustomVue (Figure 4).

These small studies show the power of con-tralateral eye studies in making direct compar-isons between wavefront platforms. CustomCorneaprovided the best results for most patients interms of reduced higher-order and spherical aber-rations and better contrast sensitivity.

Stephen G. Slade, MD, is national co-director of theLaser Center in Houston, Texas. Dr. Slade is also a memberof the editorial advisory board for OCULAR SURGERY NEWS.

Figure 2. The manifest refractive MRSE differncewas approximately 0.33 D between the CustomCornea eyes and the CustomVue eyes over 3 months.

Figure 1. The eyes treated with CustomVue wereconsistently undercorrected and the accuracy wasbetter at 3 months with CustomCornea. Figures 1-4 courtesy of Stephen G. Slade, MD.

Figure 4. Contrast sensitivity was also better forpatients treated with CustomCornea.

Figure 3. With nomogram adjustments toCustomCornea and CustomVue, patients reportedbetter 1 month results with CustomCornea.

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Durrie: The Alcon platform was developed in theUnited States during the U.S. clinical trials, soeach time the algorithm changed, the clinical

investigators performed anothersubstudy to refine the algorithm.We collected preoperative wave-front measurements and comparedthem with postoperative data todetermine how well the algorithmworked. The Alcon engineers rec-ognized early in the trials thatspherical aberration and comawere not being fully corrected.Based on this information, thealgorithm was changed to dial upspherical aberration.

Although these substudiesrequired more patients to be treat-ed and took longer, I think it iswhy the Alcon platform seems tobe correcting higher-order aberra-tions better than other systems.

Last year at the WavefrontCongress in Canada, some of thepapers presented concluded thatmore pulses are required on theperiphery in order to optimize thecorrection and reduce sphericalaberration.

Speaker: I have compared the postoperativewavefronts of patients treated with the

LADARVision system to those treated withCustomVue technology and have been impressedby the fact that postoperative LADARWave mea-surements show significant reduction in preoper-ative higher-order aberrations. Alcon hasimproved their algorithms to make the postopera-tive higher-order aberrations as minimal as possi-ble, from the standpoint of not only correctingpreoperative higher-order aberrations, but also inpreventing the induction of spherical aberrationswhen performing ablations on patients withmyopia.

Steinert: Zero spherical aberration is notrequired to have good night vision. Most peoplehave some element of spherical aberration. As arefractive surgeon, I have always struggled tounderstand why one patient following a typicalmyopic correction will have night vision issuesand another patient treated exactly the same waywill not. My hunch is that the patients who havepostoperative night vision problems already haveborderline-high spherical aberrations thatbecome symptomatic after treatment. To usewavefront technology only for patients with pre-operative high-order aberrations is incorrect. Theconcept of not inducing aberrations is one thatshould be applied to every patient.

A number of laser manufacturers are suppos-edly incorporating wavefront options into theirrefractive platforms, but those systems fail toconsider preoperative baseline corneal curvature.If the lens is playing a significant role in a given

OCULAR SURGERY NEWS

Alcon has improved

their algorithms to

make the

postoperative

higher-order

aberrations as

minimal as

possible …

— Mark G.

Speaker, MD

Figure 3. A survey performed by Kerry Solomon, MD,and colleagues shows that physicians in most coun-tries had better results with wavefront ablation,compared to conventional LASIK. Figures 3-8 courtesy of Kerry D. Solomon, MD.

Figure 4. When asked to break their responses downinto actual systems, more surgeons reported betterresults with CustomCornea compared to conventionalLASIK.

(Roundtable, continued from page 5)

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patient, such a simplistic approach may end upmaking the patient worse rather than better. Thereare no substitutes for accurately measuring totalwavefront error, not just guessing, and having analgorithm to drive the correction to compensate.

Donnenfeld: I would not call measuring preoper-ative baseline corneal curvature an algorithm.The LADARWave provides hard data as to thecorrect ablation profile for each patient.

The inability to measure wavefront aberrationsand to place that wavefront on the cornea in atherapeutic way will not allow surgeons toachieve the best vision for patients. When adjust-ments must be made based on the simplistic ideaof a mathematical formula that may not apply toall patients, the results cannot be accurate.

Every patient is different — the surgeonshould perform wider measurements, capturethese measurements and apply them to the cornea

in the right position. An algorithm is no substitutefor hard data that can directly be applied to thecornea.

My clinical experience is similar to that of thedata compiled by Dr. Solomon in his compar-isons of traditional vs. wavefront LASIK plat-forms (Figures 3 and 4).2

There is a definite improvement in Snellenacuity from conventional to wavefront, but thebig difference occurs with quality of vision.

Our experience with the LADARWave systemhas been that patients’ perception of quality ofvision, both mesopic and scotopic, and contrastsensitivity were markedly improved (Figures 5-8). However, the quality of vision withCustomVue showed no significant improvementin quality of vision.3

Speaker: We presented our data at the 2004American Society of Cataract and Refractive

OCULAR SURGERY NEWS

Figure 5. Three-month mesopic contrast sensitivitywithout glare (change from preoperative).

Figure 6. Three-month photopic contrast sensitivitywithout glare (change from preoperative).

Figure 8. Three-month photopic contrast sensitivitywith glare (change from preoperative).

Figure 7. Three-month mesopic contrast sensitivitywith glare (change from preoperative).

Mesopic contrast sensitivity without glare. Photopic contrast sensitivity without glare.

Mesopic contrast sensitivity with glare. Photopic contrast sensitivity with glare.

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OCULAR SURGERY NEWS

The lasers used by refractive surgeons haveundergone progressive technological advances inthe past 12 years. Currently, nearly all platformsused guarantee a greater than 90% chance ofachieving 20/20 Snellen acuity after surgery.Wavefront-guided refractive surgery has pushedthe visual system to new postoperative limits inthe results that ophthamologists are able toachieve for their patients. However, the methodsthat are used in testing for high-contrast visualacuity are inadequate to assess the quantitativeand qualitative aspects of vision after refractivesurgery. Not all patients are satisfied with a 20/20result.

Several image plane metrics describe the opti-cal system of the eye after surgery, includingpoint-spread function (PSF), Strehl Ratio, modula-tion transfer function (MTF) and optical transferfunction (OTF). While these metrics are useful,clinicians require clinical descriptive metrics thattest the entire visual system (i.e., optical, retinal,neural and higher cortical functions). No singlemetric can accomplish this testing adequately. Inorder to adequately describe and compare therefractive results with wavefront, the visual sys-tem must be pushed beyond high contrastSnellen acuity. Postoperative measurements mustbe as complex as the results.

David R. Williams, MD, and colleagues havedeveloped an image plane metric called the“Visual Benefit.”1 In Wavefront CustomizedVisual Correction: The Quest for Super Vision II,the Visual Benefit is described as the measureof visual improvement at the retinal planeresulting from a perfect theoretical correctionof the eye’s higher-order aberrations or “theincrease in retinal contrast at each spatial fre-quency that would occur if one were to correctall aberrations instead of just correcting defo-cus and astigmatism as one does with conven-tional refraction. More specifically, the VisualBenefit is the ratio of the eye’s polychromatic(white light) MTF when all monochromaticaberrations are corrected when only defocusand astigmatism are corrected.”1

The Visual Benefit may be a useful imageplane metric to describe “how much” the opticalsystem of the eye is improved by correcting theeye’s aberrations.

Dr. Williams and colleagues wrote, “[VisualBenefit] is directly applicable to visual perfor-mance as assessed with contrast sensitivity mea-surements. That is, a Visual Benefit of 2 will leadto a two-fold increase in contrast sensitivity aswell as a two-fold increase in retinal image con-trast.”1 This measure is intuitively grasped as auseful measure of optical visual improvement.

New visual function measurementsneeded

I believe we need a similar quantitative orsemi-quantitative measure to describe “howmuch” the entire visual system has beenimproved by wavefront-guided surgery. Such anindex should include several measures of visualfunction, each of which tests the whole system(optical, retinal, neural and cortical). I proposean index titled the “Surgical Visual Benefit Index”(SVBI). The SVBI could include five tests of visualfunction as follows:

1. Low-contrast acuity: Gain or loss2. Postoperative uncorrected visual acuity

(UCVA) to preoperative best-corrected visualacuity (BCVA) (efficacy): Gain or loss

3. Contrast sensitivity, both photopic andmesopic: Gain or loss

4. Higher-order aberrations: Gain or loss5. Quality-of-vision questionnaire: Improvement

or worsening

The SVBI could be constructed with weights toeach term. It would range numerically from 0 to10, but in theory could be less than 0 (poorresult) or more than 10 (an extraordinary result).A significant increase in total higher-order rootmean square would deduct points and a signifi-cant decrease would add points.

As an example, an eye that improves two linesof BCVA is two lines of postoperative UCVA better

Surgical Visual Benefit IndexMarc A. Mullie, MD

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Surgery (ASCRS) Annual Meeting comparingour outcomes with CustomVue andCustomCornea.1 In these data, it was clear thatboth systems provided a marked improvement inSnellen acuity. I have no doubt that patients per-ceive an improvement in quality of vision withboth systems, but there was a definite differencebetween the results obtained with CustomCorneaand CustomVue with regard to the number ofpatients achieving 20/15 or better vision. At 6 months, 62% of the patients treated withLADARVision system achieved 20/15 or better,and 7% achieved 20/10. Only 42% of patientstreated with CustomVue technology achieved20/15 vision, a full 20% less than withLADARVision, and there were no patients treatedwith CustomVue technology system who were 20/10.

Brint: Did you compare higher-order aberra-tions, either induction or reduction, preoperative-ly and postoperatively between the two plat-forms?

Speaker: Although we are still in the process ofperforming that analysis, preliminary data showthat there was no significant induction of higher-order aberrations in the LADARVision group anda small but statistically significant increase in theCustomVue group. It was also interesting to methat in the LADARVision group, 63% of patientsimproved one or more lines of best-correctedvisual acuity (BCVA) at 6 months. In theCustomVue group, approximately 40% ofpatients improved one or more lines of BCVA.

These better results for patients who were treatedwith the LADARVision system highlight theimportance of registration and centration of thewavefront during treatment.

Durrie: Ophthalmologists are moving away fromusing high-contrast acuity as the only measure-ment. Although it still is important that a patientcan identify the black-on-white letters on an eyechart to measure visual acuity, in the real worldthere are few black-on-white comparisons, makingcontrast testing more important. In looking at mypatients, it is clear to me that patients who havenight-vision symptoms also have loss of low-con-trast vision and also have higher-order aberrations.

I have performed off-label treatments usingthe CustomCornea platform for 300 patients whohave had previous refractive surgery and had sig-nificant higher-order aberrations. In all cases,their night-vision symptoms improved, higher-order aberrations decreased and contrast sensitiv-ity improved. Before the introduction of wave-front-guided ablation, I never had patients tell mehow good their night vision was after surgery.With CustomCornea, this is something that I hearfrequently.

Speaker: Quality of vision cannot be underrated.For example, when I first began performing cus-tom treatments and had patients who were slight-ly undercorrected by as little as 0.5 D after stan-dard ablation, they were unhappy with that resultand would insist on retreatment. Now, withCustomCornea, these same patients are happyeven with 0.5 D of under-correction because the

OCULAR SURGERY NEWS

than the preoperative BCVA; has improved pho-topic and mesopic contrast, decreased higher-order aberrations and decreased spherical aberra-tions; and has fewer halos at night and betternight vision would score a perfect 10 (if lowercoma was present, the score would be 11). An eyethat improved one line of BCVA and one line bet-ter UCVA than preoperative BCVA, but had worsemesopic contrast sensitivity, more aberrations andworse night-vision ratings would score -3. In gen-eral, we could say that a score of less than 0 repre-sents little to questionable benefit, 1 to 3 is mar-ginal to good benefit, 4 to 6 very good benefit, 7 to 9 high benefit and over 9 exceptional benefit.

Combining the factors that surgeons nowconsider crucial to the overall success of wave-front-guided surgery into one index would ben-efit patients and help direct the improvement ofthe technology involved in refractive surgicaloutcomes.

Reference1. Williams DR, Applegate RA, Thibos LN. Metrics to

predict the subjective impact of the eye’s waveaberration. In: Kreuger R, Applegate R, MacRae S,eds. Wavefront Customized Visual Correction: TheQuest for Super Vision II. Thorofare, NJ: SLACKIncorporated; 2004:25.

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entire quality of their vision, including fewerhigher-order aberrations, better night vision andbetter contrast, is improved.

Mullie: Now that sophisticated aberrometers areavailable, a more advanced method of visual test-ing is needed that goes beyond the capability ofSnellen high-contrast acuity (See “SurgicalVisual Benefit Index,” page 10).

RetreatmentsBrint: What advice do you have for surgeons

who want to retreat patients?

Durrie: First, I would advise sur-geons to use the CustomCorneasystem because it has the best reg-istration and tracking capabilities.Second, it is important that thewavefront data are accurate — thisis especially important when per-forming retreatments becausespherical aberrations are prevalentin these patients and so the mea-surements taken from the periph-ery of these eyes are often difficultto obtain. If I have a patient onwhom I can obtain good wavefrontdata and who has spherical aberra-tion, coma and/or secondary astig-matism, the patient seems to dowell when treated withCustomCornea.

When performing retreatmentswith the CustomCornea system, Iuse a 0.75-D target offset to com-pensate for the mild overcorrec-tion of the sphere seen in earliercases.

Steinert: At the 2004 ASCRS annual meeting, Ipresented data that clearly showed a benefit tousing surgeon offsets. I compared patients in whomno surgeon offset was used with patients whounderwent retreatments with a surgeon offset. Thefirst group of patients experienced a hyperopic shiftthat correlated to the amount of spherical aberra-tion; as spherical aberration increased, so did theunintended hyperopic shift. This was particularlytrue when spherical aberration was approximately0.8 µm root mean square (RMS) or higher.5 Thisoccurred even when there was a good match of

manifest and wavefront refraction. My hypothesisis that using mid-peripheral treatment to reducespherical aberrations causes a secondary healingeffect of hyperopic shift. In the second group ofpatients, we started performing surgeon offsets ofmostly 0.5 D. In other words, I was driving treat-ment in the myopic direction, and I found that themean correction was more accurate as a result.

In the future, ophthalmologists will be able tobetter analyze aberrations and assign offsets thatare driven by the amount of aberration present. Ihave become more aggressive with my surgeonoffsets as aberrations increase because I want toavoid overcorrection.

In cases where there is a significant disparitybetween the manifest refraction and the wave-front refraction in terms of cylinder, patientsoften have vertical coma. When I am determininga wavefront for a patient and see that the cylinderis lower on the wavefront refraction than on themanifest refraction, I usually know I am on theright track. Upon viewing the orientation, themeasurements line up as vertical and horizontalcoma components.

Donnenfeld: I agree. With patients who have sig-nificant coma, the wavefront refraction is oftenundercorrecting their cycloplegic refraction. Thistells the surgeon that most of the aberration iscoma that is not detected by the wavefront.However, an offset must be used when the wave-front refraction is significantly more myopic.

I rarely find that I overcorrect patients usingthe LADARWave. This is most likely because, incapturing the wavefront image, I also capture thecycloplegic refraction.

When performing retreatments, surgeons mustnote that other systems do not capture cyclo-plegic measurements while obtaining the wave-front information. Under these circumstances,accommodation will be introduced to the equa-tion and successful retreatment becomes almostimpossible. Removing accommodation from thewavefront image on the LADARWave gives thesurgeon more certainty on exactly what data arebeing collected for a patient’s wavefront. When Iperform surgery on virgin eyes using WaveScanmeasurements, I overcorrect patients by 1 D to1.5 D. The LADARWave allows me to be almostalways exact in my correction and I rarely have touse a physician adjustment.

I have performed many retreatments with

OCULAR SURGERY NEWS

Now that

sophisticated

aberrometers are

available, a more

advanced method of

visual testing is

needed that goes

beyond the

capability of Snellen

high-contrast acuity.

— Marc A.

Mullie, MD

13

both CustomCornea and CustomVue and havefound that retreatments with CustomCornea arebetter than any system I have ever used. Many ofthe complications that I encounter during theseprocedures are associated with decentration. Ifdecentration occurs with CustomVue because ofpupil movement and the surgeon retreats withthe same system, he or she will add insult to injury. When decentration is a problem,registration is the key issue and ifwavefronts can be applied to thearea in question, the issue will beresolved. The registration on theLADARVision system allows forthis resolution.

Speaker: I have found that when Iam retreating patients who have awavefront profile refraction of lessthan 1 D, it is helpful to carefullymeasure at the maximum ablationdepth. I have seen planned retreat-ments for 0.5-D correction, butwhere the ablation depth was 38 µmor more. In these cases, the surgeonmust be careful not to overcorrectthe patient by scaling back themyopic component of the wavefronttreatment to reduce the ablationdepth, or by performing a standardenhancement.

Brint: When Dr. Durrie first startedperforming retreatments on patientswho were plano, these procedurestook 1 minute, a long time to manyophthalmologists. However, nowthat the CustomCornea software planning sys-tem is available, we can see what is beingremoved at every location on the cornea, even inthe periphery. This shows us that 38 µm periph-erally is not the same as an additional 38 µmcentrally.

Durrie: Patients who are close to plano and havea large amount of spherical aberration may easilybe overcorrected. This is partly due to the pho-totherapeutic keratectomy effect, from prolongedablation times and aberration in the sphere, whichis not yet understood. However, more of a physi-cian adjustment is needed on all laser systems forthese patients.

Speaker: How do patients with 6-mm opticalzones respond to retreatment with theLADARVision system?

Durrie: Patients with a 6-mm optical zonerespond well, but only if a good wavefront read-ing is taken. I have performed upgrades onpatients with 5-mm optical zones who had beentreated back in the early 1990s, and the results

have been excellent. These patientshave lived with up to 2 µm of spher-ical aberration for many years, sothey were more than satisfied withtheir improved night vision.

Donnenfeld: I treated patients fromEurope who had their original treat-ments in the early 1990s. Their opti-cal zones were 4 mm and they werefunctionally incapacitated by prob-lems with quality of vision such asglare and halos. We enlarged the opti-cal zones, reduced their higher-orderaberrations and resolved their resid-ual myopia. These patients were hap-pier with their results than any otherpatients I have ever treated.

Clinical comparisonsamong wavefront platformsDurrie: Based on my personalexperience, I would recommend thatwhether a surgeon is using theZyoptix, CustomVue orLADARVision platforms, wave-front-guided correction provides the

best results for the majority of patients in that itinduces fewer aberrations and contrast sensitivityresults are better.

The 2004 ASCRS annual meeting was signifi-cant for me because I was able to hear surgeonswho were using two different platforms offeringtheir clinical comparisons. Everyone I spoke withreported better outcomes with the Alcon platformthan any other system.

My most recent data came from using theIntraLase femtosecond laser (Irvine, Calif.) withthe CustomCornea platform on patients with anaverage of 4.8 D of myopia. Fifty-five percent ofpatients had postoperative visual acuity of 20/12and 20/10. I have never had results this good.

OCULAR SURGERY NEWS

… wavefront-

guided correction

provides the best

results for the

majority of patients

in that it induces

fewer aberrations

and contrast

sensitivity results

are better.

— Daniel S.

Durrie, MD

14

Additionally, approximately 50% of the patientswho I treated gained one or more lines of BCVA.The patients reported a decrease in problems withnight driving and in glare and halos.

The success that Alcon has hadwith their platform has put consid-erable pressure on the other lasersystems.

Steinert: Spot size is an importantfactor in a laser because we canonly treat aberrations that are assmall as our laser spot. While regis-tration seems to be the new focus,ophthalmologists must rememberthat the patterns of spots applied tothe cornea are also important. Inthis respect, the LADARVision hasan advantage because of its consis-tently small spots and accuratescanning control capabilities.

There is still curious disparityamong the aberrometers — I havefound, as have many others, that thesame eye measured with differentaberrometers yields different measure-ments. I have measured the same eyewith the WaveScan, ZyWave andLADARWave and have not found thesame measurements. I have consistent-ly found that the LADARWave mea-surements show more aberration in terms of RMSerror than the WaveScan. Pupil size is not the onlyreason for these disparities.

Mullie: In terms of agreement with the manifestmean spherical equivalent, the LADARWave isstatistically significantly better (Figure 9). The

percentage of wavefront derivedrefractions within 0.25 D of themanifest is just over 50% with theLADARWave, but only 18% withthe ZyWave system. All of theLADARWave values are within 1 Dof the manifest refraction, but only93% of the ZyWave data fall intothis range. Also, the ZyWave mea-sures more spherical aberration thanLADARWave (Figure 10).

Steinert: Regardless of what I triedto compensate for pupil size, if Icannot measure the aberration, Icannot treat it. The best way to tellwhich systems measure aberrationsmost correctly is to look at surgicaloutcomes and, based on outcomes, Ibelieve that the LADARWave mea-surements are more accurate.

The numerical measurements ofRMS are so much lower on theWaveScan that there are fewer fac-tors driving the laser to correct it.

Mullie: Also of importance is thereproducibility of the measurements

taken. I have noticed that the LADARWaveselects three out of the five measurements, andinvariably they are close to one another. There is

OCULAR SURGERY NEWS

… if I cannot

measure the

aberration, I

cannot treat it.

The best way to

tell which systems

measure

aberrations most

correctly is to look at

surgical outcomes …

— Roger F.

Steinert, MD

Figure 9. Comparison of the accuracy of mean spher-ical equivalent with the LADARWave and theZyWave. (Figures 9 and 10 courtesy of Marc A. Mullie,MD.)

Figure 10. The ZyWave measures a significantlygreater amount of spherical aberration at the 6-mmzone.

15

much more variability in the measurements of theZyWave — the standard deviation seems to besignificantly larger on the ZyWave compared tothe LADARWave.

Durrie: I performed a study using six differentaberrometers on patients with the same pupildiameter. We input the measurements into theCTView software program (Sarver andAssociates, Inc., Celebration, Fla.). The differ-ences that we found among the six aberrometerswere significant.

Zernike vs. FourierBrint: All of the aberrometers that drive lasers inthe United States are based on the Hartmann-Shack system. Two mathematical formulas,Zernike and Fourier, have been used for manyyears. Laser manufacturers have traditionallyrelied on the Zernike system, which can measurean infinite number of aberration orders. Theinformation that the Zernike data provide is basedon the law of diminishing returns to the eighthorder. In hindsight, it is possible that there is noneed to go above the sixth order because theinformation obtained from the seventh and eighthorders is minimal to none.

There have been proposals that a switch bemade to Fourier, which is said to provide infor-mation equal to the 20th Zernike order. However,because so little information in these higherorders is useful, it seems that there would be lit-tle advantage to using Fourier. It has also beensuggested that basing ablations on aberrations inthe higher orders up to the 20th can actually domore harm than good.

At the ASCRS annual meeting, Julian Stevens,MD, presented preliminary results using theFourier system with CustomVue technology.6 In hispresentation, he stressed that the tear film must beperfect so that the surgeon does not pick up arti-facts that would result in a poor ablation.

Donnenfeld: Surgeons must use the availableresources to the point that achieves the best returnon investment. Currently, Zernike polynomialsprovides excellent results. I predict that theimprovements in excimer laser outcomes over thenext couple of years will not be based on extend-ing the Zernike readings or switching to Fourieranalysis, but on better registration and repro-ducible peripheral wavefronts.

Mullie: Most of the wavefront systems use video-based trackers, which are often highly inaccurate.Before we consider treatment based on Fourier pat-terns, the tracking methods must be improved.Lasers still require precise tracking to be able toproduce accurate wavefronts treatments. Otherthan the LADARVision system, no other laser sys-tems currently have this capability.

Durrie: Ophthalmologists are nowtreating patients who could not betreated 5 years ago. First, clinicianshave the ability to treat coma.These patients have a decenteredapex and are not seeing through thecenter of their corneas. Second,spherical aberration can be treated,which is the slope of the refractionacross the pupil. In the past, theassumption was that all patientshad the same slope, but we werewrong — not all patients have thesame refractive error at 6 mm asthey do at 3 mm. This can now bedealt with and low-contrast andnight vision is improved.

Zernike analysis has helpedimprove surgical outcomes. If bet-ter analysis comes along, I am sureit will be employed. However, theability to treat spherical aberrationand coma using Zernike analysishas benefited patients significantly.

Steinert: The eye is just a part of anoverall optical system that includesexcellent image processing — this isoften forgotten until patient surveysshow how happy people are when their visual acu-ity is improved. Patient perception must be consid-ered when deciding to what order to correct aberra-tions. When the point has been reached where apatient can no longer tell the difference in visualresults, there is little to no return on investment.

I hope to see ongoing effort toward developingbetter visual metrics to apply to wavefront,whether contrast sensitivity under certain lightingconditions or tests that are yet developed. Mostophthalmologists had never heard of wavefront 6 years ago and look where we are now.

The role of tracking also must not be forgot-ten. Even with correct wavefront diagnostics, the

OCULAR SURGERY NEWS

There have been

proposals that a

switch be made to

Fourier … However,

because so little

information in these

higher orders is

useful, it seems that

there would be little

advantage to using

Fourier.

— Stephen F.

Brint, MD

16

intended corneal treatment patterns are notachieved with the wrong latencies, responsetimes and tracking frequencies. As spot sizebecomes another 0.5 mm smaller, the demand toproperly place each spot increase.

Durrie: These data show the need to match thespot size with the tracker speed, which theLADARVision does well. [AU: To what data areyou referring?]

PearlsBrint: I would like to discuss pearlsfor surgeons who are using cus-tomized platforms.

Let’s say a patient comes into theoffice and the normal patient work-up is performed, which includedmanifest refraction and cyclorefrac-tion, etc. The preoperative measure-ments reveal no surprises in topog-raphy, pachymetry and wavefront.However, the wavefront that isobtained the day of surgery showsmore than 0.75 D of difference withwhat was obtained previously. Whatis our nomogram for this patient?

My ideal patient has a wavefrontrefraction that is slightly lessmyopic than the manifest refraction.For example, if the manifest refrac-tion is -4 D with the appropriateamount of cylinder, the ideal wave-front refraction is -3.8 D. No adjust-ments are needed for a patient withthese refractions.

For the past 6 months for my cus-tom treatments, I have been using OptimizedNomograms software (Refractive ConsultingGroup, Westlake Village, Calif.), which suggeststhat for a patient who has manifest refraction of -4 D, the offset should be between 0.15 D and 2 D.

If there is a 0.75 D difference (manifest refrac-tion of -4 D; wavefront refraction of -3.75 D),and the patient has presbyopia, I want to be care-ful not to overcorrect. Thus, I adjust the refrac-tion no more than the Optimized Nomogramssoftware instructs. I may even back off more thanthe software advises, because the nomogramtakes the wavefront reading as an absolute mea-surement and so will always adjust somewhat.

For a younger patient, I might split the differ-

ence and add in -0.37 D to compensate for themanifest refraction of 4 D and the wavefrontrefraction of 3.75 D. I use this nomogram onlywhen the wavefront refraction and the manifestrefraction are close to one another.

Donnenfeld: When I see a patient on the day ofsurgery, I consider three main points when choos-ing my offset. First, a personalized nomogram isas important for the customized platforms as with

the older generation lasers.Adjustments should be made basedon comparisons of the clinical vs.expected results.

Second, I adjust for a patient’sage because older patients ablatefaster than younger patients. I alsoadjust my nomogram for visualneeds. I am comfortable having a0.25 D offset for a 20-year-oldpatient, but would never do this for apatient in his/her 40s.

The third consideration iswhether the patient’s wavefront andmanifest refraction differ greatly.Like Dr. Brint, when the patient’swavefront is less myopic than themanifest refraction, I am usuallycomfortable treating based on thewavefront measurements. Usually,higher-order aberrations explain thedecreased spherical equivalent, mostlikely because of decreased cylinder.It is more challenging, however,when the patient does not have a sig-nificant amount of higher-orderaberrations and is still undercorrect-

ed. For this type of patient, I use an offset and addsome minus.

For patients who have a more myopic wave-front than manifest, it is important not to over-minus because this will result in hyperopia. Forthese patients, I often repeat their wavefronts andlet the cycloplegia work longer to get betterresults. I will also check to be sure that while Iam taking their wavefront measurements, theyare looking into the distance and not accommo-dating. I am able to do this easily using theLADARVision system.

These concerns are more theoretical than actu-al, because with the LADARVision system, Irarely need to use physician adjustments, other

OCULAR SURGERY NEWS

The wavefront

measurements that I

get with the

LADARVision system

coincide with the

manifest refractions

more than with any

other system that

I use.

— Eric D.

Donnenfeld, MD

17

than for a patient’s age. The wavefront measure-ments that I get with the LADARVision systemcoincide with the manifest refractions more thanwith any other system that I use.

Mullie: A personalized nomogram is important.For example, in my surgery, I keep the humidityat approximately 40% and I find I tend to getslight undercorrections with the LADARVision,while most surgeons report overcorrections, so Iroutinely add -0.25 D to even -0.50 D to the off-set to improve my results.

Speaker: I routinely use a nomogram based onage and amount of correction, and my resultshave been excellent. Less adjustment is requiredwith LADARVision than with CustomVue tech-nology. With the LADARWave, we capture fiveimages and treat based on an average of three, butcannot do this on the WaveScan system becausethere is too much variability in the individualmeasurements due to accommodation. As aresult, the surgeon must treat based on only onemeasurement with CustomVue technology.

I find that if there is a significant discrepancybetween the wavefront measurement and thecycloplegic refraction, the manifest does notworry me, because accommodation or higher-order aberrations may be the explanation.However, if a big difference between wavefrontand the cycloplegic refraction exists, we usuallyfind better agreement if we go back and do a so-called wavefront-adjusted cycloplegic refraction.[AU: Please explain this comment.] I have fewproblems using the LADARVision system interms of the accuracy of the wavefront measure-ments. It has been consistent and reliable.

I also find it helpful to ask patients to useSystane lubricant tears (Alcon Laboratories) fourto six times per day starting 1 week preoperative-ly to improve the condition of their tear film. Asa result, the image quality on the LADARWave isbetter and more consistent. Without stabilizingthe tear film, it may be difficult to get a goodimage due to a thin tear film or rapid break-uptime.

Durrie: I also must let my patients know thatthey cannot wear their soft contact lenses atleast 3 days preoperatively, because theircorneas may become warped and the wavefrontwill pick that up. For patients who use gas

permeable lenses, I prefer that they take themout for 3 weeks preoperatively.

Speaker: Wavefront analyzers areso sensitive that any residualwarpage of the cornea from con-tact lenses becomes more signifi-cant. In the past, as long as thepatient’s spherical equivalent andastigmatism were correct, thesurgery would go well, but now, ifa lens fits tightly and is creating alot of distortion, this will transmitinto the final results.

Donnenfeld: The accuracy of theLADARVision system is such thatsignificantly fewer adjustmentsare required compared to othersystems. I appreciate the reliabili-ty of the aberrometer data as it canbe applied directly to the laser.The LADARVision system pro-vides surgeons with the comfortthat they are treating the patientappropriately.

Speaker: For surgeons who do nothave much experience with per-forming customized ablations,CustomVue technology requires that the staff beskilled in operating the aberrometer to ensure thataccommodation is controlled. Although techni-cians must be trained on the LADARVision sys-tem, the machine is less dependent on technicianskill, which is another advantage to using thissystem.

Brint: The more adjustment that a surgeon mustmake translates to more room for error. It is vir-tually impossible to develop a consistent nomo-gram based on a random reading.

Donnenfeld: In the past, when I used the Star S4(Visx) laser more often, I would use a +0.75 Dadjustment in one eye and a -0.75 D adjustmentin the other eye looking for plano in both eyesbecause the patient was accommodating. Usingthese adjustments made me feel uneasy about thetreatment and I do not think that my outcomeswere as good as they could have been.

When performing surgery on virgin eyes,

OCULAR SURGERY NEWS

With the

LADARWave, we cap-

ture five images and

treat based on an

average of three, but

we cannot do this on

the waves can

because there is too

much variability …

— Mark G.

Speaker, MD

18

more adjustments in the platform will usuallyyield less accurate results. When the surgeon isadjusting for factors other than age and his orher own nomogram, this takes away some relia-bility of the laser. When a surgeon cannot relyon his or her own data and must adjust for trans-lation into the laser, clinical outcomes suffer.

FutureBrint: How do you think centration will changein the future?

Donnenfeld: Currently, accurate limbal regis-tration is the most important stepin laser surgery. I have made apoint to train my technicians inthis step and I always check thelimbal registration manually toensure that the preoperative lim-bus is the same on which I amperforming the ablation.However, there is still room forsome human error.

My colleagues and I performeda study that showed a 44-µm dif-ference between technicians inmatching the limbus. This mea-surement is significantly betterthan the 177-µm difference inpupil movement we showed in thesame study with pupil trackingsystems.7

Alcon is working on incorpo-rating a computerized limbalrecognition system, which willenable surgeons to more accu-rately recognize the limbus.Computerized limbal recognitionwill allow for even more accuratepreoperative wavefront measure-

ments, that when applied surgically, will pro-duce extraordinary refractive results.

In the next 6 months, surgeons should be ableto see improved surgical outcomes based on thisnew feature to the LADARVision system.Computerized limbal registration will widen thegap in quality of vision obtained with limbal reg-istration vs. pupil tracking system, making thelatter an obsolete form of measuring the eye dur-ing the ablative process. Brint: CustomCornea surgery-planning softwareis newly available for the LADARWave. We are

using this software for every custom case. Thesoftware allows us to see the profile of the abla-tion before it is made — both the thinnest and thethickest sections. Prior to having the softwareavailable to us, we were unsure how much tissuewould be removed and where it would be takenfrom. I have found this software helpful for whenI am working on a marginal cornea or performingretreatments, because the intraoperative pachym-etry gives me an idea of how much tissue is leftin the bed for removal.

The CustomCornea software also offers thesurgeon the advantage of treating each eye indi-vidually. Before the CustomCornea planningsoftware was available, I had to use the same tar-get offset for both eyes to avoid the complicatedprocess of treating the fellow eye as a newpatient.

Steinert: I agree. With CustomCornea software, Ihave one nomogram for primary treatments and acompletely different nomogram for enhance-ments. This makes planning easier and more pre-cise.

Durrie: I would like to have even more flexibili-ty with the laser also. Alcon has developedexpansion software for their laser. I participatedin a study performing customized ablation on 85eyes with high myopia and high astigmatism. Of15 eyes that were 7.0 D with -9.75 D sphericalequivalent, 100% were 20/20 postoperatively,with 62% achieving 20/16 vision. I have neverseen results this good in patients with highmyopia. Additionally, low-contrast acuityimproved and symptoms of glare and halodecreased for these patients.

The LADARVision expansion software wasapproved by the Food and Drug Administrationin June. Now that it is available, surgeons willbe able to correct more cylinder and myopia andwill be able to treat more patients who may nothave previously been candidates for laser cor-rection.

Brint: A solid-state laser with a 1,000-Hz laserand a 0.25-mm Gaussian beam is being devel-oped. The treatment time is not shortened andthis small of a beam will require a phenomenaltracker. Considering the accuracy that we havewith our small-spot lasers and the upcoming soft-ware to improve them, will solid-state lasers have

OCULAR SURGERY NEWS

With CustomCornea

software, I have

one nomogram for

primary treatments

and a completely

different nomogram

for enhancements.

This makes

planning easier and

more precise.

— Roger F.

STeinert, MD

19

a place in the future?

Mullie: Ophthalmology must find the right bal-ance in spot size repetition rate. Studies show thata 1-mm or smaller spot size enables surgeons tocorrect up to fifth-order aberrations in virgineyes. [AU: Please provide reference.] I am notsure that the extremely small spot size and highrepetition rate are going to improve our resultsthat much. As the repetition rate increases,extremely fast and accurate trackers will berequired. Otherwise, the potential for error inspot placement will be high in the presence ofmicrosaccades.

Durrie: When considering solid-state lasers, it isimportant to question how a wavelength of 213 MHz (solid-state lasers) vs. 193 MHz(excimer lasers) will affect ocular tissue in regardto wound healing. These new lasers will have togo through Food and Drug Administrationapproval, so more data will be required beforethey are even a viable option in the United States.

I do not think that the curve on excimer lasers hasflattened yet. As registration becomes more auto-mated, there will be more capabilities on excimerlasers. The industry has a long way to go beforesolid-state laser platforms are a realistic option.

Donnenfeld: The most interesting aspect of asolid-state laser is its convenience. However,there is nothing, in terms of improving surgicalresults, that can be accomplished with a solid-state laser that cannot be done with an excimerlaser.

I agree that tissue reaction will be a significantfactor in whether these lasers are approved in theUnited States and I would estimate that theapproval process would take at least 5 years.

Durrie: I have heard surgeons say that solid-statelasers will cost less than excimer lasers. However, Ialready own a solid-state laser, the IntraLase, and itis more expensive than an excimer laser. By thetime these lasers go through the regulatory, serviceand manufacturing process, the cost savings maydisappear. Whatever takes the place of our currentplatform must prove better visual outcomes and,

currently, that target has been set high byCustomCornea.

Mullie: One of the most important variables thatmust be controlled with laser treatment is treat-ment time. A 1,000-Hz laser with a 0.25-mm spotsize will take the same amount of time to treat asthe current excimer lasers. I would like to see a 1-mm spot moving at 300 Hz to 400 Hz.

Durrie: Dr. Mullie makes a valid point abouttreatment time. Increasing the speed of the lasercould reduce the variability of outcomes. Theshorter the amount of time that the flap is liftedthe better. Currently, the treatment times withZyoptix are longer than with CustomCornea, andI see recovery times that reflect this. Bausch &Lomb is currently working on improving thetreatment times with Zyoptix.

Brint: This has been an interesting discussion oncustom ablation technology and the capabilitiesthat it provides now and may provide in thefuture. I would like to thank the faculty for theirparticipation, Alcon Laboratories, Inc. for its sup-port and OCULAR SURGERY NEWS for organizingthis roundtable discussion.

References1. Mullie to provide reference. 2. Solomon K. CustomCornea vs. CustomVue. Presented at

the 2004 American Society of Cataract and RefractiveSurgery Annual Meeting. May 1-4, 2004; San Diego, Calif.

3. Slade S. Contralateral study of CustomCornea vs.CustomVue. Presented at the 2004 American Society ofCataract and Refractive Surgery Annual Meeting. May 1-4,2004; San Diego, Calif.

4. Speaker M, Tullo W, Custom LASIK Outcomes:CustomCornea versus CustomVue. Presented at the 2004American Society of Cataract and Refractive SurgeryAnnual Meeting. May 1-4, 2004; San Diego, Calif.

5. Steinert RF. Effect of measured wavefront diameter onestimating peripheral wavefront data. Presented at the2004 American Society of Cataract and Refractive SurgeryAnnual Meeting. May 1-4, 2004; San Diego, Calif.

6. Stevens JD. Therapeutic use of wavefront corrections inhighly aberrated eyes after refractive surgery. Presentedat the 2004 American Society of Cataract and RefractiveSurgery Annual Meeting. May 1-4, 2004; San Diego, Calif.

7. Donnenfeld ED. The pupil is a moving target: Centration,repeatability, and registration as a critical element ofaccurate custom ablation. J Cataract Refract Surg. In press.

OCULAR SURGERY NEWS

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