ARTICLE

Refractive outcom

es of laser-assistedsubepithelial keratectomy for myopia,hyperopia, and astigmatism using

a 213 nm wavelength solid-state laserSunil Shah, FRCS, Amy L. Sheppard, PhD, Jennifer Castle, BSc, David Baker, BSc,

Phillip J. Buckhurst, PhD, Shehzad A. Naroo, PhD, Leon N. Davies, PhD, James S. Wolffsohn, PhD

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PURPOSE: To study the visual and refractive outcomes after laser-assisted subepithelialkeratectomy (LASEK) performed with a 213 nm solid-state laser for a broad range of refractiveerrors.

SETTING: Private practice, Jersey, United Kingdom.

DESIGN: Case series.

METHODS: The LASEK was performed using a Pulzar Z1 213 nm solid-state laser. Manifestrefraction and uncorrected (UDVA) and corrected (CDVA) distance visual acuities were measuredpreoperatively and 2 and 6 months postoperatively. Accuracy, safety, efficacy, and stability wereassessed at 6 months.

RESULTS: The study enrolled 245 eyes (134 patients). The preoperative spherical equivalent (SE)refractive errors ranged from �9.50 to C6.50 diopters (D); 24 eyes had more than 2.50 D ofastigmatism. At 6 months, 60.4% of eyes were within G0.25 D of the intended SE, 89.4% werewithin G0.50 D, and 97.9% were within G1.00 D. No eye lost 2 or more lines of CDVA; 95.5%of eyes were unchanged or gained 1 line. The mean cylinder power decreased from �0.98 G1.17 D to �0.14 G 0.28 DC at 6 months. The mean SE was unchanged over the follow-upperiod; �0.01 G 0.57 D and �0.01 G 0.55 D at 2 months and 6 months, respectively.

CONCLUSION: Laser-assisted subepithelial keratectomy performed using the 213 nm wavelengthsolid-state laser was safe, accurate, and effective for the treatment of myopia, hyperopia, andastigmatism.

Financial Disclosure: No author has a financial or proprietary interest in any material or methodmentioned.

J Cataract Refract Surg 2012; 38:746–751 Q 2012 ASCRS and ESCRS

Corneal photoablation using excimer laser systemswith a 193 nm wavelength has been performed safelyand effectively for approximately 25 years.1–4 Morerecently, solid-state laser platforms have been devel-oped,5,6 providing an alternative to traditional excimerlasers while overcoming some of the associated disad-vantages. The benefits of newer solid-state lasersinclude ahigher pulse-to-pulse energy stability, a smallspot size (0.6 mm), and the absence of dangerous gas,reducing maintenance costs and noise levels duringsurgery. Furthermore, the 213 nm wavelength iswithin the 190 to 220 nm window of ablation7 relatedto the absorption spectrum of corneal collagen and is

SCRS and ESCRS

by Elsevier Inc.

significantly less sensitive to corneal hydration than193 nm due to its better transmissibility throughwater.8 Corneas that become dehydrated during exci-mer laser photoablation are frequently overcorrected,while superhydration is linked to undercorrection.9

Solid-state laser systems can therefore reduce variabil-ity in final refraction associated with corneal hydra-tion. However, solid-state lasers are more complex tobuild and therefore more expensive.

Previous studies of refractive procedures performedwith 213 nm solid-state lasers have identified smoothablation surfaces5 and clinical courses similar to 193nm excimer laser systems.10 Clinical and visual results

0886-3350/$ - see front matter

doi:10.1016/j.jcrs.2011.11.035

747LASEK USING A 213 NM SOLID-STATE LASER

in the few published studies to date with up to 30 eyesindicate that photorefractive keratectomy (PRK) andlaser in situ keratomileusis (LASIK) using 213 nmsolid-state lasers are effective, stable, and safe.10–13

The PulzarZ1 solid-state laser (CustomVis) generatesa 213 nm wavelength by transmission of a 1064 nmneodymium:YAG laser beam through 3 nonlinearcrystals. It has a 0.6 mm quasi–Gaussian-shaped flyingspot with a 300 Hz pulse repetition rate and 3 forms ofeye-tracking technology; that is, a rapid limbus-basedeye trackerwitha closed-loop responseof 1kHz, avideoeye tracker for greater accuracy, and a video gazetracker to verify patient fixation.

The purpose of the present studywas to evaluate therefractive outcomes of laser-assisted subepithelialkeratectomy (LASEK) performed using the PulzarZ1 solid-state refractive laser in a large cohort repre-senting a broad range of refractive errors (myopia,hyperopia, and significant astigmatism).

PATIENTS AND METHODS

This prospective noncomparative study comprising patientshaving LASEK was approved by the institutional reviewboard. Patients were informed about the nature of the studyand gave written informed consent before participation, inaccordance with institutional guidelines and the Declarationof Helsinki.

Submitted: August 13, 2011.Final revision submitted: November 11, 2011.Accepted: November 14, 2011.

From Jersey Vision Correction (Shah, Castle, Baker), Little GroveClinic, St. Lawrence, Jersey, the School of Life and Health Sciences(Shah, Sheppard, Buckhurst, Naroo, Davies, Wolffsohn), AstonUniversity, Birmingham, the Midland Eye Institute (Shah), Solihull,West Midlands, and the Birmingham Midland Eye Centre (Shah),City Hospital NHS Trust, Birmingham, West Midlands, UnitedKingdom.

The School of Life and Health Sciences, Aston University, receivesfinancial support from a variety of intraocular lens companiesincluding Lenstec, Inc., Saint Petersburg, Florida, USA, AbbottMedical Optics Inc., Santa Ana, California, USA, and TopconEurope, Capelle a/d IJssel, The Netherlands.

Presented at the 14th Winter Meeting of the European Society ofCataract & Refractive Surgeons, Budapest, Hungary, February2010; the XXVIII Congress of the European Society of Cataractand Refractive Surgeons, Paris, France, September 2010; theASCRS Symposium on Cataract, IOL and Refractive Surgery, SanDiego, California USA, March 2011; the 26th Congress of theAsia-Pacific Academy of Ophthalmology, Sydney, Australia, March2011; and the XXIX Congress of the European Society of Cataract &Refractive Surgeons, Vienna, Austria, September 2011.

Corresponding author: James S. Wolffsohn, PhD, School of Lifeand Health Sciences, Aston University, Birmingham, B4 7ET, UnitedKingdom. E-mail: j.s.w.wolffsohn@aston.ac.uk.

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All patients had a complete preoperative ophthalmicexamination to exclude ocular disease. Exclusion criteriawere active anterior segment disease, residual or activeocular disease, previous intraocular or corneal surgery, his-tory of herpes keratitis, previously diagnosed autoimmunedisease, systemic connective tissue disease or atopy, andcorneal topographic findings suggestive of keratoconus.Pre-LASEK examinations included logMAR uncorrecteddistance visual acuity (UDVA), manifest refraction (maxi-mumplus while maintaining best acuity), logMAR correcteddistance visual acuity (CDVA), slitlamp biomicroscopywith dilated fundus assessment, Goldmann applanationtonometry, corneal Scheimpflug imaging (Pentacam, OculusGmbH), and ultrasound pachymetry (Palmscan, MicroMedical Devices).

The same surgeon (S.S.) performed all LASEK proceduresusing the Pulzar Z1 laser system. A standard LASEK tech-nique14 was used, and bilateral surgery was performed asrequired. Mitomycin-C 0.02% was applied for 30 secondsto all hyperopic eyes being treated and to myopic eyeswith an ablation depth greater than 75 mm. Postoperatively,patients received topical ketorolac for 2 days, topical ofloxa-cin for 1 week, and a generic carbomer as required. In addi-tion, 3 days of meloxicam 7.5 mg were recommended.

Follow-up examinations were performed 5 days and 1, 2,and 6 months postoperatively and included slitlamp evalua-tion, UDVA, manifest subjective refraction, and CDVA. Thekey outcome measures were efficacy, safety, accuracy, andstability.

Statistical Analysis

Efficacy was evaluated using the mean UDVA (logMAR)at 6 months. The cumulative proportion of eyes fallingwithin each visual acuity group for preoperative CDVAand postoperative UDVAwas plotted on a histogram. Safetywas assessed on the basis of the change in lines of CDVAbetween the preoperative visit and 6-month visit. The safetyindex was calculated as the mean postoperative CDVA(logMAR)/mean preoperative CDVA (logMAR). Accuracywas assessed by plotting the attempted change in sphericalequivalent (SE) against the achieved change in SE at6 months, with the linear regression trend line allowingobservation of undercorrected and overcorrected eyes. Thestability of treatment was evaluated by comparing themean postoperative SE at 2 months and 6 months. Resultswere displayed using the standard graphs for reportingrefractive surgery outcomes.15

RESULTS

The cohort of 245 eyes of 134 patients (72 women[53.7%]) had a mean age of 41.0 years G 12.2 (SD)(range 19 to 82 years). The mean preoperative spherewas �1.59 G 3.22 diopters (range �9.50 to C6.50 D)and the mean preoperative cylinder, �0.98 G 1.17 D(range 0.00 to �5.50 D). One hundred eighty eyeswere classified as myopic (preoperative meanSE �3.65 G 1.91 D; range �0.63 to �10.63 D), and58 eyes as hyperopic (preoperative mean SE C2.76 G1.33 D; range C0.50 to C6.00 D). Twenty-four eyeshad a preoperative cylinder of 2.50 D or more. BeforeLASEK, the mean central corneal thickness was

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Figure 1. A: The UDVA. B: Change in CDVA. C: The SE of attempted versus achieved refraction. D: The SE of refractive accuracy. E: Refractiveastigmatism. F: Stability of SE refraction (CDVAZ corrected distance visual acuity; SEZ spherical equivalent; UDVAZ uncorrected distancevisual acuity).

748 LASEK USING A 213 NM SOLID-STATE LASER

558.3 G 38.4 mm (range 477 to 687 mm). The resultsreported are based on the postoperative follow-upvisitsat 2.2 G 2.1 months and 6.1 G 3.4 months.

Efficacy

At 6 months, the mean UDVA was 0.02 G 0.06 log-MAR (range 0.18 to �0.12 logMAR) in the 220 eyestargeted for plano postoperative refraction. In the

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myopic group and hyperopic group, the meanUDVA at 6 months was 0.00 G 0.03 logMAR and0.03 G 0.08 logMAR, respectively. Figure 1, A, showsthe cumulative percentage of eyes falling within eachSnellen visual acuity group. The efficacy index (ratioof the mean postoperative UDVA to the mean preop-erative CDVA) was 1.01 in myopic eyes, 1.00 in hyper-opic eyes, and 1.01 overall.

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Table 1. Summary of present and previous studies of clinical outcomes after refractive surgery performed with solid-state laser systems.

Study*/Year Study Type and Cohort Key Conclusions

Anderson12/2004 3 eyes with irregular astigmatism treated using PRK 213 nm solid-state laser allowed successfulcustom ablation in patients with irregular astigmatism

Roszkowska11/2006 11 eyes (SE range �7.63 to C1.50 D) treated with PRKand followed for 12 months

High accuracy and safety; all eyes within G1.00 D ofemmetropia; no eye lost lines of CDVA

Tsiklis10/2007 20 eyes having PRK and 20 eyes having LASIK (bothperformed with solid-state laser) followed for12 months; all eyes low to moderate myopia

No late postoperative complications occurred; all eyesin both groups within G1.00 D of emmetropia at12 months; no eye lost lines of CDVA during follow-up

Tsiklis13/2007 30 eyes having PRK with excimer laser and 30 eyeshaving PRK with solid-state laser followed for12 months

No significant change in corneal endothelial cell densityusing either type of laser up to 12months postoperatively

Present 245 eyes; 181 myopic (SE range �0.63 to �10.63 D),59 hyperopic (SE range C0.50 to C6.00 D); 24 eyeswith R2.50 D cylinder astigmatism; all eyeshaving LASEK

50% of eyes within G0.13 of targeted refraction; 89%within G0.50 D

CDVAZ corrected distance visual acuity (spectacle); LASEKZ laser-assisted subepithelial keratectomy; PRKZ photorefractive keratectomy; SEZ sphericalequivalent*First author

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Safety

In the whole cohort, the mean CDVA was 0.01 G0.05 logMAR (range 0.63 to �0.12 logMAR) preo-peratively and 0.01 G 0.05 logMAR (range 0.30to �0.12 logMAR) logMAR at 6 months. At 6 months,the safety index was 1.0. In the myopic group, themean CDVA was 0.00 G 0.03 logMAR (range 0.10 to�0.08 logMAR) preoperatively and 0.00 G 0.03 log-MAR (range 0.10 to �0.08 logMAR) at 6 months. At6 months, the safety index was 1.0. In the hyperopicgroup, the mean CDVA was 0.03 G 0.08 logMAR(range 0.30 to �0.12 logMAR) preoperatively and0.00 G 0.08 logMAR (range 0.30 to �0.12 logMAR)at 6 months. At 6 months, the safety index was 1.0.Figure 1, B, shows the change in lines of CDVA be-tween the preoperative and 6-month visits.

Accuracy

At 6 months, the mean SE in all eyes targeted foremmetropia was C0.07 G 0.40 D. The R2 betweenthe attempted SE and the achieved SE, representingthe accuracy of treatment, was 0.97 (Figure 1, C). At6 months, the mean SE was C0.02 G 0.27 D in themyopic group and C0.24 G 0.62 D in the hyperopicgroup. One hundred twenty-three (50.2%) of all eyeswere within G0.13 D of the intended SE, 148 eyes(60.4%) were within G0.25 D, 219 eyes (89.4%) werewithin G0.50 D, and 240 eyes (97.9%) were withinG1.00 D (Figure 1, D). Preoperatively, the meancylinder power was �0.98 G 1.17 D (range 0.00 to�5.50 D), which decreased to �0.14 G 0.28 D at6 months. Figure 1, E, shows the distribution of

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preoperative and postoperative cylindrical refractiveerrors. In the myopic group, 99 eyes (55.0%) werewithin G0.13 D of the intended SE, 128 eyes (71.1%)were within G0.25 D, 163 eyes (90.6%) were withinG0.50 D, and 180 eyes (100%) were within G1.00 D.Preoperatively, the mean cylinder power was�0.98 G 0.92 D (range 0.00 to �4.50 D), whichdecreased to �0.14 G 0.28 D at 6 months. In the hy-peropic group, 23 eyes (39.6%) were within G0.13 Dof the intended SE, 28 eyes (48.2%) were withinG0.25 D, 41 eyes (70.7%) were within G0.50 D, and53 eyes (91.4%) were within G1.00 D. Preoperatively,the mean cylinder power was �0.95 G 1.10 D (range0.00 to �5.50 D), which decreased to �0.21 G 0.34 Dat 6 months.

Stability

At 2 months, the mean SE was �0.01 G 0.57 D,which was stable at 6 months (mean SE �0.01 G0.55 D) (Figure 1, F). In the myopic group at 2 months,the mean SE was �0.08 G 0.48 D, which was stable at6 months (mean �0.02 G 0.27 D). In the hyperopicgroup at 2 months, the mean SE was 0.17 G 0.75 D,which was stable at 6 months (mean 0.21 G 0.66 D).In 4 eyes (1.6%), the mean SE changed by more than0.50 D between the 2-month and 6-month visits.

DISCUSSION

Laser-assisted subepithelial keratectomy in this cohortof 245 eyes, which included a broad range of refractiveerrors, was safe, effective, and accurate. No eye lostmore than 2 lines of CDVA, with 95.5% of eyes

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750 LASEK USING A 213 NM SOLID-STATE LASER

maintaining the same CDVA or gaining 1 line postop-eratively. Of the 11 eyes that lost a line of acuity, 4 werein the hyperopic group and 7 were in the myopicgroup. The only postoperative complication wasrecurrent epithelial erosion syndrome. The accuracyof treatment at the 6-month stage was good acrossthe whole range of preoperative refractive errorstreated. In the myopic, hyperopic, and high astig-matism (R2.50 D) groups, the mean SE at 6 monthswas C0.02 G 0.27 D, C0.21 G 0.66 D, and C0.01 G0.84 D, respectively.

Regarding the stability of treatment, the postopera-tive mean SE was stable between 2 months (�0.01 G0.57 D) and 6 months (�0.01 G 0.55 D). A limitationof the present study is that patients were followedonly until the 6-month stage. However, recently pub-lished reports of LASEK outcomes using excimer laserplatforms have shown refractive stability between the6-month and 12-month stages in myopic eyes16 andhyperopic eyes.17 Both these studies found a lowincidence (1%) of refractive change greater than0.50 D between 6 months and 12 months.

The advantages of the Pulzar Z1 laser system includea small spot diameter (0.6 mm) compared with that oftypical excimer lasers (0.95 mm and 0.85 mm forAllegretto and Ladarvision, respectively) and that themechanical stress on the cornea caused by acousticshock waves is reduced; the stress is known to increasewith larger spot diameters.18 Cellular changes anddamage to corneal collagen may therefore bereduced.19 The small spot size and true Gaussian inten-sity distribution, in conjunction with high pulse-to-pulse stability and rapid eye tracking, results ina smoothablation surface. Thismeans thePulzarZ1 sys-tem is a good choice for custom refractive treatments.

Despite the numerous potential advantages ofsolid-state lasers over excimer lasers, there are rela-tively few published reports of refractive outcomesafter treatment with solid-state platforms. Previousstudies have shown PRK and LASIK solid-state lasertreatments to be effective and safe in cohorts of 3 to30 eyes. To our knowledge, the present study is the firstto document LASEK outcomes using a solid-state laserand represents the largest cohort (245 eyes) analyzed todate. Table 1 shows the key findings in previousstudies of solid-state laser refractive surgery out-comes.10–13 The efficacy, safety, and accuracy resultsseem as good as reported excimer laser ablationoutcomes, whether wavefront guided or not.20,21

Although the results in the present study are prom-ising in terms of LASEK outcomes using the Pulzar Z1solid-state laser, there are limitations to the study de-sign. There was no control group having treatmentby excimer laser, meaning that a direct comparisonof the 2 types of laser systems was not possible. No

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subjective outcomes were evaluated with a validatedquestionnaire, which would have assessed patientsatisfaction with the technology. Furthermore, manypatients (111 of 134) had bilateral LASEK; thus, eacheye cannot be considered statistically independent.However, strong accuracy and safety results areshown when assessing just 1 eye of each patient.

In conclusion, LASEK surgery performed with thePulzar Z1 213 nmwavelength solid-state laser appearsto be safe and effective for the treatment of a broadrange of refractive errors including significant levelsof myopia, hyperopia, and astigmatism.

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WHAT WAS KNOWN

� Compared with traditional excimer laser systems, solid-state lasers have a higher pulse-to-pulse energy stability,a small spot size (0.6 mm), and reduced maintenance andintraoperative noise related to excimer laser gases.

� The 213 mm wavelength is less sensitive to cornealhydration than 193 mm due to its better transmissibilitythrough water. However, accuracy and stability with thesolid-state laser has been tested only for PRK in a fewstudies with up to 30 eyes.

WHAT THIS PAPER ADDS

� Laser-assisted subepithelial keratomileusis performedusing the 213 mm wavelength solid-state laser wassafe and accurate for the treatment of myopia, hyperopia,and astigmatism in a large cohort of 245 eyes. Resultswere similar to those reported for excimer laser systemsusing conventional or wavefront-guided approaches.

REFERENCES1. Ang EK, Couper T, Dirani M, VajpayeeRB, Baird PN. Outcomes

of laser refractive surgery for myopia. J Cataract Refract Surg

2009; 35:921–933

2. McDonaldMB, KaufmanHE, Frantz JM, Shofner S, SalmeronB,

Klyce SD. Excimer laser ablation in a human eye. Arch Ophthal-

mol 1989; 107:641–642

3. Leaming DV. Practice styles and preferences of ASCRS mem-

bersd1996 survey. J Cataract Refract Surg 1997; 23:527–535

4. Trokel SL, Srinivasan R, Braren B. Excimer laser surgery of the

cornea. Am J Ophthalmol 1983; 96:710–715

5. Roszkowska AM, Korn G, Lenzer M, Kirsch M, Kittelmann O,

Zatonski R, Ferreri P, Ferreri G. Experimental and clinical inves-

tigation of efficiency and ablation profiles of new solid-state

deep-ultraviolet laser for vision correction. J Cataract Refract

Surg 2004; 30:2536–2542

6. Dair GT, Pelouch WS, van Saarloos PP, Lloyd DJ, Paz

Linares SM, Reinholz F. Investigation of corneal ablation effi-

ciency using ultraviolet 213-nm solid state laser pulses. Invest

Ophthalmol Vis Sci 1999; 40:2752–2756. Available at: http://

www.iovs.org/cgi/reprint/40/11/2752.pdf. Accessed December

17, 2011

VOL 38, MAY 2012

751LASEK USING A 213 NM SOLID-STATE LASER

7. Lembares A, Hu X-H, Kalmus GW. Absorption spectra of

corneas in the far ultraviolet region. Invest Ophthalmol Vis Sci

1997; 38:1283–1287. Available at: http://www.iovs.org/cgi/

reprint/38/6/1283.full.pdf. Accessed December 17, 2011

8. Dair GT, Ashman RA, Eikelboom RH, Reinholz F, van

Saarloos PP. Absorption of 193- and 213-nm laser wavelengths

in sodium chloride solution and balanced salt solution. Arch Oph-

thalmol 2001; 119:533–537. Available at: http://archopht.ama-

assn.org/cgi/reprint/119/4/533. Accessed December 17, 2011

9. Dougherty PJ, Wellish KL, Maloney RK. Excimer laser abla-

tion rate and corneal hydration. Am J Ophthalmol 1994; 118:

169–176

10. Tsiklis NS, Kymionis GD, Kounis GA, Pallikaris AI, Diakonis VF,

Charisis S, Markomanolakis MM, Pallikaris IG. One-year results

of photorefractive keratectomy and laser in situ keratomileusis

for myopia using a 213 nm wavelength solid-state laser.

J Cataract Refract Surg 2007; 33:971–977

11. Roszkowska AM, de Grazia L, Ferreri P, Ferreri G. One-year

clinical results of photorefractive keratectomy with a solid-

state laser for refractive surgery. J Refract Surg 2006; 22:

611–613

12. Anderson I, Sanders DR, van Saarloos PP, ArdreyWJ IV. Treat-

ment of irregular astigmatism with a 213 nm solid-state, diode-

pumped neodymium:YAG ablative laser. J Cataract Refract

Surg 2004; 30:2145–2151. Available at: http://www.customvis.

com/assets/media/171008treatirreg.pdf. Accessed December

17, 2011

13. Tsiklis NS, Kymionis GD, Pallikaris AI, Diakonis VF, Ginis HS,

Kounis GA, Panagopoulou SI, Pallikaris IG. Endothelial cell

density after photorefractive keratectomy for moderate myopia

using a 213 nm solid-state laser system. J Cataract Refract

Surg 2007; 33:1866–1870

14. Shah S, Sebai Sarhan AR, Doyle SJ, Pillai CT, Dua HS. The

epithelial flap for photorefractive keratectomy. Br J Ophthalmol

2001; 85:393–396. Available at: http://www.ncbi.nlm.nih.gov/

pmc/articles/PMC1723920/pdf/v085p00393.pdf. Accessed

December 17, 2011

J CATARACT REFRACT SURG

15. Dupps WJ Jr, Kohnen T, Mamalis N, Rosen ES, Koch DD,

Obstbaum SA, Waring GO III, Reinstein DZ, Stulting RD.

Standardized graphs and terms for refractive surgery results

[editorial]. J Cataract Refract Surg 2011; 37:1–3

16. McAlinden C, Skiadaresi E, Moore JE. Visual and refractive

outcomes followingmyopic laser-assisted subepithelial keratec-

tomy with a flying spot excimer laser. J Cataract Refract Surg

2011; 37:901–906

17. McAlinden C, Skiadaresi E, Moore JE. Hyperopic LASEK

treatments with mitomycin C using the SCHWIND AMARIS.

J Refract Surg 2011; 27:380–383

18. Krueger RR, Seiler T, Gruchman T, Mrochen M, Berlin MS.

Stress wave amplitudes during laser surgery of the cornea.

Ophthalmology 2001; 108:1070–1074

19. Kermani O, Lubatschowski H. Struktur undDynamik photoakus-

tischer Schockwellen bei der 193 nmExcimerlaserphotoablation

der Hornhaut [Structure and dynamics of photoacoustic shock-

waves in 193 nm excimer laser photoablation of the cornea].

Fortschr Ophthalmol 1991; 88:748–753

20. Fares U, Suleman H, Al-Aqaba MA, Otri AM, Said DG, Dua HS.

Efficacy, predictability, and safety of wavefront-guided refractive

laser treatment: metaanalysis. J Cataract Refract Surg 2011;

37:1465–1475

21. Villarrubia A, Palac�ın E, Bains R, Gersol J. Comparison of

custom ablation and conventional laser in situ keratomileusis

for myopia and myopic astigmatism using the Alcon excimer

laser. Cornea 2009; 28:971–975

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First author:Sunil Shah, FRCS

Midland Eye Institute,Solihull, United Kingdom