ORIGINAL STUDY
EpipolisYLaser In Situ Keratomileusis Discarding Epithelium Versus Laser In Situ Keratomileusis for Myopia and Myopic Astigmatism in Asian Eyes Yen H. Tran, MD, PhD
Purpose: To compare long-term safety, efficacy, predictability, and visual outcomes of epipolisYlaser in situ keratomileusis (epi-LASIK) discarding epithelium versus LASIK in Asian eyes. Design: This was a prospective, randomized, bilateral case series. Methods: This study included 166 eyes of 83 patients with myopia and myopic astigmatism who received epi-LASIK in 1 eye and LASIK in the contralateral eye. Automated separation of the epithelium was performed with epi-Ki, and LASIK was performed with M2 microkeratome using 90-Km calibrated heads. Patients were seen post-operatively at 1 and 3 days, 1 week, and on days 1, 3, 7 at 1, 3, 6, and 12 months. Uncorrected visual acuity, best corrected visual acuity, spherical equivalent (SE), contrast sensitivity, total higher-order aberration, corneal sensitivity, and clarity were analyzed. Results: Mean preoperative SE was Y4.26 (SD, 1.64) diopters (D) in epiLASIK and Y4.27 (SD, 1.63) D in the LASIK group. Twelve months after surgery, mean SE was 0.04 (SD, 0.40) and 0.11 (SD, 0.30) D, respectively. There was no significant difference in uncorrected visual acuity (P = 0.451), SE (P = 0.157) and contrast sensitivity between groups at the 1-year follow-up (P 9 0.05). During 6 months after operation, corneal sensitivity values were significantly lower in the LASIK group (P G 0.05). No eye lost line of best corrected visual acuity in both groups. In epi-LASIK eyes, there was no haze in 97.5% and haze grade 1 in 2.5% at 3 months postoperatively. From 6 months onward, alls corneas were clear. Conclusions: Epi-LASIK was safe, predictable, and effective and may be considered an alternative for LASIK. Key Words: LASIK, epi-LASIK, excimer laser, visual outcomes (Asia-Pac J Ophthalmol 2012;1: 277Y282)
S
ince its approval for use in human eyes in the 1990s, excimer laser refractive surgery has become a popular and successful method to correct myopia and myopic astigmatism. Among the various techniques, laser in situ keratomileusis (LASIK) is most used, as it induces minimal discomfort and has fast recovery, less regression, and least effect on corneal transparency. The disadvantages of LASIK relate to its flap complications, which can occur early or many years after surgery.1Y3 In addition, LASIK is not suitable for individuals with thin cornea or to-
From the Refractive Department, Eye Hospital of Ho Chi Minh City, Vietnam. Received for publication May 2, 2012; accepted July 9, 2012. The article has been presented at the 28th annual meeting of the European Society of Cataract and Refractive Surgery, September 6, 2011, Paris, France. The author has no funding or conflicts of interest to declare. Reprints: Yen H. Tran, MD, PhD, Refractive Department, Eye Hospital of Ho Chi Minh City, 280 Dien Bien Phu St, District 3, Ho Chi Minh, Vietnam. E-mail: [email protected]. Copyright * 2012 by Asia Pacific Academy of Ophthalmology ISSN: 2162-0989 DOI: 10.1097/APO.0b013e318268b3c1
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pography indicative of keratoectasia. The solution in those cases is surface ablation. However, disadvantages of the previous generations of surface ablation, photorefractive keratectomy (PRK), or laser-assisted subepithelial keratomileusis (LASEK) discourage surgeons from using them widely. Photorefractive keratectomy causes damage to corneal epithelial cells and release of proinflammatory cytokines, which is responsible for corneal haze and regression. Laser-assisted subepithelial keratomileusis was introduced by Camellin and Wyler4 in 1999. This meticulous procedure to create an epithelial flap challenges the doctor’s skill and patience, but does not give any obvious superior outcome over PRK.5 In certain cases, the LASEK epithelial flaps were torn and needed to convert to PRK. In 2003, Pallikaris et al6 presented epipolis-LASIK (epiLASIK), an automated method of creating the epithelial flap. Epipolis-LASIK can be performed easily, in a shorter time and with less epithelial trauma. To our best knowledge, there has been no comparison of the visual and refractive outcomes of LASIK and epi-LASIK in treatment of myopia and myopic astigmatism in Asian patients. In this study, we bilaterally compared the visual, refractive outcomes, corneal sensitivity, contrast sensitivity, and higher-order aberration (HOA) in patients who had LASIK in one eye and epi-LASIK in the other eye. We also assessed the clarity of the cornea in the epi-LASIKY treated eyes.
MATERIALS AND METHODS One hundred sixty-six eyes of 83 patients were prospectively enrolled in this study at Eye Hospital of Ho Chi Minh City, Vietnam, between June 2007 and December 2008. All patients signed an informed consent form before participating in the study. Patients were included in the study if they qualified for the following criteria: 18 years of age or older, manifest spherical equivalent (SE) refraction less than or equal to j10.0 diopters (D), astigmatism less than or equal to 6.0 D, maximum difference of 1 D between eyes, baseline best corrected visual acuity (BCVA) of 20/20 or better, and stable refraction for at least 6 months before surgery. Patients were excluded from the study if they were pregnant or had any past or present ocular disease or a systemic disease that might cause abnormal wound healing. Patients were randomized to receive epi-LASIK or LASIK for the first eye, and the remaining type of surgery for the second eye. All eyes were targeted to emmetropia after surgery.
Preoperative Examination All patients underwent thorough ophthalmic examination before surgery, including uncorrected visual acuity (UCVA), BCVA, manifest and cycloplegic refraction, mesopic pupil size measurement, corneal keratometry, topography (Orbscan; Technolas Perfect Vision, Heidelberg, Germany), corneal pachymetry, central corneal sensitivity (Cochet-Bonnet esthesiometer, Luneau, France), total HOA at 6-mm pupil diameter (central area) (Zyoptix
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Diagnostic Workstation; Technolas Perfect Vision), aspherity quotient (Q value), contrast sensitivity, and slitlamp biomicroscopy.
Surgical Technique Patients were randomly assigned epi-LASIK in one eye and LASIK in the other eye. The surgeries were performed simultaneously by 1 surgeon. The conventional ablation program with 6.5-mm optical zone of Ladarvision (Alcon, Fort Worth, Tex) or Technolas 217 Z100 (Technolas Perfect Vision) was applied to all eyes. The same nomogram was used for both procedures. After topical anesthesia with 0.5% proparacaine hydrochloride, both eyes were cleaned with 5% Betadine (povidoneiodine) solution, after which a sterile surgical drape and speculum were placed.
EpipolisYLaser In Situ Keratomileusis The nasal-hinged epithelial sheet was created using an epikeratome (epi-KTM; Moria, Antony, France) following instructions of use from manufacturer. One single-use epi-KTM head was used per patient in combination with a reusable metallic epi-KTM ring (sizing ‘‘j1’’) for the removal of 9- to 9.5-mm epithelial diameter. The flap was reflected nasally and completely removed by forceps to reveal the corneal stroma and to allow ablation. If the ablation depth exceeded 75 Km, after excimer laser ablation, a 6-mm-diameter sponge soaked with 0.02% mitomycin C (MMC) was applied to the ablated stroma for 30 seconds and then removed. The corneal surface and the entire conjunctival fornix were irrigated with 30 mL of balanced salt solution (BSS) to remove residual MMC. A plano Focus Night and Day (CIBA Vision Ophthalmics, Embrach, Switzerland) bandage contact lens was placed on the eye at the end of the procedure. If the ablation depth was less than 75 Km, the ablation surface was cleaned using BSS, and then a contact lens was placed.
Laser In Situ Keratomileusis The cornea was marked, and then an M2 automated microkeratome (Moria) with single-use 90-Km calibrated heads was used to create a superior-hinged flap based on nomogram provided by the manufacturer. One disposable head was used per patient, and all created corneal flaps were between 110 to 140 Km in thickness. The flap was reflected and followed by excimer ablation of the stromal bed. At the end of the laser treatment, the interface was irrigated with 1 to 2 mL of BSS, and the flap was repositioned. The striae test was performed to check flap adhesion before removing speculum.
Follow-Up Patients were instructed to apply topical antibiotic (Oflovid 0.3%; Santen, Osaka, Japan) in both eyes for the first week.
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Corticosteroid eye drops [prednisolone acetate (Pred Forte 1%); Allergan, Irvine, CA] were started in LASIK eyes from the first day after surgery, in epi-LASIK eyes when epithelium was completely healed, and continued in both eyes for 1 month, then tapered following 2 months. Nonpreservative artificial tear was used for at least 3 months. The bandage contact lenses in epiLASIK eyes were removed on day 3 postoperatively. Postoperative examinations were scheduled at days 1, 3, and 7 and at 1, 3, 6, and 12 months after operation. Pain score was collected for days 1, 3, and 7 using a numerical rating scale, rating from 0 (no pain) to 10 (maximum pain). Slitlamp examination and UCVA were performed at all examinations; BCVA, manifest refraction, and corneal sensitivity from day 7; and remaining data were collected at 1 month. Subepithelial haze was graded as follows: 0, clear cornea; 1, trace haze that could be seen only with broad beam illumination; 2, mild haze visible by slit beam illumination; 3, moderate haze somewhat obscuring iris details; and 4, marked haze obscuring iris details. Safety and efficacy indexes were recorded. Safety index is calculated by dividing postoperative BCVA by preoperative BCVA. Efficacy index is calculated by dividing postoperative UCVA by preoperative BCVA. Visual acuity and contrast sensitivity were changed to logMAR unit for analysis and back for expression. Statistical analysis was performed using SPSS statistical software (version 11.0; SPSS, Inc, Chicago, Ill).
RESULTS Preoperatively, there were no statistically significant differences in any of the parameters between the 2 groups (Table 1). The operations were completed uneventfully in all eyes of both groups.
Epithelial Healing and Pain Scores in the Epi-LASIK Group Epithelium healing was completed in 91% of the eyes by day 3 and in 100% of the eyes by day 5. The highest average pain score recorded on the first day after surgery was 1.84; it reduced rapidly to 0.25 on day 3, and no pain at all at 1 week. Patients experienced burning sensation, tearing, and discomfort, which did not require any additional medication.
Safety Safety indexes at 12 months in both laser systems are higher than 1.0. There was no significant difference between the epi-LASIK and the LASIK groups (Table 2). At 1 year, no eye lost lines of BCVA in any group; 20% of epi-LASIK and 18.7% of LASIK eyes gained 2 lines. The difference was not significant (Table 3).
TABLE 1. Preoperative Parameters in Epi-LASIK and LASIK Groups
SE, D K reading, D Ablation depth, Km Total HOA, Km Q value Corneal sensitivity, mm
Epi-LASIK Mean (SD)
LASIK Mean (SD)
P
j4.26 (1.64) (range, j0.75 to j8.25) 44.40 (1.40) 69.65 (22.57) 0.40 (0.16) j0.14 (0.11) 55.71 (9.42)
j4.27 (1.63 (range, j0.50 to j8.25) 44.38 (1.37) 71.27 (25.24) 0.40 (0.15) j0.13 (0.12) 55.10 (9.71)
0.969 0.89 0.481 0.986 0.805 0.387
HOA, higher order abberation.
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TABLE 2. Safety Index 12 Months After Epi-LASIK and LASIK Using 2 Different Excimer Lasers
TABLE 4. Efficacy Index 12 Months after Epi-LASIK and LASIK Using 2 Different Excimer Lasers
Epi-LASIK Mean (SD)
LASIK Mean (SD)
P*
n
1.28 (0.19) 1.17 (0.11) 1.22 (0.16)
1.27 (0.19) 1.18 (0.11) 1.22 (0.15)
0.847 0.688 0.959
68 82 150
Technolas Ladarvision Total
Epi-LASIK for Myopia and Myopic Astigmatism
*t Test.
Technolas Ladarvision Total
Epi-LASIK Mean (SD)
LASIK Mean (SD)
P*
n
1.24 (0.22) 1.06 (0.22) 1.14 (0.24)
1.25 (0.19) 1.16 (0.16) 1.20 (0.18)
0.817 0.025 0.093
68 82 150
*t Test.
Efficacy
Higher-Order Aberration
The efficacy index of both groups in the 2 laser systems is higher than 1.0. The efficacy index in the LASIK group is higher than that in the epi-LASIK if treated with Ladarvision (Table 4). Before surgery, only 4.8% of both epi-LASIK and LASIK groups have BCVA of 20/16; after surgery, 60% of epiLASIK and 82.7% of LASIK eyes can see 20/16 and above without glasses. There was no significant difference between the epi-LASIK and LASIK groups (Tables 5 and 6).
Both types of surgery induced more HOA significantly after the operation (P G 0.05) (Fig. 4). Laser in situ keratomileusis induced more than did epi-LASIK, but the difference was not statistically significant between the 2 groups (P 9 0.05) (Fig. 4).
Predictability There was little change in SE during the follow-up period. Laser in situ keratomileusis had an overcorrection tendency compared with epi-LASIK, but not significantly. There was no case with postoperative SE exceeding 1 D after surgery; 72% of epi-LASIK and 76% of LASIK eyes were within 0.25 D (Fig. 1).
Complications No intraoperative complications occurred in both groups. There were 2 eyes with filamentary keratitis in the epi-LASIK group during the first month after surgery. After treating with artificial tears, the epithelium was healed, and vision restored to 20/16 at 3 months. No other postoperative complication was recorded in both groups.
DISCUSSION
Haze After Epi-LASIK Figure 2 summarizes recorded haze scores during follow-up period after epi-LASIK surgery. Maximum haze happened in the first month after surgery. Among them, 12.5% were grade 1, and no eye had haze more than grade 1. From 6 months onward, all corneas were clear. Thus, corneal haze was transient, mild, and improved over time.
Corneal Sensitivity Before surgery, corneal sensitivity was not different between groups. From 1 week to 6 months after surgery, corneal sensitivity in LASIK group was decreased significantly compared with epi-LASIK (P G 0.05) (Fig. 3). In both groups, corneal sensitivity was restored at the preoperative level by 12 months after surgery.
Contrast Sensitivity Contrast sensitivity in both groups improved after surgery, and there was statistical difference between preoperation and postoperation at 3, 6, 12, and 18 cycles per degree (Table 7).
Epipolis-LASIK is an advanced surface ablation procedure for correction of refractive error. Using an automated epithelial separator such as the epi-KTM (Moria), epi-LASIK creates less damage to the epithelial cells than its predecessors, as there is neither debridement of the epithelium nor use of alcohol. One of the major disadvantages of surface ablation is postoperative pain, which relates to epithelial manipulation. In traditional epi-LASIK and LASEK, the epithelial sheet is replaced over the ablated stroma in hope of minimizing pain and hastening the healing process. However, some studies do not support this hypothesis.5,7 Previous results suggest that discomfort and pain after surface ablation is due to the remnant sheet of epithelium causing an irregular surface and sometimes sloughing. In our study, we use the off-flap technique where the devitalized epithelial sheet was removed to allow faster reepithelialization on a clean, smooth stromal surface. As a result, the epithelium was completely healed in 91% of epi-LASIK eyes by day 3. Therefore, pain level was reduced. Maximum pain level was recorded on the first day after surgery and then decreased rapidly on the third day after surgery.
TABLE 3. Gain and Lost BCVA 12 Months After Epi-LASIK and LASIK Using 2 Different Excimer Lasers Epi-LASIK n (%) Line of BCVA Technolas Ladarvision Total
j1 0 (0) 0 (0) 0 (0)
0 6 (17.6) 9 (22) 15 (20)
+1 15 (44.1) 30 (73.2) 45 (60)
LASIK n (%) +2 13 (38.2) 2 (4.9) 15 (20)
j1 0 (0) 0 (0) 0 (0)
0 6 (17.6) 7 (17.1) 13 (17)
+1 16 (47.1) 32 (78) 48 (64)
P*
n
0.965 0.854 0.872
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+2 12 (35.3) 2 (4.9) 14 (18.7)
*W2 Test.
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TABLE 5. Postoperative UCVA Efficacy Index 12 Months After Epi-LASIK and LASIK Using 2 Different Excimer Lasers Technolas (%) Preoperative BCVA
P* Postoperative UCVA
Ladarvision (%)
Total (%)
Epi-LASIK
LASIK
Epi-LASIK
LASIK
Epi-LASIK
LASIK
20/20 20/16 20/12.5
94.6 5.4 0
94.7 5.3 0
95.6 4.4 0
95.6 4.4 0
95.2 4.8 0
95.2 4.8 0
20/20 20/16 20/12.5
17.6 38.2 38.2
14.7 47.1 35.3
19.5 58.5 2.4
9.8 75.6 7.3
18.7 49.3 18.7
0.978
P*
1.0
0.837
1.0
0.344
12 62.7 20 0.451
*W2 Test.
TABLE 6. Preoperative and Postoperative Manifest Refraction 3, 6, and 12 Months After Epi-LASIK and LASIK Using 2 Different Excimer Lasers Technolas, D Mean (SD) Preoperative 3 mo 6 mo 12 mo P*
Ladarvision, D Mean (SD)
Total, D Mean (SD)
Epi-LASIK
LASIK
Epi-LASIK
LASIK
Epi-LASIK
LASIK
j4.27 (1.65) 0.28 (0.33) 0.16 (0.3) 0.09 (0.3)
j4.26 (1.58) 0.39 (0.36) 0.32 (0.32) 0.16 (0.25)
j4.25 (1.65) 0.13 (0.43) 0.08 (0.43) j0.01 (0.4)
j4.28 (1.69) 0.26 (0.32) 0.19 (0.34) 0.07 (0.33)
j4.26 (1.64) 0.2 (0.4) 0.12 (0.37) 0.04 (0.36)
j4.27 (1.63) 0.32 (0.34) 0.25 (0.34) 0.11 (0.3)
0.255
0.349
0.157
*t Test.
All patients claimed that epi-LASIK eyes had more discomfort than LASIK eyes, but at an acceptable level. Comparing postoperative pain after epi-LASIK, LASEK, and PRK, the results of O’Doherty et al8 showed that epi-LASIK is less painful and with shortest duration. In our study, although patients
did not receive any painkiller method, except bandage contact lens, the pain level was mild, and patients’ tolerance was good. Haze is another limitation for surface ablation, especially when treating moderate and high myopia. Mitomycin C is known to reduce subepithelial fibrosis formation after surface ablation.9
FIGURE 1. Predictability at 12 months after epi-LASIK and LASIK.
FIGURE 2. Corneal haze in epi-LASIK group at 1, 3, 6, and 12 months after surgery.
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Epi-LASIK for Myopia and Myopic Astigmatism
FIGURE 3. Corneal sensitivity over time at 1 week and at 1, 3, 6, and 12 months after epi-LASIK and LASIK.
FIGURE 4. Preoperative and 12-month postoperative HOAs after epi-LASIK and LASIK (root mean square).
We use MMC 0.02% for 30 seconds when the ablation depth was greater than 75 Km. Off-flap epi-LASIK resulted in minimal postoperative haze level. The maximum haze happened at 1 month after surgery, correlating with the peak of myofibroblasts reaction in the stroma. Even then, the highest haze level at 1 month was limited to grade 2, and from 3 months onward, all corneas were clear. Our clinical results showed that epi-LASIK is a safe, effective, and predictable method for correction of myopia up to j8.25 D with both types of excimer lasers. At 1 year postoperatively, no eye in the epi-LASIK group lost line of BCVA, whereas 20% gained 2 lines. In 60% of epi-LASIK eyes, UCVA was equal to or greater than 20/16. Refraction of 72% of epiLASIK eyes was within 0.25 D, and no eye exceeded 1.0 D of attempted correction. Manifest SE in epi-LASIK and LASIK was found to be statistically different at 1 month after surgery; however, from 3 months, this difference was not significant. Corneal stromal nerves are damaged by microkeratome cutting and laser ablation in LASIK, whereas in epi-LASIK, they are affected by laser pulses only. The change in corneal innervation can decrease corneal sensation and is associated with dry eye symptoms. Similar to results reported by Kalyvianaki et al10 and Pe´rez-Santonja et al,11 our results showed that corneal sensitivity was more decreased after LASIK than epi-LASIK and returned to its preoperative level at 12 months postoperatively. Excimer laser ablation changes the corneal shape from prolate to oblate. This corneal asphericity induces HOAs after
surgery. In our study, postoperative HOA increased significantly compared with preoperative HOA in both groups. Although, LASIK induced more HOA than epi-LASIK, there was no statistical difference between groups. Buzzonetti and associates12 reported similar outcome in a series of 36 eyes after LASEK and LASIK, where there was not a difference in total aberration after LASEK and LASIK surgeries. Contrast sensitivity measurement at 6 and 12 cpd is most useful in assessment of patients who underwent laser refractive surgery.13 In our study, contrast sensitivity was increased both after LASIK and epi-LASIK surgery, and it was statistically significant in the middle and high frequencies. It may have resulted from magnification effect of images after myopic correction and smoothness of ablated surface when using small Gaussian beam profile. In conclusion, this study demonstrates that, in early postoperative period, epi-LASIK is uncomfortable and more painful than LASIK. However, epi-LASIK delivers the same safety, effectiveness, predictability, and visual quality in the long term as LASIK. Intraoperative application of 0.02% MMC is effective to prevent subepithelial haze formation. Epipolis-LASIK has less impact on corneal sensitivity than LASIK. Although visual recovery is slower with epi-LASIK in the short term compared with LASIK, in the long term this no-cut procedure preserves more the integrity of the cornea and should be considered as an alternative.
TABLE 7. Contrast Sensitivity Before and 12 Months After Epi-LASIK and LASIK Epi-LASIK Mean Frequency, cpd 1.5 3 6 12 18
LASIK Mean
Preoperative
Postoperative
P
Preoperative
Postoperative
P
52.28 63.48 51.3 18.93 5.98
53.29 67.84 67.3 30.45 12
0.85 0.05 0.00 0.00 0.00
52.86 60.86 49.25 20.02 6.52
53.26 66.93 66.39 30.73 11.9
0.94 0.00 0.00 0.00 0.00
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REFERENCES
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1. Tumbocon JA, Paul R, Slomovic A, et al. Late traumatic displacement of laser in situ keratomileusis flaps. Cornea. 2003;22:66Y69.
8. O’Doherty M, Kirwan C, O’Keeffe M, et al. Postoperative pain following epi-LASIK, LASEK, and PRK for myopia. J Refract Surg. 2007;23:133Y138.
2. Kymionis GD, Diakonis VF, Bouzoukis DI, et al. Idiopathic recurrence of diffuse lamellar keratitis after LASIK. J Refract Surg. 2007;23:720Y721.
9. Lee DH, Chung HS, Jeon YC, et al. Photorefractive keratectomy with intraoperative mitomycin-C application. J Cataract Refract Surg. 2005;31:2293Y2298.
3. Ramı´rez M, Quiroz-Mercado H, Hernandez-Quintela E, et al. Traumatic flap dislocation 4 years after LASIK due to air bag injury. J Refract Surg. 2007;23:729Y730.
10. Kalyvianaki MI, Katsanevaki VJ, Kavroulaki DS, et al. Comparison of corneal sensitivity and tear function following epi-LASIK or laser in situ keratomileusis for myopia. Am J Ophthalmol. 2006;142: 669Y671.
4. Camellin M, Wyler D. Epi-LASIK versus epi-LASEK. J Refract Surg. 2008;24:S57YS63. 5. Cui M, Chen X, Lu P. Comparison of laser epithelial keratomileusis and photorefractive keratectomy for the correction of myopia: a meta-analysis. Chin Med J. 2008;121:2331Y2335. 6. Pallikaris IG, Katsanevaki VJ, Kalyvianaki MI, et al. Advances in subepithelial excimer refractive surgery techniques: epi-LASIK. Curr Opin Ophthalmol. 2003;14:207Y212. 7. Litwak S, Zadok D, Garcia-de Quevedo V, et al. Laser assisted subepithelial keratectomy versus photorefractive keratectomy for the correction of myopia; a prospective comparative study. J Cataract Refract Surg. 2002;28:1330Y1333.
11. Pe´rez-Santonja JJ, Sakla HF, Cardona C, et al. Corneal sensitivity after photorefractive keratectomy and laser in situ keratomileusis for low myopia. Am J Ophthalmol. 1999;127:497Y504. 12. Buzzonetti L, Iarossi G, Valente P, et al. Comparison of wavefront aberration changes in the anterior corneal surface after laser-assisted subepithelial keratectomy and laser in situ keratomileusis: preliminary study. J Cataract Refract Surg. 2004;30:1929Y1933. 13. Monte´s-Mico´ R, Charman N. Choice of spatial frequency for contrast sensitivity evaluation after corneal refractive surgery. J Refract Surg. 2001;17:646Y651.
‘‘What we plant in the soil of contemplation, we shall reap in the harvest of action.’’ - Meister Eckhart
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EpipolisYLaser In Situ Keratomileusis Discarding Epithelium Versus Laser In Situ Keratomileusis for Myopia and Myopic Astigmatism in Asian Eyes Yen H. Tran, MD, PhD
Purpose: To compare long-term safety, efficacy, predictability, and visual outcomes of epipolisYlaser in situ keratomileusis (epi-LASIK) discarding epithelium versus LASIK in Asian eyes. Design: This was a prospective, randomized, bilateral case series. Methods: This study included 166 eyes of 83 patients with myopia and myopic astigmatism who received epi-LASIK in 1 eye and LASIK in the contralateral eye. Automated separation of the epithelium was performed with epi-Ki, and LASIK was performed with M2 microkeratome using 90-Km calibrated heads. Patients were seen post-operatively at 1 and 3 days, 1 week, and on days 1, 3, 7 at 1, 3, 6, and 12 months. Uncorrected visual acuity, best corrected visual acuity, spherical equivalent (SE), contrast sensitivity, total higher-order aberration, corneal sensitivity, and clarity were analyzed. Results: Mean preoperative SE was Y4.26 (SD, 1.64) diopters (D) in epiLASIK and Y4.27 (SD, 1.63) D in the LASIK group. Twelve months after surgery, mean SE was 0.04 (SD, 0.40) and 0.11 (SD, 0.30) D, respectively. There was no significant difference in uncorrected visual acuity (P = 0.451), SE (P = 0.157) and contrast sensitivity between groups at the 1-year follow-up (P 9 0.05). During 6 months after operation, corneal sensitivity values were significantly lower in the LASIK group (P G 0.05). No eye lost line of best corrected visual acuity in both groups. In epi-LASIK eyes, there was no haze in 97.5% and haze grade 1 in 2.5% at 3 months postoperatively. From 6 months onward, alls corneas were clear. Conclusions: Epi-LASIK was safe, predictable, and effective and may be considered an alternative for LASIK. Key Words: LASIK, epi-LASIK, excimer laser, visual outcomes (Asia-Pac J Ophthalmol 2012;1: 277Y282)
S
ince its approval for use in human eyes in the 1990s, excimer laser refractive surgery has become a popular and successful method to correct myopia and myopic astigmatism. Among the various techniques, laser in situ keratomileusis (LASIK) is most used, as it induces minimal discomfort and has fast recovery, less regression, and least effect on corneal transparency. The disadvantages of LASIK relate to its flap complications, which can occur early or many years after surgery.1Y3 In addition, LASIK is not suitable for individuals with thin cornea or to-
From the Refractive Department, Eye Hospital of Ho Chi Minh City, Vietnam. Received for publication May 2, 2012; accepted July 9, 2012. The article has been presented at the 28th annual meeting of the European Society of Cataract and Refractive Surgery, September 6, 2011, Paris, France. The author has no funding or conflicts of interest to declare. Reprints: Yen H. Tran, MD, PhD, Refractive Department, Eye Hospital of Ho Chi Minh City, 280 Dien Bien Phu St, District 3, Ho Chi Minh, Vietnam. E-mail: [email protected]. Copyright * 2012 by Asia Pacific Academy of Ophthalmology ISSN: 2162-0989 DOI: 10.1097/APO.0b013e318268b3c1
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pography indicative of keratoectasia. The solution in those cases is surface ablation. However, disadvantages of the previous generations of surface ablation, photorefractive keratectomy (PRK), or laser-assisted subepithelial keratomileusis (LASEK) discourage surgeons from using them widely. Photorefractive keratectomy causes damage to corneal epithelial cells and release of proinflammatory cytokines, which is responsible for corneal haze and regression. Laser-assisted subepithelial keratomileusis was introduced by Camellin and Wyler4 in 1999. This meticulous procedure to create an epithelial flap challenges the doctor’s skill and patience, but does not give any obvious superior outcome over PRK.5 In certain cases, the LASEK epithelial flaps were torn and needed to convert to PRK. In 2003, Pallikaris et al6 presented epipolis-LASIK (epiLASIK), an automated method of creating the epithelial flap. Epipolis-LASIK can be performed easily, in a shorter time and with less epithelial trauma. To our best knowledge, there has been no comparison of the visual and refractive outcomes of LASIK and epi-LASIK in treatment of myopia and myopic astigmatism in Asian patients. In this study, we bilaterally compared the visual, refractive outcomes, corneal sensitivity, contrast sensitivity, and higher-order aberration (HOA) in patients who had LASIK in one eye and epi-LASIK in the other eye. We also assessed the clarity of the cornea in the epi-LASIKY treated eyes.
MATERIALS AND METHODS One hundred sixty-six eyes of 83 patients were prospectively enrolled in this study at Eye Hospital of Ho Chi Minh City, Vietnam, between June 2007 and December 2008. All patients signed an informed consent form before participating in the study. Patients were included in the study if they qualified for the following criteria: 18 years of age or older, manifest spherical equivalent (SE) refraction less than or equal to j10.0 diopters (D), astigmatism less than or equal to 6.0 D, maximum difference of 1 D between eyes, baseline best corrected visual acuity (BCVA) of 20/20 or better, and stable refraction for at least 6 months before surgery. Patients were excluded from the study if they were pregnant or had any past or present ocular disease or a systemic disease that might cause abnormal wound healing. Patients were randomized to receive epi-LASIK or LASIK for the first eye, and the remaining type of surgery for the second eye. All eyes were targeted to emmetropia after surgery.
Preoperative Examination All patients underwent thorough ophthalmic examination before surgery, including uncorrected visual acuity (UCVA), BCVA, manifest and cycloplegic refraction, mesopic pupil size measurement, corneal keratometry, topography (Orbscan; Technolas Perfect Vision, Heidelberg, Germany), corneal pachymetry, central corneal sensitivity (Cochet-Bonnet esthesiometer, Luneau, France), total HOA at 6-mm pupil diameter (central area) (Zyoptix
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Diagnostic Workstation; Technolas Perfect Vision), aspherity quotient (Q value), contrast sensitivity, and slitlamp biomicroscopy.
Surgical Technique Patients were randomly assigned epi-LASIK in one eye and LASIK in the other eye. The surgeries were performed simultaneously by 1 surgeon. The conventional ablation program with 6.5-mm optical zone of Ladarvision (Alcon, Fort Worth, Tex) or Technolas 217 Z100 (Technolas Perfect Vision) was applied to all eyes. The same nomogram was used for both procedures. After topical anesthesia with 0.5% proparacaine hydrochloride, both eyes were cleaned with 5% Betadine (povidoneiodine) solution, after which a sterile surgical drape and speculum were placed.
EpipolisYLaser In Situ Keratomileusis The nasal-hinged epithelial sheet was created using an epikeratome (epi-KTM; Moria, Antony, France) following instructions of use from manufacturer. One single-use epi-KTM head was used per patient in combination with a reusable metallic epi-KTM ring (sizing ‘‘j1’’) for the removal of 9- to 9.5-mm epithelial diameter. The flap was reflected nasally and completely removed by forceps to reveal the corneal stroma and to allow ablation. If the ablation depth exceeded 75 Km, after excimer laser ablation, a 6-mm-diameter sponge soaked with 0.02% mitomycin C (MMC) was applied to the ablated stroma for 30 seconds and then removed. The corneal surface and the entire conjunctival fornix were irrigated with 30 mL of balanced salt solution (BSS) to remove residual MMC. A plano Focus Night and Day (CIBA Vision Ophthalmics, Embrach, Switzerland) bandage contact lens was placed on the eye at the end of the procedure. If the ablation depth was less than 75 Km, the ablation surface was cleaned using BSS, and then a contact lens was placed.
Laser In Situ Keratomileusis The cornea was marked, and then an M2 automated microkeratome (Moria) with single-use 90-Km calibrated heads was used to create a superior-hinged flap based on nomogram provided by the manufacturer. One disposable head was used per patient, and all created corneal flaps were between 110 to 140 Km in thickness. The flap was reflected and followed by excimer ablation of the stromal bed. At the end of the laser treatment, the interface was irrigated with 1 to 2 mL of BSS, and the flap was repositioned. The striae test was performed to check flap adhesion before removing speculum.
Follow-Up Patients were instructed to apply topical antibiotic (Oflovid 0.3%; Santen, Osaka, Japan) in both eyes for the first week.
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Corticosteroid eye drops [prednisolone acetate (Pred Forte 1%); Allergan, Irvine, CA] were started in LASIK eyes from the first day after surgery, in epi-LASIK eyes when epithelium was completely healed, and continued in both eyes for 1 month, then tapered following 2 months. Nonpreservative artificial tear was used for at least 3 months. The bandage contact lenses in epiLASIK eyes were removed on day 3 postoperatively. Postoperative examinations were scheduled at days 1, 3, and 7 and at 1, 3, 6, and 12 months after operation. Pain score was collected for days 1, 3, and 7 using a numerical rating scale, rating from 0 (no pain) to 10 (maximum pain). Slitlamp examination and UCVA were performed at all examinations; BCVA, manifest refraction, and corneal sensitivity from day 7; and remaining data were collected at 1 month. Subepithelial haze was graded as follows: 0, clear cornea; 1, trace haze that could be seen only with broad beam illumination; 2, mild haze visible by slit beam illumination; 3, moderate haze somewhat obscuring iris details; and 4, marked haze obscuring iris details. Safety and efficacy indexes were recorded. Safety index is calculated by dividing postoperative BCVA by preoperative BCVA. Efficacy index is calculated by dividing postoperative UCVA by preoperative BCVA. Visual acuity and contrast sensitivity were changed to logMAR unit for analysis and back for expression. Statistical analysis was performed using SPSS statistical software (version 11.0; SPSS, Inc, Chicago, Ill).
RESULTS Preoperatively, there were no statistically significant differences in any of the parameters between the 2 groups (Table 1). The operations were completed uneventfully in all eyes of both groups.
Epithelial Healing and Pain Scores in the Epi-LASIK Group Epithelium healing was completed in 91% of the eyes by day 3 and in 100% of the eyes by day 5. The highest average pain score recorded on the first day after surgery was 1.84; it reduced rapidly to 0.25 on day 3, and no pain at all at 1 week. Patients experienced burning sensation, tearing, and discomfort, which did not require any additional medication.
Safety Safety indexes at 12 months in both laser systems are higher than 1.0. There was no significant difference between the epi-LASIK and the LASIK groups (Table 2). At 1 year, no eye lost lines of BCVA in any group; 20% of epi-LASIK and 18.7% of LASIK eyes gained 2 lines. The difference was not significant (Table 3).
TABLE 1. Preoperative Parameters in Epi-LASIK and LASIK Groups
SE, D K reading, D Ablation depth, Km Total HOA, Km Q value Corneal sensitivity, mm
Epi-LASIK Mean (SD)
LASIK Mean (SD)
P
j4.26 (1.64) (range, j0.75 to j8.25) 44.40 (1.40) 69.65 (22.57) 0.40 (0.16) j0.14 (0.11) 55.71 (9.42)
j4.27 (1.63 (range, j0.50 to j8.25) 44.38 (1.37) 71.27 (25.24) 0.40 (0.15) j0.13 (0.12) 55.10 (9.71)
0.969 0.89 0.481 0.986 0.805 0.387
HOA, higher order abberation.
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TABLE 2. Safety Index 12 Months After Epi-LASIK and LASIK Using 2 Different Excimer Lasers
TABLE 4. Efficacy Index 12 Months after Epi-LASIK and LASIK Using 2 Different Excimer Lasers
Epi-LASIK Mean (SD)
LASIK Mean (SD)
P*
n
1.28 (0.19) 1.17 (0.11) 1.22 (0.16)
1.27 (0.19) 1.18 (0.11) 1.22 (0.15)
0.847 0.688 0.959
68 82 150
Technolas Ladarvision Total
Epi-LASIK for Myopia and Myopic Astigmatism
*t Test.
Technolas Ladarvision Total
Epi-LASIK Mean (SD)
LASIK Mean (SD)
P*
n
1.24 (0.22) 1.06 (0.22) 1.14 (0.24)
1.25 (0.19) 1.16 (0.16) 1.20 (0.18)
0.817 0.025 0.093
68 82 150
*t Test.
Efficacy
Higher-Order Aberration
The efficacy index of both groups in the 2 laser systems is higher than 1.0. The efficacy index in the LASIK group is higher than that in the epi-LASIK if treated with Ladarvision (Table 4). Before surgery, only 4.8% of both epi-LASIK and LASIK groups have BCVA of 20/16; after surgery, 60% of epiLASIK and 82.7% of LASIK eyes can see 20/16 and above without glasses. There was no significant difference between the epi-LASIK and LASIK groups (Tables 5 and 6).
Both types of surgery induced more HOA significantly after the operation (P G 0.05) (Fig. 4). Laser in situ keratomileusis induced more than did epi-LASIK, but the difference was not statistically significant between the 2 groups (P 9 0.05) (Fig. 4).
Predictability There was little change in SE during the follow-up period. Laser in situ keratomileusis had an overcorrection tendency compared with epi-LASIK, but not significantly. There was no case with postoperative SE exceeding 1 D after surgery; 72% of epi-LASIK and 76% of LASIK eyes were within 0.25 D (Fig. 1).
Complications No intraoperative complications occurred in both groups. There were 2 eyes with filamentary keratitis in the epi-LASIK group during the first month after surgery. After treating with artificial tears, the epithelium was healed, and vision restored to 20/16 at 3 months. No other postoperative complication was recorded in both groups.
DISCUSSION
Haze After Epi-LASIK Figure 2 summarizes recorded haze scores during follow-up period after epi-LASIK surgery. Maximum haze happened in the first month after surgery. Among them, 12.5% were grade 1, and no eye had haze more than grade 1. From 6 months onward, all corneas were clear. Thus, corneal haze was transient, mild, and improved over time.
Corneal Sensitivity Before surgery, corneal sensitivity was not different between groups. From 1 week to 6 months after surgery, corneal sensitivity in LASIK group was decreased significantly compared with epi-LASIK (P G 0.05) (Fig. 3). In both groups, corneal sensitivity was restored at the preoperative level by 12 months after surgery.
Contrast Sensitivity Contrast sensitivity in both groups improved after surgery, and there was statistical difference between preoperation and postoperation at 3, 6, 12, and 18 cycles per degree (Table 7).
Epipolis-LASIK is an advanced surface ablation procedure for correction of refractive error. Using an automated epithelial separator such as the epi-KTM (Moria), epi-LASIK creates less damage to the epithelial cells than its predecessors, as there is neither debridement of the epithelium nor use of alcohol. One of the major disadvantages of surface ablation is postoperative pain, which relates to epithelial manipulation. In traditional epi-LASIK and LASEK, the epithelial sheet is replaced over the ablated stroma in hope of minimizing pain and hastening the healing process. However, some studies do not support this hypothesis.5,7 Previous results suggest that discomfort and pain after surface ablation is due to the remnant sheet of epithelium causing an irregular surface and sometimes sloughing. In our study, we use the off-flap technique where the devitalized epithelial sheet was removed to allow faster reepithelialization on a clean, smooth stromal surface. As a result, the epithelium was completely healed in 91% of epi-LASIK eyes by day 3. Therefore, pain level was reduced. Maximum pain level was recorded on the first day after surgery and then decreased rapidly on the third day after surgery.
TABLE 3. Gain and Lost BCVA 12 Months After Epi-LASIK and LASIK Using 2 Different Excimer Lasers Epi-LASIK n (%) Line of BCVA Technolas Ladarvision Total
j1 0 (0) 0 (0) 0 (0)
0 6 (17.6) 9 (22) 15 (20)
+1 15 (44.1) 30 (73.2) 45 (60)
LASIK n (%) +2 13 (38.2) 2 (4.9) 15 (20)
j1 0 (0) 0 (0) 0 (0)
0 6 (17.6) 7 (17.1) 13 (17)
+1 16 (47.1) 32 (78) 48 (64)
P*
n
0.965 0.854 0.872
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+2 12 (35.3) 2 (4.9) 14 (18.7)
*W2 Test.
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TABLE 5. Postoperative UCVA Efficacy Index 12 Months After Epi-LASIK and LASIK Using 2 Different Excimer Lasers Technolas (%) Preoperative BCVA
P* Postoperative UCVA
Ladarvision (%)
Total (%)
Epi-LASIK
LASIK
Epi-LASIK
LASIK
Epi-LASIK
LASIK
20/20 20/16 20/12.5
94.6 5.4 0
94.7 5.3 0
95.6 4.4 0
95.6 4.4 0
95.2 4.8 0
95.2 4.8 0
20/20 20/16 20/12.5
17.6 38.2 38.2
14.7 47.1 35.3
19.5 58.5 2.4
9.8 75.6 7.3
18.7 49.3 18.7
0.978
P*
1.0
0.837
1.0
0.344
12 62.7 20 0.451
*W2 Test.
TABLE 6. Preoperative and Postoperative Manifest Refraction 3, 6, and 12 Months After Epi-LASIK and LASIK Using 2 Different Excimer Lasers Technolas, D Mean (SD) Preoperative 3 mo 6 mo 12 mo P*
Ladarvision, D Mean (SD)
Total, D Mean (SD)
Epi-LASIK
LASIK
Epi-LASIK
LASIK
Epi-LASIK
LASIK
j4.27 (1.65) 0.28 (0.33) 0.16 (0.3) 0.09 (0.3)
j4.26 (1.58) 0.39 (0.36) 0.32 (0.32) 0.16 (0.25)
j4.25 (1.65) 0.13 (0.43) 0.08 (0.43) j0.01 (0.4)
j4.28 (1.69) 0.26 (0.32) 0.19 (0.34) 0.07 (0.33)
j4.26 (1.64) 0.2 (0.4) 0.12 (0.37) 0.04 (0.36)
j4.27 (1.63) 0.32 (0.34) 0.25 (0.34) 0.11 (0.3)
0.255
0.349
0.157
*t Test.
All patients claimed that epi-LASIK eyes had more discomfort than LASIK eyes, but at an acceptable level. Comparing postoperative pain after epi-LASIK, LASEK, and PRK, the results of O’Doherty et al8 showed that epi-LASIK is less painful and with shortest duration. In our study, although patients
did not receive any painkiller method, except bandage contact lens, the pain level was mild, and patients’ tolerance was good. Haze is another limitation for surface ablation, especially when treating moderate and high myopia. Mitomycin C is known to reduce subepithelial fibrosis formation after surface ablation.9
FIGURE 1. Predictability at 12 months after epi-LASIK and LASIK.
FIGURE 2. Corneal haze in epi-LASIK group at 1, 3, 6, and 12 months after surgery.
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Epi-LASIK for Myopia and Myopic Astigmatism
FIGURE 3. Corneal sensitivity over time at 1 week and at 1, 3, 6, and 12 months after epi-LASIK and LASIK.
FIGURE 4. Preoperative and 12-month postoperative HOAs after epi-LASIK and LASIK (root mean square).
We use MMC 0.02% for 30 seconds when the ablation depth was greater than 75 Km. Off-flap epi-LASIK resulted in minimal postoperative haze level. The maximum haze happened at 1 month after surgery, correlating with the peak of myofibroblasts reaction in the stroma. Even then, the highest haze level at 1 month was limited to grade 2, and from 3 months onward, all corneas were clear. Our clinical results showed that epi-LASIK is a safe, effective, and predictable method for correction of myopia up to j8.25 D with both types of excimer lasers. At 1 year postoperatively, no eye in the epi-LASIK group lost line of BCVA, whereas 20% gained 2 lines. In 60% of epi-LASIK eyes, UCVA was equal to or greater than 20/16. Refraction of 72% of epiLASIK eyes was within 0.25 D, and no eye exceeded 1.0 D of attempted correction. Manifest SE in epi-LASIK and LASIK was found to be statistically different at 1 month after surgery; however, from 3 months, this difference was not significant. Corneal stromal nerves are damaged by microkeratome cutting and laser ablation in LASIK, whereas in epi-LASIK, they are affected by laser pulses only. The change in corneal innervation can decrease corneal sensation and is associated with dry eye symptoms. Similar to results reported by Kalyvianaki et al10 and Pe´rez-Santonja et al,11 our results showed that corneal sensitivity was more decreased after LASIK than epi-LASIK and returned to its preoperative level at 12 months postoperatively. Excimer laser ablation changes the corneal shape from prolate to oblate. This corneal asphericity induces HOAs after
surgery. In our study, postoperative HOA increased significantly compared with preoperative HOA in both groups. Although, LASIK induced more HOA than epi-LASIK, there was no statistical difference between groups. Buzzonetti and associates12 reported similar outcome in a series of 36 eyes after LASEK and LASIK, where there was not a difference in total aberration after LASEK and LASIK surgeries. Contrast sensitivity measurement at 6 and 12 cpd is most useful in assessment of patients who underwent laser refractive surgery.13 In our study, contrast sensitivity was increased both after LASIK and epi-LASIK surgery, and it was statistically significant in the middle and high frequencies. It may have resulted from magnification effect of images after myopic correction and smoothness of ablated surface when using small Gaussian beam profile. In conclusion, this study demonstrates that, in early postoperative period, epi-LASIK is uncomfortable and more painful than LASIK. However, epi-LASIK delivers the same safety, effectiveness, predictability, and visual quality in the long term as LASIK. Intraoperative application of 0.02% MMC is effective to prevent subepithelial haze formation. Epipolis-LASIK has less impact on corneal sensitivity than LASIK. Although visual recovery is slower with epi-LASIK in the short term compared with LASIK, in the long term this no-cut procedure preserves more the integrity of the cornea and should be considered as an alternative.
TABLE 7. Contrast Sensitivity Before and 12 Months After Epi-LASIK and LASIK Epi-LASIK Mean Frequency, cpd 1.5 3 6 12 18
LASIK Mean
Preoperative
Postoperative
P
Preoperative
Postoperative
P
52.28 63.48 51.3 18.93 5.98
53.29 67.84 67.3 30.45 12
0.85 0.05 0.00 0.00 0.00
52.86 60.86 49.25 20.02 6.52
53.26 66.93 66.39 30.73 11.9
0.94 0.00 0.00 0.00 0.00
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REFERENCES
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1. Tumbocon JA, Paul R, Slomovic A, et al. Late traumatic displacement of laser in situ keratomileusis flaps. Cornea. 2003;22:66Y69.
8. O’Doherty M, Kirwan C, O’Keeffe M, et al. Postoperative pain following epi-LASIK, LASEK, and PRK for myopia. J Refract Surg. 2007;23:133Y138.
2. Kymionis GD, Diakonis VF, Bouzoukis DI, et al. Idiopathic recurrence of diffuse lamellar keratitis after LASIK. J Refract Surg. 2007;23:720Y721.
9. Lee DH, Chung HS, Jeon YC, et al. Photorefractive keratectomy with intraoperative mitomycin-C application. J Cataract Refract Surg. 2005;31:2293Y2298.
3. Ramı´rez M, Quiroz-Mercado H, Hernandez-Quintela E, et al. Traumatic flap dislocation 4 years after LASIK due to air bag injury. J Refract Surg. 2007;23:729Y730.
10. Kalyvianaki MI, Katsanevaki VJ, Kavroulaki DS, et al. Comparison of corneal sensitivity and tear function following epi-LASIK or laser in situ keratomileusis for myopia. Am J Ophthalmol. 2006;142: 669Y671.
4. Camellin M, Wyler D. Epi-LASIK versus epi-LASEK. J Refract Surg. 2008;24:S57YS63. 5. Cui M, Chen X, Lu P. Comparison of laser epithelial keratomileusis and photorefractive keratectomy for the correction of myopia: a meta-analysis. Chin Med J. 2008;121:2331Y2335. 6. Pallikaris IG, Katsanevaki VJ, Kalyvianaki MI, et al. Advances in subepithelial excimer refractive surgery techniques: epi-LASIK. Curr Opin Ophthalmol. 2003;14:207Y212. 7. Litwak S, Zadok D, Garcia-de Quevedo V, et al. Laser assisted subepithelial keratectomy versus photorefractive keratectomy for the correction of myopia; a prospective comparative study. J Cataract Refract Surg. 2002;28:1330Y1333.
11. Pe´rez-Santonja JJ, Sakla HF, Cardona C, et al. Corneal sensitivity after photorefractive keratectomy and laser in situ keratomileusis for low myopia. Am J Ophthalmol. 1999;127:497Y504. 12. Buzzonetti L, Iarossi G, Valente P, et al. Comparison of wavefront aberration changes in the anterior corneal surface after laser-assisted subepithelial keratectomy and laser in situ keratomileusis: preliminary study. J Cataract Refract Surg. 2004;30:1929Y1933. 13. Monte´s-Mico´ R, Charman N. Choice of spatial frequency for contrast sensitivity evaluation after corneal refractive surgery. J Refract Surg. 2001;17:646Y651.
‘‘What we plant in the soil of contemplation, we shall reap in the harvest of action.’’ - Meister Eckhart
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