Outcomes of Wavefront-Optimized Surface Ablation

Outcomes of Wavefront-Optimized Surface Ablation J. Bradley Randleman, MD,1,2 Evan S. Loft, MD,1 Christopher S. Banning, MD,1 Michael J. Lynn, MS,3 R. Doyle Stulting, MD, PhD1,2 Purpose: To compare early visual outcomes after wavefront-optimized advanced surface ablation (ASA) with those after wavefront-optimized LASIK. Design: Retrospective comparative series. Participants: One hundred thirty-six eyes undergoing ASA and 136 preoperative refraction–matched eyes undergoing LASIK from June 2004 through October 2005. Methods: Database review of preoperative characteristics, including patient age, gender, refraction, and central corneal pachymetry; perioperative information, including type of surgery, flap thickness (for LASIK cases), ablation depth, and residual stromal bed thickness; and postoperative information, including uncorrected visual acuity (UCVA) at 1 day, 1 week, 2 weeks, and 3 months, refraction at 3 months, and complications. All ASA patients had topical mitomycin C applied intraoperatively. Main Outcomes Measures: Postoperative UCVA, best spectacle-corrected visual acuity (BSCVA), spherical equivalent (SE) refraction, speed of visual recovery, and postoperative complications. Results: Surface ablation patients were younger (35.4 years vs. 39.8 years, P ⫽ 0.0002) and had thinner corneas (514 ␮m vs. 549 ␮m, P⬍0.0001) preoperatively. Average UCVA was significantly better after LASIK at 1 day (20/26.8 vs. 20/50.4, P⬍0.0001) and 2 weeks (20/24.4 vs. 20/33.3, P ⫽ 0.0002) postoperatively. However, by 3 months postoperatively, UCVA was better after ASA (20/20.8 vs. 20/22.7, P ⫽ 0.05), and 81.5% of patients achieved 20/20 or better UCVA after ASA, compared with 70.5% after LASIK (P ⫽ 0.05). More ASA eyes had postoperative UCVA that achieved or surpassed preoperative BSCVA than LASIK eyes (66% vs. 41.6%, P⬍0.0001). There were 53 patients who underwent bilateral simultaneous ASA. By 1 week, 87.5% had 20/40 or better UCVA in at least one eye and 62.5% had 20/40 or better UCVA in both eyes. By 2 weeks, 86.8% had 20/40 or better UCVA in one eye and 82.6% had 20/40 or better UCVA in both eyes. Conclusion: Initial visual recovery is more rapid after LASIK; however, by 3 months postoperatively UCVA and SE refractions were better after ASA. Advanced surface ablation is an effective alternative to LASIK, and based on early visual recovery, bilateral simultaneous surface ablation is a reasonable alternative to sequential surgery for the majority of patients. Ophthalmology 2007;114:983–988 © 2007 by the American Academy of Ophthalmology.

LASIK is the most commonly utilized technique for the surgical correction of refractive error. LASIK surpassed photorefractive keratectomy (PRK) in popularity in the mid1990s due to its rapid visual recovery, minimal postopera-

Originally received: August 21, 2006. Accepted: October 15, 2006. Manuscript no. 2006-937. 1 Department of Ophthalmology, Emory University, Atlanta, Georgia. 2 Emory Vision, Atlanta, Georgia. 3 Rollins School of Public Health at Emory University, Atlanta, Georgia. Presented at: American Academy of Ophthalmology Annual Meeting, November 2006, Las Vegas, Nevada. Supported in part by Research to Prevent Blindness, Inc., New York, New York, and the National Institutes of Health, Bethesda, Maryland (core grant no. P30 EYO6360). Dr Banning is now in private practice in Kansas City, Kansas. The authors have no financial interests in any of the products or topics mentioned in the article. Reprint requests to J. Bradley Randleman, MD, 1365 B Clifton Road NE, Suite 4500, Atlanta, GA 30322. E-mail: [email protected]. © 2007 by the American Academy of Ophthalmology Published by Elsevier Inc.

tive discomfort, potentially better optical quality,1–5 and concerns about postoperative corneal haze after PRK.6,7 By 2001, the vast majority of refractive surgical procedures performed were LASIK, and ⬍1% of International Society of Refractive Surgery members surveyed were routinely performing PRK.8 However, disadvantages of LASIK include flap complications,9 –11 diffuse lamellar keratitis,12 and an increased incidence of postoperative ectasia.13–15 Recently, there has been renewed interest in advanced surface ablation (ASA), which involves a variety of techniques in which only the epithelial layer is removed, with or without the intraoperative application of mitomycin C, in contradistinction to LASIK, which requires the creation of a stromal flap but does not utilize mitomycin C. Advanced surface ablation techniques include PRK, laser subepithelial keratectomy, and epi-LASIK, among others. The numbers of surface ablation cases have risen recently.16,17 Although all of these techniques have more potential early postoperative discomfort and usually slower visual recovery, surface ablation techniques avoid LASIK flap complications and ISSN 0161-6420/07/$–see front matter doi:10.1016/j.ophtha.2006.10.048

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Ophthalmology Volume 114, Number 5, May 2007 Table 1. Patient Demographics Preoperative Characteristic Age (yrs) Preoperative SE (D) Pachymetry (␮m) BSCVA (20/x)

ASA

LASIK

P Value

35.4 ⫺5.10 514 19.3

39.8 ⫺5.01 549 18.5

0.0002 0.5 ⬍0.0001 0.04

ASA ⫽ advanced surface ablation; BSCVA ⫽ best spectacle-corrected visual acuity; D ⫽ diopters; SE ⫽ spherical equivalent.

cluded subtle epithelial abnormalities, such as epithelial basement membrane disease, and patient preference. There were significantly more patients undergoing LASIK than ASA during the study period. Therefore, we included all ASA patients with all necessary information, and for comparison, we selected a consecutive contemporaneous population of preoperative refraction–matched LASIK patients. Statistical analyses were performed using Student’s t Test, chi-square analysis, and Levene’s test for equal variances. P values of ⱕ0.05 were considered significant.

Results potentially decrease the risk of postoperative ectasia. Recent advancements in technique, including the intraoperative use of mitomycin C, have improved early visual recovery and reduced the incidence of haze formation,18 making ASA a more viable option for routine refractive surgical correction. The purpose of this study is to compare early postoperative visual acuity (VA) outcomes after wavefront-optimized ASA and LASIK and to evaluate the efficacy of bilateral simultaneous ASA.

Materials and Methods We performed a retrospective chart review to identify patients undergoing ASA or LASIK at Emory Vision from June 2004 through October 2005. Institutional review board approval was granted for this study. Preoperative information recorded included patient gender, age, date of surgery, surgeon, previous surgery, pachymetry, manifest and cycloplegic refraction, and target refraction. Perioperative information recorded included flap thickness for LASIK cases, intraoperative pachymetry, calculated ablation depth, residual stromal bed thickness (intraoperative pachymetry minus ablation depth), and epithelial removal technique for ASA cases. All surgeries were performed with the Allegretto Wave excimer laser (Wavelight AG, Erlangen, Germany). All LASIK flaps were created with the Amadeus I microkeratome (AMO Inc., Irvine, CA) using a 140-␮m plate with Surgical Instrument Systems Surepass blades (AMO). Epithelial removal was performed for ASA cases in one of two ways based on surgeon preference: 20% ethanol in a well or on a 20% ethanol-soaked corneal light shield for 30 seconds, or the Amoils brush (Innovative Excimer Solutions, Toronto, Canada). All ASA patients had mitomycin C (0.02%) applied to the stromal bed after laser ablation for 30 seconds to 2 minutes based on individual surgeon preference. No nomogram adjustments were made for either ASA or LASIK treatments. Postoperative outcome measures included uncorrected VA (UCVA) at 1 day, 2 weeks, and 3 months; best spectacle-corrected visual acuity (BSCVA) at 2 weeks and 3 months; manifest refraction at 3 months; and complications. Advanced surface ablation patients with all necessary preoperative data who were targeted for emmetropia and at least 3 months of follow-up were included for analysis; however, patients were excluded if they had had any previous corneal refractive surgery (12 eyes) or lacked essential postoperative refraction information (6 eyes). There were no specific criteria for patients undergoing ASA instead of LASIK, but the majority appeared to have thinner corneas preoperatively. Other common indications for ASA in-

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We analyzed 136 eyes from 73 patients undergoing ASA and 136 eyes from 92 patients undergoing LASIK. Surgical procedures were performed by 5 surgeons at Emory Vision. Patient demographics are shown in Table 1. Patients undergoing ASA were younger and had significantly thinner corneas preoperatively than those undergoing LASIK. For LASIK patients, average flap thickness was 139 ␮m (range, 87–209; standard deviation [SD], 22.3). Average residual stromal bed thicknesses were 376 ␮m (range, 293–531; SD, 49.9) after ASA and 326 ␮m (range, 247– 438; SD, 37.6) after LASIK (P⬍0.0001). Postoperative VA results are shown in Table 2. At 1 day and 2 weeks postoperatively, UCVA was significantly better after LASIK than it was after ASA; however, at 3 months postoperatively UCVA was better after ASA than it was after LASIK. At 1 day postoperatively, 54.1% of eyes achieved 20/40 or better UCVA after ASA, compared with 89.8% of eyes after LASIK (P⬍0.0001) (Fig 1). At 1 week postoperatively, 71.4% of eyes achieved 20/40 or better UCVA after ASA. At 2 weeks postoperatively, 28.7% of eyes achieved 20/20 or better UCVA after ASA, compared with 58.4% of eyes after LASIK (P⬍0.0001), and 87.8% of eyes achieved 20/40 or better UCVA after ASA, compared with 96.0% of eyes after LASIK (P ⫽ 0.05) (Fig 2). At 3 months postoperatively, 81.5% of eyes achieved 20/20 or better UCVA after ASA, compared with 70.5% of eyes after LASIK (P ⫽ 0.05), and 99.2% of eyes achieved 20/40 or better UCVA after ASA, compared with 96.7% of eyes after LASIK (P ⫽ 0.2) (Fig 3). Thirty eyes (9 ASA, 21 LASIK) had UCVA worse than 20/25 at 3 months after surgery. Data past 3 months were available for 20 of these eyes (3 ASA, 17 LASIK). One patient declined enhancement to retain unintended monovision, 5 eyes eventually achieved Table 2. Postoperative Visual Acuity (VA) Results ASA UCVA (20/x) 1 day 1 wk 2 wks 3 mos BSCVA (20/x) 3 mos Postoperative SE 3 mos

LASIK

P Value

50.4 43.7 33.3 20.8

26.8 NA* 24.4 22.7

⬍0.0001

18.3

18.4

⫹0.08 D

⫺0.23 D

0.0002 0.05 0.9 ⬍0.0001

ASA ⫽ advanced surface ablation; BSCVA ⫽ best spectacle-corrected VA; D ⫽ diopters; NA ⫽ data not available; SE ⫽ spherical equivalent; UCVA ⫽ uncorrected VA. *One-week VA was not routinely measured after LASIK.

Randleman et al 䡠 Wavefront-Optimized Surface Ablation

Figure 1. At 1 day postoperatively, uncorrected visual acuity (UCVA) was significantly better after LASIK at each measurement level. Uncorrected visual acuity of 20/40 or better was achieved by 54.1% of eyes after advanced surface ablation (ASA), compared with 89.8% of eyes after LASIK (P⬍0.0001).

20/25 or better UCVA without enhancement surgery, and 11 eyes had enhancements performed. All eyes achieved UCVA of 20/25 or better after enhancement. Fifty-three patients (106 eyes; 77.9%) had bilateral simultaneous ASA. Of these, 40 (75.5%) had 1-week postoperative UCVA recorded, and 46 (87%) had 2-week postoperative UCVA recorded. At 1 week, 35 patients (87.5%) had 20/40 or better UCVA in one eye, and 25 patients (62.5%) had 20/40 or better UCVA in both eyes. Only 2 patients (5%) had UCVA worse than

Figure 2. At 2 weeks postoperatively, uncorrected visual acuity (UCVA) was significantly better after LASIK at each measurement level. Uncorrected visual acuity of 20/20 or better was achieved by 28.7% of eyes after advanced surface ablation (ASA), compared with 58.4% of eyes after LASIK (P⬍0.0001), and 87.8% of eyes achieved 20/40 or better UCVA after ASA, compared with 96.0% of eyes after LASIK (P ⫽ 0.05).

Figure 3. At 3 months postoperatively, uncorrected visual acuity (UCVA) was significantly better after advanced surface ablation (ASA) at the 20/20 and 20/25 measurement levels. Uncorrected visual acuity of 20/20 or better was achieved by 81.5% of eyes after ASA, compared with 70.5% of eyes after LASIK (P ⫽0.05), and 93% of eyes achieved 20/25 or better UCVA after ASA, compared with 82.8% of eyes after LASIK (P ⫽ 0.02). Uncorrected visual acuity of 20/40 or better was achieved by 99.2% of eyes after ASA, compared with 96.7% of eyes after LASIK (P ⫽ 0.2).

20/60 in both eyes. At 2 weeks, 43 patients (86.8%) had 20/40 or better UCVA in one eye, and 38 patients (82.6%) had 20/40 or better UCVA in both eyes. Only 3 patients (6.5%) had UCVA worse than 20/60 in both eyes. Binocular VA was not recorded at any postoperative visit. Three months postoperatively, average spherical equivalent (SE) manifest refraction was ⫹0.08 diopters (D) (SD, 0.45) after ASA, compared with ⫺0.23 D (SD, 0.45) after LASIK (P⬍0.0001) (Table 2). There were no significant differences in variability of SE refractions at 3 months between the two populations (P ⫽ 0.36). There were no significant differences between percents of ASA and LASIK eyes within 0.5 D of emmetropia postoperatively (86.4% vs. 81.9%, P ⫽ 0.4); however, significantly more eyes were more than 0.5 D myopic after LASIK (16.4% vs. 5.3%, P ⫽ 0.005) and significantly more eyes were more than 0.5 D hyperopic after ASA (8.3% vs. 1.6%, P ⫽ 0.02) (Fig 4). Three months postoperatively, there were no significant differences in BSCVA between ASA and LASIK groups (Fig 5). The majority of eyes after ASA (83.7%) and LASIK (83.6%) maintained or gained lines of BSCVA at 3 months postoperatively (Fig 6). There were no significant differences for lines of BSCVA gained or lost. There were only 2 eyes that lost 2 lines of BSCVA at 3 months. Both of these eyes had LASIK, and in both cases, the decreased BSCVA was attributed to surface dryness. There were no significant complications in either group. Specifically, there were no flap-related complications in the LASIK group, and there was no visually significant haze in the ASA group. Most eyes had postoperative UCVA within 1 line of preoperative BSCVA after both ASA (88.6%) and LASIK (72%) (P ⫽ 0.001) (Fig 7). Significantly more eyes had UCVA that achieved or surpassed preoperative BSCVA after ASA (66%) than after LASIK (41.6%) (P⬍0.0001).

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Figure 4. Spherical equivalent refractions 3 months postoperatively. There were no significant differences between percents of advanced surface ablation (ASA) and LASIK eyes within 0.5 diopters (D) of emmetropia postoperatively (86.4% vs. 81.9%, P ⫽ 0.4). Significantly more eyes were more than 0.5 D myopic after LASIK (16.4% vs. 5.3%, P ⫽ 0.005), and significantly more eyes were more than 0.5 D hyperopic after ASA (8.3% vs. 1.6%, P ⫽ 0.02).

Discussion Studies have demonstrated excellent long-term refractive stability after PRK19,20; however, delayed visual recovery, postoperative pain, and the potential for visually significant corneal haze traditionally have limited the use of surface ablation procedures. Recent modifications in technique have increased the rate of healing, reduced postoperative discom-

Figure 5. At 3 months postoperatively, there were no significant differences in best spectacle-corrected visual acuity (BSCVA) between the 2 study groups at any measurement level. ASA ⫽ advanced surface ablation.

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Figure 6. At 3 months postoperatively, there were no significant differences between the 2 groups for lines of best spectacle-corrected visual acuity (BSCVA) gained or lost. The majority of eyes after advanced surface ablation (ASA) (83.7%) and LASIK (83.6%) maintained or gained lines of BSCVA. Both of the eyes that lost 2 lines of BSCVA after LASIK had decreased BSCVA attributed to surface dryness.

fort, and prevented significant haze formation, resulting in a resurgence in the popularity of surface ablation.16 The results of this study demonstrate good visual recovery after surface ablation within 1 week postoperatively for the majority of patients. By 3 months postoperatively, UCVA outcomes favored surface ablation over LASIK. The prophylactic and therapeutic use of mitomycin C has reduced the incidence of postoperative haze after surface ablation significantly.18,21–27 Mitomycin C application ap-

Figure 7. Comparison of preoperative best spectacle-corrected visual acuity (BSCVA) with postoperative uncorrected visual acuity (UCVA). At 3 months postoperatively, significantly more eyes had UCVA that achieved or surpassed preoperative BSCVA after advanced surface ablation (ASA) (66%) than after LASIK (41.6%, P⬍0.0001).

Randleman et al 䡠 Wavefront-Optimized Surface Ablation pears safe, with minimal side effects.18,21 However, mitomycin C may reduce the density of keratocytes in the anterior stroma,26 may increase the likelihood of postoperative tear deficiency,24 and may penetrate into the anterior chamber.27 Netto et al26 have advocated the use of mitomycin C only for patients at high risk of postoperative haze. In this study population, we applied mitomycin C (0.02%) for 30 seconds to 2 minutes based on individual surgeon preference to all eyes without any short-term complications. We recently reduced the mitomycin C application time to 12 seconds for prophylactic use and found no differences in outcomes (unpublished observations). Recent studies have demonstrated comparable long-term visual outcomes for LASIK and surface ablation with traditional excimer laser treatment platforms, especially in patients with less extreme prescriptions.28 –30 All patients in this study had wavefront-optimized ablations performed with the Wavelight Allegretto Wave. Excellent VA outcomes have been reported after LASIK for myopia31 and hyperopia32 (Stonecipher KG. Comparison of wavefrontguided and wavefront-optimized treatments with the Allegretto Excimer Laser. Paper presented at: American Society of Cataract and Refractive Surgery Annual Meeting, April 2006, San Francisco, California) with this laser; however, to our knowledge outcomes after ASA have not been reported previously. This study suggested a potential advantage for surface ablation at 3 months postoperatively. At 3 months, average UCVA was better, more eyes achieved 20/20 UCVA, and significantly more cases had postoperative UCVA that reached or exceeded preoperative BSCVA after surface ablation. There were no differences in BSCVA at 3 months, nor were there any differences in the number of patients within 0.5 D of emmetropia postoperatively. However, significantly more eyes were myopic after LASIK and hyperopic after ASA. Thus, the differences in postoperative UCVA simply may be related to difference in SE refractive outcomes. Because SDs for the 2 populations were identical and there were no significant differences in variability of refractions between groups, nomogram adjustments should improve refractive outcomes in both groups and thereby may equalize outcomes. Due to the retrospective nature of this study, early postoperative pain levels could not be analyzed accurately. There are a variety of postoperative pain management strategies currently employed for surface ablation. Nonsteroidal antiinflammatory drugs may play an increasing role in pain management in the future; however, these medications may delay epithelial healing and should be used with caution in the early postoperative period. Although surgeons frequently performed surface ablation sequentially in the past, by 2004 most (87%) International Society of Refractive Surgery members surveyed performed simultaneous bilateral surface ablation.16 The results of this study and previous ones33–35 indicate that bilateral simultaneous surface ablation is a safe and reasonable surgical strategy for appropriate surgical candidates. Most patients in this study underwent bilateral simultaneous ASA. Within 1 week, the vast majority of patients had 20/40 or better UCVA in one eye, and most had 20/40 or better

UCVA in both eyes. By 2 weeks, only 3 patients (6%) had 20/60 or worse acuity bilaterally. However, given the potential for slow healing with delayed visual recovery, all patients should be informed specifically about this possibility. Given recent concerns about postoperative ectasia after LASIK, some surgeons have advocated surface ablation for patients at higher risk for this complication, especially young patients or those with thinner corneas preoperatively. In this study, patients undergoing ASA were significantly younger and had significantly thinner corneas than patients undergoing LASIK. Average residual stromal bed thickness was significantly higher after ASA than after LASIK, and though average flap thickness was nearly equal to microkeratome plate markings, flap thickness varied widely, from 87 ␮m to 209 ␮m. Given the well-documented potential for flap thickness variation with both mechanical and laser flap-creating devices,36,37 we recommend surface ablation instead of LASIK for any patient with borderline corneal thickness without other significant risk factors for ectasia. In conclusion, visual outcomes after surface ablation are at least equivalent to those after LASIK with the Wavelight Allegretto Wave excimer laser by 3 months postoperatively. More eyes had postoperative UCVA after surface ablation that met or exceeded preoperative BSCVA. Surface ablation is a viable option for most patients and especially useful in borderline LASIK candidates, in whom the potential for flap-related complications is increased; in younger patients; or in patients with thinner corneas. Based on speed of visual recovery, bilateral simultaneous surgery is a reasonable alternative to sequential surgery for the majority of patients undergoing surface ablation.

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