Description of iatrogenic corneal ectasia in patients without traditional risk factors

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1 ARTICLE Description of iatrogenic corneal ectasia in patients without traditional risk factors Julio Ortega-Usobiaga, MD, PhD 1 ; Rosario Cobo-Soriano, MD, PhD 1 ; Fernando Llovet-Osuna, MD, PhD 1 ; Stephan Linke, MD 2 ; Jaime Beltrán-Sanz, MD 1 ; Julio Baviera-Sabater, MD 1 PURPOSE: To describe the characteristics of corneal ectasia after laser in situ keratomileusis (LASIK) in patients with no traditional risk of ectasia in a single institution using the same surgical technique. METHODS: The records of 12 patients (16 eyes) who underwent LASIK and developed ectasia were retrospectively reviewed. All procedures were performed using the same microkeratome (Moria LSK One) and the same excimer laser (Technolas 217, Bausch & Lomb). No patients had any of the classic preoperative risk factors for ectasia, namely, attempted initial correction D, total ablation depth >25% of preoperative central pachymetry, calculated or measured residual stromal bed <250 μm, preoperative central pachymetry <500 μm, preoperative mean keratometry >47.2 diopters (D), and no suspicious or abnormal signs in corneal topography. RESULTS: Time from surgery (LASIK or enhancement) to the presentation of ectasia was 4.78 ± V2.31 years (range, 1.88 to 8.37 years). The scoring system of Tabbara et al and that of Randleman et al were evaluated in our series. CONCLUSIONS: Patients can experience iatrogenic corneal ectasia despite fulfilling all relevant topographic and corneal thickness criteria. Our study shows that identifying highrisk eyes remains challenging in some cases. KEYWORDS: LASIK complications; corneal ectasia. J Emmetropia 2012; 3: INTRODUCTION Submitted: 2/19/2012 Accepted: 3/8/ Clínica Baviera, Bilbao, Spain. 2 Care Vision, Hamburg, Germany. Presented at XXVIII Congress of the ESCRS (París, France, Sep/4-8/10), with the title «Long-term evolution of iatrogenic corneal ectasia in patients without apparent risk factors». This study was awared first prize for the Best Poster Presentation (Refractive Surgery category). Sources of public and private financial support: none. Statement about the authors financial or proprietary interest: none. Address: Julio Ortega Usobiaga. Henao, 31-3A (Bilbao, 48009, Spain). jortega@clinicabaviera.com One of the risks of laser in situ keratomileusis (LASIK) that can permanently threaten vision is the development of postoperative corneal ectasia 1-2. Risk factors for ectasia include preexisting keratoconus (or forme fruste keratoconus [keratoconus suspect], ie, eyes with topographic features of ectasia but no clinical evidence), low residual stromal bed thickness, low preoperative corneal thickness, removal of an excessive amount of corneal thickness during ablation, younger age (<30 years), high keratometry and high myopia 1-5,13. Most reported cases had preoperative topographic and/or clinical evidence of forme fruste keratoconus, frank keratoconus, forme fruste pellucid degeneration, or pellucid marginal degeneration 6,7. As risk factors are numerous, scoring systems have been developed to predict ectasia 4,8. Some authors now believe a variety of factors contribute to a continuum of risk for ectasia, as opposed to commonly used criteria with defined critical values The 2005 consensus opinion of a panel of refractive surgeons concluded that «the decision to perform LASIK should take the entire clinical picture into account» 5. However, reports of ectasia in patients with no apparent preoperative risk factors have been published 13. The purpose of this study was to describe the characteristics of a series of patients who developed ectasia after undergoing LASIK at the same institution, using the same surgical technique, microkeratome, and excimer laser SECOIR Sociedad Española de Cirugía Ocular Implanto-Refractiva ISSN:

2 84 IATROGENIC ECTASIA IN PATIENTS WHITHOUT TRADITIONAL RISK FACTORS PATIENTS AND METHODS This descriptive, retrospective case series comprised over 387,858 eyes that underwent primary laser in situ keratomileusis or enhancement surgery consecutively at Clínica Baviera from 1995 to More than 40,000 refractive procedures are performed each year at the clinic, a private ophthalmologic institution with 19 centers and 84 surgeons throughout Spain. Of the total sample, 68 eyes (47 patients) had postoperative corneal ectasia (prevalence of 0.017%). The study inclusion criterion was a diagnosis of post-lasik corneal ectasia. Our criteria for ectasia were increasing myopia (with or without increasing astigmatism), keratometric steepening (with or without central and paracentral corneal thinning), and topographic evidence of asymmetric inferior corneal steepening. The exclusion criteria were the following risk factors for ectasia: attempted initial correction D, preoperative central pachymetry <500 μm, preoperative mean keratometry >47.2 diopters (D), and suspicious or abnormal signs in corneal topography. In our institution, we have computerized clinical records since 1999, when we established a consensus on leaving a residual stromal bed thicker than 300 microns. Before that date, from 1995 to 1999, the consensus was that the residual stromal bed should thicker than 250 microns. Therefore, we do not have any cases of ectasia with a residual stromal bed thinner than 250 microns from 1995 to 1999 or thinner than 300 microns from Since 1999, our consensus (primary LASIK plus enhancement) has been that no more than 25% of the central corneal thickness should be ablated. Preoperative topography was obtained with a Placido-based device: EyeSys (EyeSys Laboratories, Houston, Texas, USA) (figs. 1-6) or Topcon KR7000 (Topcon, Tokyo, Japan) or Humphrey (Carl Zeiss Meditec, Dublin, California, USA) (fig. 7) until From that date onward, all preoperative topographies have been obtained using an Orbscan II (Bausch&Lomb, Claremont, California, USA) (figs. 8-13). All the topograph- Figure 3. Preoperative corneal topographies of case 4 (OU; ectasia only developed in OD). Figure 1. Preoperative corneal topography of case 1 (OS). Figure 4. Preoperative corneal topographies of case 5 (OU; ectasia only developed in OD). Figure 2. Preoperative corneal topographies of case 2 (OU). Figure 5. Preoperative corneal topographies of case 6 (OU; ectasia only developed in OD).

3 IATROGENIC ECTASIA IN PATIENTS WHITHOUT TRADITIONAL RISK FACTORS 85 Figure 6. Preoperative corneal topography of case 7 (OU). ic maps shown in the figures were achieved before laser surgery. The inclusion and exclusion criteria were determined by examining the clinical records. Sixteen eyes from 12 patients fulfilled the inclusion criterion and none of the exclusion criteria. The records of these cases were then analyzed. The medical histories were reviewed to collect the following data: age, gender, involved eye, procedure type (primary versus enhancement), time from surgery to presentation, refractive data, and preoperative and postoperative distance corrected visual acuity (DCVA). Figure 7. Preoperative corneal topographies of case 8 (OD). Figure 10. Preoperative corneal topography of case 10 (OD). Figure 8. Preoperative corneal topography of case 9 (OD). Figure 11. Preoperative corneal topography of case 11 (OS). Figure 9. Preoperative corneal topography of case 9 (OS). Figure 12. Preoperative corneal topography of case 12 (OD).

4 86 IATROGENIC ECTASIA IN PATIENTS WHITHOUT TRADITIONAL RISK FACTORS Figure 13. Preoperative corneal topography of case 12 (OS). To obtain the average postoperative DCVA, we converted Snellen visual acuities to their decimal equivalent to calculate mean final visual acuity. When all required data were available, the ectasia risk factor score was calculated according to the systems of Randleman et al 4 and Tabbara et al 8. Data collection fulfilled Spanish legal requirements and institutional review board approval was obtained. Given the retrospective nature of the research design, no informed consent was needed. Operative Technique Patients underwent a complete ophthalmologic examination before surgery following a standard protocol to determine whether they were suitable candidates for corneal refractive surgery. Preoperative pachymetry was always determined using ultrasound (DGH Technologies, Exton, Pennsylvania, USA). Written informed consent was obtained before surgery in each case. All procedures were performed according to the same standard protocol. LASIK was performed using the Moria LSK-One microkeratome (Microtech Inc., Moria, France). In bilateral cases, the same microkeratome blade was used in both eyes. Lamellar keratectomy was always performed first in the left eye (OS) and then in the right eye (OD), and was followed by laser ablation first in the OD and then in the OS using the Technolas 217C or 217-Z-100 excimer laser (Bausch & Lomb, Claremont, California, USA). From 2000, all patients underwent intraoperative ultrasound pachymetry (DGH Technologies, Exton, Pennsylvania, USA) after the flap was lifted. Flap thickness was calculated by subtracting stromal bed thickness from total central corneal thickness. RESULTS We identified 16 eyes from 12 patients (4 women, 8 men) with post-lasik corneal ectasia and no traditional risk factors. Mean age was 27.8 ± 5.0 years (range, 19 to 39). Nine (56.25%) ectasias involved the OD and 7 (43.75%) involved the OS. Ectasia was bilateral in 4 patients. Ten (63.5%) ectasias presented after primary procedures and 6 ectasias (37.5%) appeared after an enhancement procedure. Mean preoperative manifest spherical equivalent (SE) was 3.78 ± 3.00 D (range, 0.63 to D), mean keratometry was ± 1.41 D (range, to 47), and mean keratometric astigmatism was 1.38 ± 0.67 D (range, 0.25 to 2.75 D). These data and the preoperative keratometric axis are shown in table 1. Time from surgery (LASIK or enhancement) to the presentation of ectasia was 4.78 ± 2.31 years (range, 1.88 to 8.37 years). One case was treated with glasses, Table 1. Preoperative refractive data Case no. Eye Preop sphere (D) Preop MK (D) Preop keratometric astigmatism and axis 1 OS OD OS OD 5.00/ 1.00* OD OD 2.75/0.00* OS 6.00/+0.50* OD OS +1.75/0.00* OD OS 1.00/+0.50* OD 1.50/+0.50* OD OS OD OS * Data about enhancement; MK: mean keratometry.

5 IATROGENIC ECTASIA IN PATIENTS WHITHOUT TRADITIONAL RISK FACTORS 87 5 with contact lenses, 2 with corneal cross-linking, and 4 with corneal rings; 1 case was followed up without treatment and 3 were lost (table 2). No eyes required keratoplasty. Pachymetric data are summarized in table 3. Visual and refractive results at the time of presentation of the ectasia are summarized in table 4. The mean preoperative DCVA was 0.91 ± 0.11 (range, 0.60 to 1.00) and the mean DCVA when the ectasia appeared was 0.69 ± 0.22 (range, 0.25 to 0.95). The ectasia risk factor score was calculated according to Randleman et al. 4 for every case. The Randleman risk assessment system applies only to myopes. As every patient had a negative manifest refraction spherical equivalent, this system could be applied. Although Tabbara s system 8 was developed with myopes with an SE between 4.00 and 8.00 D, it has been applied in all cases with available data. Tabbara s system takes 6 items into account (keratometry, oblique cylinder, pachymetry, posterior surface elevation, difference between inferior and superior corneal dioptric power, and posterior best fit sphere/anterior best fit sphere). As 3 items (posterior surface elevation, difference between inferior and superior corneal dioptric power, and posterior best fit sphere/anterior best fit sphere) were missing in cases 1-8, the risk factor score of Tabbara was calculated for the other 6 eyes. These data are summarized in table 5. DISCUSSION Postoperative corneal ectasia remains a disconcerting complication of LASIK. The incidence of ectasia has been estimated to be 1 in 2500 (0.04%) 13. However, the incidence we recorded was less than half this value (0.017%). In our series, corneal ectasia was Table 2. Time to the appearance of ectasia Case no. Date of LASIK Time to ectasia (years) Follow-up period (years) /1998* 8.80/8.37* 12.37/11.94* /1999* 7.42/7.25* 11.11/10.94* /2000* 7.95/ /9.64* /2001* 9.17/7.50* 10.66/8.99* /2003* 2.21/1.88* 4.61/4.28* /2003* 2.21/1.88* 4.61/4.28* * Data on enhancement. mostly associated with at least 1 of the main traditional risk factors stated in the Introduction. Patients can experience iatrogenic corneal ectasia without having any of the traditional risk factors cited in the Introduction (16 out of 68 cases, 23.5% in our study). Although the topographic maps are not classically described or associated with post-lasik ectasia, some of them may have abnormalities that had increased the risk: cases 2 (fig. 2) and 7 (fig. 6) had symmetric but truncated bowties; case 3 had superior steepening in OU, but ectasia only developed in OD; case 4 (fig. 3) may be considered to have had asymmetrical astigmatism with skewed radial axes by some surgeons; case 9 (fig. 8) had significant corneal thickness asymmetry; case 10 (fig. 10) had a de- Table 3. Pachymetric data Preop US pachymetry Case no. (µm) Flap thickness (µm) Total ablation (µm) Ablated cornea (%) Residual stromal bed (µm) NA ** NA ** NA ** NA 145* 25.00* 337** ** * 24.95* 326** * 20.38* * 15.73* * 18.64* * 19.01* * LASIK plus enhancement; ** Calculated residual stromal bed). The preoperative ultrasound pachymetric data apply to eyes before laser surgery.

6 88 IATROGENIC ECTASIA IN PATIENTS WHITHOUT TRADITIONAL RISK FACTORS Table 4. Refractive data at the date of diagnosis of ectasia Case no. Eye Postop refraction Postop MK (D) Postop keratometric astigmatism (D) and axis (º) 1 OS x OD x OS x OD x OD x OD x OS x OD x OS x OD x OS x OD x OD x OS x OD x OS x MK: mean keratometry. Table 5. Ectasia risk factor score according to Randleman et al. 4 and to Tabbara et al. 8 Case no. Eye Sex Age (years) Preop SE (D) Preop US pachymetry (µm) Residual stromal bed (µm) Ectasia risk (Randleman) Ectasia risk (Tabbara) 1 OS Male * High (6) NA 2 OD Male * Moderate (3) NA 2 OS Male * Moderate (3) NA 3 OD Male * Moderate (3) NA 4 OD Female * High (4) NA 5 OD Female * Low (0) NA 6 OS Female Low (1) NA 7 OD Male Low (0) NA 7 OS Male Low (0) NA 8 OD Male Low (1) NA 9 OS Male Low (1) High (10) 9 OD Male Moderate (3) Low (7) 10 OD Male High (6) Low (7) 11 OS Male Moderate (3) Low (7) 12 OD Female Low (2) High (8) 12 OS Female Low (1) Low (7) * Calculated residual stromal bed; NA: not available. centered posterior float and inferior steepening on the map with 1 D color steps and a 2-color I-S difference on rough observation; case 11 (fig. 11) had an asymmetric bowtie; and case 12 (figs. 12 and 13) had central steepening and possibly an asymmetric bow tie. Klein et al 13 described 6 cases of ectasia with no apparent preoperative risk factors. However, this study had several limitations. Only 1 of the eyes included underwent intraoperative pachymetry, compared with 12 out of 16 intraoperative pachymetries performed in our study. In addition, Klein et al used different microkeratomes, excimer lasers, and surgical techniques. As in our study, different surgeons performed the operations. Instead of copies of the topographic maps, we used the original ones, although some of were of poor quality. The average age of patients selected for our series was similar to that of the Klein study, which identified age as a risk factor for ectasia. Thirteen of the 16 eyes are from patients less than 30 years old, so this population clearly confirms age as a risk factor. Published screening strategies, such as those of Randleman et al (Ectasia Risk Factor Score System [ERF- SS]) 4,9,14 and Tabbara et al 8 remain controversial. Although predictive strategies based on current diagnostic tools are still inaccurate, we have evaluated the scoring system of Tabbara et al 8 (based on Orbscan s elevation topography parameters) and the ERFSS 4. However, only 6 cases were evaluated using Tabbara s system, and no cases of successful LASIK without ectasia were analyzed. In addition, 4 eyes that were reoperated (cases 3,

7 IATROGENIC ECTASIA IN PATIENTS WHITHOUT TRADITIONAL RISK FACTORS 89 5, 6, and 7-OS) were evaluated using Randleman s system, and 2 eyes that were reoperated (cases 9-OD and 9-OS) were evaluated using both systems. This could lead to a potential error, because these systems were developed based on primary procedures. This sample size is much too small to support that one system is better than the other. In the most rigorous study published to date,1 mean time to the development of ectasia was 16.3 months (range, 1 to 45 months). Nevertheless, as we report, this can occur long after the primary refractive procedure, even by as long as 8 years after LASIK. Our study shows that identifying high-risk eyes remains challenging in some cases. It is possible that some of our patients were destined to develop keratoconus, even in the absence of LASIK. Having the same surgical protocol may reduce the incidence of ectasia. REFERENCES 1. Randleman JB, Russell B, Ward MA, Thompson KP, Stulting RD. Risk factors and prognosis for corneal ectasia after LASIK. Ophthalmology 2003; 110(2): Binder PS. Ectasia after laser in situ keratomileusis. J Cataract Refract Surg 2003; 29(12): Randleman JB. Ectatic disorders associated with a clawshaped pattern on corneal topography. Am J Ophthalmol 2007; 144(6): Randleman JB, Woodward M, Lynn MJ, Stulting RD. Risk assessment for ectasia after corneal refractive surgery. Ophthalmology 2008; 115(1): Binder PS, Lindstrom RL, Stulting RD, Donnenfeld E, Wu H,McDonnell P, Rabinowitz Y. Keratoconus and corneal ectasia after LASIK. J Cataract Refract Surg 2005; 31(11): Binder PS. Analysis of ectasia after laser in situ keratomileusis: risk factors. J Cataract Refract Surg 2007; 33(9): Rabinowitz YS. Videokeratographic indices to aid in screening for keratoconus. J Refract Surg 1995; 11(5): Tabbara KF, Koth AA. Risk factors for Corneal Ectasia after LASIK. Ophthalmology 2006; 113(9): Randleman JB, Trattler WB, Stulting RD. Validation of the ectasia risk score system for preoperative laser in situ keratomileusis screening. Am J Ophthalmol 2008; 145(5): Binder PS. Risk factors for ectasia after LASIK. J Cataract Refract Surg 2008; 34(12): Condon PI, O Keefe M, Binder PS. Long-term results of laser in situ keratomileusis for high myopia: risk for ectasia. J Cataract Refract Surg 2007; 33(4): Kymionis GD, Bouzoukis D, Diakonis V, Tsiklis N, Gkenos E, Pallikaris AI, Giaconi JA, Yoo SH. Long-term results of thin corneas after refractive laser surgery. Am J Ophthalmol 2007; 144(2): Klein SR, Epstein RJ, Randleman JB, Stulting RD. Corneal ectasia after laser in situ keratomileusis in patients without apparent preoperative risk factors. Cornea 2006; 25(4): Binder PS, Trattler WB. Evaluation of a risk factor scoring system for corneal ectasia after LASIK in eyes with normal topography. J Refract Surg 2010; 26(4): First author: Julio Ortega Usobiaga, MD, PhD Clínica Baviera Bilbao, Spain