Gur Munzer

Factors Predicting the Need for Retreatment After Laser Refractive Surgery.

Purpose: To identify the potential risk factors that increase the likelihood of requiring retreatment after refractive surgery. Methods: This retrospective study included patients who underwent laser in situ keratomileusis or photorefractive keratectomy between January 2005 and December 2012 at the Care-Vision Laser Centers, Tel-Aviv, Israel. Patients were divided into 2 groups according to whether they underwent additional refractive surgery (retreatment) during the study period. Results: Overall, 41,504 eyes (n = 21,313) were included in the final analysis of this study. Throughout the study period, there was a significant reduction in the 2-year annual retreatment rates with a decline from 4.52% for primary surgeries done in 2005 to 0.18% for surgeries performed in 2012 (quadratic R2 = 0.96, P < 0.001). The retreatment group had significantly higher preoperative age, maximum keratometric power, sphere, cylinder, and better best-corrected visual acuity. They were more likely to have preoperative hyperopia, photorefractive keratectomy as opposed to laser in situ keratomileusis, intraoperative higher humidity conditions and lower temperature, and higher ablation depths. Significant differences in retreatment rates were found between the 5 high-volume surgeons (>1500 procedures performed) ranging from 0.48 to 3.14% (P < 0.0001). Multiple logistic regression analysis demonstrated that age, astigmatism, hyperopia, temperature, and surgeons experience all significantly affected the need for retreatment. Conclusions: The following factors significantly increase the need for refractive retreatment: older preoperative age, higher degrees of astigmatism, hyperopia, colder operating room temperature, and less surgeon experience. Some of these factors may be incorporated into nomograms to reduce future retreatment rates.

Comparison of Three Epithelial Removal Techniques in PRK: Mechanical, Alcohol-assisted, and Transepithelial Laser.

PURPOSE To compare the visual and refractive results obtained after photorefractive keratectomy (PRK) in patients who underwent one of three different epithelial removal techniques. METHODS The authors reviewed the medical files of consecutive eyes with myopia and myopic astigmatism that were treated during a 10-year period by mechanical PRK, alcohol-assisted PRK, or transepithelial PRK (in the phototherapeutic keratectomy mode), and observed for more than 1 year. RESULTS A total of 3,417 patients (3,417 eyes) were included in this study. At 3 and 6 months postoperatively, the outcome of alcohol-assisted PRK was superior both in efficacy (P < .01) and safety (P < .001) to those of both mechanical PRK and transepithelial PRK, which were similar. At more than 1 year postoperatively, the mean efficacy index was still high for alcohol-assisted PRK, but low for the transepithelial PRK, corresponding to a mean uncorrected visual acuity of more than one Snellen line lower than those of the other two techniques (P < .0001). All three techniques showed a regression toward myopia more than 1 year postoperatively, with significant undercorrection obtained in eyes treated with transepithelial PRK (P < .0001). CONCLUSIONS Significant differences were detected in both the visual outcomes and the refractive results of the three epithelial removal techniques. The long-term outcomes were best for alcohol-assisted PRK.

Myopic laser in situ keratomileusis retreatment: Incidence and associations

Purpose To determine the factors associated with retreatment after laser in situ keratomileusis (LASIK) for myopic eyes in the modern LASIK era. Setting Care‐Vision Laser Centers, Tel‐Aviv, Israel. Design Retrospective cohort study. Methods All cases of myopic LASIK performed between January 2005 and December 2012 were analyzed according to whether they had retreatment refractive surgery. Result The study evaluated 9177 right eyes in 9177 consecutive LASIK cases. The mean preoperative subjective spherical equivalent and astigmatism were −3.30 diopters (D) ± 1.53 (SD) (range −0.50 to −12.00 D) and 0.69 ± 0.94 D (range 0.00 to 6.00 D), respectively. Of the eyes, 165 (1.80%) had at least 1 retreatment. Over the course of the study, the 2‐year retreatment rate decreased from 2.58% to 0.38% (P < .001). Multiple binary logistic regression analysis showed that older age (odds ratio [OR], 1.03; P = .007), higher astigmatism (OR, 1.23; P = .008), sphere (OR, 1.15; P = .026), and mean keratometric power (OR, 1.13; P = .036) significantly increased the odds for retreatment. A larger optical zone ablation (7.0 mm) significantly decreased the odds for retreatment (OR, 0.10; P = .022). Significant cutoffs associated with retreatments were age greater than 50 years, astigmatism more than 1.5 D, and sphere more than 2.0 D. Conclusions Older age and higher preoperative astigmatism, sphere, and corneal steepness were associated with myopic LASIK retreatment. Larger optical ablation zones might decrease retreatment rates. Financial Disclosure None of the authors has a financial or proprietary interest in any material or method mentioned.

The Effect of Astigmatism Axis on Visual Acuity

Purpose To evaluate the effect of astigmatism axis on uncorrected distance visual acuity (UDVA) in emmetropic eyes that underwent laser refractive surgery. Methods This retrospective study included patients who underwent laser in situ keratomileusis or photorefractive keratectomy between January 2000 and December 2015 at the Care-Vision Laser Centers, Tel Aviv, Israel. Eyes with a 3-month postoperative spherical equivalent between -0.5 D and 0.5 D were included in this study. Eyes with ocular comorbidities and planned ametropia were excluded. Study eyes were divided into 3 groups according to the steep astigmatic axis: with the rule (WTR) (60-120), oblique (31-59 or 121-149), and against the rule (ATR) (0-30 or 150-180). The UDVA of these 3 groups was compared. The oblique group was divided into oblique ATR and oblique WTR, which were compared with each other. Results A total of 17,416 consecutive eyes of 8,708 patients were studied. The WTR eyes (n = 10,651) had significantly better UDVA (logMAR 0.01 ± 0.08) than the oblique (n = 3,141, logMAR 0.02 ± 0.09) and ATR eyes (n = 3,624, logMAR 0.02 ± 0.10) (p<0.001). The oblique WTR group had significantly better UDVA than the oblique ATR group (p<0.001). The UDVA of the oblique and ATR groups was similar. Stepwise multiple regression analysis showed that the group accounted for 15% of the UDVA variance (p = 0.04). Conclusions The astigmatic axis has a small but significant effect on UDVA in emmetropic eyes; WTR was better than oblique and ATR astigmatism. Therefore, when correcting astigmatism, it may be preferable to err towards WTR astigmatism.

Corneal Breakthrough Haze After Photorefractive Keratectomy With Mitomycin C: Incidence and Risk Factors

Purpose: To identify preoperative and intraoperative factors affecting breakthrough corneal haze incidence after photorefractive keratectomy (PRK) with mitomycin C (MMC). Methods: In this retrospective study of PRK performed at the Care Vision Refractive Laser Center, Tel Aviv, Israel, a total of 7535 eyes (n = 3854 patients; mean age ± SD, 26 ± 6 years; 55% men) underwent PRK with intraoperative MMC application. Patients with histories of corneal pathology or surgery were excluded. Incidence, time of onset, and corneal haze severity were documented on follow-up of 118 ± 110 days. Eyes were grouped by preoperative refraction [low (⩽−3D), moderate (−3D to −6D), or high (>−6D) myopia; low (⩽3D) or high (>3D) astigmatism; low or high hyperopia]; by intraoperative time (above or below 40 seconds); and by MMC application time (above or below 40 seconds). The main outcome measures were incidence, onset time, and severity of corneal haze. Results: The haze incidence was 2.1% in eyes with high myopia versus 1.1% in those with low to moderate myopia (P = 0.002), and 3.5 times higher in eyes with high than with low astigmatism (P < 0.05). The overall incidence was higher in eyes treated for hyperopia (10.8%) than for myopia (1.3%) (P = 0.0001). In eyes with moderate myopia, the haze incidence was lower in MMC application time ≥40 seconds (0%) than in <40 seconds (1.3%) (P = 0.03). After surgery, a mild early haze incidence peaked at 68.8 ± 6 days and severe late haze at 115 ± 17 days (P = 0.02). Conclusions: Hyperopic and large myopic or astigmatic corrections carry higher risk of haze. Longer MMC application might have beneficial haze prevention.

Effect of Anisometropia on the Predictability and Accuracy of Refractive Surgery.

Purpose: To evaluate the predictability and accuracy of refractive surgery among adults with myopic anisometropia. Methods: Consecutive cases of myopic eyes that underwent bilateral laser-assisted in situ keratomileusis (LASIK) or bilateral photorefractive keratectomy (PRK) during a 12-year period in a single center were included. Myopic anisometropia was defined as a difference greater than 1.5 D in spherical equivalent between eyes preoperative. Results: A total of 10,046 paired, operated nonamblyopic eyes of 5023 patients were analyzed. Of these, 472 eyes of 236 (4.7%) patients had myopic anisometropia without amblyopia, and 9574 eyes of 4787 patients served as isometropic controls. After refractive surgery, in the anisometropic group the more myopic eye was corrected by +0.47 ± 0.78 (D) more than the contralateral eye (P < 0.0001). Relative to the target refraction, the more myopic eye was overcorrected by 0.21 ± 0.79 D compared with an undercorrection of 0.16 ± 0.60 D in the less myopic contralateral eye (P < 0.0001) and compared with an undercorrection of 0.15 ± 0.62 D in the isometropic controls (P < 0.0001). Additionally, the variability in the correction of the more myopic eyes was significantly higher compared with the less myopic contralateral eyes and isometropic controls (P < 0.0001). These trends were evident both in PRK and LASIK treatments. The effect of anisometropia was found to be independent of the magnitude of preoperative myopia or surgeon identity. Conclusions: The more myopic eye of anisometropes undergoing refractive surgery has lower predictability and accuracy and tends to be overcorrected, whereas the less myopic eye has outcome similar to isometropic controls. These results suggest that refractive surgery nomograms should take into account anisometropia.

Factors affecting laser in situ keratomileusis flap thickness: Comparison of 2 microkeratome heads

Purpose To identify the potential factors affect that affect the thickness of corneal flaps created using 2 different microkeratome heads. Setting Care‐Vision Laser Centers, Tel‐Aviv, Israel. Design Retrospective comparative study. Methods The study included eyes in which bilateral laser in situ keratomileusis (LASIK) was performed from January 1, 2005, to December 31, 2012, using an SBK‐90 microkeratome head (Group 1) or an M2‐90 microkeratome head (Group 2). Inclusion criteria were at least 18 years of age, a stable refraction for 12 months, an intraocular pressure of less than 21 mm Hg, and no history of autoimmune disease, diabetes, ocular surgery, or eye disease. In addition, patients had to cease wearing contact lenses for 2 weeks (rigid lenses) or 4 days (soft lenses) before the preoperative evaluation and before surgery. The disposable blade was used in the right eye first and then reused in the left eye. Results The study evaluated 6242 eyes of 3121 patients with a mean age of 32.2 years ± 9.8 (SD). Group 1 comprised 2560 eyes (41%), and Group 2 comprised 3682 eyes (59%). The eyes in Group 1 had thinner flaps (P < .001). The right eyes had thicker flaps (P < .001). Flap thickness had a positive correlation with precutting central corneal thickness (CCT) and operating room humidity and a negative correlation with patient age, preoperative sphere and cylinder, and operating room temperature. Statistically significant differences were found in flap thickness between surgeons (P < .001). Larger suction rings created thicker flaps (P < .001). Stepwise regression models accounted for up to 28.1% of the variation in flap thickness. Conclusions Factors that were significantly correlated with flap thickness included the precutting CCT, whether the right or the left eye, the microkeratome head used, the surgeon performing the procedure, and the preoperative sphere. These findings might help prevent post‐LASIK corneal ectasia. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.

Risk Factors for Re-treatment Following Hyperopic LASIK

PURPOSE To determine the risk factors for re-treatment following LASIK in hyperopic eyes. METHODS In this retrospective study, consecutive hyperopic eyes underwent LASIK at the Care Vision Laser Centers, Tel-Aviv, Israel, between January 2000 and October 2014. Patients were divided into two groups according to whether or not they underwent additional refractive surgery (re-treatment). Logistic regression was performed to determine predictors of re-treatment. RESULTS Overall, 1,776 eyes of 888 patients were included, of which 82 (4.6%) needed re-treatment. Eyes that underwent re-treatment were of older age (49.1 ± 7.5 vs 46.9 ± 10.3 years, P = .01), had better preoperative CDVA (1.0 ± 0.14 vs 0.95 ± 0.15 decimal, P = .001), were treated more often with the Allegretto EX200 (Alcon Laboratories, Inc., Fort Worth, TX) as opposed to the EX-500 (90.2% vs 63.7%, P < .001), and were treated with a Moria M2-90 microkeratome (Moria S.A., Antony, France) as opposed to Moria SBK-90 (66.7% vs 36.4%, P < .001). Multiple logistic regresison analysis demonstrated that treatment with Allegretto EX200 (odds ratio: 2.67, P = .04), and Moria M2-90 microkeratome (odds ratio: 2.23, P = .04) and older age (odds ratio: 1.03, P = .03) were significant risk factors for re-treatment. CONCLUSIONS Factors associated with a higher risk of re-treatment following hyperopic LASIK include type of laser, type of microkeratome used, and older age. Identifying such factors may aid in reducing future retreatment rates in hyperopic LASIK. [J Refract Surg. 2018;34(5):316-320.].

Risk Assessment for Corneal Ectasia following Photorefractive Keratectomy

Purpose To analyze the risk factors associated with a series of ectasia cases following photorefractive keratectomy (PRK) and all published cases. Methods In a retrospective study on post-PRK ectasia patients, 9 eyes of 7 patients were included, in addition to 20 eyes of 13 patients from the literature. Risk of post-PRK ectasia was calculated using the ectasia risk score system (ERSS) for laser in situ keratomileusis (LASIK) patients. The percent tissue altered (PTA) was also evaluated. Results ERSS scoring of zero for age, RSB, and spherical equivalent was found in 66%, 86%, and 86% of the eyes, respectively. Pachymetry risk score was 2 in 60% of the eyes and 3 or 4 in 16% of the eyes. Topography risk score was 3 in 41% of the eyes and 4 in 21% of the eyes. Cumulative ectasia risk score was ≥4 (high risk) in 77% of the eyes and ≥3 (medium and high risk) in 86% of the eyes. Average PTA was 23.2 ± 7.0%. All eyes but one had a PTA < 40%. Conclusions Preoperative corneal topographic abnormalities and thin corneas may be significant risk factors for developing ectasia following PRK. Post-LASIK ectasia risk scoring also has relevance in the risk for developing post-PRK ectasia.

Flap Thickness Using the Moria One Use-Plus and Moria M2 Microkeratomes

Flap Thickness Using the Moria One Use-Plus and Moria M2 Microkeratomes To the Editor: In the June 2010 issue of the Journal of Refractive Surgery, Chen et al1 analyzed the accuracy and consistency of corneal fl ap thickness created using the Moria One Use-Plus microkeratome compared with the Moria M2 Single Use 90-μm microkeratome (Moria, Antony, France). The authors used anterior segment optical coherence tomography (AS-OCT; Visante, Carl Zeiss Meditec, Jena, Germany) to measure fl ap thickness at fi ve locations on the fi rst postoperative day. The authors found that central fl ap thickness was dramatically thinner in the One Use-Plus group (114.7 10.1 μm and 109.4 11.0 μm for right and left eyes, respectively) than in the M2 group (155.6 14.8 μm and 151.6 2.5 μm for right and left eyes, respectively). The authors should be commended on this well designed and important study. We conducted a similar comparison on 632 consecutive eyes operated with the M2 microkeratome and 415 consecutive eyes operated with the One Use-Plus microkeratome. Both groups were operated between January 2010 and August 2010 at Care-Vision Center, Tel Aviv, Israel, by the same four surgeons (each surgeon used both devices equally). In all cases, fl ap thickness was measured intraoperatively by ultrasound pachymetry using the subtraction method. In contrast to Chen et al, we did not fi nd a signifi cant difference in central fl ap thickness between the microkeratomes (113 15 vs 111 22 μm in the Single Use-Plus and M2 groups, respectively [P=.1, t test]). Similar results were reported by Huhtala et al2 who found the mean fl ap thickness in 300 eyes operated with the M2 microkeratome to be 115.4 12.5 μm and by Aslanides et al3 who found a mean fl ap thickness of 109 18 μm (range: 67 to 152 μm) and 103 15 μm (range: 65 to 151 μm) for right and left eyes, respectively. Thus, we cannot determine why the fl ap thickness in the study by Chen et al1 was dramatically thicker with the M2 microkeratome (a mean thickness that is more suitable to the Moria M2 Single Use 130 head). However, we noticed a signifi cantly tighter distribution of fl ap thicknesses in the One Use-Plus group (Fig). This resulted in a signifi cantly lower standard deviation in this group (15 vs 22 μm [P .001, F test]). Similarly, the range of fl ap thicknesses in the One UsePlus group was tighter (73 to 152 μm) than in the M2 group (52 to 174 μm). Regarding complications, Chen et al reported no intraoperative fl ap complications using either microkeratome and a similar proportion of postoperative microstriae (6% and 4% in the One Use-Plus and M2 groups, respectively) and interface particles (4% in both groups). In our experience, we noted a slightly increased rate of buttonholes in the M2 group (0.24%, n=1 vs 0.47%, n=3; P=.9) and one incomplete fl ap and one free fl ap in the One Use-Plus group. We also noted a similar proportion of postoperative microstriae (2.7% vs 2.1%, respectively) and diffuse lamellar keratitis (1.2% vs 2.4%, respectively) in the One Use-Plus and M2 groups. Overall, we agree with Chen et al that the Moria One Use-Plus is a safe and effective mechanical microkeratome, which has better predictability and accuracy than the Moria M2. Igor Kaiserman, MD, MSc, MHA Tzahi Sela, BSc Yuval Domniz, MD Mark Visokovsky, MD Yuli Suhodrev, MD Gur Munzer, BSc, LLB Tel Aviv, Israel