Comparison of 10-year Clinical Results between Laser in situ Keratomileusis and Surface Ablation for Moderate to High Myopia

PURPOSE: To compare the long-term prognosis of laser in situ keratomileusis (LASIK) and surface ablation in moderate to high myopia. METHODS: A retrospective study including 87 eyes of 44 myopic patients treated with LASIK or surface ablation from 1995 to 2005 was performed. Follow-up visits were performed at 3 months, 1 year, 5 years, and 8 years. All treated eyes were divided into 2 groups according to preoperative spherical equivalent (SE)- moderate myopia (<-6.0 diopters [D]) and high myopia (≥-6.0 D). The main outcome measures were postoperative uncorrected visual acuity (UCVA), best corrected visual acuity, SE, mean keratometry, safety index, efficacy index, predictability, and complications. RESULTS: Mean SE was -7.05 ± 2.49 D in the LASIK group and -5.25 ± 1.23 D in the surface ablation group. The 10-year SE was -1.78 ± 1.22 D in the LASIK group and -1.35 ± 1.09 D in the surface ablation group, and there was no statistical difference between the 2 groups. At 10 years postoperatively, UCVA was log MAR 0.155 ± 0.161 in the LASIK group and log MAR 0.095 ± 0.140 in the surface ablation group. There were no significant differences in postoperative mean SE, safety index, efficacy index, or complications between the LASIK and surface ablation group at 10 years. CONCLUSIONS: This 10-year follow-up study shows that LASIK and surface ablation for moderate to high myopia have no statistical differences in mean SE, safety index, efficacy index, or complications.

Surface Ablation with 0.02% Mitomycin C for Retreatment after LASIK and LASEK

PURPOSE: To evaluate the efficacy and safety of surface ablation with mitomycin C (MMC) for the retreatment of refractive errors following laser-assisted in-situ keratomileusis (LASIK) and laser-assisted sub-epithelial keratectomy (LASEK). METHODS: In this retrospective clinical study conducted at a single center, we evaluated 23 eyes that received surface ablation with MMC (0.02%, 20 seconds) between 2009 and 2013 for the treatment of residual refractive errors following myopic LASIK and LASEK. All eyes were evaluated for corneal thickness, initial refractive error, time interval to retreatment, amount of retreatment, duration of postoperative topical steroids use as well as uncorrected vision, spherical equivalent and corneal haziness preoperatively and 1, 3, 6 and 12 months postoperatively. RESULTS: Initially corrected myopia in the LASIK group was -6.47 +/- 2.17 D and -5.68 +/- 2.51 D in the LASEK group. Mean time between initial and retreatment by surface ablation was 11.88 +/- 5.59 months for LASIK and 14.07 +/- 10.10 for LASEK. Retreat amount was 1.49 +/- 0.36 D after LASIK and -1.65 +/- 0.41 D after LASEK. At postoperative 12 months, uncorrected visions were -0.061 +/- 0.886 (log MAR) in the LASIK group and -0.004 +/- 0.745 (log MAR) in the LASEK group and spherical equivalents were -0.55 +/- 0.56 D in the LASIK group and 0.36 +/- 0.33 D in the LASEK group. Postoperative hazes developed in 1 of 8 LASIK eyes and 3 of 15 LASEK eyes which resolved with application of topical steroid for 2-3 months postoperatively. CONCLUSIONS: Surface ablation with 0.02% MMC is safe and highly effective for treating myopic regression following LASIK or LASEK. Application of 0.02% MMC for 20 seconds was effective in preventing postoperative haze formation and maintaining stable vision and spherical equivalent at 12 months after retreatment.

Surface Ablation with 0.02% Mitomycin C for Retreatment after LASIK and LASEK

PURPOSE: To evaluate the efficacy and safety of surface ablation with mitomycin C (MMC) for the retreatment of refractive errors following laser-assisted in-situ keratomileusis (LASIK) and laser-assisted sub-epithelial keratectomy (LASEK). METHODS: In this retrospective clinical study conducted at a single center, we evaluated 23 eyes that received surface ablation with MMC (0.02%, 20 seconds) between 2009 and 2013 for the treatment of residual refractive errors following myopic LASIK and LASEK. All eyes were evaluated for corneal thickness, initial refractive error, time interval to retreatment, amount of retreatment, duration of postoperative topical steroids use as well as uncorrected vision, spherical equivalent and corneal haziness preoperatively and 1, 3, 6 and 12 months postoperatively. RESULTS: Initially corrected myopia in the LASIK group was -6.47 +/- 2.17 D and -5.68 +/- 2.51 D in the LASEK group. Mean time between initial and retreatment by surface ablation was 11.88 +/- 5.59 months for LASIK and 14.07 +/- 10.10 for LASEK. Retreat amount was 1.49 +/- 0.36 D after LASIK and -1.65 +/- 0.41 D after LASEK. At postoperative 12 months, uncorrected visions were -0.061 +/- 0.886 (log MAR) in the LASIK group and -0.004 +/- 0.745 (log MAR) in the LASEK group and spherical equivalents were -0.55 +/- 0.56 D in the LASIK group and 0.36 +/- 0.33 D in the LASEK group. Postoperative hazes developed in 1 of 8 LASIK eyes and 3 of 15 LASEK eyes which resolved with application of topical steroid for 2-3 months postoperatively. CONCLUSIONS: Surface ablation with 0.02% MMC is safe and highly effective for treating myopic regression following LASIK or LASEK. Application of 0.02% MMC for 20 seconds was effective in preventing postoperative haze formation and maintaining stable vision and spherical equivalent at 12 months after retreatment.

Pain control after excimer laser corneal surface ablation / 国际眼科杂志(Guoji Yanke Zazhi)

By reshaping the cornea without the creation of a stromal flap, excimer laser corneal surface ablation eliminates flap-related complications and avoids the risk of ectasia that may occur after laser assisted in situ keratomileusis ( LASIK ) . Post-operative pain is one of the most significant disadvantages of surface ablation and thus the management of pain and discomfort following surface ablation is of great importance. We summarize mechanism of corneal pain and current approaches to pain management after surface ablation.

Changes in Corneal Sensation, Tear Film Stability and Ocular Surface after Advanced Surface Ablation

PURPOSE: To evaluate the changes in tearfilm, corneal sensation and ocular surface after advanced surface ablation. METHODS: Tearfilm break-up time (BUT), Schirmer test without local anesthesia, fluorescein staining, corneal sensitivity test, ocular surface disease index (OSDI), and conjunctival impression cytology were evaluated in 50 eyes of 25 patients who underwent advanced surface ablation preoperatively and postoperatively at 2 weeks and at 1, 2, 3, and 6 months. Each value was compared to the preoperative value. RESULTS: OSDI diminished by 2 weeks postoperatively, and corneal sensation diminished by 1 month postoperatively (p < 0.05). There were significant decreases in BUT by 2 weeks to 1 month postoperatively as well as decreases in the Schirmer test by 2 to 3 months postoperatively (p < 0.05). Fluorescein staining increased at 2 weeks postoperatively (p < 0.05). Goblet cells decreased substantially by 1 month postoperatively and conjunctival squamous metaplasia increased significantly by 2 months postoperatively (p < 0.05). CONCLUSIONS: Advanced surface ablation may affect tearfilm, corneal sensation and ocular surface up to 3 months postoperatively. Early treatment of dry eye syndrome following advanced surface ablation should strongly be considered.

Clinical Outcomes of Advanced Surface Ablation with Smoothing in High Myopia

PURPOSE: To investigate the results of Advanced Surface Ablation (ASA) coupled with "smoothing" to smooth the ablation surface after covering masking fluid. METHODS: ASA was performed in 61 eyes with ablation depth of more than 75 microm. The mean refractive error was -5.88 +/- 1.27 D and mean ablation depth was 102.93 +/- 12.06 microm. Smoothing was performed in all patients (mean depth 16.79 +/- 2.43 microm, mean diameter 8.77 +/- 0.16 mm). Customized Aspheric Transition zone (CATz) was used in the laser algorithm. RESULTS: The mean refractive error was -0.29 +/- 0.41 D at postoperative 6 months and 97% of patients had an UCVA of 1.0 or better at postoperative 6 months. There was no statistically significant difference in magnitude of high-order aberrations at postoperative 6 months. The magnitude of total spherical aberrations increase was 0.084 microm at postoperative 6 months (p<0.05, paired t-test). The cornea was maintained clear in the majority of eyes. CONCLUSIONS: Excellent results were obtained by ASA coupled with "smoothing" in high myopia patients with an ablation depth greater than 75 microm.

Clinical Outcomes of Advanced Surface Ablation with Smoothing / 고신대학교의과대학학술지

OBJECTIVES: To investigate the results of AdvancedSurface Ablation (ASA) coupled with "smoothing" to smoothen ablation surface after covering masking fluid. METHODS: ASA was performed in 48 eyes that had myopic refractive error. The case with ablation depth over 100 microm was assigned into subgroup. Mean refractive error was -5.71 +/- 1.25D and mean ablation depth was 101.74 +/- 11.15 microm. Smoothing was performed in all patients (mean time 15.59 +/- 1.34 seconds, mean diameter 8.60 +/- 0.21 mm). RESULTS: Mean refractive error was -0.16 +/- 0.42D, -0.30 +/- 0.40D at postoperative 3 and 6 months. 92% and 96% of patients had an uncorrected visual acuity (UCVA) of 1.0 or better at postoperative 3 and 6 months, respectively. There was no statistically significant difference in magnitude of high order aberrations at postoperative 6 months. Cornea was maintained clear in the majority. CONCLUSIONS: Excellent results were obtained by ASA coupled with "smoothing" in high myopia patients. And subgroup with ablation depth over 100 microm was also obtained satisfactory results.

Effects of Eye Registration on the Astigmatism Correction in the Surface Laser Ablation

PURPOSE: To compare the effect of astigmatism correction upon Mel 80 excimer laser surgery with or without an eye registration system. METHODS: This retrospective analysis investigates a group (eye registration group) of surface laser ablation surgeries for myopic astigmatism correction, with operation on 27 eyes from 15 patients with guidance of the eye registration system and 40 eyes from 29 patients without guidance from the eye registration system. The evaluation of astigmatism correction was performed by the Alpins method, measuring the amount and axis of astigmatism before and after the operations. RESULTS: The average of the correction index (the ratio of the surgically induced amount of astigmatism correction to the intended amount of astigmatism correction) for the eye registration group was calculated to be 0.94+/-0.30 and, for non-eye registration group, was 0.92+/-0.41, showing no statistical significant difference between the two groups (p=0.762). However, the comparison of the index of success (the ratio of the difference vector to the intended amount of astigmatism correction) favorably demonstrated the effectiveness of eye registration (0.23+/-0.34 for eye registration group, 0.47+/-0.54 for non-eye registration group, p=0.03). The absolute angle of error (AE), a measure of difference in angle between the ablated axis of astigmatism correction and the desired axis of astigmatism correction, was lower on average for the eye registration group than for the non-eye registration group (3.52+/-7.69 to 12.5+/-20.69 degrees, p=0.015). CONCLUSIONS: Eye registration-guided surface laser ablation is suggested to be beneficial for the reduction of errors in astigmatism correction.

Comparison of Short Term Clinical Results Between LASEK and Epi-LASIK

PURPOSE: To compare short-term clinical results of LASEK and epi-LASIK. METHODS: Fifteen subjects (30 eyes) underwent uncomplicated LASEK on one eye and uncomplicated epi-LASIK on the other eye by a single surgeon, and uncorrected visual acuity, refractive change, postoperative pain, and postoperative satisfaction were compared at postoperative week one, at one month, and at three months. RESULTS: Postoperative uncorrected visual acuities were 0.68+/-0.20, 0.96+/-0.22, and 1.05+/-0.17 for LASEK and 0.75+/-0.21, 0.92+/-0.14, and 1.01+/-0.21 for epi-LASIK at one week, one month, and three months, respectively. Epi-LASIK showed faster improvement in visual acuity at one week, while LASEK showed faster improvement afterward. However, no statistical significance was found. Spherical equivalet of LASEK was -0.66+/-1.28D and that of epi-LASIK was -0.61+/-0.92D at postoperative week one, implying faster refractive recovery for epi-LASIK, but after one month, LASEK was faster in refractive recovery and all these changes were not statistically significant. Durations of postoperative pain were 3.13+/-1.25 days for LASEK and 3.02+/-1.32 days for epi-LASIK. Pain scores (0~10 point scale), however, were also lower for LASEK by 0.33 point, 0.57 point, and 0.45 point for postoperative day 1, 2, and 3, respectively. No statistical significance was noted in either pain duration or pain score. When asked for overall satisfaction, six subjects preferred LASIK, four subjects preferred epi-LASIK, and five subjects showed no preference. CONCLUSIONS: Both LASEK and epi-LASIK are effective for surgical correction of myopia, and no significant difference in visual recovery, refractive change or degree of postoperative pain was noted in this study.

Accuracy of Surgeon-Selected Ablation Center in Active Eye-Tracker-Assisted Advanced Surface Ablation-Photorefractive Keratectomy (ASA-PRK)

PURPOSE: To evaluate the accuracy of the surgeon-selected ablation center in active eye-tracker-assisted ASA-PRK and to identify factors influencing the ablation center. METHODS: This retrospective study included 109 eyes of 62 patients who underwent active eye-tracker-assisted ASA-PRK (VISX STARTM S4 with ActiveTrakTM System). The location the surgeon-selected ablation center and its distance from the center of the entrance pupil were analyzed by corneal topography (EyeSys Corneal Analysis SystemTM with pupil finding software). The factors influencing centration were investigated. RESULTS: The mean decentration was 0.24+/-0.13 mm (range 0.04 to 0.83 mm). One-hundred and five eyes (96%) were within 0.5 mm of the pupillary center. Supero-nasal displacement of the ablation center occurred most frequently in 44 eyes (40%) after ASA-PRK. The decentration amount was not dependant on factors related to the patient, the surgeon, or the surgery. There was no significant correlation between the amount of decentration and the vertical scale bar of the ActiveTrakTM icon on the screen representing the distance from the pupil center determined by the tracking system, to the surgeon-selected ablation center. CONCLUSIONS: This method of tracking the ablation center, which was selected by the surgeon according to each patient's specific pupil decentration with the active eye tracking system, was highly accurate and effective in avoiding severe decentration in ASA-PRK.

Advanced Surface Ablation-Photorefractive Keratectomy (ASA-PRK): Safety and Clinical Outcome for the Correction of Mild to Moderate Myopia with a Thin Cornea

PURPOSE: To evaluate the safety, clinical outcome, and change in higher-order wavefront aberrations (HOAs) of Advanced Surface Ablation-Photorefractive Keratectomy (ASA-PRK) for the correction of mild to moderate myopia in cases with a thin cornea. METHODS: ASA-PRK was performed, using a rotary epithelial scrubber, post-laser chilled BSS(R) irrigation, and bandage contact lens, in 127 eyes of 70 patients who had a preoperative spherical equivalent within -7.0 D and who were followed-up for more than six months. The patients were divided into two groups, according to their central corneal thickness (CCT), by ultrasonic pachymetry (Group: CCT520 micrometer, 95 eyes, mean 552.3+/-24.8 micrometer). The clinical outcomes of Group I and II were compared. RESULTS: At six months, 100% of Group I (32/32 eyes) and 93.7% of Group II (89/95 eyes) had an UCVA of 1.0 or better (p>0.05). At six months, a spherical equivalent within 0.5 D of emmetropia was observed in 100% (32/32) of the eyes in Group I and in 94.7% (90/95) of the eyes in Group II (p>0.05). At the 12-month follow-up, all eyes showed good stability of the refractive errors, and none showed corneal haze of grade 1 or more, loss of two or more lines of BSCVA, or serious iatrogenic keratectasia. The magnitude of total HOAs, spherical ablation, and coma were significantly higher six and 12 months after surgery in both groups (p0.05). CONCLUSIONS: ASA-PRK performed on patients with mild to moderate myopia and a thin cornea (> or =490 micrometer) showed a high level of efficacy, predictability, stability, and safety. There was no statistically significant difference in surgically induced HOAs between Groups I and II. The authors suggest that ASA-PRK be used for the correction of mild to moderate myopia, especially in cases with a thin cornea. Further study will be needed to determine the safety of this procedure for thinner corneas in surface keratorefractive surgery.

Effects of Interleukin-6 on Corneal Epithelial Wound Closure after Excimer Laser Surface Ablation in Rabbits

To evaluate the effects of interleukin-6(IL-6) on epithelial migration in corneal epithelial wound healing process after excimer laser surface ablation, the morphologic changes as well as the healing rate of the defect area were observed on 30 rabbits(60 eyes). The animals were divided into three groups of twenty each: the control group and the two IL-6 treated groups(eye dropping with 0.1mg/L and 1.0mg/L of IL-6). On light microscopic examination, after 9 hours, centripetal migration of epithelial cells and covering of bare stroma with monolayered epithelial cells were more remarkable in the 1.0mg/L group than in the control group, reaching the peak at 18 hours. On transmission electron microscopic examination after 18 hour, the 1.0mg/L group showed the loss of hemidesmosome beneath the leading edge of sliding epithelial cell, other intracellular structures were well preserved. On scanning electron microscopic examination, epithelial migration started at 9 hour in all three groups and the epithelial migration was more rapid in the 1.0mg/L group than in the control group. Fifteen hours and afterwards, the healing rate was significantly accelerated in the 1.0mg/L group than in the control group. In view of the above findings, it was speculated that IL-6 could be used effectively in the early treatment of excimer laser keratectomy and other corneal epithelial injury.