Comparison of visual results in initial and re-treatment laser in situ keratomileusis procedures for myopia and astigmatism

Associations of Near Work, Time Outdoors, and Sleep Duration With Myopic Regression 5 Years After SMILE and FS-LASIK: A Cross-sectional Study

PURPOSE

To investigate the association of near work, time outdoors, and sleep duration with myopic regression 5 years after small incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK) .

METHODS

This cross-sectional study included patients who received SMILE or FS-LASIK at Beijing Tongren Hospital 5 years ago. The patients underwent ophthalmic examinations including visual acuity, intraocular pressure, subjective refraction, slit-lamp examination, keratometry, corneal topography, optical coherence tomography, and fundus examination from January 2020 to March 2023. Fluorescein break-up time was measured and the Ocular Surface Disease Index questionnaire was completed to exclude dry eye. A self-administered questionnaire was used to collect data on near work exposure, physical activities, and sleep duration.

RESULTS

A total of 323 eyes were included in the analysis, with a 5-year incidence rate of myopic regression after SMILE or FSLASIK of 16.1%. After adjusted for all confounders, total near work more than 8 hours/day revealed a significant association with myopic regression (odds ratio: 2.461; 95% CI: 1.143 to 5.298, P = .021), particularly in younger adults, women, and patients with high myopia and FS-LASIK treatment. The significant association between sleep duration 8 hours/day or more and myopic regression was restricted to women and patients with FS-LASIK (near significant). However, no significant associations were observed between continuous near work or time outdoors and myopic regression.

CONCLUSIONS

Excessive near work exposure was associated with greater myopic regression 5 years after SMILE or FS-LASIK. It is crucial to maintain good visual behavior and care for preventing regression after SMILE or FS-LASIK, especially for younger patients and eyes with high myopia. [J Refract Surg. 2024;40(1):e10-e19.].

Femtosecond LASIK for the correction of low and high myopic astigmatism

INTRODUCTION

Higher preoperative myopic astigmatism is associated with a higher probability of retreatment due to patient dissatisfaction as a result of residual cylindrical error. Nonetheless, retreatment is safe and the final clinical results are comparable to those of patients with lower preoperative astigmatism who were satisfied with the primary treatment. Our purpose is to compare the efficacy and safety of femtosecond LASIK (FS-LASIK) for the refractive correction of patients with low (< 1.5 Diopters (D) versus high (≥ 1.5 D) myopic astigmatism.

METHODS

Retrospective observational study of 841 eyes of 825 eligible patients treated with FSLASIK for the correction of simple or compound myopic astigmatism. Outcome measures included residual error, best corrected and uncorrected distance visual acuity (BCVA and UCVA), efficacy and safety 3 months after the primary procedure or the retreatment.

RESULTS

Of 841 eyes in total, 432 (51.37%) had < 1.5 D (Group 1) and 409 (48.63%) had ≥ 1.5 D (Group 2) preoperative myopic astigmatism. The efficacy index of primary treatment was 0.94 ± 0.18 in Group 1 and 0.89 ± 0.22 in Group 2 (P = 0.001). Of 138 eyes (16.41%) that were retreated due to dis-satisfaction related to residual refractive error, 28 belonged to Group 1 (6.5%) and 110 (26.9%) to Group 2 (P < 0.001). Following retreatment, small but statistically significant differences in the residual mean postoperative cylinder (-0.08 ± 0.24 vs -0.27 ± 0.46 D, P = 0.001) and UCVA (1.11 vs 0.96, P = 0.0001) were detected for Groups 1 and 2, respectively. However, there were no statistically significant differences in the safety and efficacy indices.

CONCLUSION

Following FS-LASIK, eyes with myopic astigmatism ≥ 1.5 D have approximately four times more chances of undergoing retreatment due to dis-satisfaction caused by residual refractive error compared to eyes with myopic astigmatism < 1.5 D. However, the clinical results after retreatment are highly satisfactory and comparable in both groups.

Transepithelial photorefractive keratectomy for myopia: effect of age and keratometric values

AIM

To investigate demographic and preoperative factors increasing the risk of ametropia following transepithelial photorefractive keratectomy (transPRK) in myopia and myopic astigmatism.

METHODS

This retrospective cohort study included myopic eyes (-0.50 to -8.75 D) with or without astigmatism (up to 3.50 D) enrolled at Dr. Yap Eye Hospital Yogyakarta. TransPRK was performed using Technolaz 217z100 excimer laser. Subjects were clustered into ametropia and emmetropia group based on uncorrected distance visual acuities (UDVA) 3mo post-operatively. Multiple preoperative and intraoperative parameters were analyzed using Logistic regression to obtain their effect on ametropia risk following transPRK.

RESULTS

A total of 140 eyes of 87 consecutive subjects were studied. Prevalence of ametropia following transPRK was 20 (14.29%) eyes. Subjects in ametropia group were significantly older than the emmetropia group (31.80±14.23 vs 18.88±2.41, respectively; P<0.001). Bivariate Logistic regression analysis showed that older age (OR=1.23), higher preoperative spherical equivalent (>-6 D; OR=12.78), steeper anterior keratometric readings (Kmax>45 D and mean K>44 D; OR=4.28 and 4.35, respectively) increased the risk of ametropia following transPRK. Adjusted multivariate Logistic regression analysis showed that age was the strongest predictor for the incidence of ametropia following transPRK. Complications of transPRK were overcorrection, suspected posterior keratoectasia and accommodation insuffiency.

CONCLUSION

Older age can be the strongest factor for increasing ametropia risk following transPRK. Cut-off points of Kmax and mean K at 45 and 44 D respectively are proposed as the predictors for ametropia following transPRK.

Is the axial length a risk factor for post-LASIK myopic regression?

PURPOSE

To assess the relationship between the axial length and post-LASIK regression in myopic patients.

METHODS

This is a retrospective case series study conducted at a private eye centre, Ismailia, Egypt. The clinical records of the patients, who experienced LASIK to correct myopia from January 2016 to January 2018, were analysed for myopic regression. The patients were operated on, examined, and followed-up 1 year by one surgeon (AAG).

RESULTS

This study included 1219 patients (2316 eyes) with myopia. Mean ± SD of pre-operative spherical equivalent (SE) was - 4.3 ± 2.1D, range (- 0.50 to - 10.0D). Mean ± SD age of the patients was 26.4 ± 6.8 years, range (21 to 50 years). Male to female ratio was 30.5 to 69.5%. The cumulative incidence rate of myopic regression according to the medical records of the patients was 25.12% (582 eyes out of total 2316 eyes) along the 2 years of this study (12.6% per year). Of the total patients, 14.94% had pre-operative high myopia, 35.84% had pre-operative moderate myopia, and 49.2% had pre-operative low myopia. Of the patients with myopic regression, 52.6% had pre-operative high myopia, 34% had pre-operative moderate myopia, and 13.4% had pre-operative low myopia. The mean ± SD of the axial length of the patients with myopic regression was 26.6 ± 0.44 mm, range (26.0 to 27.86 mm), while the mean ± SD of the axial length of other patients with stable refraction was 24.38 ± 0.73 mm, range (22.9 to 25.9 mm) (t test statistic = 69.3; P value < 0.001).

CONCLUSIONS

Pre-operative high axial length increases the risk of myopic regression after LASIK.

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.

Outcomes of retreatment after hyperopic laser in situ keratomileusis

PURPOSE

To evaluate the efficacy, predictability, and safety of laser in situ keratomileusis (LASIK) retreatment in eyes with hyperopia.

SETTING

Multicenter refractive surgery centers and University Hospital, Germany.

DESIGN

Retrospective case series.

METHODS

This multicenter study included hyperopic patients with a preoperative difference between cycloplegic and manifest refraction of 1.00 diopter (D) or less who had LASIK retreatment based on manifest refraction. The refractive outcome was analyzed according to standard graphs for reporting the efficacy, predictability, and safety of refractive surgery.

RESULTS

One hundred thirteen eyes of 113 consecutive hyperopic patients were enrolled. Efficacy (P < .001) and safety (P = .004) were statistically significantly improved by retreatment without being negatively influenced by preoperative manifest spherical equivalent (SE), manifest cylinder, or keratometry. In cases still showing a trend toward undercorrection, retreatment resulted in 88 eyes (78.0%) being within ±0.50 D of the attempted correction. The optical zone (OZ) diameter of the retreatment did not correlate with efficacy, predictability, or safety.

CONCLUSIONS

Retreatment after hyperopic LASIK resulted in high efficacy, predictability, and safety outcomes. The efficacy and safety of the retreatment were not affected by preoperative manifest SE, manifest cylinder, keratometry, or OZ diameter.

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 R = 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 surgeon's 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.

Clinical results of using a high-repetition-rate excimer laser with an optimized ablation profile for myopic correction in 10 235 eyes

PURPOSE

To evaluate the visual outcomes, safety, stability, efficacy, and predictability of laser in situ keratomileusis (LASIK) to correct myopia using a high-repetition-rate excimer laser with an optimized ablation profile.

SETTING

Private clinic, Tokyo, Japan.

DESIGN

Retrospective noncomparative study.

METHODS

In this study, patients had LASIK using the Schwind Amaris excimer laser for myopic correction.

RESULTS

The study comprised 10  235 eyes of 5191 patients. The patients' mean age was 33.9 years ± 7.84 (SD) (range 18 to 56 years). The mean preoperative manifest refraction spherical equivalent (MRSE) was -5.02 ± 2.17 diopters (D) (range -2.75 to -11.50 D). Three months postoperatively, 82.0% of patients achieved an uncorrected distance visual acuity of -0.18 logMAR or better and 96.9% achieved 0.00 logMAR or better. The MRSE was within ±0.50 D of the intended refractive target in 88.4% of eyes and within ±1.00 D in 98.8%. Despite using the profile designed to minimize postoperative aberrations, the postoperative corneal and ocular higher-order aberrations increased.

CONCLUSION

Laser in situ keratomileusis using a high-repetition-rate excimer laser was a safe and effective procedure, yielding predictable results for a wide range of myopic patients.

FINANCIAL DISCLOSURE

Mr. Magnago is an employee of Schwind Eye-Tech Solutions GmbH & Co. KG. No other author has a financial or proprietary interest in any material or method mentioned.

Effect of timolol on refractive outcomes in eyes with myopic regression after laser in situ keratomileusis: a prospective randomized clinical trial

PURPOSE

To compare the effects of timolol on refractive outcomes in eyes with myopic regression after laser in situ keratomileusis (LASIK) with a control-matched group.

DESIGN

Prospective, randomized, parallel-controlled, double-masked clinical trial. A computer-generated randomization list based on random block permutation (length 4 to 8) was used for treatment allocation.

METHODS

setting: Basir Eye Center, Tehran, Iran.

PATIENT POPULATION

Of 124 eyes with myopic regression after LASIK using Technolas 217-Z, 45 eyes in each group were analyzed.

INTERVENTION

Patients were randomly assigned into either Group 1, who received timolol 0.5% eye drops, or Group 2, who received artificial tears for 6 months.

MAIN OUTCOME MEASURE

Spherical equivalent (SE) at 6 months posttreatment.

RESULTS

In Group 1, SE improved from -1.48 ± 0.99 diopter (D) before treatment to -0.88 ± 0.91 D and -0.86 ± 0.93 D 6 months after treatment and 6 months after timolol discontinuation, respectively (P < .001). In Group 2, it was -1.57 ± 0.67 D, -1.83 ± 0.76 D, and -1.91 ± 0.70 D, respectively (P < .001). SE was significantly better in Group 1 6 months after treatment and 6 months after discontinuation of treatment (P < .001 for both comparisons). There was a 0.26 D decrease in SE improvement every 4 months after the surgery in the Group 1 (P < .001).

CONCLUSIONS

Timolol application is effective for the treatment of myopic regression after LASIK compared with control group. Its effects last for at least 6 months after its discontinuation.

Femtosecond LASIK retreatment using side cutting only

PURPOSE

To present visual and refractive outcomes in 11 eyes that underwent femtosecond LASIK and subsequent retreatment with flap lifting using only side cutting.

METHODS

Seven patients (11 eyes) with a mean age of 30.55±5.42 years (range: 24 to 39 years) underwent retreatment 18.18±5.41 months (range: 12 to 26 months) after primary LASIK treatment with side cutting only using a femtosecond laser for the correction of residual refractive error.

RESULTS

Mean follow-up after retreatment was 7.72±1.48 months (range: 6 to 10 months). No intra- or postoperative complications were found after LASIK retreatment. Uncorrected distance visual acuity (UDVA) improved in all patients. Mean UDVA improved from 0.54±0.12 (decimal scale) (range: 0.4 to 0.7) preoperatively to 0.99±0.03 (range: 0.9 to 1.0) after retreatment. No patient lost lines of corrected distance visual acuity.

CONCLUSIONS

Retreatment using a femtosecond laser to create only a side cut is an effective modality to treat residual refractive errors in postoperative LASIK patients.

Retreatment of residual refractive errors with flap lift laser in situ keratomileusis

PURPOSE

To investigate the outcomes of flap lift laser-assisted in situ keratomileusis (LASIK) for residual refractive errors.

METHODS

In this prospective study, 60 eyes of 48 patients (mean age 36 years; age range 23-53 years) underwent flap lift retreatment surgery following initial LASIK for the correction of residual refractive errors. All treatments were wavefront guided using the VISX S4 Star excimer laser. The main outcome measures were predictability, safety, efficacy, and stability.

RESULTS

Following retreatment, epithelial ingrowth occurred in 23.3% (n=14) of eyes, which required a flap lift and scrape procedure in 4 eyes and a second flap lift and scrape procedure in 2 eyes. De novo dry eye occurred in 8.3% (n=5) of eyes. At 6 months, the mean (±SD) post-retreatment Snellen decimal uncorrected visual acuity (UCVA), sphere, cylinder, spherical equivalent (SE), defocus equivalent (DE), and best corrected visual acuity (BCVA) was 1.03±0.23, 0.08±0.34 diopters (D) (range -0.75 to +1.25 D), -0.53±0.37 D (range 0 to -1.75 D), -0.04±0.34 D (range -1.11 to +1.04 D), 0.29±0.41 D (range 0 to 1.94 D), and 1.13±0.15 (range 0.5 to 1.5), respectively. Seventy-three percent (n=44) of eyes had an UCVA equal to or greater than 1 (6/6), 88.3% (n=53) and 98.3% (n=59) of eyes were within ±0.50 D and ±1.00 D of SE, respectively, and 3.3% (n=2) of eyes lost 1 line of BCVA.

CONCLUSIONS

A high incidence (23.3%, n=14) of epithelial ingrowth occurred following retreatment surgery and de novo dry eye occurred in 8.3% (n=5) of eyes. Despite this, reasonable visual and refractive outcomes were achieved at 6 months post-retreatment.

Effectiveness of laser-assisted subepithelial keratectomy to treat residual refractive errors after laser in situ keratomileusis

PURPOSE

To evaluate the effectiveness of laser-assisted subepithelial keratectomy (LASEK) to treat residual refractive errors after laser in situ keratomileusis (LASIK).

SETTINGS

Isik Eye Clinic, Ankara, Turkey.

METHODS

This retrospective study included 24 eyes of 15 patients who had retreatment by LASEK for residual refractive errors after myopic LASIK. All patients had examinations that included slitlamp biomicroscopy, subjective and cycloplegic refractions, uncorrected visual acuity (UCVA), best corrected visual acuity, corneal topography, and pachymetry preoperatively and postoperatively. Postoperative examinations were performed at 1 week and 1, 3, and 6 months.

RESULTS

The patient cohort comprised 9 men and 6 women. The median spherical equivalent (SE) of attempted correction for retreatment with LASEK was -1.25 diopters (D). The median follow-up after LASEK was 11.5 months (range 6 to 16 months). At the end of the follow-up, the median SE of the refractive error was -0.38 D. The median UCVA increased from 20/45 before LASEK to 20/25 at the last follow-up visit, which was statistically significant (P<.001). After LASEK, significant postoperative haze developed in 5 eyes. In all 5 eyes, the estimated ablation depth was more than 40 mum and the SE of attempted correction was -2.00 D or greater.

CONCLUSIONS

Laser-assisted subepithelial keratectomy retreatment in eyes with myopic regression after LASIK resulted in a significant improvement in UCVA that was comparable to the improvement after flap lifting. An SE of attempted correction greater than -2.00 D was associated with a significant rate of haze.

Analysis of the visual and refractive outcome following laser in situ keratomileusis (LASIK) retreatment over a four-year follow-up period

PURPOSE

To evaluate the safety and refractive stability following LASIK retreatment over a four-year follow-up period.

METHODS

In this retrospective study, 60 eyes of 52 patients underwent LASIK retreatment for residual refractive errors after LASIK. Retreatment was performed by lifting the original flap followed by laser ablation of the stromal bed. The main outcome measures at the latest follow-up visit were efficacy, predictability, safety and stability. The mean follow-up time after retreatment was 22.3 +/- 10.5 (range 12-48 months).

RESULTS

The baseline mean spherical equivalent (SE) was -4.85 +/- 2.57 dioptres (D) (range +2.25 to -11.75 D). At the latest follow-up visit, the uncorrected visual acuity (UCVA) was 6/9 or better in 88% of the eyes, the mean SE was -0.33 +/- 0.8 D (-2.50 to +2.25 D), and 77% of the eyes were within +/-0.50 D of target refraction. None of the patients lost lines of best corrected visual acuity (BCVA) and 25 eyes (41%) gained one or more lines. Three eyes (5%) developed peripheral epithelial in-growth and none of the patients had corneal ectasias or retinal complications.

CONCLUSION

LASIK retreatment is a safe and effective procedure for correcting residual refractive errors after LASIK. After retreatment, the visual and refractive outcome remained stable during the four-year follow-up period of the study.

Customized LASIK Treatment for Myopia: Relationship Between Preoperative Higher Order Aberrations and Refractive Outcome

PURPOSE

To analyze the effect of preoperative higher order aberrations on postoperative sphere and cylinder outcome.

METHODS

Three hundred thirty myopic eyes (mean: -3.32 +/- 1.54 diopters [D], range: -1.0 to -7.0 D) treated with customized ablation using the Technolas 217z laser (Bausch & Lomb) were followed through 6 months after LASIK. Pre- and postoperative visual acuity, higher order root mean square (RMS), third order RMS, and spherical aberration were compared to study the safety and efficacy of the treatment. The relationship between preoperative higher order aberrations and manifest refraction after LASIK was analyzed.

RESULTS

Following LASIK, 91.5% of eyes obtained an uncorrected visual acuity of > or = 20/20 and 70.3% of eyes obtained 20/16 without retreatment; 99% had a best spectacle-corrected visual acuity of > or = 20/20 (75.9% of eyes were within +/- 0.50 D). Mean value of significant increase in postoperative higher order aberrations was 0.12 +/- 0.18 microm (P<.0001). Increased spherical aberration was associated with increased myopia treatment (P<.0001). Greater positive spherical aberration after LASIK was significantly correlated to postoperative hyperopia (overcorrection). Change in third order RMS was significantly correlated to change in spherical equivalent refraction among eyes with postoperative astigmatism (P<.0001).

CONCLUSIONS

With the Bausch & Lomb Technolas 217z Zyoptix software, treatment of higher order aberrations, especially third order (coma and trefoil) and spherical aberration, significantly improved postoperative refractive status.

Posterior Corneal Curvature Changes after Undersurface Ablation of the Flap and In-the-Bed LASIK Retreatment

OBJECTIVE

To analyze LASIK retreatment-induced changes in the posterior corneal curvature (PCC) with undersurface ablation of the flap (UAF) and in-the-bed techniques.

DESIGN

Nonrandomized, comparative, interventional study.

PARTICIPANTS

Forty-six eyes with a residual spherical equivalent refraction between -0.37 and -2.75 diopters (D) and astigmatism between 0.0 and -1.25 D were included prospectively. In 23 eyes, the calculated postenhancement flap thickness exceeded 150 microm using micropachymetric optical coherence tomography, whereas with further ablation of the bed, the residual bed thickness (RBT) would have been <250 microm, or <55% of the pre-LASIK central pachymetry. In another 23 eyes, RBT allowed the planned ablation for a calculated post-retreatment RBT exceeding 250 microm, >55% of the pre-LASIK central pachymetry.

INTERVENTION

Eyes with insufficient RBT for further ablation underwent UAF retreatment, whereas those with adequate RBT received conventional in-the-bed LASIK retreatment. Examinations were performed before retreatment and 3 and 6 months postoperatively. No eye was lost to follow-up.

MAIN OUTCOME MEASURES

Micropachymetry, Orbscan II scanning-slit PCC data, and visual acuity (VA).

RESULTS

The groups did not differ in age, intraocular pressure, or retreatment ablation depth, but the UAF eyes had a lower mean pre-retreatment RBT (270.7+/-25.4 microm) than conventional enhancement eyes (353.0+/-41.5 microm) (P = 0.001). Eyes undergoing UAF had no significant change in PCC, whereas eyes undergoing conventional retreatment had an increase in the posterior corneal power within the central 3-mm zone (P = 0.008) 3 months after retreatment. No significant changes occurred thereafter. The amount of change in posterior corneal power within the 3-mm central zone from before to after retreatment differed significantly between the groups (mean difference, 0.135 D; 95% confidence interval, 0.022-0.248 D; P = 0.02). No keratectasia developed clinically, and no retreated eye lost or gained > or =2 lines of best-corrected VA. Six months after retreatment, the efficacy and safety indices for the UAF procedure were 0.96 and 1.01, respectively, and 1 and 1.06 for conventional LASIK enhancement.

CONCLUSION

Undersurface ablation of the flap retreatment appears to have less potential for changing the posterior corneal surface than conventional LASIK enhancement and can help reduce the likelihood of retreatment-induced keratectasia.

Role of flap thickness in laser in situ keratomileusis enhancement for refractive undercorrection

PURPOSE

To determine which preoperative and/or perioperative factors determine the need for an enhancement for refractive undercorrection in laser in situ keratomileusis (LASIK) for spherical or spherocylindrical myopia.

SETTING

Clinical refractive surgery outpatient facility.

METHODS

In this nested case-control study within a retrospective cohort, 3850 of the 9777 eyes operated on between January 1996 and August 2005 who met the selection criteria were studied. Only patients whose refractive goal was plano were included. Control eyes were those whose latest spherical equivalent (SE) refraction was within +/-0.37 diopters (D) of emmetropia. Cases were defined as enhancements for undercorrection with an SE refraction worse than or equal to -0.50 D performed less than 6 months following the primary surgery.

RESULTS

Factors associated with enhancement included increasing patient age (odds ratio [OR] = 1.048, P<.001), decreasing follow-up time (OR = 0.994, P<.001), increasing minus laser sphere (OR = 0.700, P<.001) and cylinder settings (OR = 0.718, P<.001), female sex (OR = 1.112, P = .046), and corneal toricity (OR = 1.237, P = .012). The Summit laser had a significant risk for enhancement (OR = 1.726, P<.001) compared with the Visx laser, whereas the Wavelight Allegretto had a lowered risk (OR = 0.630, P = .049). Enhancement risk with the Autonomous was no different from that with the Visx (OR = 1.120, P = .342). Increasing flap thickness (OR = 1.009, P<.001) was more strongly associated with enhancement risk than residual stromal bed thickness.

CONCLUSIONS

After controlling for patient age, time to follow-up or surgery, corneal cylinder, sphere and cylinder laser settings, laser manufacturer, patient sex, and corneal thickness, increasing flap thickness was found to be a more important predictor of enhancement for refractive undercorrection than residual stromal thickness.

Lipid tear deficiency in persistent dry eye after laser in situ keratomileusis and treatment results of new eye-warming device

PURPOSE

To determine whether lipid tear deficiency is a significant pathogenic factor in persistent dry eyes after laser in situ keratomileusis (LASIK).

SETTING

Ocular Surface Center, Miami, Florida, USA.

METHODS

Thirty-four eyes of 17 patients (mean 46.35 years +/- 11 [SD]) complaining of persistent dryness more than 12 months after LASIK were prospectively studied by symptom scoring and kinetic analysis of tear interference image, tear breakup time, and fluorescein clearance test. Once patients had been clear of inflammation and treated for aqueous tear deficiency, lipid tear deficiency was further confirmed and treated with Eyefeel (Kao, Inc.), an eye-warming device, 4 times daily for 4 weeks.

RESULTS

Sixteen patients were asymptomatic before LASIK but dryness persisted for 41 +/- 19.3 months. Delayed tear clearance was observed in 15 patients (88.2%) and floppy lids in 12 patients (70.5%). Aqueous tear deficiency was reconfirmed in 16 eyes (53.3%). After Eyefeel treatment, there was a subjective improvement of ocular surface diseases index from 60.6 +/- 10.6 to 25.8 +/- 18.5 (P = .0007). Tear breakup time was improved from 2.4 +/- 3.9 seconds to 7.9 +/- 3.6 seconds (P = .004). There was a tear interference pattern change from a vertical lipid tear deficiency to a horizontal normal in 7 eyes. There was a mean lipid spread time improvement from 1.3 +/- 0.4 sec to 0.8 +/- 0.4 sec (P = .001), and there was a mean lipid thickness improvement from 63.5 +/- 23 nm to 79.5 +/- 27 nm (P = .04).

CONCLUSION

Persistent nature of dry eye after LASIK is attributed to in part to delayed tear clearance, undercorrected aqueous tear deficiency, and nonrecognized lipid tear deficiency.

Results of resident-performed laser in situ keratomileusis

PURPOSE

To analyze the results of resident-performed laser in situ keratomileusis (LASIK).

SETTING

Rush University Medical Center, Department of Ophthalmology, Chicago, Illinois, USA.

METHODS

This retrospective study comprised 44 consecutive eyes of 22 patients who had LASIK performed from August 2000 through February 2002. Based on preoperative spherical equivalent, the eyes were divided into a low myopia group (A) (-1.0 to -6.0 diopter [D]) and a higher myopia group (B) (> -6.01 D). Preoperative and postoperative spherical equivalent (SE), best corrected visual acuity (BCVA), and uncorrected visual acuity (UCVA) were measured and analyzed within each group. Patients had at least 2 follow-up visits, with the second visit occurring between 1 and 9 months postoperatively.

RESULTS

Preoperatively, the mean SE in Group A was -3.93 D +/- 1.53 (SD) and in Group B, -8.49 +/- 1.70 D. At the final visit, the SE in Group A decreased to -0.29 +/- 0.55 D and in Group B, -1.09 +/- 0.87 D. The UCVA in Group A at the final visit was 20/20 or better in 43% of eyes and 20/40 or better in 100% of eyes. In Group B, the UCVA was 20/20 or better in 31% of eyes and 20/40 or better in 75% of eyes. In all eyes, the BCVA improved by 1 line in 16% or remained the same in 84%. No eyes lost any lines of BCVA. The SE taken at the last visit was within +/-0.5 D in 69% of all eyes and within +/-1.0 D in 82% of all eyes. The incidence of patients needing retreatment in resident-performed LASIK surgery was 3 of 44 (6.8%).

CONCLUSIONS

Laser in situ keratomileusis performed by residents is a safe and effective procedure for correction of refractive error. Postoperative UCVA, refractive error, retreatment rate, and loss of BCVA were consistent with published results from nonresident surgeons. These results also exceeded the U.S. Food and Drug Administration requirements for LASIK surgery.

Results of late flap removal after complicated laser in situ keratomileusis

PURPOSE

To evaluate the effect of flap removal on complications after laser in situ keratomileusis (LASIK).

SETTING

Three university-based referral centers and 1 private practice.

METHODS

This retrospective interventional case series comprised 6 eyes of 6 patients at 4 centers. Flap removal occurred 2 to 41 weeks after the LASIK procedure. The corneal flaps were excised by 2 methods: In 2 eyes, the flap was lifted and excised manually. In 4 eyes, the thin flap was removed by excimer ablation using phototherapeutic keratectomy and/or photorefractive keratectomy. Postoperative measurements included uncorrected visual acuity, best spectacle-corrected visual acuity (BSCVA), manifest refraction, slitlamp evaluation, and computerized videokeratography. All patients had an 8-month or longer convalescence to assess visual recovery.

RESULTS

After the initial flap complication, the BSCVA decreased in all 6 eyes (mean loss 3.0 lines +/- 1.5 [SD]). After flap removal, it improved in all eyes (mean gain 2.2 +/- 1.2 lines). All patients reported a reduction in or elimination of visual symptoms. Despite the improvements, a minor loss of BSCVA (mean -0.8 lines [range 0 to 2 lines]) remained in 4 patients.

CONCLUSION

In carefully selected patients, flap removal is a viable surgical option to improve visual function.

Flap and stromal bed thickness in laser in situ keratomileusis enhancement

PURPOSE

To evaluate whether flap thickness changes after the primary laser in situ keratomileusis (LASIK) procedure and to assess the accuracy of intraoperative pachymetry and ablation depth measurements in predicting stromal bed thickness before enhancement in eyes that have had primary myopic LASIK.

SETTING

Bascom Palmer Eye Institute, Miami, Florida, USA.

METHODS

This retrospective noncomparative interventional case series comprised 57 eyes of 42 patients who had LASIK enhancement between June 2001 and September 2002. Exclusion criteria included previous ocular surgery or complications during the first LASIK procedure. Only patients who had had LASIK and enhancement by the same surgeon at our institution and had intraoperative pachymetry readings for both procedures were included. The original flap was relifted in all enhancement procedures. Corneal thickness was routinely measured intraoperatively by ultrasound pachymetry. The age, eye, refraction, date of primary LASIK, central corneal thickness (CCT) and central stromal bed thickness at primary LASIK, depth of ablation, flap thickness (subtraction pachymetry), date of enhancement, CCT and central stromal bed thickness at enhancement, and flap thickness at enhancement were recorded.

RESULTS

Thirty-one eyes of 26 patients were myopic and 26 eyes of 16 patients were hyperopic before primary LASIK. The mean time between LASIK and enhancement was 218 days +/- 115 (SD) (193 +/- 88 days in myopic eyes and 248 +/- 136 days in hyperopic eyes [P = .068]). The flap tended to be thicker at enhancement than in the primary LASIK procedure by 9.3 +/- 25.7 microm in myopic eyes (P = .054) and 10.5 +/- 16.6 microm in hyperopic eyes (P = .004). A strong correlation was found between flap thickness in the first and second procedures in myopic and hyperopic eyes (r = 0.6). In myopic eyes, the mean difference between the estimated stromal bed thickness after the first procedure (central bed thickness- ablation depth) and the stromal bed thickness measured directly at enhancement was not statistically significant (3 +/- 29 microm; P = .54, paired t test). A strong correlation was found between the 2 measurements (r = 0.8, P<.001). Another strong correlation was found in myopic eyes between the estimated corneal thickness after the primary LASIK and the corneal thickness measured at enhancement (r = 0.81, P<.001). No correlation was found between the difference in flap thickness and the time to enhancement (r = 0.09 in myopic eyes and r = 0.01 in hyperopic eyes).

CONCLUSIONS

Flap thickness tended to be thicker at enhancement than at primary LASIK. Intraoperative pachymetry and ablation depth measurements proved to be precise tools to predict stromal bed thickness before enhancement in eyes that had had primary myopic LASIK. This information may help in planning LASIK enhancements.

Flap lift for LASIK retreatment in eyes with myopia

PURPOSE

To analyze the results achieved with LASIK retreatment after lifting the original flap in a large series of patients.

DESIGN

Retrospective, noncomparative, interventional consecutive case series.

PARTICIPANTS

Two thousand four hundred twenty-two consecutive eyes undergoing LASIK surgery for myopia, including 334 eyes submitted to flap lift for LASIK retreatment.

MAIN OUTCOME MEASURES

Uncorrected visual acuity, best-corrected visual acuity, refractive error, and complications.

RESULTS

LASIK retreatment was performed in 334 eyes (14%), and the mean time between initial procedure and retreatment was 8.2+/-6.2 months. The mean spherical equivalent (SE) improved from -1.2+/-0.6 diopters (D) (range, -4.2 to +1.2 D) before retreatment to +0.2+/-0.4 D (range, -3.1 to +1.1 D) after the retreatment. The uncorrected visual acuity (UCVA) after retreatment was 20/20 or better in 58% and 20/40 or better in 92% of eyes. The mean SE was within +/-1.0 D in 96% of the patients and within +/-0.5 D in 80.5% after retreatment. Eighteen eyes (5%) lost 1 line of best-corrected visual acuity, and 4 eyes (1%) lost 2 lines.

CONCLUSIONS

LASIK retreatment surgery performed by relifting the flap was a useful procedure for correcting residual refractive errors after the primary LASIK procedure. It provided good uncorrected visual acuity, predictable results, good refractive stability, and few complications.

Predictive formula for calculating the probability of LASIK enhancement

PURPOSE

To develop a formula to predict a patient's need for laser in situ keratomileusis (LASIK) enhancement.

SETTING

Northwestern Laser Vision Center, Department of Ophthalmology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA.

METHODS

In this retrospective study, charts of patients who received LASIK with the Visx Star excimer laser for myopia and myopic astigmatism were reviewed. Laser in situ keratomileusis enhancement was performed in 130 of 720 eyes. Variables such as age, keratometry, spherical power, power and axis of astigmatism, and surgeon factor were compared in patients who required retreatment and those who did not. Multivariate logistic regression analysis was used to determine a formula for the probability of enhancement surgery.

RESULTS

Age (P<.0001), preoperative cycloplegic sphere (P<.0001), and surgeon (P<.0001) were the statistically significant factors for predicting retreatment. The predictive formula derived from these factors had a sensitivity of 79%, a specificity of 61%, and positive and negative predictive values of 31% and 93%, respectively.

CONCLUSIONS

Older age, higher preoperative cycloplegic sphere, and surgeon significantly influenced a patient's likelihood for LASIK retreatment. A formula based on these predisposing factors helps to more accurately predict the need for retreatment.

Incidence and associations of retreatment after LASIK

PURPOSE

To determine the incidence and risk factors for laser in situ keratomileusis (LASIK) retreatment and to present a novel retreatment technique.

DESIGN

Retrospective noncomparative consecutive case series.

PARTICIPANTS

Two thousand four hundred eighty-five eyes (1306 patients) underwent LASIK surgery for myopia, hyperopia, or astigmatism using either the Summit Apex Plus or the Alcon LADARVision excimer laser systems. Only retreatments for residual refractive error were included.

MAIN OUTCOME MEASURES

Prevalence and incidence of retreatments were determined. Potential risk factors for retreatment, including age, gender, and attempted correction, were assessed. Refractive error and a ratio of residual sphere to cylinder in retreated eyes were also analyzed.

RESULTS

Of the total cohort studied, 288 eyes of 233 patients underwent one retreatment, and 3 eyes of 3 patients required two retreatment procedures. The overall 1-year incidence of retreatment was 10.5%. The average length of time between initial treatment and enhancement was 7.3 +/- 6.4 months; 85% of retreatments took place within 1 year. Two hundred eighty-five of the 288 retreatments were accomplished using a manual flap lift approach; 3 eyes required a repeat microkeratome cut. Higher initial corrections and residual astigmatism were associated with a significantly higher rate of retreatment. Patients older than 40 years were at greater risk for retreatment. There was no gender difference.

CONCLUSIONS

Higher initial corrections, astigmatism, and older age are risk factors for LASIK retreatment. Most LASIK flaps can be lifted using the manual technique described up to 3 years after initial surgery.

Outcomes After Laser in situ Keratomileusis Retreatment in High Myopes

PURPOSE

To evaluate the refractive and visual performance after laser in situ keratomileusis (LASIK) retreatment.

METHODS

A retrospective study was performed on 33 eyes of 23 patients who underwent LASIK (Bausch & Lomb Technolas 217C) retreatment for residual myopia with or without astigmatism. Parameters evaluated were uncorrected and best spectacle-corrected visual acuity, spherical equivalent refraction, contrast sensitivity, glare acuity, and pachymetry, preoperatively and at 1, 3, and 6 months postoperatively.

RESULTS

The mean spherical equivalent refraction before primary LASIK was -9.89 +/- 4.00 D and before retreatment was -2.85 +/- 2.17 D. Although contrast sensitivity and glare acuity decreased significantly after primary LASIK (P<.05), no significant change in these parameters was observed after retreatment. Smaller ablation zones were associated with decreased contrast sensitivity and glare acuity after primary LASIK as well as following retreatment. Contrast sensitivity and glare acuity following primary LASIK were significantly better in eyes with ablation zones > or = 5 mm than those with < 5 mm (P<.05). Eyes in which the ablation zone was the same as that for primary LASIK had significantly better contrast sensitivity than those with different ablation zones (increased or decreased) during retreatment. Attempted refractive correction during primary LASIK and retreatment had a significant negative correlation with contrast sensitivity and glare acuity following primary LASIK as well as retreatment.

CONCLUSION

The ablation zones following primary LASIK and retreatment should be > or = 5.00 mm and remain unchanged to improve visual performance.

Lasik enhancements: a comparison of lifting to recutting the flap

PURPOSE

To compare the visual outcomes and incidence of complications of lifting with recutting the lamellar flap in laser in situ keratomileusis (LASIK) enhancement surgery.

DESIGN

Retrospective case-control study.

PARTICIPANTS

Two hundred twelve consecutive eyes undergoing a LASIK enhancement procedure at a single surgery location during a 5-year period.

METHODS

Charts of participants were obtained and outcome measures obtained.

MAIN OUTCOME MEASURES

Uncorrected visual acuity, best-corrected visual acuity, refractive error, complications.

RESULTS

Relifting of flaps was performed in 164 of 212 eyes (77.4%), and recutting of flaps was performed in 48 of 212 eyes (22.6%). There were no significant differences in early visual outcomes between the two groups. At 1 year patients had significantly better uncorrected vision if the flap was lifted rather than recut (20/24.7 vs. 20/31.3, P < 0.008). In addition, the flap lift group had a significantly more stable refraction at 1 year than did the recut group (change in spherical equivalent: +0.05 diopters (D) vs. -0.57 D). The incidence of complications did not significantly differ between the two groups.

CONCLUSIONS

LASIK enhancement surgery can be performed safely and effectively by either lifting or recutting a flap. Lifting the flap may show better long-term stability of refractive error and uncorrected acuity.

Undersurface ablation of the flap for laser in situ keratomileusis retreatment

OBJECTIVE

To develop a novel technique, undersurface ablation of the flap (UAF), for laser in situ keratomileusis (LASIK) retreatment in eyes with insufficient posterior stroma.

DESIGN

Noncomparative, interventional case series.

PARTICIPANTS

From 30 eyes examined, 25 eyes with a spherical equivalent residual refraction between -0.75 and -3.25 diopters (D) and astigmatism between 0.0 and -1.5 D were prospectively included in the study. In these eyes, calculated postenhancement flap thickness was >150 micro m using micropachymetric optical coherence tomography (OCT), whereas with further ablation of the bed, posterior stromal thickness would have been <250 micro m. Primary LASIK procedures had been performed with the Hansatome microkeratome.

INTERVENTION

The flap was lifted and the eye deviated downward, so that the corneal visual axis mark aligned with the laser beam. Mirror pattern ablations with an optical zone of 5 mm were performed on the flap stroma using either the Summit Apex Plus excimer laser or the Technolas Keracor 217 spot-scanning excimer laser. New axis orientation for toric ablations was calculated with the formula: beta = 180 degrees - alpha.

MAIN OUTCOME MEASURES

Refraction, visual acuity, OCT pachymetry, tangential videokeratography, and patient satisfaction.

RESULTS

The average follow-up was 6.36 +/- 2.64 months (range, 3-12 months). Mean preenhancement spherical equivalent (-2.05 +/- 0.75 D) was reduced to -0.19 +/- 0.38 D at the last visit (P = 0.001). Mean cylinder decreased from -0.48 +/- 0.53 D before retreatment to -0.23 +/- 0.28 D at the last follow-up (P = 0.003). Best-corrected visual acuity worsened by 1 line in two eyes (8%), and no eye lost 2 or more lines. Satisfactory globe stabilization and stromal smoothness during ablation were more difficult to achieve than with conventional LASIK enhancements. The average central flap thickness before UAF, 187 +/- 13 micro m, decreased to 164 +/- 12 micro m after 1 month (P = 0.001). No keratectasia developed. Finally, 92% of cases were satisfied with surgery compared with 48% before UAF retreatment (P = 0.001).

CONCLUSIONS

UAF retreatment for low residual refractive errors after LASIK in eyes with sufficient flap stroma seems to be effective and may prevent future keratectasia.

Removal of INTACS for myopia

OBJECTIVE

To evaluate the safety and efficacy of the removal of INTACS.

DESIGN

Subgroup analysis from a nonrandomized comparative interventional trial.

PARTICIPANTS

Four hundred fifty-two patients with best spectacle-corrected visual acuity of 20/20 or better and myopia (1.0-3.5 diopters [D]) were enrolled in the U.S. Food and Drug Administration clinical trials of INTACS. Forty-six eyes among a total of 684 underwent INTACS removal.

INTERVENTION

INTACS removal.

METHODS

Safety and efficacy of INTACS removal was assessed by comparison of results from preoperative and 3-month postremoval visits. Safety was assessed by maintenance of preoperative best spectacle-corrected acuity and induction of astigmatism (measured by manifest refraction). Efficacy was assessed by comparison of mean spherical equivalent measured by both manifest and cycloplegic refraction, as well as percentage of eyes within +/- 0.5 D and +/- 1.0 D of baseline values. A subset of 27 patients completed a prospective questionnaire assessing the frequency of six visual symptoms (glare, halos, double vision, photophobia, night vision difficulties, and fluctuating vision).

MAIN OUTCOMES MEASURES

Best spectacle-corrected visual acuity, manifest refraction, and cycloplegic refraction.

RESULTS

Forty-one of 46 patients' eyes that had undergone INTACS removal had reached the 3-month postremoval visit. Of these eyes, 73% (30 of 41) had returned to within +/- 0.5 D and 97% (40 of 41) to within +/- 1.0 D of baseline spherical equivalent as measured by manifest refraction. With respect to astigmatism, 88% (36 of 41) had returned to within +/- 0.5 D and 100% (41 of 41) to within +/- 1.0 D of preoperative value. No patient had a loss of best spectacle-corrected acuity of more than 2 lines, with equal numbers of eyes having a loss or gain of 1 line (nine eyes) and 2 lines (one eye). For most eyes, INTACS removal was associated with a substantial reduction in the six types of visual symptoms; however, in some eyes (up to 15%) symptoms that had not been detected preoperatively were noted after INTACS removal.

CONCLUSIONS

INTACS removal was not associated with a loss (> 2 lines) of best spectacle-corrected visual acuity or induction (> 1 D) of astigmatism or myopia. INTACS removal was associated with a reversal to preoperative values in most cases.