Incidence and associations of retreatment after LASIK

Myopic Regression after FS-LASIK and SMILE

PURPOSE

To compare the degree of myopic regression after myopia correction with either femtosecond laser-assisted in situ keratomileusis (FS-LASIK) or small-incision lenticule extraction (SMILE) over 18 months.

METHODS

Patients undergoing FS-LASIK or SMILE surgery for myopia correction were retrospectively recruited. The propensity scores were used to match patients by age and preoperative manifest spherical equivalent (SEQ) from these 2 groups. Myopic regression was analyzed using the Cox proportional hazard model.

RESULTS

A total of 416 eyes of 416 patients undergoing FS-LASIK and 416 eyes of 416 patients undergoing SMILE were matched. Using 1-month SEQ as baseline, the SEQ regression values after FS-LASIK were 0D, -0.17 ± 0.69D, -0.24 ± 0.65D, -0.31 ± 0.65D, -0.32 ± 0.63D, and -0.33 ± 0.62D and the SEQ regression values after SMILE were 0D, -0.07 ± 0.75D, -0.18 ± 0.77D, -0.23 ± 0.82 D, -0.21 ± 0.77D, and -0.24 ± 0.68D at 1, 3, 6, 9, 12, and 18 months, respectively. The Cox proportional hazard model showed that preoperative manifest SEQ (P = 0.021) and designed optical zone (P = 0.048) are significant predictors. The selected surgical procedure had no significant effect on predicting myopic regression (P = 0.470). The cumulative survival rates of myopic regression were 54.74% and 42.10% in the FS-LASIK group and 58.66% and 43.83% in the SMILE group, at 12 and 18 months, respectively (log-rank test, P = 0.11).

CONCLUSIONS

After matching based on age and preoperative manifest SEQ, we found that higher myopia and a smaller optical zone contribute significantly to the development of myopic regression after undergoing FS-LASIK or SMILE surgery at 18 months. The selected surgical procedure, however, does not affect the likelihood of myopic regression.

Visual outcomes of early enhancement following small incision lenticule extraction versus laser in situ keratomileusis

Purpose

To compare visual outcomes of early enhancement following small incision lenticule extraction (SMILE) versus laser in situ keratomileusis (LASIK).

Methods

Retrospective analysis of eyes (patients operated in the setting of a tertiary eye care hospital between 2014 and 2020) requiring early enhancement (within one year of primary surgery) was conducted. Stability of refractive error, corneal tomography, and anterior segment Optical Coherence Tomography (AS-OCT) for epithelial thickness was performed. The correction post regression was done using photorefractive keratectomy and flap lift in eyes, wherein the primary procedure was SMILE and LASIK, respectively. Pre- and post enhancement corrected and uncorrected distance visual acuity (CDVA and UDVA), mean refractive spherical equivalent (MRSE), and cylinder were analyzed. IBM SPSS statistical software.

Results

In total, 6350 and 8176 eyes post SMILE and LASIK, respectively, were analyzed. Of these, 32 eyes of 26 patients (0.5%) post SMILE and 36 eyes of 32 patients (0.44%) post-LASIK required enhancement. Post enhancement (flap lift in LASIK, and PRK in SMILE group) UDVA was logMAR 0.02 ± 0.05 and 0.09 ± 0.16 (P = 0.009), respectively. There was no significant difference between the refractive sphere (P = 0.33) and MRSE (P = 0.09). In total, 62.5% of the eyes in the SMILE group and 80.5% in the LASIK group had a UDVA of 20/20 or better (P = 0.04).

Conclusion

PRK post SMILE demonstrated comparable results to flap lift post LASIK and is a safe and effective approach for early enhancement post SMILE.

Laser-Assisted In Situ Keratomileusis (LASIK) Enhancement for Residual Refractive Error after Primary LASIK

Background: To evaluate the safety, efficacy, and predictability of laser-assisted in situ keratomileusis (LASIK) enhancement after primary LASIK and compare to Food and Drug Administration (FDA) criteria. Methods: Patients who underwent LASIK enhancement after primary LASIK between 2002 and 2019 were compared to those who underwent LASIK without retreatment. Patient demographics, preoperative characteristics, visual outcomes, and postoperative complications were compared between groups. Epithelial ingrowth (EI) development was stratified based on duration between primary and secondary procedures. Results: We compared 901 eyes with LASIK enhancement to 1127 eyes without retreatment. Age, sex, surgical eye, sphere, cylinder, and spherical equivalent (SE) were significantly different between groups (p < 0.05). At 12 months post-enhancement, 86% of the eyes had an uncorrected distance visual acuity of 20/20 or better and 93% of eyes were within ±0.50 D of the target. Development of EI (6.1%) demonstrated an odds ratio of 16.3 in the long-term compared to the short-term (95% CI: 5.9 to 45.18; p < 0.0001). Conclusions: Older age at primary LASIK, female sex, right eye, and larger sphere, cylinder and SE were risk factors for enhancement. Risk of EI significantly increased when duration between primary and enhancement procedures exceeded five years. LASIK enhancements produce favorable outcomes and meet FDA benchmarks for safety, efficacy, and predictability.

Topography-Guided Trans-Epithelial No-Touch Photorefractive Keratectomy for High Irregular Astigmatism After Penetrating Keratoplasty: A Prospective 12-Months Follow-Up

Purpose

To describe the efficacy and safety of topography-guided trans-epithelial no-touch photorefractive keratectomy (PRK) for the correction of highly irregular astigmatism after penetrating keratoplasty (PK).

Patients and Methods

A prospective study was conducted on 12 eyes of 12 patients affected by highly irregular astigmatism after PK for keratoconus. Each patient underwent a single-step topography-guided trans-epithelial ablation (CIPTA^®2 software, iVis Technologies). Corneal topography data as well as uncorrected (UDVA) and corrected distance visual acuity (CDVA) and spherical equivalent (SEQ) were collected preoperatively (T0) and at 1 (T1), 3 (T2) and 12 (T3) months after surgery.

Results

Mean UDVA and CDVA significantly improved, respectively, from 1.22±0.17 and 0.18±0.03LogMAR at T0 to 0.63±0.17 (CI 95%, P<0.001) and 0.04±0.03LogMAR at T3 (CI 95%, P<0.001). Mean SEQ significantly decreased from −3.75±1.32 to –1.60±1.32D (CI 95%, P<0.02). Mean subjective refractive astigmatism (SRAST) and mean keratometry astigmatism (SimK) significantly decreased, respectively, from 7.83±0.98 and 8.10±1.48D to 2.83±0.98 and 5.29±1.48D (CI 95%, P<0.001). Corneal Morphological Irregularity index (CMI) significantly decreased from 62.76±7.26 µm to 23.24±7.26 µm (CI 95%, P<0.001). Apart from a single episode of graft rejection 5 days after ablation, successfully reverted with topical steroids, no other complications were noted. A mild corneal haze was observed in two eyes (16.7%) at 3 months post-PRK, and no regression was observed at 12 months.

Conclusion

Our study demonstrates the safety and long-term effectiveness of a trans-epithelial topography-guided ablation in the treatment of post-PK highly irregular astigmatism.

Flap Thickness and the Risk of Complications in Mechanical Microkeratome and Femtosecond Laser In Situ Keratomileusis: A Literature Review and Statistical Analysis

INTRODUCTION

A recent Cochrane review found no difference in visual acuity outcomes between femtosecond-assisted laser in situ keratomileusis (LASIK) and LASIK using mechanical microkeratomes (MMKs). This study compares the flap thickness and risk of complications related to flap creation using femtosecond lasers and MMKs.

METHODS

PubMed and the Web of Science are used to search the medical literature. An extensive search is performed to identify the flap thickness and complications of LASIK as reported up to 15 July 2021. The following keywords are used in various combinations: Corneal flap, femtosecond laser, laser in situ keratomileusis, laser-assisted in situ keratomileusis, LASIK, mechanical microkeratome.

RESULTS

After removing duplicates and irrelevant studies, 122 articles were included for review. Pooled differences for intended vs. postoperative flap thickness using MMKs and femtosecond laser were -4.07 μm (95% CI: -19.55, 3.24 μm) in studies on the MMK and 5.43 μm (95% CI: 2.30, 7.84 μm; p < 0.001), respectively. After removing the studies evaluating outcomes of the old generation Hansatome MMKs (which had a significantly greater variation of flap thickness), the pooled difference for newer MMKs was 4.97 μm (95% CI: 0.35, 9.58 μm; p < 0.001), but the results still favored the femtosecond laser. Uncommon and mild complications unique for the femtosecond LASIK are epithelial gas breakthrough, opaque bubble layer, transient light sensitivity syndrome, and rainbow glare. A single study reported a very low, but stastically different risk of postoperative flap slippage (0.033% for MMK LASIK, and 0.003% for femtosecond LASIK, respectively).

CONCLUSION

In both manual microkeratome and femtosecond LASIK, intra- and postoperative complications were uncommon. The evidence of the superiority of one technique in terms of complications over another cannot be indisputably stated.

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.

[Regression and ablation profiles in corneal refractive surgery]

Regression after corneal refractive surgery is a complex phenomenon which seems inevitable. The choice of surgical technique has very little influence on regression for low myopia or myopic astigmatism. However, LASIK and SMILE are the two techniques of choice in the correction of high myopia. LASIK is also better for the correction of hyperopia, hyperopic astigmatism and mixed astigmatism. Intraoperatively, the choice of a wide optical zone and adherence to a thick residual stromal bed provide stability. Regression may also be reduced by modulating anti-inflammatory therapy, treating dry eye, and using mitomycin C in PKR. In all cases, obtaining keratometry during patient follow-up helps to identify the cause of the regression. The objective of this review is to synthesize recent data from the literature on regression in refractive surgery as a function of the ablation profiles used.

Factors Predicting the Need for Re-treatment After Laser Refractive Surgery in Patients With High Astigmatism: A Large Database Analysis

PURPOSE

To identify the potential risk factors that increase the likelihood of requiring re-treatment following refractive surgery in patients with high astigmatism (3.00 diopters or greater).

METHODS

This retrospective study included patients who underwent laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) between January 2005 and December 2019 at the Care-Vision Laser Centers, Tel-Aviv, Israel. Patients with high astigmatism (3.00 diopters or greater) were included and divided into two groups according to whether or not they underwent additional refractive surgery (re-treatment) during the study period.

RESULTS

Overall, 2,024 eyes (2,024 patients) were included in the final analysis of this study. In total, 3.1% of the eyes (n = 63) underwent re-treatment. Throughout the study period, there was a significant reduction in the 2-year annual re-treatment rates, with a decline from 7.0% for primary surgeries performed in 2005 to 0.0% for primary surgeries performed in 2017 (r =-0.65, P = .015). The re-treatment group had significantly older preoperative age. They were also more likely to be male and have preoperative against-the-rule astigmatism and preoperative mixed astigmatism. Binary logistic regression analysis demonstrated that preoperative age, male gender, mixed astigmatism, and earlier year of surgery were all associated with higher re-treatment rates.

CONCLUSIONS

The following factors are associated with higher rates of re-treatment in patients with high astigmatism: older preoperative age, male gender, and mixed astigmatism. These factors may be incorporated into nomograms to reduce future re-treatment rates in this population. [J Refract Surg. 2021;37(6):366-371.].

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.

Refractive outcomes comparing small-incision lenticule extraction and femtosecond laser-assisted laser in situ keratomileusis for high myopia

PURPOSE

To compare the long-term refractive effects of small-incision lenticule extraction (SMILE) and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) on the correction of high myopia and astigmatism.

SETTING

The Eye and ENT Hospital of Fudan University, Shanghai, China.

DESIGN

Retrospective case series.

METHODS

Patients had SMILE or FS-LASIK for high myopia. Subgroup analyses of high myopia (-6.00 to -8.75 diopters [D]) and extremely high myopia (≥-9.00 D) were performed. The main outcome measure was refractive predictability, compared between SMILE and FS-LASIK groups. Secondary outcomes included efficacy, safety, and residual astigmatism.

RESULTS

This study included 121 patients (121 eyes: 75 in the SMILE group and 46 in the FS-LASIK group). No differences were found in terms of refractive predictability between SMILE and FS-LASIK in eyes with high myopia: 56% vs 58.7% achieved ± 0.50 D of attempted correction (P = .771) and 81.3% vs 76.1% achieved ± 1.00 D of attempted correction (P = .489). Efficacy indices of the SMILE and FS-LASIK groups were 1.02 ± 0.24 and 1.03 ± 0.24 (P = .742), respectively; safety indices were 1.23 ± 0.22 and 1.20 ± 0.24 (P = .324), respectively. Logarithm of the minimum angle of resolution uncorrected distance visual acuity and spherical equivalent in the high myopia subgroup were better than in the extremely high myopia subgroup after both SMILE and FS-LASIK (P < .01).

CONCLUSIONS

SMILE and FS-LASIK were both effective in correcting high myopia and myopic astigmatism. However, both techniques may require further nomogram adjustments when treating eyes with extremely high myopia.

Refractive surgery with simultaneous collagen cross-linking for borderline corneas - A review of different techniques, their protocols and clinical outcomes

Simultaneous corneal cross-linking (CXL) has been proposed as an adjunct therapy to corneal refractive procedures to prevent future ectasia, especially when performed in borderline corneas. This review analyses the currently available literature (minimum follow-up 6 months) on corneal refractive surgery and simultaneous CXL (PRK Xtra, LASIK Xtra, and SMILE Xtra) to evaluate the overall results including the safety, efficacy, and potential complications associated with these procedures. A comprehensive literature search of various electronic databases (PubMed, PubMed Central, Cochrane database, and MEDLINE) was performed up to 20^th May 2020. Four relevant studies were found for PRK Xtra, 12 for LASIK Xtra, and 3 for SMILE Xtra. The total number of eyes included in this review was 1,512: 294 for PRK Xtra, 221 for PRK-only, 446 eyes for LASIK Xtra, 398 eyes for LASIK-only, 91 for SMILE Xtra and 62 for SMILE-only. Current literature suggests that refractive surgery and simultaneous CXL is generally safe and delivers comparable results in terms of visual and refractive outcomes than refractive surgery alone. However, there is no consensus on a standard cross-linking protocol, and complications such as diffuse lamellar keratitis, central toxic keratopathy, and corneal ectasia following Xtra procedures have been reported. It is therefore suggested that surgeons exercise caution in case-selection and counsel their patients regarding the potential risks and benefits with Xtra procedures. Also, further studies are required to standardize the UV-A irradiation protocols and to evaluate the long-term effect on safety, refractive predictability, and stability of these procedures.

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.

Three-Year Outcomes of Simultaneous Accelerated Corneal Crosslinking and Femto-LASIK for the Treatment of High Myopia in Asian Eyes

Purpose

To determine the long-term visual outcomes of simultaneous femtosecond laser-assisted laser in situ keratomileusis (femto-LASIK) and accelerated cross-linking (CXL) [LASIK Xtra] for the treatment of high myopia.

Patients and Methods

All 163 consecutive eyes of 85 patients who underwent LASIK Xtra for the treatment of high myopia and/or myopic astigmatism (spherical equivalent ≥ −6.00 D) in Singapore National Eye Centre from the years 2013 to 2017 were included in this retrospective case series. Post-operative follow-up was up to 3 years.

Results

Of the 163 eyes, 67 were followed up for 1 year (mean 12.9 months), 69 for 2 years (mean 24.0 months) and 43 for 3 years (mean 36.4 months). Overall mean follow-up was 22.8 months (9–46 months). The mean pre-operative spherical equivalent (SE) was −8.60 ± 1.47 D [range: −11.75 to −4.75] (n = 163) and mean attempted correction SE was −8.84 ± 1.41 D [range: −11.88 to −5.25]. Most eyes (>95%) maintained an uncorrected distance visual acuity of 6/12 or better over 3 years. Visual outcomes were predictable with ≥95% of eyes achieving a SE correction within ± 1D of attempted correction over 3 years. There was a mild regression in SE refraction over 3 years with a mean of −0.10 ± 0.45 D three years post-operatively (p = 0.03). The safety index was >1.05 at 3 years follow-up. There were no significant post-operative complications though 24 eyes had mild haze and 2 eyes had grade 1 diffuse lamellar keratitis that resolved within 1 month.

Conclusion

Our 3-year LASIK Xtra results show favorable safety, efficacy, predictability and stability outcomes in Asian patients with high myopia.

Correlation and regression analysis between residual gradation and uncorrected visual acuity one year after refractive surgery with LASIK, FS-LASIK, PRK, PRK Xtra techniques and the implantation of ICL® posterior chamber phakic lens in myopic correction

Purpose

To analyze the influence of the final spherical equivalent (SE) in LogMAR uncorrected distance visual acuity (UDVA) one year after refractive surgery. We analysed refractive results, their predictability and efficacy, and the safety results of the different methods as secondary outcomes.

Setting

Refractive Surgery Unit of the Institut Català de Retina (ICR) in Barcelona, Spain.

Design

Retrospective, analytical observational study.

Methods

Retrospective and observational study of 654 eyes of 327 patients who underwent refractive surgery to treat their myopia or myopic astigmatism using LASIK, FS-LASIK, PRK, PRK Xtra or ICL-type lens implantation surgery were included.

Results

The correlation between the SE in absolute value was statistically significant in all techniques utilized, reaching higher values in the FS-LASIK and LASIK techniques, 0.774 and 0.706 respectively, and lesser values in PRK (0.480) and PRK Xtra (0.482). A significant adjustment via a univariate linear regression model could be implemented in all techniques, albeit the R² coefficient of determination values were higher than those for the FS-LASIK (0.599) and LASIK (0.494) techniques.

Conclusions

There is a positive correlation between post-surgical SE value and post-operative LogMAR UDVA. These regression models can be adjusted to predict the final UDVA according to the final SE. The techniques that are most influenced by the final SE in terms of their visual results are FS-LASIK and LASIK.

Advantages of Small Incision Lenticule Extraction (SMILE) for Mass Eye and Ear Special Issue

This review summarizes the advantages of Small-incision lenticule extraction (SMILE), including improved patient intraoperative experience, improved postoperative ocular surface, low incidence of regression, low re-treatment rates, and advantageous biomechanical corneal stability. Visual and refractive outcomes are similar to those achieved with LASIK, notably in large population studies. Since the inception of SMILE almost 10 years ago, the procedure has been rapidly growing in popularity. With the implementation of the novel SMILE technology in their practice, refractive surgeons generate excitement and potential for expanding the refractive market. Other parts of the world, including Asia, Europe, and Russia, SMILE has become the most popular refractive procedure performed. It is speculated that as SMILE continues to grow in popularity in the US since FDA approval in 2016 and more refractive surgeons implement this technology into their practice, it will drive an increase in the refractive market similar to what is seen in other countries.

The relationship between patient age and residual refractive error after uneventful laser in situ keratomileusis for moderate-to-high hyperopia

PURPOSE

To determine if the manifest sphero-cylindrical residual refractive error, at various time points over a 12-month postop period after laser in situ keratomileusis (LASIK) was associated with patient age at time of surgery.

METHODS

Patients with moderate to high hyperopia (3.00-7.00 DS) and astigmatism ⩽2 DC underwent LASIK using Wavelight Allegretto Eye Q (400 Hz). Treatments were centered on corneal vertex, flaps were made with Moria M2 mechanical microkeratome. Pre-and postoperative uncorrected and corrected distant visual acuity, best corrected spherical equivalent (SEQ) were measured. Measurements were taken at 1 week, 1, 3, 6, and 12 months after the surgery. Target refraction was emmetropia. Total of 161 patients were treated. In binocular cases, data from the right eyes were included for analysis. In this article, we report on refraction data only. Raw data were subjected to several permutations to elicit any links between refractive outcomes and patient age.

RESULTS

The key findings were as follows y = postop SEQ (diopters), x = patient age (years), ln(x) = natural logarithm of patient age: At 1 month, y = x[0.049 -0.011.ln(x)] (R = -0.205, p = 0.001, n = 161). At 3 months, y = x[0.077 -0.017.ln(x)] (R = -0.355, p < 0.001, n = 161). At 6 months, y = x[0.088 -0.020.ln(x)] (R = -0.382, p < 0.001, n = 161). At 12 months, y = x[0.093 -0.021.ln(x)] (R = -0.409, p < 0.001, n = 161). There was no significant association between x and y at 1 week (p > 0.05).

CONCLUSION

Residual postop refractive error after LASIK for hyperopia has a logarithmic association with patient age at time of surgery. In younger patients there is tendency toward undercorrection, the opposite occurs in older patients and this persists 1 year after treatment.

Survey of Ehlers-Danlos Patients' ophthalmic surgery experiences

Background

Ehlers‒Danlos Syndrome (EDS) is a rare disease affecting approximately 1 in 5,000 people. Although ophthalmic conditions associated with EDS have been described, little data exist concerning ophthalmic surgical outcomes experienced by EDS patients.

Methods

Patients with EDS were surveyed via the EDS Society and asked about their ophthalmic surgical experiences including procedure, complications, and the timing with respect to receiving the EDS diagnosis. Complications were confirmed as such by subspecialists.

Results

Of 579 respondents, 467 reported confirmed EDS, and 112 of those had an ophthalmic procedure, including refractive surgery, cataract/lens surgery, retinal surgery, strabismus surgery, oculoplastic surgery, corneal surgery, and laser surgery for glaucoma. The rate of confirmed complications was: 23%‐refractive, 33%‐lens/cataract, 33%‐retina, 59%‐strabismus, 23%‐ oculoplastics, 0%‐cornea, and 25%‐glaucoma laser. In addition, 76% of patients underwent surgery prior to the EDS diagnosis.

Conclusions

Patients with EDS may have elevated risk of postoperative ophthalmic surgical complications. It would seem reasonable to systemically and prospectively explore how patients with EDS respond to ophthalmic surgery. Furthermore, it would seem circumspect to ask surgical candidates patients about whether they carry a diagnosis of EDS or have signs and symptoms of EDS prior to surgery.

The risk of vision loss in contact lens wear and following LASIK

PURPOSE

To compare the risk of vision loss following contemporary laser-assisted in situ keratomileusis (LASIK) with different types and modality of use of contact lenses.

METHODS

Data from a previously published study were used to derive the incidence of vision loss (≥ 2 line loss of best corrected spectacle acuity) following microbial keratitis for different contact lens types and wearing modality, stratified by duration of lens wear. A literature search on vision loss following LASIK was performed between 2003 and 2019. The prevalence of vision loss at six months post-surgery was captured from clinical trials published after 2003. A proportion meta-analysis was applied to derive the prevalence of vision loss following LASIK. A least-squares fitting of cumulative vision loss (P, /10 000 wearers) over time (t, years) using an exponential model estimated the years of contact lens wear to which the risk of vision loss with LASIK was equivalent.

RESULTS

Vision loss following LASIK occurred in 66 (95% confidence interval [CI] 34-108) per 10 000 wearers. As a conservative estimate based on the lower confidence interval of the estimated equivalent years of contact lens wear, daily wear contact lenses and extended overnight silicone wear hydrogel contact lens need to be worn for 103 (95% [CI] 103-391) and 25 (95% [CI] 25-79) years respectively, to equal the rate of vision loss equivalent to a one-off LASIK procedure.

CONCLUSIONS

The risk of vision loss to the individual is low with either contact lens wear or refractive surgery. Contact lens wear does not pose a higher risk of vision loss than LASIK surgery for the most common wear modalities.

Re-Treatment by Flap Relift Versus Surface Ablation After Myopic Laser In Situ Keratomileusis

PURPOSE

To compare clinical outcomes of patients undergoing first re-treatment by flap relift with those re-treated by surface ablation on the flap after an initial myopic laser-assisted in situ keratomileusis (LASIK) procedure.

METHODS

This is a retrospective cohort analysis of consecutive patients who underwent myopic LASIK and required re-treatment between January 2007 and December 2016. Cases re-treated by flap relift were propensity score matched with cases re-treated by surface ablation, and clinical outcomes were compared. One eye from each patient was included.

RESULTS

A total of 1,234 out of 21,191 cases required re-treatment after myopic LASIK during the follow-up period. Surface ablation was performed in 75% of cases and relift in 25%. Patients re-treated by surface ablation were more commonly male (61.8% vs. 48.1%, P < 0.001), were younger (33.2 ± 7.8 vs. 35.2 ± 10 years, P = 0.005), and had thinner corneas (483 ± 46 vs. 502 ± 43 μm, P < 0.001). Propensity score matching was performed for 416 eyes (208 from each group). After matching, differences in baseline characteristics became nonsignificant (P > 0.05). Cases re-treated by surface ablation had a worse safety index (0.98 ± 0.12 vs. 1.02 ± 0.17, P = 0.049), yet better predictability (0.14 ± 0.6 vs. 0.35 ± 0.5 diopters of deviation, P = 0.009), a similar efficacy index (0.92 ± 0.2 vs. 0.93 ± 0.3, P = 0.814), higher rates of haze (5.8% vs. 0.5%, P = 0.002), and a lower risk for epithelial ingrowth (0.5% vs. 8.2%, P < 0.001).

CONCLUSIONS

Re-treatment after myopic LASIK with surface ablation resulted in worse safety and higher rates of haze, yet more predictable outcomes and reduced ingrowth rates, compared with re-treatment with flap relift.

Predictors affecting myopic regression in - 6.0D to - 10.0D myopia after laser-assisted subepithelial keratomileusis and laser in situ keratomileusis flap creation with femtosecond laser-assisted or mechanical microkeratome-assisted

PURPOSE

To investigate the predictive factors of postoperative myopic regression among subjects who have undergone laser-assisted subepithelial keratomileusis (LASEK), laser-assisted in situ keratomileusis (LASIK) flap created with a mechanical microkeratome (MM), and LASIK flap created with a femtosecond laser (FS). All recruited patients had a manifest spherical equivalence (SE) from - 6.0D to - 10.0D myopia.

METHODS

This retrospective, observational case series study analyzed outcomes of refraction at 1 day, 1 week, and 1, 3, 6, and 12 months postoperatively. Predictors affecting myopic regression and other covariates were estimated with the Cox proportional hazards model for the three types of surgeries.

RESULTS

The study enrolled 496 eyes in the LASEK group, 1054 eyes in the FS-LASIK group, and 910 eyes in the MM-LASIK group. At 12 months, from - 6.0D to - 10.0D myopia showed that the survival rates (no myopic regression) were 52.19%, 59.12%, and 58.79% in the MM-LASIK, FS-LASIK, and LASEK groups, respectively. Risk factors for myopic regression included thicker postoperative central corneal thickness (P ≦ 0.01), older age (P ≦ 0.01), aspherical ablation (P = 0.02), and larger transitional zone (TZ) (P = 0.03). Steeper corneal curvature (K_max) (P = 0.01), thicker preoperative central corneal thickness (P < 0.01), smaller preoperative myopia (P < 0.01), longer duration of myopia (P = 0.02), with contact lens (P < 0.01), and larger optical zone (OZ) (P = 0.02) were protective factors. Among the three groups, the MM-LASIK had the highest risk of postoperative myopic regression (P < 0.01).

CONCLUSIONS

The MM-LASIK group experienced the highest myopic regression, followed by the FS-LASIK and LASEK groups. Older age, aspheric ablation used, thicker postoperative central corneal thickness, and enlarging TZ contribute to myopic regression; steeper preoperative corneal curvature (K_max), longer duration of myopia, with contact lens, thicker preoperative central corneal thickness, lower manifest refraction SE, and enlarging OZ prevent postoperative myopic regression in myopia from - 6.0D to - 10.0D.

Review of Laser Vision Correction (LASIK, PRK and SMILE) with Simultaneous Accelerated Corneal Crosslinking - Long-term Results

Purpose: Laser in-situ keratomileusis (LASIK), photorefractive keratectomy (PRK) and small-incision lenticule extraction (SMILE) are safe and effective refractive surgical procedures. However, complications include regression of treatment and iatrogenic keratectasia which can be severe and sight-threatening. In order to reduce these complications, simultaneous corneal cross-linking (CXL) is currently being added to these refractive procedures. This review analyses current long-term literature (≥ 1 year follow-up) on refractive surgery and simultaneous CXL (LASIK Xtra, PRK Xtra and SMILE Xtra) to determine its overall safety and efficacy.Methods: A comprehensive literature search of various electronic databases (PubMed, PubMed Central and MEDLINE) was performed up to 9^th February 2019. Efficacy and safety indices are calculated where possible.Results: Ten relevant studies were found for LASIK Xtra, 4 for PRK Xtra and 1 for SMILE Xtra. The total number of eyes included in this review was 1,189: 347 eyes for LASIK Xtra, 300 eyes for LASIK-only, 298 for PRK Xtra, 204 for PRK-only, 40 for SMILE Xtra and none for SMILE-only. Current studies show that refractive surgery and simultaneous CXL produces comparable or better results in terms of refractive and keratometric stability than refractive surgery alone. However, case reports of complications such as corneal ectasia, diffuse lamellar keratitis and central toxic keratopathy have also recently been published.Conclusions: Simultaneous accelerated CXL and refractive surgery is effective for the treatment of myopia. However, it is as yet unclear if the additional CXL step reduces the incidence of iatrogenic keratectasia. Further long-term comparative studies would be useful in evaluating safety and efficacy of this procedure. More research should also be performed to titrate the UV-A irradiation settings for an optimal outcome.

Factors Affecting Myopic Regression after Laser in Situ Keratomileusis and Laser-Assisted Subepithelial Keratectomy for High Myopia

To evaluate the factors affecting the amount of myopic regression after laser refractive surgery for high myopia, we retrospectively reviewed medical records of 1591 eyes with high myopia treated by laser in situ keratomileusis or laser-assisted subepithelial keratectomy at Shandong Eye Hospital between January 2008 and December 2012. Thirty-five eyes suffering a postoperative myopic shift of manifest spherical equivalent (MSE) of 0.25 diopter (D) or greater were included in this study. The mean refractive error was -9.34 ± 1.89 D before surgery, and the mean regression was -1.22 ± 0.70 D. Correlation analysis and multiple regression analysis were performed to assess the factors that were associated with the refractive regression. The age displayed a negative correlation with the diopter of regression (R = -0.404, P = .016), while the optical zone diameter had a positive correlation with it (R = 0.406, P = .016). Explanatory variables relevant to the diopter of regression were age (partial regression coefficient B = -0.045, P = .016) and optical zone diameter (partial regression coefficient B = 0.979, P = .014). Advanced-age patients with small optical zones were more predisposed to a larger amplitude of regression after laser refractive surgery for high myopia.

Predicting Refractive Outcome of Small Incision Lenticule Extraction for Myopia Using Corneal Properties

Purpose

To investigate whether preoperative corneal topographic and biomechanical parameters (CTBPs) predict postoperative residual refractive error (RRE).

Methods

We retrospectively included 151 eyes from 151 patients of small-incision lenticule extraction (SMILE) with target RRE of plano and 3-month measurements of refractive error from Tianjin Eye Hospital. Multivariate linear/logistic regressions were performed to associate age, gender, preoperative refractive error, lenticule thickness, and CTBPs with postoperative RRE/the occurrence of myopic RRE ≤ −0.25 diopter (D). Stepwise regression was used for feature selection. Leave-one-cross-validation was used for model evaluation by the area under the receiver operating characteristic curve (AUC).

Results

From linear regression, more myopic RRE was associated with higher preoperative myopia, intraocular pressure (IOP), flattest curvature of anterior cornea (AC), and highest concavity deformation (HCD), and was associated with lower anterior elevation, anterior asphericity, steepest curvature of AC, and second applanation velocity. The occurrence of ≤ −0.25 D RRE was associated with higher myopia, IOP, posterior elevation and asphericity, flattest curvature of AC, first applanation velocity and HCD, and was associated with lower first applanation stiffness parameter, central corneal thickness, anterior elevation and asphericity, steepest curvature of AC, and second applanation velocity as well as thinner lenticule thickness. Compared to the baseline model using age, gender, and preoperative refractive error, adding CTBPs significantly (P < 0.001) improved the AUC performance to 0.771 from 0.615.

Conclusions

Postoperative outcomes of SMILE can be predicted by individual CTBPs.

Translational Relevance

Our findings could be used to customize a refractive nomogram based on individual corneal properties improving outcomes and patient satisfaction.

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.].

Comparison of the efficiency of femtoLASIK and ReLEx SMILE in terms of dioptric error reduction

BACKGROUND AND AIMS

Refractive eye surgery is a rapidly expanding field of ophthalmology and corneal surgery is undergoing constant development leading to less invasive technologies. The goal of this study was to compare the most common femtoLASIK surgery with the newer ReLEx SMILE surgery which is gentler to the cornea. The comparison was made in terms of dioptric error reduction.

METHODS

The studied cohort of patients consisted of two major groups: 30 patients who underwent femtoLASIK surgery and 30 who underwent ReLEx SMILE surgery. -30 patients, 60 eyes. All patients were aged 18-45 years with moderate myopia or astigmatism ranging from -3.25 to -6.0 spherical diopters and from 0 to -1.0 cylindrical diopters. In all, the best corrected visual acuity measured prior to surgery was 1.0. Pachymetry was not comparable because each surgical method was performed at a different time point and the introduction of an innovative method into practice led to a change in selection criteria.

RESULTS

During postsurgical check-ups, the ReLEx SMILE method (0.74) led to lower values of non-corrected visual acuity compared to the femtoLASIK method (0.88), (P<0.001). However, the results changed at the one-year post-surgery check-up, when ReLEX SMILE patients achieved non-corrected visual acuity of 0.97 compared to femtoLASIK patients, who scored 0.83, (P=0.007). Based on data analysis from the automatic refractometer, the average spherical diopters of the femtoLASIK (-0.32 D) were higher than those of the ReLEx SMILE (-0.07 D), (P<0.001). The results for the cylindrical diopters were also significant, (P=0.021). When we compared the spherical equivalent one year after surgery, the difference between methods was significant. The FemtoLASIK method resulted in an average SE -0.55 D compared to -0.09 D for the ReLEx SMILE method, (P<0.001).

CONCLUSION

This study showed that there was a significant difference in results between the two surgical methods of treatment of moderate myopia and astigmatism, in terms of regression of dioptric error, as well as in achievement and maintenance of visual acuity during the observed period. The ReLEx SMILE had better results.

Refractive regression after laser in situ keratomileusis

Uncorrected refractive errors are a leading cause of visual impairment across the world. In today's society, laser in situ keratomileusis (LASIK) has become the most commonly performed surgical procedure to correct refractive errors. However, regression of the initially achieved refractive correction has been a widely observed phenomenon following LASIK since its inception more than two decades ago. Despite technological advances in laser refractive surgery and various proposed management strategies, post-LASIK regression is still frequently observed and has significant implications for the long-term visual performance and quality of life of patients. This review explores the mechanism of refractive regression after both myopic and hyperopic LASIK, predisposing risk factors and its clinical course. In addition, current preventative strategies and therapies are also reviewed.

Epithelial ingrowth following laser in situ keratomileusis (LASIK): prevalence, risk factors, management and visual outcomes

The number of laser in situ keratomileusis (LASIK) procedures is continuing to rise. Since its first application for correcting simple refractive errors over 25 years ago, the role of LASIK has extended to treat other conditions, including postkeratoplasty astigmatism/ametropia, postcataract surgery refractive error and presbyopia, among others. The long-term effectiveness, predictability and safety have been well established by many large studies. However, due to the creation of a potential interface between the flap and the underlying stroma, interface complications such as infectious keratitis, diffuse lamellar keratitis and epithelial ingrowth may occur. Post-LASIK epithelial ingrowth (PLEI) is an uncommon complication that usually arises during the early postoperative period. The reported incidence of PLEI ranged from 0%–3.9% in primary treatment to 10%–20% in retreatment cases. It can cause a wide spectrum of clinical presentations, ranging from asymptomatic interface changes to severe visual impairment and flap melt requiring keratoplasty. PLEI can usually be treated with mechanical debridement of the affected interface; however, additional interventions, such as alcohol, mitomycin C, fibrin glue, ocular hydrogel sealant, neodymium:yttriumaluminum garnet laser and amniotic membrane graft, may be required for recurrent or refractory cases. The aims of this review are to determine the prevalence and risk factors of PLEI; to describe its pathogenesis and clinical features and to summarise the therapeutic armamentarium and the visual outcome of PLEI.

Retreatment strategies following Small Incision Lenticule Extraction (SMILE): In vivo tissue responses

With any refractive correction, including Small Incision Lenticule Extraction (SMILE), there may be a residual refractive error that requires a retreatment. Here, we investigated the tissue responses following various retreatment procedures in a rabbit model of SMILE. All rabbits underwent a -6.00D correction with SMILE. Two weeks later, they underwent -1.00D enhancement by: (i) VisuMax Circle, followed by excimer ablation (S+C); (ii) secondary SMILE anterior to the primary procedure (S+SE); or (iii) surface ablation (S+P), and were examined for 28 days. S+P induced corneal edema and haze, and more CD11b- (23±6 cells) and TUNEL-positive (36±4 cells) cells in the central stromal superficial layers early post-operatively (p<0.001 compared to other procedures). The corneas appeared normal on day 28 after S+P, but had a lower number of keratocytes near the laser ablated plane compared to other procedures. S+SE and S+C did not induce corneal haze and resulted similar level of fibronectin. However, S+C resulted in more inflammatory (10±2 cells; p = 0.001) and apoptotic cells (25±2 cells; p<0.001) compared to S+SE (7±1 inflammatory cells and 21±3 apoptotic cells) early post-operatively. In conclusion, each SMILE retreatment method resulted in unique tissue responses. S+SE offers advantages, such as minimal inflammation and cell death, as well as maintaining a ‘flap-less’ surgery, over other procedures. However, depending on the degree of enhancement, the lenticule may become too thin to be extracted and the procedure becomes more difficult to perform than S+C and S+P. S+P can maintain corneal integrity by avoiding flap creation and is technically more simple to perform than the others, but the surgery needs to be supplemented with mitomycin-C in order to reduce inflammation and modulate better wound healing.

Corneal Refractive Procedures for the Treatment of Presbyopia

Purpose:

Refractive surgery has been in use for a long time and is evolving at a fast pace with several new corneal procedures being used for the correction of presbyopia. The purpose of this article is to give a comprehensive review of the literature to evaluate the outcome and success of different corneal refractive surgical procedures in presbyopic patients.

Methods:

We performed a comprehensive search on PubMed to identify published reports of the various procedures utilized in the past and present to correct presbyopia. The outcomes of these procedures were recorded.

Results and conclusion:

We found that varying rates of success have been reported with these procedures. The results of our exhaustive search are presented in this report for review.

Enhancement after Small-Incision Lenticule Extraction: Incidence, Risk Factors, and Outcomes

PURPOSE

To report the incidence, risk factors, and outcomes of enhancement after small-incision lenticule extraction (SMILE).

DESIGN

Retrospective cohort study.

PARTICIPANTS

Five hundred twenty-four eyes of 307 patients who underwent SMILE at Singapore National Eye Center between February 2012 and March 2016.

METHODS

The data collected included patient age at primary SMILE, gender, race, preoperative and postoperative manifest refraction spherical equivalent (MRSE), preoperative and postoperative uncorrected distance visual acuity and corrected distance visual acuity, the occurrence of suction loss during the procedure, and the need for enhancement. All enhancements were carried out by performing an alcohol-assisted photorefractive keratectomy (PRK) procedure with application of mitomycin C (MMC).

MAIN OUTCOME MEASURES

Incidence, prevalence, preoperative and intraoperative risk factors for enhancement, and outcomes after enhancement.

RESULTS

The prevalence of enhancement was 2.7%, and 71.4% eyes had enhancement within 1 year of primary SMILE. The incidence of enhancement was 2.1% and 2.9% at 1 and 2 years, respectively. Age older than 35 years, preoperative MRSE more than -6.00 diopters (D), preoperative myopia more than 6.00 D, preoperative astigmatism more than 3.00 D, and intraoperative suction loss were significant risk factors for enhancement after SMILE after adjusting for all other covariates (odds ratios, 5.58, 4.80, 1.41, 3.06, and 2.14, respectively; P = 0.004, 0.021, 0.022, 0.002, and 0.020, respectively). In the patients who underwent bilateral SMILE, the first-operated eye had a marginal trend toward significance for enhancement (P = 0.054). There was no gender or racial difference. In the 14 eyes requiring enhancement, the uncorrected distance visual acuity before enhancement ranged from 20/80 to 20/25, and the mean attempted enhancement spherical equivalent was -0.50±0.86 D. The uncorrected distance visual acuity improved in most patients (92.9%) after enhancement.

CONCLUSIONS

The 2-year incidence of enhancement after SMILE was 2.9%. Risk factors associated with enhancement included older age at SMILE procedure, greater preoperative MRSE, greater preoperative myopia, greater preoperative astigmatism, and the occurrence of intraoperative suction loss. Clinical outcomes of using PRK with application of MMC for enhancement were good.

Clinical Outcomes of an Optimized Prolate Ablation Procedure for Correcting Residual Refractive Errors Following Laser Surgery

Purpose

The purpose of this study was to investigate the clinical efficacy of an optimized prolate ablation procedure for correcting residual refractive errors following laser surgery.

Methods

We analyzed 24 eyes of 15 patients who underwent an optimized prolate ablation procedure for the correction of residual refractive errors following laser in situ keratomileusis, laser-assisted subepithelial keratectomy, or photorefractive keratectomy surgeries. Preoperative ophthalmic examinations were performed, and uncorrected distance visual acuity, corrected distance visual acuity, manifest refraction values (sphere, cylinder, and spherical equivalent), point spread function, modulation transfer function, corneal asphericity (Q value), ocular aberrations, and corneal haze measurements were obtained postoperatively at 1, 3, and 6 months.

Results

Uncorrected distance visual acuity improved and refractive errors decreased significantly at 1, 3, and 6 months postoperatively. Total coma aberration increased at 3 and 6 months postoperatively, while changes in all other aberrations were not statistically significant. Similarly, no significant changes in point spread function were detected, but modulation transfer function increased significantly at the postoperative time points measured.

Conclusions

The optimized prolate ablation procedure was effective in terms of improving visual acuity and objective visual performance for the correction of persistent refractive errors following laser surgery.

Use of a hydrogel sealant in epithelial ingrowth removal after laser in situ keratomileusis

We describe 2 cases in which clinically significant epithelial ingrowth was removed by debridement and followed by the use of a hydrogel sealant (Resure) to seal the flap edge. In both cases, the epithelial ingrowth was seen after otherwise uneventful laser in situ keratomileusis retreatment. The visual outcomes were good with no recrudescence of interface epithelium.

FINANCIAL DISCLOSURE

Neither author has a financial or proprietary interest in any material or method mentioned.

Outcomes of photorefractive keratectomy following laser in situ keratomileusis: a cohort study

OBJECTIVE

To analyze the outcomes of photorefractive keratectomy (PRK) on residual myopia and hyperopia post-laser in situ keratomileusis (LASIK) and to compare these results with PRK on eyes without previous laser refractive surgery.

DESIGN

Retrospective comparative cohort study.

PARTICIPANTS

Patients undergoing PRK between 2006 and 2010 were reviewed.

METHODS

Patients were divided into 4 groups, myopic or hyperopic PRK post-LASIK (mPRK-PL and hPRK-PL, respectively) and myopic or hyperopic PRK on corneas without previous laser refractive surgery (mPRK and hPRK, respectively). Uncorrected and corrected distance visual acuity, mean refractive spherical equivalent (MRSE), and mean keratometry and aberrations (total, higher order [HOA], coma, trefoil, and spherical aberration) were recorded at months 3 and 6 postoperatively, as were complications and attempted versus achieved MRSE.

RESULTS

Thirty-three eyes of 25 patients who underwent PRK post-LASIK (21 eyes of 14 patients for hPRK-PL and 12 eyes of 11 patients for mPRK-PL) and 35 eyes of 21 patients who underwent PRK on virgin eyes (11 eyes of 8 patients for hPRK and 24 eyes of 13 patients for mPRK) were included in the study. The only significant differences in outcomes were found to be HOA at 3 months for hPRK-PL as compared with both hPRK and mPRK. Achieved MRSE was significantly different from expected MRSE for hPRK-PL at 3 months postoperatively. No haze- or flap-related complications were observed.

CONCLUSION

Outcomes of PRK were not different in myopic and hyperopic corrections post-LASIK by 6 months or when compared with PRK in virgin eyes. HOA may render hPRK-PL results less predictable early in the postoperative period.

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.

Comparison of Patient-Specific Computational Modeling Predictions and Clinical Outcomes of LASIK for Myopia

Purpose

To assess the predictive accuracy of simulation-based LASIK outcomes.

Methods

Preoperative and 3-month post-LASIK tomographic data from 20 eyes of 12 patients who underwent wavefront-optimized LASIK for myopia were obtained retrospectively. Patient-specific finite element models were created and case-specific treatment settings were simulated. Simulated keratometry (SimK) values and the mean tangential curvature of the central 3 mm (Kmean) were obtained from the anterior surfaces of the clinical tomographies, and computational models were compared. Correlations between Kmean prediction error and patient age, preoperative corneal hysteresis (CH), and corneal resistance factor (CRF) were assessed.

Results

The mean difference for Kmean between simulated and actual post-LASIK cases was not statistically significant (-0.13 ± 0.36 diopters [D], P = 0.1). The mean difference between the surgically induced clinical change in Kmean and the model-predicted change was -0.11 ± 0.34 D (P = 0.2). Kmean prediction error was correlated to CH, CRF, and patient age (r = 0.63, 0.53, and 0.5, respectively, P < 0.02), and incorporation of CH values into predictions as a linear offset increased their accuracy. Simulated changes in Kmean accounted for 97% of the variance in actual spherical equivalent refractive change.

Conclusions

Clinically feasible computational simulations predicted corneal curvature and manifest refraction outcomes with a level of accuracy in myopic LASIK cases that approached the limits of measurement error. Readily available preoperative biomechanical measures enhanced simulation accuracy. Patient-specific simulation may be a useful tool for clinical guidance in de novo LASIK cases.

Flap lift and photorefractive keratectomy enhancements after primary laser in situ keratomileusis using a wavefront-guided ablation profile: Refractive and visual outcomes

PURPOSE

To analyze results of wavefront-guided laser vision correction retreatments performed either by lifting the original flap or by surface ablation over the flap.

SETTING

Optical Express, Glasgow, United Kingdom.

DESIGN

Retrospective case series.

METHODS

This retrospective study included patients grouped according to whether they had flap lift enhancement or photorefractive keratectomy (PRK) performed over the LASIK flap. All retreatment procedures were performed with the Visx Star S4 IR excimer laser with wavefront-guided ablation profile derived from the iDesign aberrometer. Visual acuities, refractive outcomes, vector analysis of refractive cylinder and complications were analyzed in this study. The results of the last available clinical visit are presented.

RESULTS

This retrospective study included 290 eyes of 202 patients divided into 2 groups: 119 eyes that had flap lift enhancement (Group A), and 171 eyes in which photorefractive keratectomy (PRK) was performed over the LASIK flap (Group B). The mean follow-up was 4.0 ± 1.9 months in Group A and 4.2 ± 1.6 in Group B. The mean postoperative manifest spherical equivalent was -0.01 ± 0.35 D and +0.06 ± 0.39 D in Groups A and B, respectively. The percentage of eyes with postenhancement UDVA 20/20 or better was 87.4% in Group A and 79.5 % in Group B (P = .09). In Group A, 22 eyes (18.5%) developed epithelial ingrowth, of which surgical intervention was required in 2 eyes (1.7%). Grade 1 or less haze was noted in 9 (5.3%) eyes in Group B, and resolved in all cases within the first 6 postoperative months.

CONCLUSION

Both retreatment techniques were considered to be effective, predictable, and safe.

FINANCIAL DISCLOSURE

Steven C Schallhorn MD is a consultant to Abbott Medical Optics and Zeiss, and Global Medical Director for Optical Express. None of the other authors have a financial or proprietary interest in the products and materials presented in this paper.

Wavefront-optimized surface retreatments of refractive error following previous laser refractive surgery: a retrospective study

Background

Retreatments are sometimes necessary to correct residual or induced refractive errors following refractive surgery. Many different combinations of primary treatment methods and retreatment techniques have been studied, however, few studies have investigated wavefront-optimized (WFO) technology for retreatment following primary refractive surgery. This study aimed to report the outcomes of WFO photorefractive keratectomy (PRK) retreatments of refractive error following previous laser refractive surgery with PRK, laser in situ keratomileusis (LASIK), or laser-assisted subepithelial keratectomy (LASEK).

Methods

We reviewed records of patients who underwent WFO PRK retreatments using the Allegretto Wave Eye-Q 400 Hz Excimer Laser System (Alcon Surgical) between January 2008 and April 2011 at Walter Reed Army Medical Center and Madigan Army Medical Center. Outcomes were recorded in terms of uncorrected distance visual acuity (UDVA), manifest refraction spherical equivalent (MRSE), corrected distance visual acuity (CDVA), and complications at 1 month (M), 3 M, and 6 M post-op.

Results

Seventy-eight patients (120 eyes) underwent WFO PRK retreatment during the study period. Primary surgery was surface ablation in 87 eyes (78 PRK, 9 LASEK) and LASIK in 33 eyes. The mean spherical equivalent before retreatment was −0.79 ± 0.94 D (−3.00 to 1.88 D). UDVA was ≥ 20/20 in 69 eyes (60.0 %) at 1 M, 54 eyes (71.1 %) at 3 M, and 27 eyes (73.0 %) at 6 M follow-up. MRSE was within ±0.50 D of emmetropia in 78 eyes (67.8 %) at 1 M, 59 eyes (77.6 %) at 3 M, and 25 eyes (67.6 %) at 6 M follow-up. CDVA was maintained within ±1 line of pre-op in 113 of 115 eyes (98.3 %) at 1 M, 74 of 76 eyes (97.4 %) at 3 M, and 37 eyes (100 %) at 6 M follow-up.

Conclusion

Although follow-up was limited beyond 3 M, WFO PRK retreatments in patients with residual refractive error may be a safe and effective procedure. Further studies are necessary to determine the long-term safety and stability of outcomes.

Lasik Xtra® Provides Corneal Stability and Improved Outcomes

A new procedure which combines LASIK and corneal cross-linking (Lasik Xtra®) has been proposed as an alternative to traditional LASIK. It is aimed at restoring strength to the cornea, increasing stability in visual outcomes, increasing the accuracy of the refractive correction, and potentially lowering enhancement rates. This article reviews the current clinical evidence which has been published on the topic and reviews both the safety and efficacy argument for the procedure.

Risk factors of regression and undercorrection in photorefractive keratectomy: a case-control study

AIM

To determine risk factors of regression and undercorrection following photorefractive keratectomy (PRK) in myopia or myopic astigmatism.

METHODS

A case-control study was designed in which eyes with an indication for re-treatment (RT) were defined as cases; primary criteria for RT indication, as assessed at least 9mo postoperatively, included an uncorrected distance visual acuity (UDVA) of 20/30 or worse and a stable refraction for more than 3mo. Additional considerations included optical quality symptoms and significant higher order aberrations (HOAs). Controls were chosen from the same cohort of operated eyes which had complete post-operative follow up data beyond 9mo and did not need RT. The cohort included patients who had undergone PRK by the Tissue-Saving (TS) ablation profile of Technolas 217z100 excimer laser (Bausch & Lomb, Rochester, NY, USA). Mitomycin C had been used in all of the primary procedures.

RESULTS

We had 70 case eyes and 158 control eyes, and they were comparable in terms of age, sex and follow-up time (P values: 0.58, 1.00 and 0.89, respectively). Pre-operative spherical equivalent of more than -5.00 diopter (D), intended optical zone (OZ) diameter of less than 6.00 mm and ocular fixation instability during laser ablation were associated with RT indications (all P values <0.001). These factors maintained their significance in the multiple logistic regression model with odd ratios of 6.12, 6.71 and 7.89, respectively.

CONCLUSION

Higher refractive correction (>-5.00 D), smaller OZ (<6.00 mm) and unstable fixation during laser ablation of PRK for myopia and myopic astigmatism were found to be strong predictors of undercorrection and regression.

Effect of Myopic Defocus on Visual Acuity after Phakic Intraocular Lens Implantation and Wavefront-guided Laser in Situ Keratomileusis

This study aimed to investigate the effect of myopic defocus on visual acuity after phakic intraocular lens (IOL) implantation and wavefront-guided laser in situ keratomileusis (wfg-LASIK). Our prospective study comprised thirty eyes undergoing posterior chamber phakic IOL implantation and 30 eyes undergoing wfg-LASIK. We randomly measured visual acuity under myopic defocus after cycloplegic and non-cycloplegic correction. We also calculated the modulation transfer function by optical simulation and estimated visual acuity from Campbell &Green's retinal threshold curve. Visual acuity in the phakic IOL group was significantly better than that in the wfg-LASIK group at myopic defocus levels of 0, -1, and -2 D (p < 0.001, p < 0.001, and p = 0.02, Mann-Whitney U-test), but not at a defocus of -3 D (p = 0.30). Similar results were also obtained in a cycloplegic condition. Decimal visual acuity values at a myopic defocus of 0, -1, -2, and -3 D by optical simulation were estimated to be 1.95, 1.21, 0.97, and 0.75 in the phakic IOL group, and 1.39, 1.11, 0.94, and 0.71 in the wfg-LASIK group, respectively. From clinical and optical viewpoints, phakic IOL implantation was superior to wfg-LASIK in terms of the postoperative visual performance, even in the presence of low to moderate myopic regression.

3-Year follow-up after Lasik: assessing the risk factors for retreatment

The purpose of this study was to evaluate the correlation of important risk factors for LASIK retreatment and the retreatment rate. A retrospective cohort study was conducted. Records of patients who underwent LASIK between January 2011 and January 2012 at the Zambrano-Hellion Medical Center, Tec de Monterrey (México), and posteriorly underwent LASIK retreatment were identified and risk factors to receive retreatment were assessed using relative risk. Main outcomes were retreatment rate, risk factors for retreatment, and uncorrected distance visual acuity (UDVA). 482 eyes from 241 patients were available for a 36-month follow-up analysis. 68.5 % had primary myopic LASIK; 37 % were ≤ 2 diopters (D), 52 % were > 2 and < 6 D, and 11 % were ≥ 6 D of myopia. 31.5 % of the eyes had hyperopic LASIK. Retreatment was performed in 6.85 % eyes. Myopia > 6 D (RR 4.13), hyperopic refraction (RR 3.18), and age > 40 (RR 3.07) were the most important risk factors for retreatment (P = 0.004, P = 0.007, P = 0.006, respectively). UDVA was ≥ 20/40 in 92.1 % and ≥ 20/20 in 81.6 % of the retreated eyes and 82 % of the eyes within ± 0.50 D of target refraction. Increasing degrees of myopia, followed by hyperopic refraction, and age were the most important associated factors to retreatment. LASIK retreatment was safe and effective.

Rescue of primary incomplete microkeratome flap with secondary femtosecond laser flap in LASIK

For laser-assisted in situ keratomileusis (LASIK) retreatments with a previous unsuccessful mechanical microkeratome-assisted surgery, some surgical protocols have been described as feasible, such as relifting of the flap or the creation of a new flap and even the change to a surface ablation procedure (photorefractive keratectomy (PRK)). This case shows the use of femtosecond technology for the creation of a secondary flap to perform LASIK in a cornea with a primary incomplete flap obtained with a mechanical microkeratome. As we were unable to characterize the interface of the first partial lamellar cut, a thick flap was planned and created using a femtosecond laser platform. As the primary cut was very thick in the nasal quadrant, a piece of loose corneal tissue appeared during flap lifting which was fitted in its position and not removed. Despite this condition and considering the regularity of the new femtosecond laser cut, the treatment was uneventful. This case report shows the relevance of a detailed corneal analysis with an advanced imaging technique before performing a secondary flap in a cornea with a primary incomplete flap. The femtosecond laser technology seems to be an excellent tool to manage such cases successfully.