Laser in situ keratomileusis for myopia and astigmatism: safety and efficacy: a report by the American Academy of Ophthalmology

Investigating the role of large language models on questions about refractive surgery

BACKGROUND

Large language models (LLMs) are becoming increasingly popular and are playing an important role in providing accurate clinical information to both patients and physicians. This study aimed to investigate the effectiveness of ChatGPT-4.0, Google Gemini, and Microsoft Copilot LLMs for responding to patient questions regarding refractive surgery.

METHODS

The LLMs' responses to 25 questions about refractive surgery, which are frequently asked by patients, were evaluated by two ophthalmologists using a 5-point Likert scale, with scores ranging from 1 to 5. Furthermore, the DISCERN scale was used to assess the reliability of the language models' responses, whereas the Flesch Reading Ease and Flesch-Kincaid Grade Level indices were used to evaluate readability.

RESULTS

Significant differences were found among all three LLMs in the Likert scores (p = 0.022). Pairwise comparisons revealed that ChatGPT-4.0's Likert score was significantly higher than that of Microsoft Copilot, while no significant difference was found when compared to Google Gemini (p = 0.005 and p = 0.087, respectively). In terms of reliability, ChatGPT-4.0 stood out, receiving the highest DISCERN scores among the three LLMs. However, in terms of readability, ChatGPT-4.0 received the lowest score.

CONCLUSIONS

ChatGPT-4.0's responses to inquiries regarding refractive surgery were more intricate for patients compared to other language models; however, the information provided was more dependable and accurate.

Visual and Safety Outcomes of Refractive Correction Procedures Following Lens Removal for Residual Refractive Error: A Systematic Review and Meta-analysis

PURPOSE

To evaluate residual refractive errors after intraocular lens (IOL) extraction and the safety and effectiveness of refractive correction procedures.

METHODS

The eligibility criteria for this systematic review were patients who had undergone cataract or clear lens extraction and had experienced residual refractive error. All study designs were considered for inclusion and non-English publications, non-peer reviewed articles, books, and systematic reviews were excluded. A comprehensive electronic search strategy was employed on PubMed, Scopus, Web of Science, Cochrane, and Embase databases from January 1, 1950, to August 1, 2023.

RESULTS

This review examined 55 articles with 2,223 eyes. Piggyback IOL and IOL exchange are highly effective in correcting both myopia and hyperopia, showing significant improvements in spherical and cylindrical errors. Among corneal-based procedures, laser in situ keratomileusis offers a strong balance, with substantial reductions in both spherical and cylindrical errors, along with a favorable safety profile. Small incision lenticule extraction improves uncorrected distance visual acuity (UDVA), particularly in hyperopic patients, whereas photorefractive keratectomy is effective for both UDVA and astigmatism correction, although it has less impact on corrected distance visual acuity (CDVA). Conductive keratoplasty is effective but has greater variability and a higher incidence of complications.

CONCLUSIONS

Significant improvements in spherical equivalent were consistently observed after treatment across the different procedures. Both UDVA and CDVA demonstrated notable enhancements, suggesting an overall efficacy in improving visual function. Although complications were reported, they were generally low in incidence and varied across procedure types. [J Refract Surg. 2025;41(1):e73-e87.].

Longitudinal change in central corneal thickness among primary schoolchildren

PURPOSE

To investigate the longitudinal changes in corneal thickness and its contributing factors in primary schoolchildren.

METHODS

This study is a part of the Shahroud Schoolchildren Eye Cohort Study, conducted longitudinally in two phases; in 2015 and then in 2018. Participants were tested for uncorrected visual acuity, best-corrected visual acuity, cycloplegic refraction, biometry, and Scheimpflug corneal imaging.

RESULTS

After applying the exclusion criteria, 8782 eyes from 4432 participants were analysed. Of these, 2309 (52.1%) were male. Average three-year changes in central corneal thickness (CCT) and corneal apex thickness were -0.58 (95% CI: -0.94 to -0.22) and -0.59 (95% CI: -0.95 to -0.23) microns, respectively. There was an increase of 8.63 (95% CI: 8.1 to 9.17) microns in the superior corneal thickness after three years while the inferior corneal thickness decreased by an average of -5.75 (95% CI: -6.3 to -5.2) microns. The multiple generalized estimating equation (GEE) model showed that the three-year changes in the CCT were lower in rural than in urban students (β = -1.71; p < 0.001). Moreover, the baseline CCT (β = -0.04; p < 0.001), anterior chamber depth (β = -1.6; p = 0.003), and corneal diameter (β = -1.18; p < 0.001) had a significant inverse association while the body mass index (β = 0.12; p = 0.002) and axial length (β = 0.84; p < 0.001) had a significant direct association with the 3-year changes in CCT. After three years, CCT decreased by advancing age in boys, while remaining almost constant in girls.

CONCLUSION

The 3-year change in CCT was clinically negligible and could indicate its stability in schoolchildren. However, CCT thinning was more remarkable in urban students.

Refractive Surgery Patient Characteristics Associated With Satisfaction Scores

PURPOSE

To determine factors influencing patient satisfaction scores in recipients of refractive surgery.

METHODS

In this prospective survey-based study, patients who had refractive surgery at an outpatient refractive clinic completed a survey of selected questions from the Press Ganey survey and the National Eye Institute Visual Function Questionnaire-25. Correlation between patient-specific variables and survey questions were assessed using Student's t-tests.

RESULTS

Fifty-three patients were recruited over a 3-year period. Most were male (55%) and middle aged (mean age: 34 years). Eleven percent underwent photorefractive keratectomy surgery and the rest had laser in situ keratomileusis, with no complications. Twenty-four percent of surveyed patients reported mild to moderate eye pain postoperatively, with the rest reporting no pain. All patients reported a full score for overall satisfaction.

CONCLUSIONS

This study found persistent high patient satisfaction score across a variation of characteristics, suggesting that optimal scores are mainstay after refractive surgery procedures with excellent visual outcomes, independent of patient clinical and sociodemographic characteristics. [J Refract Surg. 2024;40(8):e539-e543.].

Safety and efficacy of a laser refractive procedure in eyes with previous keratoplasty: systematic review and meta-analysis

Post-keratoplasty (KP) patients' visual acuity can be severely limited by ametropia. Irregular astigmatisms are frequently encountered in these patients and is commonly associated with high degrees of hyperopia or myopia. This systematic review investigates the safety and efficacy of laser refractive surgery for post KP vision correction. 31 studies with 683 participants (732 eyes) enrolled in this review. Mean astigmatism improved significantly (mean difference [MD] = -2.70, 95% CI, -3.13 to -2.28, P < .0001). As well as Mean spherical equivalent (MD = -3.35, 95% CI, -3.92 to -2.78, P < .0001). From 586 participants 5.8% lost 2 or more lines of corrected distance visual acuity after treatment. The proportion of eyes with 20/40 uncorrected distance visual acuity or better was reported and the percentage was 46.79% overall. Laser refractive procedures (laser in situ keratomileusis [LASIK] or photorefractive keratectomy [PRK] or transepithelial PRK) on eyes with corneal transplantation were found to be relatively safe and effective. Our systematic review shows there is improvement in all outcomes. Main adverse effects were haze for PRK and epithelial ingrowth for LASIK.

IMI-Onset and Progression of Myopia in Young Adults

Myopia typically starts and progresses during childhood, but onset and progression can occur during adulthood. The goals of this review are to summarize published data on myopia onset and progression in young adults, aged 18 to 40 years, to characterize myopia in this age group, to assess what is currently known, and to highlight the gaps in the current understanding. Specifically, the peer-reviewed literature was reviewed to: characterize the timeline and age of stabilization of juvenile-onset myopia; estimate the frequency of adult-onset myopia; evaluate the rate of myopia progression in adults, regardless of age of onset, both during the college years and later; describe the rate of axial elongation in myopic adults; identify risk factors for adult onset and progression; report myopia progression and axial elongation in adults who have undergone refractive surgery; and discuss myopia management and research study design. Adult-onset myopia is common, representing a third or more of all myopia in western populations, but less in East Asia, where onset during childhood is high. Clinically meaningful myopia progression continues in early adulthood and may average 1.00 diopters (D) between 20 and 30 years. Higher levels of myopia are associated with greater absolute risk of myopia-related ocular disease and visual impairment, and thus myopia in this age group requires ongoing management. Modalities established for myopia control in children would be options for adults, but it is difficult to predict their efficacy. The feasibility of studies of myopia control in adults is limited by the long duration required.

Small Incision Lenticule Extraction (SMILE) and Laser in Situ Keratomileusis (LASIK) Used to Treat Myopia and Myopic Astigmatism: A Systematic Review and Meta-analysis of Randomized Clinical Trials

PURPOSES

The purpose of this meta-analysis is to systematically compare the safety, efficacy, and predictability of small incision lenticule extraction (SMILE) and laser in situ keratomileusis (LASIK).

METHODS

This study covered the data searched from the PubMed, the EMBASE and the Cochrane Library. The Cochrane Handbook was also referred to as evaluating the quality of the included studies. In addition, this meta-analysis was performed using Revman 5.4 software.

RESULTS

A total of 11 randomized controlled trails (RCTs) were included. The proportion of eyes with refraction within ±0.5D was higher in LASIK group compared with SMILE group (RR, 0.91; 95% CI, 0.83 to 0.99; p = .04). The spherical aberration (SA) was smaller in SMILE group compared with LASIK group (RR, -0.12; 95% CI, -0.23 to -0.01; p = .04). There were no significant differences between two groups with regard to final mean refractive spherical equivalent (SE) (MD, -0.04; 95% CI, -0.12 to 0.03; p = .22), proportion of eyes losing one or more lines of corrected distance visual acuity (CDVA) (RR, 1.14; 95% CI, 0.58 to 2.27; p = .70), proportion of eyes with uncorrected distance visual acuity (UCVA) of 20/20 or better (RR, 0.99; 95% CI, 0.94 to 1.05; p = .71), postoperative mean logMAR UCVA (MD, 0.01; 95% CI, -0.00 to 0.03; p = .13), postoperative refraction within ±1.0D (RR, 1.00; 95% CI, 0.98 to 1.02; p = .60), postoperative astigmatism within ±0.25, 0.5 and 1.0D (RR, 0.80, 0.99, 1.00; 95% CI, 0.35 to 1.83, 0.94 to 1.05, 0.98 to 1.02; p = .60, 0.86, 0.87), postoperative higher order aberrations (HOAs) (RR, 0.00; 95% CI, -0.16 to 0.16; p = .99).

CONCLUSION

For predictability, LASIK was superior to SMILE. There were comparably safety and efficacy for the correction of myopia and myopic astigmatism in SMILE and LASIK. SA was smaller after SMILE than after LASIK.

Outcomes of LASIK vs PRK enhancement in eyes with prior cataract surgery

PURPOSE

To compare postenhancement visual acuity between patients who underwent postcataract laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK).

SETTING

A private, tertiary referral practice in Sioux Falls, South Dakota.

DESIGN

3-year, retrospective chart review.

METHODS

Patients who underwent postcataract extraction excimer laser enhancement surgery targeted for emmetropia (±0.50 diopter). Postenhancement uncorrected distance visual acuity (UDVA) and manifest refraction spherical equivalent (MRSE) was recorded for all available follow-ups and compared for both groups.

RESULTS

822 postcataract enhanced eyes (491 LASIK; 331 PRK). For patients with at least 6-month follow-up, mean UDVA was 0.05 ± 0.13 logMAR in LASIK-enhanced patients and 0.15 ± 0.20 in PRK-enhanced patients ( P < .001). Mean absolute value MRSE was 0.22 ± 0.36 and 0.48 ± 0.62 for LASIK-enhanced and PRK-enhanced patients at or beyond 6 months, respectively ( P < .001). 330 (67%) LASIK-enhanced patients achieved 20/20 or better postenhancement UDVA, compared with 142 (43%) PRK-enhanced patients ( P < .001). Controlling for pre-enhancement UDVA, LASIK-enhanced patients showed significantly better postenhancement UDVA than PRK-enhanced patients, except in those with pre-enhancement vision of 20/20 or better, or those worse than 20/50. LASIK-enhanced virgin corneas had mean postenhancement of 0.05 ± 0.14 UDVA compared with 0.13 ± 0.19 UDVA in PRK-enhanced virgin cornea patients ( P < .001).

CONCLUSIONS

LASIK provides better and more predictable outcomes in UDVA than PRK in postcataract enhancement patients, even when controlling for pre-enhancement visual acuity and prior ocular procedures.

Comparison of corneal flap thickness predictability and architecture between femtosecond laser and sub-Bowman keratomileusis microkeratome in laser in situ keratomileusis

PURPOSE OF THE STUDY

The purpose of the study is to assess and compare the corneal flap thickness predictability and uniformity between Visumax femtosecond laser and Moria sub-Bowman keratomileusis microkeratome in laser in situ keratomileusis procedure to correct myopic and myopic astigmatism refractive errors.

METHODS

One hundred eyes from 100 patients were enrolled in this study. Only one eye (right eye) of each patient was chosen for this study. They were divided into two groups of equal size (50 each). Target flap thickness was 90 μm. Flap thickness was measured by anterior segment optical coherence tomography in 7 specified positions at 3 months postoperative.

RESULTS

For femtosecond laser group, the average central flap thickness (CFT) was 91.35 µm ± 4.97. There was no statistically significant difference between the target flap thickness and the resultant flap thickness (p = 0.12). When the central, nasal and temporal thicknesses in the same flap were compared, there was no statistically significant difference among these measurements (p = 0.9). For the microkeratome group, CFT was 102.18 µm ± 5.63. There was statistically significant difference between the target flap thickness and the resultant flap thickness (p = 0.001). The central, nasal and temporal thicknesses were compared and there was a statistically significant difference (p = 0.000).

CONCLUSIONS

Our study is among few studies in the literature comparing femtosecond laser flap to SBK microkeratome flap. Femtosecond laser creates more predictable flap thickness and more uniform flap architecture. Trial registration Trial registration number: NCT04684888. Trial Registration date: December 2020. Registered at www.

CLINICALTRIALS

gov .

Posterior chamber toric implantable collamer lenses vs LASIK for myopia and astigmatism: systematic review

This systematic review compares the visual and refractive outcome of laser in situ keratomileusis with (toric) implantable collamer lens (ICL) in the treatment of myopic astigmatism. An electronic literature search led to 19 comparative articles. Refractive outcome, efficacy, safety, predictability, and stability as well as differences in contrast sensitivity and higher-order aberrations (HOAs) were analyzed for moderate (-3 to -6 diopters [D]) and high (≥-6 D) myopia. Results were either significantly in favor of (toric)-ICL or equal. Fewer HOAs and better contrast sensitivity after (toric)-ICL seem to be the largest asset in its refractive and clinical superiority. However, longer follow-up studies are indicated, specifically for systematically comparing long-term adverse effects.

Vector analysis of astigmatic correction after single-step transepithelial photorefractive keratectomy and femtosecond-assisted laser in-situ keratomileusis for low to moderate myopic astigmatism

Purpose

This study aimed to evaluate the outcomes of astigmatic correction by single-step transepithelial photorefractive keratectomy (TransPRK) and femtosecond-assisted laser in-situ keratomileusis (Femto-LASIK) surgeries.

Methods

A total of 218 subjects received TransPRK or Femto-LASIK surgery for the treatment of myopia and astigmatism (-2.25 to -0.25 D). Refraction errors and uncorrected (UDVA) and corrected distance visual acuity (CDVA) were examined before and at 3 months after surgery. Astigmatism changes were assessed by vector analysis.

Results

Preoperative parameters of the TransPRK group were similar to the Femto-LASIK group. UDVA and CDVA at 3 months were similar between both groups. Manifest refraction (MR) spherical equivalent in the TransPRK group (0 ± 0.20 D) was slightly lower compared with the Femto-LASIK group at 3 months (0.11 ± 0.25 D, P = 0.001). MR cylinder was -0.06 ± 0.19 D in the TransPRK group and -0.02 ± 0.15 D in the Femto-LASIK group at 3 months (P = 0.135). The index of success (IS) was 0.15 ± 0.36 in the TransPRK group and 0.06 ± 0.17 in the Femto-LASIK group (P = 0.125). The correction index (CI) was 1.03 ± 0.19 in the TransPRK group and 1.01 ± 0.11 in the Femto-LASIK group (P = 0.815).

Conclusion

For low to moderate myopic astigmatism, TransPRK provided a comparable astigmatic treatment effect as Femto-LASIK. Myopic astigmatism was both slightly overcorrected after TransPRK and Femto-LASIK surgeries.

Femtosecond Laser-Assisted Ophthalmic Surgery: From Laser Fundamentals to Clinical Applications

Femtosecond laser (FSL) technology has created an evolution in ophthalmic surgery in the last few decades. With the advantage of high precision, accuracy, and safety, FSLs have helped surgeons overcome surgical limits in refractive surgery, corneal surgery, and cataract surgery. They also open new avenues in ophthalmic areas that are not yet explored. This review focuses on the fundamentals of FSLs, the advantages in interaction between FSLs and tissues, and typical clinical applications of FSLs in ophthalmology. With the rapid progress that has been made in the state of the art research on FSL technologies, their applications in ophthalmic surgery may soon undergo a booming development.

Clinical Efficacy of Auricular Acupressure plus Eye Exercises in the Treatment of Adolescent Pseudomyopia

Objective

To assess the clinical efficacy of auricular acupressure plus eye exercises in the treatment of adolescent pseudomyopia, to discover an easier and safer way to treat pseudomyopia.

Methods

Forty adolescent patients with pseudomyopia were randomly recruited and assigned (1 : 1) to receive either eye exercises (single group, including 11 males and 9 females) or auricular acupressure plus eye exercises (combined group, including 12 males and 8 females). The clinical endpoint was the clinical efficacy after 28 days of treatment.

Results

The baseline characteristics of the combined group were comparable with those of the single group (P > 0.05). Auricular acupressure plus eye exercises was associated with a significantly higher clinical efficacy versus eye exercises alone (P < 0.05).

Conclusion

Ear acupressure plus eye exercises features promising clinical efficacy in the treatment of adolescent pseudomyopia, effectively arresting the progression of pseudomyopia to true myopia.

A trend of Medical Negligence in Laser Therapy in the Capital City: A Nine-Year Survey

Introduction: The purpose of the present study is to investigate the common causes of injuries, claims, and decisions related to laser therapy medical malpractice during a nine-year survey. Methods: The legal documents in the Coroner's Office of Forensic Medicine were investigated in a national database from 2012 to 2020 in Tehran, Iran. The frequency and nature of the cases, including the year of litigation, the location and certificate of the provider, the injury sustained, and the cause of legal action and judgment were collected. Results: Three hundred and eighty-three cases related to injury from laser therapy were registered in the coroner's Office of Forensic Medicine during the study period. The incidence of litigation related to laser surgery showed an increasing trend, with a peak occurrence in 2020. Laser hair removal was the most common (51.2%) litigated procedure. General practice operators (48%) recorded the highest rate of laser-related medical complaints. Lack of skill was the most common reason for failure. Among 383 cases with public decisions, 62.4% of them were fault liability in paid judgment. Conclusion: Medical claims related to laser application are increasing. However, as it is clear, the growth of laser technology and the increasing demand for lasers in medical science require more surveillance to avoid probable injuries and improve patient safety, especially surveillance of the physicians who work outside the scope of their specialty.

The impact of learning curve on flap thickness outcome in femtosecond laser assisted LASIK performed with new LenSx dual platform

Purpose

To evaluate the effect of learning curve on flap thickness (FT) outcome in femtosecond (FS) laser-assisted laser in situ keratomileusis (LASIK) operation for myopia performed with recently introduced LenSx dual platform using curved applanation cone.

Methods

Seventy eyes of 36 patients with myopia or myopic astigmatism operated with FS laser-assisted LASIK with recently introduced LenSx dual platform were evaluated in this retrospective study. Operations were divided into two groups: first 20 operations (20 eyes of 10 patients) and next 50 operations (50 eyes of 26 patients). Data on patient demographics, preoperative and postoperative keratometric and aberrometric parameters, and FT related outcome, including mean central FT, mean total FT, intra-FT range, and FT homogeneity were compared in study groups.

Results

Except for significantly lower preoperative steepest keratometry values in the next 50 operations versus first 20 operations (p = 0.033), no significant difference was noted between study groups in terms of preoperative and postoperative parameters. When compared to first 20 operations, next 50 operations were associated with significantly higher values for mean central FT (median, 123 μm vs. 114 μm; p = 0.007) and mean total FT (median, 123 μm vs. 113 μm; p = 0.015), whereas significantly lower intra-FT range (median, 4.0 μm vs. 4.5 μm; p = 0.003).

Conclusions

In conclusion, our findings related to FS laser-assisted LASIK surgery for myopia with new LenSx dual platform using curved applanation cone revealed significant impact of learning curve on the corneal FT outcome in terms of closer FT to the intended value and lower intra-flap range.

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.

Impact of femtosecond laser-assisted in situ keratomileusis on retinal ganglion cell function

PURPOSE

To analyse the effect of femtosecond laser-assisted in situ keratomileusis (FS-LASIK) on the electrical response of retinal ganglion cells using pattern electroretinography (pERG).

METHODS

This was a longitudinal, prospective, observational pilot study. We included consecutive myopic patients who underwent FS-LASIK to correct up to 6 dioptres of myopia and up to 2 dioptres of astigmatism. Patients with excessive blinking or tearing and those with Snellen uncorrected visual acuity less than 0.9 dec on postop day 1 were excluded. Diopsys NOVA^® (Diopsys Inc., NJ) pERG records, using high- and low-contrast patterns, were obtained 16 h and 1 month after FS-LASIK was performed. Magnitude (μV), Magnitude D (μV), Magnitude D/Magnitude ratio and signal-to-noise ratio (dB) were analysed. Wilcoxon test for nonparametric paired data was employed.

RESULTS

pERG data from 24 eyes were analysed from 24 patients who underwent FS-LASIK. Mean age was 35.79 ± 9.86 years. Mean preoperative refraction was -2.69 ± 7.6 D (spherical) and -0.38 ± 0.40 D (cylinder). Mean surgical time was 56.88 ± 7.6 s. No statistically significant differences were obtained for any of the studied parameters when comparing 16 h with 1 month after FS-LASIK, with the exception of Magnitude with low contrast, which increased from 1.21 ± 0.2 to 1.39 ± 0.29 µV at 16 h and 1 month postoperatively, respectively (p = 0.03).

CONCLUSIONS

FS-LASIK seems to induce a mild and transitory defect in retinal ganglion cell function. Only a mild decrease was detected in the magnitude value for low-contrast stimuli when pERG was performed 16 h postoperatively, and it returned to normal 1 month after surgery.

Outcomes of bioptics with small-incision lenticule extraction as a sequential treatment after implantable collamer lens for management of extreme myopia

PURPOSE

To study the safety and efficacy of bioptics using implantable collamer lens (ICL) followed by small-incision lenticule extraction (SMILE) for management of extreme myopia.

SETTING

Nethradhama Superspeciality Eye Hospital, Bangalore, India.

DESIGN

Retrospective case series.

METHODS

Data were analyzed for patients who underwent bioptics using ICL in the first stage and SMILE in the second stage for correction of the residual refractive error. The mean interval between stage 1 and stage 2 correction was 24.2 ± 13.33 days. The mean follow-up after the SMILE procedure was 12.26 ± 1.39 (range 11 to 14) months.

RESULTS

Fifteen eyes from 9 patients with mean age 26 ± 4.69 years were included. Preoperatively, the mean SE was -22.89 ± 3.04 diopter (D) (-16.50 to -28.00 D), which decreased to -3.40 ± 1.89 D after ICL and further reduced to -0.48 ± 0.24 D after final correction with SMILE, at the end of the mean follow-up. The mean cylinder reduced from -2.88 ± 1.69 D to -1.93 ± 1.07D post-ICL and to -0.38 ± 0.24 D post-SMILE surgery. The mean corrected distance visual acuity (CDVA) significantly improved from 0.38 ± 0.22 to 0.068 ± 0.09 logMAR after SMILE correction (P = .00). The mean uncorrected distance visual acuity (UDVA) at the end of follow-up was 0.15 ± 0.09 logMAR, with all eyes achieving UDVA of 0.3 logMAR or greater. All eyes had gain in CDVA, with 53% eyes gaining 2 or more lines. No wound-, intraocular pressure-, or ICL-related complications were observed during and after the SMILE surgery. No patient required spectacles, contact lenses, or enhancement for further improvement of vision.

CONCLUSIONS

Bioptics with SMILE after ICL implantation might be a valid option for extremely myopic patients, resulting in significant improvements in visual acuity and high patient satisfaction.

Laser refractive surgery in corneal dystrophies

Twenty-eight case reports and case series published between 2000 and 2019 concerning laser refractive surgery in patients with corneal dystrophies, resulting in 173 eyes from 94 patients, were included in this systematic review. Best results were achieved in posterior corneal polymorphous and Cogan dystrophy. Unfavorable results were found in Avellino dystrophy and Fuchs endothelial corneal dystrophy (FECD). Photorefractive keratectomy was not indicated in Meesmann and Avellino dystrophy. Laser in situ keratomileusis was indicated in posterior polymorphous corneal dystrophy but not in FECD, Avellino, or Cogan dystrophy. Small-incision lenticule extraction and other dystrophies such as lattice, fleck, Lisch, or François did not achieve enough scientific evidence to report any recommendation.

Advances in refractive corneal lenticule extraction

Refractive errors are the leading cause of reversible visual impairment worldwide. In addition to the desired spectacle independence, refractive procedures can improve quality of life, working ability, and daily working performance. Refractive corneal lenticule extraction (RCLE) is a relatively new technique, dependent only on a femtosecond laser (FS). This leads to potential benefits over laser-assisted in situ keratomileusis (LASIK) including a quicker recovery of dry eye disease, a larger functional optical zone, and no flap-related complications. SMILE, available with the VisuMax FS (Carl Zeiss Meditec AG, Jena, Germany), is the most established RCLE application, offering visual and refractive outcomes comparable to LASIK. SmartSight (SCHWIND eye-tech-solutions GmbH, Kleinostheim, Germany) and CLEAR (Ziemer Ophthalmic Systems AG, Port, Switzerland) are two new RCLE applications that received Conformité Européenne (CE) approval in 2020. In this article, we review refractive and visual outcomes, advantages, and disadvantages of RCLE and also report on the latest advances in RCLE systems.

Measurement of the Intraocular Pressure Elevation During Laser-Assisted In Situ Keratomileusis Flap Creation Using a Femtosecond Laser Platform

Purpose

The purpose of this study was to measure the intraocular pressure (IOP) elevation during laser assisted in situ keratomileusis (LASIK) flap creation using the WaveLight FS200 femtosecond (FS) laser platform.

Methods

We conducted an ex vivo experimental study in an animal model. The WaveLight FS200 FS laser platform was used to perform the corneal LASIK flap in freshly enucleated porcine eyes. We measured the changes in IOP from the application of the suction ring (suctioning phase) through the creation of the lamellar corneal flap (cutting phase). The IOP was recorded using a manometric technique with direct cannulation to the anterior chamber.

Results

Nine freshly enucleated porcine eyes were included in the study. The mean baseline IOP before the procedure was 20.33 ± 5.9 mm Hg. The mean IOP increase over baseline IOP was 32.33 ± 11.3 mm Hg at the suctioning phase, and 38.22 ± 11.3 mm Hg at the cutting phase. The total surgical time needed to complete the procedure was 29.5 ± 4.4 seconds.

Conclusions

The WaveLight FS200 FS laser platform produces a low to moderate increase in IOP during LASIK flap creation.

Translational Relevance

The WaveLight FS200 is a safe FS laser platform because it induces a low to moderate IOP increase during LASIK flap creation.

Three-Year Outcomes of Implantable Collamer Lens Followed by Excimer Laser Enhancement ("Bioptics") in the Treatment of High Myopic Astigmatism

Purpose

Describe three-year outcomes of spherical implantable Collamer lens (ICL) followed by excimer laser enhancement (bioptics) in eyes with high myopic astigmatism.

Patients and Methods

Retrospective case series of thirty-four cases that underwent bioptics enhancement at the Johns Hopkins Wilmer Eye Institute. All eyes had a preoperative sphere of −6.00 D or more with a cylinder of at least 2.00 D. Uncorrected and corrected distance visual acuity (UDVA and CDVA), manifest spherical equivalent refraction (MSE), ICL vault measurements and central corneal thickness (CCT) were collected. Endothelial cell counts (ECC), root mean square (RMS) of higher order aberrations (HOAs), adverse events and subsequent surgeries were also assessed.

Results

All patients had a minimum follow-up of 3 years. Preoperative UDVA was 2.29 ± 0.46 logMAR and improved to 0.03 ± 0.23 logMAR at 3 years (p<0.05). MSE was −12.30 ± 4.05 preoperatively and changed to −0.21 ± 0.46 at 3 years (p<0.05). The efficacy and safety indices were 1.28 ± 0.32 and 1.47 ± 0.27 at 3 years post-enhancement. HOA did not significantly change throughout the follow-up (p<0.05). Endothelial cell loss at 12 months was calculated at 5.7%. Two eyes required ICL exchange due to vault-related issues.

Conclusion

Bioptics offered excellent long-term safe, predictable, and efficient outcomes for high myopic astigmatism and can be considered an option if toric ICL is not available. Results confirm that wavefront-guided photoablation remains an excellent option to manage residual refractive error after phakic IOL.

Evolution of visual acuity, flap thickness, and optical density after laser in situ keratomileusis performed with a femtosecond laser

PURPOSE

To describe the postoperative evolution of visual acuity, flap morphology, and stromal optical density femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK).

SETTING

Clínica Rementería, Madrid, Spain.

DESIGN

Prospective case series.

METHODS

The study comprised 44 consecutive eyes that had FS-LASIK performed with the WaveLight FS200 and the Allegretto excimer laser to correct myopia. Visual outcomes, flap thickness, and stromal optical density were assessed 1 day, 1 week, 1 month, and 3 months postoperatively.

RESULTS

A statistically significant improvement in the mean uncorrected distance visual acuity at 1 day (0.94 ± 0.2) and 1 week (0.93 ± 0.2) to 1 month (1.04 ± 0.2) and 3 months (1.11 ± 0.1) postoperatively (P < .05). At 3 months postoperatively, the femtosecond laser had good outcomes in efficacy (0.98 ± 0.1), safety (0.98 ± 0.1), and predictability (100% of eyes were within ± 0.5 D of emmetropia). The femtosecond-created flaps were slightly thicker than intended, the mean SD intraflap was 7.1 μm, the range between the thickest and thinnest points in each flap was 25.4 μm, and the mean flap thickness homogeneity was 7.6 μm at 3 months postoperatively. A progressive decrease in the optical density of the flap stroma and the residual stromal bed was detected during follow-up.

CONCLUSIONS

The femtosecond laser study appears to be a safe, effective, and predictable platform to obtain LASIK flaps. The flaps were planar and homogeneous but slightly thicker than intended. The optical density of the flap stroma was slightly higher at early follow-up and decreased over time.

Impact of Refractive Outcomes on Bias in Follow-up and Completion of Patient-Reported Outcome Measures after Laser Vision Correction

PURPOSE

To examine factors contributing to completion of a patient-reported outcome (PRO) measure in patients undergoing laser vision correction.

DESIGN

Retrospective, population-based study.

PARTICIPANTS

All patients who underwent primary laser vision correction with a target of plano from July 1, 2014, to June 30, 2016, at a large refractive surgery center.

METHODS

Patients were asked to complete a PRO measure at the time of their preoperative and months 1 and 3 postoperative visits. Characteristics between patients who attended and did not attend the follow-up visits and completed and did not complete the PRO measure were compared. A logistic regression was performed to identify factors associated with likelihood of follow-up and completion of PRO measure. An inverse probability censoring weighted model was created to account for selective loss to follow-up and used to adjust the PRO satisfaction measure.

MAIN OUTCOME MEASURE

Completion of the PRO measure at 1 and 3 months.

RESULTS

A total of 37 043 patients were identified. Of these, 20 501 completed a 1-month postoperative PRO measure and 10 474 completed a 3-month postoperative PRO measure. Patients completing a PRO measure were more likely to be older, be female, have had photorefractive keratectomy (PRK), have completed a preoperative PRO measure, and have had a preoperative hyperopic correction (P < 0.001 for all comparisons). For every line of postoperative uncorrected acuity worse than 20/16, the odds ratio of completing a PRO measure was 1.33 (95% confidence interval [CI], 1.30-1.36, P < 0.001) at 1 month and 1.29 (95% CI, 1.26-1.33, P < 0.001) at 3 months. At 1 month, there was no difference between the raw and model-adjusted rates of satisfaction with vision, but at 3 months the adjusted rate was significantly higher than the raw rate.

CONCLUSIONS

Patients with worse objective visual outcomes were more likely to complete PRO measures in this population-based study. In a setting with loss to follow-up, PRO measures require methods to address missing data for correct interpretation.

Study of change in contrast sensitivity in relation to depth of ablation after wavefront optimized myopic laser-assisted in situ keratomileusis

Purpose:

The aim of this work was to study the change in contrast sensitivity (CS) in relation to depth of stromal ablation after wavefront-optimized (WFO) myopic laser in situ keratomileusis (LASIK).

Methods:

This was as prospective, longitudinal, comparative study. The study participants were divided into two groups: Group 1 ≤50 μ ablation depth; 60 eyes and group 2 >50 μ ablation depth; 60 eyes. All underwent WFO LASIK. Uncorrected and corrected distance visual acuity (UDVA and CDVA) and CS were measured preoperatively and postoperatively at 1 week, 2 weeks, and 2 and 6 months. Two-way repeated-measures analysis of variance (ANOVA), Unpaired t test and one-way repeated measures ANOVA were used to test differences across time periods within each treatment group. A value of P < 0.05 was considered as statistically significant.

Results:

The mean ablation depths in groups 1 and 2 were 39.30 μ ± 7.22 μ and 69.90 μ ± 12.09 μ, respectively; the maximum depth was 94.62 μ. In group 1, the preoperative mean CS was 1.91 ± 0.07, which improved postoperatively at 1 week (1.93 ± 0.06) and remained stable in subsequent follow-ups (1.94 ± 0.05). In group 2, the mean CS preoperatively was 1.87 ± 0.12, which postoperatively at 1 week and 6 months were 1.93 ± 0.07 and 1.94 ± 0.03, respectively (P < 0.05). Between the groups, preoperative CS was significantly different (P = 0.04), but the change in CS post-LASIK was insignificant (P > 0.05).

Conclusion:

There was a significant improvement in CS after WFO myopic LASIK in all patients irrespective of ablation depth (up to 94.62 μ).

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.

Comparison of clinical outcomes after femtosecond laser in situ keratomileusis in eyes with low or high myopia

AIM

To compare the clinical results of femtosecond (FS) laser in situ keratomileusis (LASIK) in high myopic patients and low myopic patients.

METHODS

This study included 212 myopic eyes undergoing LASIK using a VisuMax 500kHz FS laser. All treated eyes were assigned to one of two groups according to preoperative manifest spherical refraction: low myopia group (A, >-4.0 D) and high myopia group (B, ≤-4.0 D). Uncorrected and corrected distance visual acuity (UDVA, CDVA), refractive errors, and higher-order aberrations (HOAs) were measured preoperatively and 1wk, 1, 3 and 6mo postoperatively.

RESULTS

At 6mo of follow-up, 92% and 76% had a UDVA of 20/20 or better in group A and B, respectively (P=0.037) and UDVA was significantly different between two groups (P=0.042). Six and seven percentage lost one line of CDVA in group A and B, respectively (P=0.572) and no eyes in both groups lost more than two lines. Each group had 87% and 76% of treated eyes within ±0.5 D of the intended correction (P=0.186), and 13% and 43% with a change of >0.50 D in spherical equivalent from 1wk to 6mo postoperatively (P=0.005). In terms of postoperative astigmatism, each group had 89.1% and 76.6% within ±0.50 D, respectively and there was significant difference (P=0.006). Group A tends to induce smaller HOAs than group B.

CONCLUSION

FS LASIK is effective and safe for correcting high myopia as well as low myopia. However, high myopic eyes showed more postoperative astigmatism and HOAs which affect visual acuity.

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.

Refractive surgery beyond 2020

Refractive surgery refers to any procedure that corrects or minimizes refractive errors. Today, refractive surgery has evolved beyond the traditional laser refractive surgery, embodied by the popular laser in situ keratomileusis or 'LASIK'. New keratorefractive techniques such as small incision lenticule extraction (SMILE) avoids corneal flap creation and uses a single laser device, while advances in surface ablation techniques have seen a resurgence in its popularity. Presbyopic treatment options have also expanded to include new ablation profiles, intracorneal implants, and phakic intraocular implants. With the improved safety and efficacy of refractive lens exchange, a wider variety of intraocular lens implants with advanced optics provide more options for refractive correction in carefully selected patients. In this review, we also discuss possible developments in refractive surgery beyond 2020, such as preoperative evaluation of refractive patients using machine learning and artificial intelligence, potential use of stromal lenticules harvested from SMILE for presbyopic treatments, and various advances in intraocular lens implants that may provide a closer to 'physiological correction' of refractive errors.

Preliminary effects of treating the half of high latent hyperopia on refractive and visual results of femtosecond laser-assisted in situ keratomileusis in subjects with hyperopia

BACKGROUND

To evaluate the preliminary effects of treating the half of high latent hyperopia on refractive and visual outcomes of femtosecond laser-assisted in situ keratomileusis (LASIK) in young subjects with hyperopia.

METHODS

This non-randomized comparative study includes 120 eyes of 60 subjects who underwent femtosecond LASIK to correct hyperopia. Group 1 (n = 60) includes subjects with ≤ 1D algebraic difference (DRSE) between cycloplegic (CRSE) and manifest (MRSE) refraction spherical equivalents and was treated by entering manifest refraction values. Group 2 includes subjects with > 1D DRSE and was treated by entering the mean manifest and cycloplegic refraction values. Refractive and subjective outcomes obtained at the 1-, 3-, and 6-month postoperative visits were compared.

RESULTS

The mean age of the subjects was 26.2 ± 3.5 and 26.2 ± 5.2 years for Group 1 and Group 2, respectively. The male-to-female ratios were 10/10 in both groups. Demographic values of the groups were similar (p > 0.05). Preoperative MRSE values were similar (p = 0.924), while CRSE and DRSE values were significantly higher in Group 2 (p < 0.001). At the 1- and 3-month postoperative visits, MRSE was higher and uncorrected distance visual acuity (UDVA) was lower in Group 2 (p < 0.001). Subjective visual parameters and quality of vision scores were also worse in Group 2 during these visits (p < 0.001); however, at the 6-month visit, all outcomes for Group 2 improved, and MRSE, UDVA, some subjective visual parameters, and quality of vision scores became similar between groups (p > 0.05).

CONCLUSION

At the 6-month visit after treating the half of > 1D latent hyperopia with femtosecond LASIK, refractive and visual outcomes like MRSE, UDVA, subjective visual parameters, and quality of vision scores become similar to those obtained in ≤ 1D latent hyperopia.

Comparison of choroidal thickness in high myopic eyes after FS-LASIK versus implantable collamer lens implantation with swept-source optical coherence tomography

AIM

To investigate the changes in choroidal thickness (CT) in high myopic eyes after femtosecond laser-assisted in situ keratomileusis (FS-LASIK) surgery or central hole implantable collamer lens (ICL V4c) implantation using swept-source optical coherence tomography (SS-OCT).

METHODS

We examined the right eyes of 116 patients with high myopia who were candidates for FS-LASIK surgery and ICL implantation. Sixty eyes underwent ICL V4c implantation and 56 eyes were subjected to FS-LASIK surgery. The CT was measured with SS-OCT. All data were recorded preoperatively and 2h, 1wk, 1 and 3mo postoperatively. Other demographic information was collected, including age, sex, uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), spherical equivalent (SE), intraocular pressure (IOP) and axial length (AL).

RESULTS

The UCVA improved in both groups and showed no significant differences between groups. There also were no significant differences between the two groups in postoperative BCVA and SE (P=0.581 and 0.203, respectively). The foveal CTs, inner nasal and outer nasal CTs were significantly thicker at 2h postoperatively in both groups (P<0.05) but returned to baseline levels in 1wk; after 1mo, no significant differences were found relative to the preoperative values. At 3mo in each group, nine regions showed variations in the CT as compared with preoperative thickening, but only the foveal and nasal area CTs preoperative differences were statistically significant (P<0.05). In addition, there was no significant difference in 9 regions of CT between the two groups at all follow-up times (P>0.05).

CONCLUSION

The CTs after ICL implantation and FS-LASIK surgery are significantly thicker than those before operation, especially in the foveal and nasal areas, but there is no significant difference between the two methods.

Comparison of FDA-Reported Visual and Refractive Outcomes of the Toric ICL Lens, SMILE, and Topography-Guided LASIK for the Correction of Myopia and Myopic Astigmatism

PURPOSE

To compare U.S. Food and Drug Administration (FDA)-reported visual and refractive outcomes following surgical correction of myopia and myopic astigmatism using the Visian Toric Implantable Collamer Lens (STAAR Surgical, Monrovia, CA) (Toric ICL), small incision lenticule extraction (SMILE), and topography-guided laser in situ keratomileusis (TG-LASIK).

METHODS

FDA summary of safety and effectiveness data (SSED) were analyzed for each of the three platforms. Primary outcomes measured were efficacy, safety, stability, and accuracy of refractive correction. Stratified mean refractive spherical equivalent (MRSE) data were assessed.

RESULTS

One hundred twenty-four Toric ICL patients (210 eyes), 357 SMILE patients (357 eyes), and 212 TG-LASIK patients (249 eyes) were included. SMILE eyes had a significant improvement in postoperative uncorrected distance visual acuity with respect to preoperative corrected distance visual acuity from 3 to 12 months (P < .001), whereas TG-LASIK had no further improvement from 3 to 12 months (P = .79). For preoperative MRSE greater than 10.00 diopters (D), there was a significant difference in the percentage of eyes achieving postoperative MSRE within ±0.50 D between Toric ICL (66%) and SMILE (100%) (P < .001). SMILE was consistently more accurate than Toric ICL for cylinder within ±0.25 D (P < .001), ±0.50 D (P < .001), and ±1.00 D (P = .0014).

CONCLUSIONS

All three platforms analyzed in this study had excellent efficacy, safety, stability, and accuracy. Stratified analysis revealed that SMILE may be comparable to Toric ICL for patients with high myopia or myopic astigmatism, and SMILE may have a longer visual recovery compared to TG-LASIK than previously indicated. [J Refract Surg. 2019;35(11):699-706.].

A quantitative evaluation of the use of medical lasers in German hospitals

The laser has become an integral part of modern medicine, procedures based on this technique have found their way into a multitude of medical disciplines. There is, however, no data available on the detailed quantitative development of laser use in the medical sector. This fact gave rise to the idea of the present study, which analyzed the raw data of the quality report of German hospitals with respect to this subject. Over the 9 years of report, a steady increase in the cumulative number of cases was evident, although not all body regions in which the medical laser is used followed this trend. The CO₂ laser was found to be the most commonly applied laser, even though a large spectrum of different laser types is used. Based on the present study, the importance of the laser for medical purposes can be confirmed.

Results of laser enhancement for residual myopia after primary laser in situ keratomileusis

PURPOSE:

The purpose of the study is to evaluate and analyze the results and outcomes after laser enhancement for residual myopia after primary laser in situ keratomileusis (LASIK).

MATERIALS AND METHODS:

This retrospective interventional consecutive case series clinical study was performed on 112 consecutive eyes (82 patients) that had undergone primary LASIK before the enhancement procedure. The study was done in the Refractive Surgery Unit in Yemen Magrabi Hospital between 2006 and 2014. The retreatment was for residual myopia with or without astigmatism. Either the original flap was lifted or surface ablation was performed. Parameters evaluated were uncorrected visual acuity (UCVA) and best spectacle-corrected visual acuity (VA), spherical equivalent (SE) refraction, corneal topography, and pachymetry. Complications after laser enhancement were also evaluated.

RESULTS:

Mean age of the study group was 26.72 ± 6.89 years (range from 18 to 44 years). Males accounted for 37/82 (45.1%) and females for 45/82 (54.9%). The right eye was treated in 67/112 (59.8%) and the left eye in 45/112 (40.2%). Before primary LASIK, the mean SE (MSE) was −5.78 ± 1.89 D. Before enhancement, the MSE was −1.32 ± 0.61 D (range −3.25 D to −0.50 D), and none of the eyes had an UCVA of 20/40 or better. Twelve months after retreatment, the percentage of eyes having UCVA of 20/40 or better increased to 67.9% (76 of 112). There were no vision-threatening complications seen.

CONCLUSION:

Retreatment or enhancement after LASIK surgery by lifting the original flap or surface ablation is a safe and effective method for the treatment of regressed or undercorrected myopia. The risk of postoperative complications is very minimal.

Corneal Ectasia Risk And Percentage Tissue Altered In Myopic Patients Presenting For Refractive Surgery

Purpose

A percentage tissue altered (PTA) score of ≥40% has been advocated as an independent indicator of post-operative ectasia risk following laser in-situ keratomileusis (LASIK). This study was performed to test the hypothesis that refractive procedures, such as laser-assisted sub-epithelial keratectomy (LASEK) or small incision lenticule extraction (SMILE), may alter the range of PTA, within which refractive corneal surgery can be safely performed.

Setting

Refractive department, tertiary ophthalmic hospital.

Design

Retrospective observational study.

Methods

Review of case notes was performed for patients who presented for refractive surgeries, other than LASIK. To determine the risk of corneal ectasia for each patient prior to refractive surgery, we estimated what each patient’s PTA would have been if they had undergone LASIK. The Randleman Ectasia Risk Score System (ERSS) was also calculated.

Results

114 eyes (66 patients) were included. 94 eyes underwent SMILE. 20 eyes underwent LASEK. A significant proportion of eyes had PTA ≥40% – SMILE eyes: up to 31.9%, LASEK eyes: up to 60.0% (at presumed LASIK flap of 120 μm). The maximum calculated PTA was up to 47.9% in the SMILE group and up to 51.5% in the LASEK group. Using ERSS, 12.8–16% of SMILE eyes and 15.0–80.0% of LASEK eyes would have been considered to have moderate-to-high ectasia risk. No post-surgical ectasia was observed at 3 years.

Conclusion

SMILE and LASEK alter the range of PTA, within which corneal refractive surgery may be performed with a lower risk of developing post-operative corneal ectasia; a safe PTA threshold needs to be determined for these procedures before recommendations for clinical practice can be made.

Excimer Laser Correction of Myopia Using Aspheric Technology. Literature Review

The article presents a literature review of scientific sources on the use of aspheric technology for the correction of refractive errors at the present stage of development of excimer laser surgery. The article highlights the pressing challenge of developing algorithms that improve quality indicators, maintaining subtle visual functions (low-contrast visual acuity, visual acuity in various illuminating conditions) after excimer laser correction of ametropy. The literature data on the etiology of visual acuity reduction after refractive operations are given. Special consideration is given to the description of asphericity indicators by the researchers, the importance of influence of the indicators on the qualitative characteristics of vision. The mechanism of influence of the modified aberration balance of the cornea after refractive interventions on the indicators of spatial-contrasting characteristics of vision in refractive patients is clarified; the importance of evaluating these indicators before and after refractive surgeries is emphasized. The types of aspherical ablation algorithms used in modern, both foreign and domestic, excimer laser systems, and their differences are described. Advantages and disadvantages of the aspherical algorithms used have been analyzed, historical evolution of the software that was developed and introduced into the new excimer laser systems for aspherical operations has been traced. Fundamental difference between aspheric ablation optimized with respect to wavefront with average asphericity index, introduced by the manufacturer of the facility, and the algorithm, where aspheric ablation is performed with personalized Q-factor, which can be controlled by the surgeon himself, is presented in detail. The problem of developing optimized technology of aspheric ablation algorithm in correcting myopia due to the existence of restrictions on the use of aspheric techniques on domestic “Microscan-VIZUM” excimer laser unit is emphasized.

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.

The effect of different optical zone diameters on the results of high-order aberrations in femto-laser-assisted in situ keratomileusis

PURPOSE

To evaluate the postoperative high-order aberration differences of femto-LASIK surgery in 6.5 and 7 mm optic zones.

PATIENTS AND METHODS

We retrospectively reviewed 80 eyes of 40 patients with myopia or myopia with astigmatism who underwent femtosecond LASIK surgery. Q values, z3, 3 (h. trefoil), z3, -3 (v. trefoil), z3, 1 (h. coma), z3, -1 (vertical coma), z4, 0 (spherical aberration), z5, -1 (second other v. coma), aberration coefficients were evaluated 3 months after surgery. Central corneal thicknesses, intraocular pressures, patient ages and genders, optical zone diameters and ablation depths are collected from patients' medical records.

RESULTS

The mean age was 28.4 ± 0.69 years (range, 20-47 years). Lower z4, 0 spherical aberrations and aberration coefficient values were associated with larger optical zones (7 mm) (z4, 0 spherical aberrations = 1.25, p = 0.01; coefficient value = -1.21, p < 0.01). Although a smaller optical zone (6.5 mm) was associated with an increase in most of the wave-front aberration variables, measurements were not statistically different between the two groups other than z4, 0 spherical aberrations and aberration coefficients.

DISCUSSION

LASIK treatment with 6.5 and 7 mm optical zones is safe and effective for correcting myopia and myopic astigmatism and has statistically similar visual outcomes. Moreover, larger optical zone (7 mm) was found to be associated with lower spherical aberration induction and smaller aberration coefficient values compared to 6.5 mm optical zone. This can be important for decision-making in femto-LASIK surgery for better postoperative results.

Comparison of Laser In Situ Keratomileusis Flap Morphology and Predictability by WaveLight FS200 Femtosecond Laser and Moria Microkeratome: An Anterior Segment Optical Coherence Tomography Study

PURPOSE

To evaluate laser in situ keratomileusis (LASIK) flap thickness predictability and morphology by femtosecond (FS) laser and microkeratome (MK) using anterior segment optical coherence tomography.

METHODS

Fifty-two candidates for the LASIK procedure were stratified into two groups: FS laser-assisted (Allegretto FS-200) and MK flap creation (Moria 2). Flap thickness was determined at five points. The side-cut angle was measured in three directions at the margin interface. LASIK flap assessment was performed one month postoperatively by Spectralis anterior segment optical coherence tomography.

RESULTS

Fifty-two patients (93 eyes) were recruited; 49 eyes were stratified to the FS group and 44 eyes to the MK group. The FS group had relatively even flap configurations, and the MK group had meniscus-shaped flaps. Mean differences between planned and actual flap thickness were 12.93 ± 8.89 and 19.91 ± 5.77 μm in the FS and MK groups, respectively. In thin flaps (100 to 110 μm), there was a significant disparity between the two groups (7.80 ± 4.71 and 19.44 ± 4.46 μm in the FS and MK groups, respectively). However, in thicker flaps (130 μm), comparable flap thickness disparity was achieved (18.54 ± 9.52 and 20.83 ± 5.99 μm in the FS and MK groups, respectively). Mean side-cut angle was 74.29 ± 5.79 degrees and 32.34 ± 4.94 degrees in the FS and MK groups, respectively.

CONCLUSIONS

Comparable flap thickness predictability was achieved in thicker flaps (130 μm), while the FS laser technique yielded a more predictable result in thinner flaps (100 to 110 μm). Different flap morphology was observed in meniscus flaps in MK-LASIK and flap morphology in FS-LASIK.

Refractive surgery

Refractive surgery has evolved beyond laser refractive techniques over the past decade. Laser refractive surgery procedures (such as laser in-situ keratomileusis), surface ablation techniques (such as laser epithelial keratomileusis), and photorefractive keratectomy have now been established as fairly safe procedures that produce excellent visual outcomes for patients with low-to-moderate amounts of ametropia. Additionally, a broader selection of options are now available to treat a wider range of refractive errors. Small incision lenticule extraction uses a femtosecond laser to shape a refractive lenticule, which is removed through a small wound. The potential advantages of this procedure include greater tectonic strength and less dry eye. In the future, intracorneal implants could be used to treat hyperopia or presbyopia. Phakic intraocular implants and refractive lens exchange might be useful options in carefully selected patients for correcting high degrees of ametropia. Thus, physicians are now able to provide patients with the appropriate refractive corrective option based on the individual's risk-benefit profile.

Femtosecond-assisted laser in situ keratomileusis for high myopia correction: Long-term follow-up outcomes

OBJECTIVE

Report the outcomes of laser in situ keratomileusis (LASIK) for high myopia correction after long-term follow-up.

METHODS

Retrospective, consecutive, clinical study including 70 eyes that underwent LASIK using a 500 Hertz (Hz) repetition rate excimer laser and femtosecond technology for flap creation. Visual, refractive, corneal aberrations, and correlation among the variables were evaluated during 3 years. In addition, 34 eyes were followed during 5 years.

RESULTS

Significant improvement of 17 logMAR lines was observed in uncorrected vision at 5 years (p < 0.01). This was consistent with spherical equivalent reduction that came from mean preoperative -7.79 diopters (D) to 5 years postoperative -0.24 D (p < 0.01). Significant induction of primary spherical aberration and coma aberration was also found (p < 0.01) at 3 months with levels of 0.61 µm and 0.47 µm, respectively, with no further changes at 5 years (p > 0.05). Pearson correlation showed that the amount of high-order aberrations at 3 months postoperativeley was significantly correlated with the changes in the keratometry throughout the 5 years (delta K) (R2 0.242 p = 0.05). Finally, preoperative corneal asphericity showed an inverse correlation with the delta K (R2 -308 p = 0.01).

CONCLUSIONS

Results from this study suggests that LASIK for high myopia correction using 500 Hz repetition rate excimer laser provides stable visual, refractive and aberrometric results after 5 years of follow-up. A more prolate cornea and the amount of higher-order aberrations induced after LASIK are factors that negatively impact in the long-term stability of the procedure.

Recurrent corneal erosion: a comprehensive review

Purpose

To comprehensively review the literature regarding recurrent corneal erosion (RCE) and to present treatment options and recommendations for management.

Overview

RCE usually presents with sharp, unilateral pain upon awakening, in an eye with an underlying basement membrane dystrophy, prior ocular trauma, stromal dystrophy or degeneration, or prior surgery for refractive errors, cataracts, or corneal transplantation. Making the correct diagnosis requires a careful slit-lamp examination of both eyes coupled with a high degree of suspicion. Several treatments are commonly used for RCE but new therapies have been introduced recently. Conservative treatment consists of antibiotic and preservative-free lubricating drops, with topical cycloplegics and oral analgesics to control pain. Patients who are unresponsive to these therapies may benefit from therapeutic bandage contact lenses (BCL). Newer therapies include oral matrix metalloproteinase (MMP) inhibitors, blood-derived eye drops, amniotic membrane graft application, and judicious application of topical corticosteroids. Once the epithelium is healed, a course of hypertonic saline solution and/or ointment can be used. Surgical procedures may be performed in patients who fail conservative therapy. Punctal occlusion with plugs increases the tear film volume. Epithelial debridement with diamond burr polishing (DBP), anterior stromal puncture (ASP), or alcohol delamination should be considered in selected patients. DBP can be used for patients with basement membrane dystrophies and is the preferred treatment overall due to a low recurrence rate. ASP can be used for erosions outside the central visual axis. Excimer laser phototherapeutic keratectomy is an attractive option in eyes with central RCE since it precisely removes tissue while preserving corneal transparency. In patients with RCE who are also candidates for refractive surgery, photorefractive keratectomy can be considered.

Summary

Newly introduced therapies for RCE enable therapy to be individualized and lower the recurrence rate.

Under-the-Flap Crosslinking and LASIK in Early Ectasia with Hyperopic Refractive Error

Purpose

To present safety, efficacy, and early results of a new combinational treatment for early corneal ectasia with hyperopic refractive error aimed to reinstate emmetropia and stabilize cornea.

Method

This is a retrospective case series. All surgeries were performed at the Beirut Eye Specialist Hospital, Lebanon. Surgical procedure consisted of (1) lifting flap (post-LASIK ectasia)/creation of corneal flap (keratoconus), (2) application of excimer laser ablation to correct refractive error, (3) loose repositioning of flap, (4) under-the-flap irrigation with riboflavin 0.1% dextran solution, and (5) application of UVA light.

Results

A total of 7 eyes (4 patients; mean age 24.25 years; all male) were included. 2 patients had early keratoconus, and 2 patients had early post-LASIK ectasia. Pretreatment vs. last postoperative follow-up visit (mean 11.25 months; range 6–15 months) UDVA (logMAR), spherical equivalent (SE) (D), astigmatism (D), and central pachymetry (µm) were 0.35 ± 0.18 vs. 0.05 ± 0.07, p=0.017; −0.81 ± 0.67 vs. −0.46 ± 0.57, p=0.078; 2.46 ± 0.53 vs. 0.68 ± 0.28, p=0.018; and 547 ± 58 vs. 536 ± 49, p=0.07, respectively. In all eyes, BCVA was 0.1 logMAR or better before and after treatment. No eye showed a decrease in BCVA. Two eyes of one patient had an epithelial ingrowth, which was removed in one case. Follow-up results showed no major complications and no progression of corneal ectasia.

Conclusion

Early results showed that under-the-flap CXL with excimer laser correction is an effective treatment for early hyperopic keratectasia, with the advantage of rapid recovery, postoperative corneal stability, and no epithelial healing complications. The procedure seems to bear a risk for postoperative epithelial growth into the flap interface.

Intraocular pressure changes in eyes with small incision lenticules and laser in situ keratomileusis

BACKGROUND

Measuring intraocular pressure after refractive surgery is a challenge in the diagnosis, evaluation, and treatment of glaucoma. Intraocular pressure characteristics after laser in situ keratomileusis (LASIK) are well known. However, intraocular pressure measurement and characteristics after small incision lenticule extraction (SMILE) are still unknown, providing an interesting point of comparison in terms of biomechanical differences from LASIK.

METHODS

An intraocular pressure analytical model utilising fluid dynamics (simulating air puff) was developed using OpenFoam and Scilab. In addition, solid mechanics (simulating the deformation of the corneal structure) and a ray-tracing technique (simulating applanation detection) simulated by a previously established air-puff Tonovue tonometer were used to simulate post-SMILE and post-LASIK intraocular pressure.

RESULTS

Based on the proposed model, while at a myopic correction of zero dioptres the difference in intraocular pressure before and after SMILE was 0 mmHg, whereas the difference before and after LASIK was -2.2 mmHg. This trend was observed with a myopic correction up to 12 dioptres.

CONCLUSION

In a numerical simulation, differences in intraocular pressure in LASIK and SMILE largely resulted from the completeness of the Bowman's membrane resulting from cap or flap creation.

Comparison Between Q-Adjusted LASIK and Small-Incision Lenticule Extraction for Correction of Myopia and Myopic Astigmatism

PURPOSE

To compare Q-adjusted femtosecond-assisted laser in situ keratomileusis (FS-LASIK) and small-incision lenticule extraction (SMILE) in terms of safety, efficacy, and predictability, as well as in terms of changes in dry eye parameters, corneal biomechanics, higher-order aberrations (HOAs), and corneal asphericity.

METHODS

A total of 60 eyes were enrolled in this prospective comparative study: 30 underwent SMILE and 30 underwent FS-LASIK. Changes in manifest refraction, uncorrected distance visual acuity and corrected distance visual acuity, corneal topography, corneal hysteresis (CH), and corneal resistance factor (CRF) (Ocular Response Analyzer, ORA), and dry eye parameters were evaluated during a 3-month follow-up.

RESULTS

Mean manifest refraction spherical equivalent (MRSE) was -4.17 (±1.86) preoperatively in FS-SMILE group and -3.97 (±2.02) in FS-LASIK group (P=0.69). Mean postoperative MRSE in FS-SMILE group was -0.25±0.38 diopter (D) and -0.183±0.33 D in FS-SMILE group (P=0.50). A total of 93% of treated eyes in both groups had a MRSE within ±0.5 D. The mean percentage change of CH was 14.23±17.59 and 18.89±7.2 mm Hg (P=0.1871) in FS-SMILE and FS-LASIK groups, respectively. The mean percentage change of CRF was 27.43±16.8 and 21.32±17.1 mm Hg (P=0.1682) in FS-SMILE and FS-LASIK groups, respectively. A statistically significant difference between techniques were found in the values of Schirmer test (P=0.0002) and tear breakup time (P=0.0035). Regarding corneal HOAs, no statistically significant differences between groups were found in the change in the root mean square of HOAs (P=0.2), coma aberration (P=0.0589), and spherical aberration (P=0.0543).

CONCLUSION

SMILE is as safe and predictable as FS-LASIK. According to the ORA system, SMILE is not better than FS-LASIK in terms of biomechanical changes. However, SMILE causes less effect on dry eye parameters during the first 3 postoperative months.