Improved Safety in Contemporary LASIK

Flap amputation for long-standing post-LASIK flap dislocation with epithelial ingrowth

A man aged 26 years presented with complaints of diminution of vision in his right eye for 1 year following a fist injury. He had a history of laser-assisted in situ keratomileusis in both eyes 5 years earlier. On examination, his uncorrected distance visual acuity (UDVA) in the right eye was 1.0 logMAR. Slit-lamp examination of the right eye revealed a superotemporal dislocation of the flap with coexisting epithelial ingrowth encroaching the pupillary area. Due to the presence of long-standing fixed flap folds, a flap amputation was performed along with removal of the epithelial ingrowth using 0.02% mitomycin C as adjunct. Postoperatively, the UDVA was 0.3 logMAR on day 1, which improved to 0.2 logMAR at 1 week. At 1 year, the UDVA was 0.2 logMAR improving to 0.1 logMAR with refraction, with minimal paracentral corneal haze and no signs of corneal ectasia.

Characteristics, Behaviors, and Awareness of Contact Lens Wearers Purchasing Lenses Over the Internet

OBJECTIVES

To describe the characteristics and hygiene habits of contact lens (CL) wearers who acquire CLs over the Internet, as well as their awareness of modifiable risk factors (RFs).

METHODS

A web-based survey was conducted among clients of an online CL sales platform during 6 months. Demographic data, CL hygiene-related awareness, and compliance were collected and analyzed.

RESULTS

The questionnaire was completed by 1,264 CL wearers: the average age was 40.8 years; most were women (71.1%), had myopia (76.4%), and wore monthly disposable CLs (63.6%). The frequency of eye examination was significantly lower among those buying the CL exclusively online (15.8% vs. 6.6%, P<0.001) and those who had begun CL use on their own (17.5% vs. 8.8%, P<0.001). Initiation to CL wear without the intervention of an eye care practitioner was more frequent in wearers with less experience. Common risk behaviors included water exposure (68.1% in swimming and 64.9% in the shower), use of the case (61.9%) and CL (65.1%) beyond the recommended replacement time, and reuse of the maintenance solution (31.9%). Ignorance of recommended hygiene increased the probability of risky behavior.

CONCLUSION

There were no differences in compliance or awareness of risks between those purchasing exclusively online and other CL wearers. However, the growing frequency of self-taught initiation in CL wear among less-experienced online customers and online exclusive purchase was associated with a decrease in eye examination frequency and therefore worse compliance and increased risks. This finding underlines the importance of publicizing correct hygiene habits by all possible means so as to increase compliance.

Pyramidal Aberrometry in Wavefront-Guided Myopic LASIK

PURPOSE

To evaluate measurement repeatability and clinical results for pyramidal aberrometry in routine myopic wavefront-guided laser in situ keratomileusis (LASIK).

METHODS

Results from 265 consecutive eyes treated with myopic wavefront-guided LASIK using the Amaris 1050RS Excimer Laser and Peramis pyramidal aberrometer (SCHWIND eye-tech-solutions GmbH) were reviewed. Limits of repeatability were calculated for the aberrometric refraction spherical equivalent and higher order aberrations for the Peramis aberrometer using results from three consecutive scans acquired preoperatively and postoperatively for the first 100 eyes treated.

RESULTS

The 95% limits of repeatability for pyramidal aberrometric measurement were: 0.3 diopters (D) for sphere, 0.2 D for cylinder, and 0.1 D (dioptric equivalent) for 3rd and 4th order aberration indices. A total of 95% of eyes were within ±0.50 D of the manifest refraction spherical equivalent target postoperatively. Uncorrected distance visual acuity was 20/20 or better in 96% of 232 eyes with a plano refraction target outcome. A total of 97% of eyes had a refraction cylinder of 0.50 D or less. No eyes lost one or more line of corrected distance visual acuity.

CONCLUSIONS

These data demonstrate good measurement repeatability, safety, and efficacy for pyramidal aberrometry in routine myopic LASIK. [J Refract Surg. 2020;36(7):442-448.].

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.

Contralateral Eye Comparison Between Femtosecond Small Incision Intrastromal Lenticule Extraction at Depths of 100 and 160 μm

PURPOSE

To compare the visual results, higher-order aberrations, and corneal biomechanical properties of femtosecond small incision lenticule extraction (SMILE) at depths of 100 and 160 μm.

METHODS

A prospective comparative interventional clinical trial of a series of patients who underwent SMILE. In the right eye, a refractive lenticule was created at a depth of 100 μm, and in the left eye, a depth of 160 μm was used. Manifest refraction, uncorrected visual acuity, total high-order aberrations (THOA), and corneal biomechanical properties of both eyes were evaluated 1 month postoperatively.

RESULTS

Thirty patients with bilaterally stable refractive errors were included in this study. One month postoperatively, mean corneal hysteresis was 9.71 ± 0.68 in the right eyes and 9.97 ± 0.77 in the left eyes, whereas the mean corneal resistant factor was 9.13 ± 1.04 and 9.31 ± 0.92 in the right and left eyes, respectively. Both corneal hysteresis and corneal resistant factor showed statistically significantly higher values in the left eyes (lenticule at a depth of 160 μm). No statistically significant differences were found between the right and the left eyes regarding manifest refraction, uncorrected visual acuity, and THOA.

CONCLUSIONS

Creating the refractive lenticule at a depth of 160 μm in SMILE had less effect on the corneal biomechanics than did creating a lenticule at a depth of 100 μm with no statistically significant differences in the refractive outcome and THOA between both groups.

Multiple regression analysis in nomogram development for myopic wavefront laser in situ keratomileusis: Improving astigmatic outcomes

PURPOSE

To describe and evaluate a new multiple regression-derived nomogram for myopic wavefront laser in situ keratomileusis (LASIK).

SETTING

Moorfields Eye Hospital, London, United Kingdom.

DESIGN

Prospective comparative case series.

METHODS

Multiple regression modeling was used to derive a simplified formula for adjusting attempted spherical correction in myopic LASIK. An adaptation of Thibos' power vector method was then applied to derive adjustments to attempted cylindrical correction in eyes with 1.0 diopter (D) or more of preoperative cylinder. These elements were combined in a new nomogram (nomogram II).

RESULTS

The 3-month refractive results for myopic wavefront LASIK (spherical equivalent ≤11.0 D; cylinder ≤4.5 D) were compared between 299 consecutive eyes treated using the earlier nomogram (nomogram I) in 2009 and 2010 and 414 eyes treated using nomogram II in 2011 and 2012. There was no significant difference in treatment accuracy (variance in the postoperative manifest refraction spherical equivalent error) between nomogram I and nomogram II (P = .73, Bartlett test). Fewer patients treated with nomogram II had more than 0.5 D of residual postoperative astigmatism (P = .0001, Fisher exact test). There was no significant coupling between adjustments to the attempted cylinder and the achieved sphere (P = .18, t test).

CONCLUSIONS

Discarding marginal influences from a multiple regression-derived nomogram for myopic wavefront LASIK had no clinically significant effect on treatment accuracy. Thibos' power vector method can be used to guide adjustments to the treatment cylinder alongside nomograms designed to optimize postoperative spherical equivalent results in myopic LASIK. mentioned.

Fifteen years follow-up of photorefractive keratectomy up to 10 D of myopia: outcomes and analysis of the refractive regression

PURPOSE

To evaluate outcomes of photorefractive keratectomy up to -10.00 D of myopia and -4.50 of astigmatism and to develop a predictive model for the refractive changes in the long term.

SETTING

Vissum Corporation and Miguel Hernandez University (Alicante, Spain).

DESIGN

Retrospective-prospective observational series of cases.

METHODS

This study included 33 eyes of 33 patients aged 46.79±7.04 years (range 40-57) operated with the VISX 20/20 excimer laser with optical zones of 6 mm. No mitomycin C was used in any of these cases. The minimum follow-up was 15 years. The main outcome measures were: uncorrected and corrected distance visual acuity, manifest refraction and corneal topography. Linear regression models were developed from the observed refractive changes over time.

RESULTS

Safety and efficacy indexes at 15 years were 1.18 and 0.83, respectively. No statistically significant differences were detected for any keratometric variable during the follow-up (p≥0.103). 15 years after the surgery 54.55% of the eyes were within ±1.00 D of spherical equivalent and 84.85% within ±2.00 D. The uncorrected distance visual acuity at 15 years was 20/25 or better in 60.6% of the eyes and 20/40 or better in 72.73% of the eyes. The correlation between the attempted and the achieved refractions was r=0.948 (p<0.001) at 1 year, and r=0.821 (p<0.001) at 15 years. No corneal ectasia was detected in any case during the follow-up.

CONCLUSIONS

Photorefractive keratectomy is a safe refractive procedure in the long term within the range of myopia currently considered suitable for its use, although its efficacy decreases with time, especially, in high myopia. The model developed predicts a myopic regression of 2.00 D at 15 years for an ablation depth of 130 µm.

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.

A 10-year prospective audit of LASIK outcomes for myopia in 37,932 eyes at a single institution in Asia

PURPOSE

This study evaluates the efficacy, predictability and safety of LASIK surgery as a treatment for myopia performed as part of a large-scale, prospective clinical audit spanning 10 years in an Asian study population and to evaluate the outcomes and trends.

DESIGN

Prospective, nonrandomized, single-center, multisurgeon study.

PARTICIPANTS

We included 37,932 eyes of 19,753 patients that underwent myopic LASIK at the Singapore National Eye Centre between 1998 and 2007.

METHODS

All eyes underwent LASIK as a treatment for myopia. Pre- and postoperative refractions, uncorrected visual acuity (UCVA), and best-corrected visual acuity (BCVA) were documented.

MAIN OUTCOMES MEASURES

Safety, efficacy, refractive predictability, treatment trends, retreatment rates, and complications for mild, moderate, and high myopia according to spherical equivalence (SE) of less than -5.00 diopters (D), -5.00 D or more to less than -10.0 D, and -10.00 D or more, respectively.

RESULTS

Patients' median age was 32 years (mean, 33.0+/-7.9 years); there were 6832 males (34.6%) and 12,921 females included. Patients were predominantly ethnic Chinese (90.5%). Mean follow-up time was 68.8 days. The mean spherical error corrected was -5.90+/-2.57 D (median, -5.625 D), and outcomes were categorized into low, moderate, or high myopia. The UCVA achieving > or =20/40 has been consistently above 90% since 2000, with 72.8% achieving > or =20/20. More than 93.0% of eyes achieved within +/-1.00 D target in the last 4 years. An improvement in safety was observed since the start of the study, with the best outcomes observed in 2007; loss of 1 and 2 Snellen line BCVA postoperatively was 2.4% and 0.1%, respectively. The overall retreatment rate was 3.8%; 91% of retreated eyes achieved UCVA of > or =20/30. Between 1998 and 2007, there was a significant improvement in postoperative UCVA and BCVA (P<0.001).

CONCLUSIONS

Myopic LASIK performed in Asian eyes within a comprehensive LASIK clinical program with appropriate clinical audit governance can be safe and effective, with high refractive predictability. Improvements in the nomograms to prevent undercorrection and to compensate for myopic regression have led to better efficacy after LASIK, with an increasing percentage of patients achieving 20/15 visual acuity postoperatively.

Back-calculation to model strategies for pretreatment adjustment of the ablation sphere in myopic wavefront laser in situ keratomileusis

PURPOSE

To examine strategies for adjusting the ablation sphere in myopic wavefront laser in situ keratomileusis (LASIK) with reference to preoperative manifest refraction.

SETTING

Refractive Surgery Service, Moorfields Eye Hospital, London, United Kingdom.

METHODS

The variance in the 3-month postoperative manifest refraction spherical equivalent (MRSE) results in 295 consecutive cases of myopic wavefront LASIK treated with a nonsystematic, intuitive approach to pretreatment adjustment of the ablation sphere was compared with the variance in modeled results obtained by back-calculation using 4 systematic strategies: (1) no adjustment (No Adj), (2) addition of the difference between the preoperative MRSE and the preoperative 4.0 mm pupil wavefront refraction spherical equivalent (WRSE) (4.0 mm), (3) addition of the difference between the preoperative MRSE and the preoperative maximum pupil WRSE (Max), and (4) addition of the difference between the preoperative MRSE and the preoperative effective blur (EB). The EB is a theoretical value for the dioptric SE of all aberrations at the pupil size calculated for the Hartmann-Shack images acquired (wavefront diameter). A stratified analysis of results for different wavefront diameters was also performed.

RESULTS

Variance in the postoperative MRSE was least (0.116) when nonsystematic, intuitive adjustments to the ablation sphere were used. In ascending order, the back-calculated variance was as follows: EB (0.142; P = .09, Bartlett test), 4.0 mm pupil (0.163; P = .004), No Adj (0.171; P = .001), and Max (0.225; P<.0001). There was a strong trend toward reduced variance in results in patients with a larger wavefront diameter.

CONCLUSION

Back-calculation to model results with different pretreatment ablation adjustment strategies may be useful to eliminate unpromising new approaches before clinical trials.

Late traumatic LASIK flap loss during contact sport

Three years and 5 months after uneventful laser in situ keratomileusis, the left eye of a 39-year-old man was struck by the finger of a friend while the two were practicing karate, resulting in loss of the flap. The patient had performed this contact sport regularly for years. When last seen 16 weeks after injury, the best corrected visual acuity in the left eye was 20/40 with -1.75 -0.50x30. Mild central corneal haze was observed under slitlamp examination, the flap was missing, and the patient complained of dysphotopsia. Pachymetry in the left eye was 394 mum, with an irregular corneal contour. Flap loss is a serious complication because severe irregular astigmatism and unpredictable refractive change can occur. This case highlights the vulnerability of flaps to trauma even late postoperatively.

The epidemiology of contact lens related infiltrates

With estimated numbers of contact lens wearers worldwide exceeding 140 million, even complications with a low incidence will affect a significant number of individuals. Although contact lenses clearly have many advantages for wearers, certain risks have been associated with their use. Differences in risk for different types of contact lenses and wearing patterns have been demonstrated for both rare and common lens related complications. This review particularly focuses on the incidence and etiology of contact lens related corneal infection and inflammation. An understanding of the risks and contributory factors to these conditions is important for practitioners and will enable an informed choice of safer lens wear modalities, wear schedules, and hygiene regimes to be made.

LASIK in the presbyopic age group: safety, efficacy, and predictability in 40- to 69-year-old patients

OBJECTIVE

To report the safety, efficacy, and predictability of LASIK in a presbyopic population and to examine possible differences between age groups.

DESIGN

Retrospective, descriptive, comparative consecutive case series.

PARTICIPANTS

Seven hundred ten eyes of 424 patients between 40 and 69 years of age who underwent LASIK by the same surgeon between January 1999 and September 2005. Patients had manifest refractive spherical errors ranging from -10.5 to +6 diopters (D) and cylinder of up to 2.50 D.

METHODS

LASIK was performed with IntraLase femtosecond laser or Hansatome microkeratomes and VISX Star (S4 or S2; VISX Inc., Santa Clara, CA) or Baush & Lomb Technolas 217z (Zyoptix or PlanoScan; Bausch & Lomb, Claremont, CA) excimer lasers. There were 511 myopic eyes (spherical equivalent [SE], -5.03+/-2.02 D) and 199 hyperopic eyes (SE, +2.21+/-1.21 D). Patients were divided into 3 groups: group 1 (40 to 49 years old; n = 359 eyes), group 2 (50 to 59 years old; n = 293 eyes), and group 3 (60 to 69 years old; n = 58 eyes).

MAIN OUTCOME MEASURES

Uncorrected visual acuity (UCVA) and best spectacle-corrected visual acuity (BSCVA), retreatment rates, safety, efficacy, and predictability.

RESULTS

The mean age of patients in groups 1, 2, and 3 was 45, 53, and 63 years, respectively. With increasing age, there was a trend toward higher retreatment rates and more myopic end points. Safety, efficacy, and predictability were comparable between all groups. At the final follow-up (mean+/-standard deviation, 10.4+/-7.4 months), 80% to 100% of eyes had 20/30 or better UCVA and 81% to 90% were within +/-1.00 D. No eyes lost more than 2 lines of BSCVA, and only 9 eyes (1.3%) lost 2 lines. Subgroup analysis of eyes with a follow-up of 12 months or more was performed. The results were compared with those with shorter follow-up. Both subgroups had comparable outcomes; the duration of follow-up did not affect the visual outcomes.

CONCLUSIONS

Despite a trend toward worse final BSCVA and higher retreatment rates in older patients, a greater risk of visual loss after LASIK was not observed. LASIK for myopia and hyperopia has reasonable safety, efficacy, and predictability profiles in the 40- to 69-year-old presbyopic population.

Evidence for Superior Efficacy and Safety of LASIK over Photorefractive Keratectomy for Correction of Myopia

PURPOSE

To examine possible differences in efficacy and safety between LASIK and photorefractive keratectomy (PRK) for correction of myopia.

DESIGN

Meta-analysis/systematic review.

PARTICIPANTS

Patient data from previously reported prospective randomized controlled trials (PRCTs) and a systematic review of prospective case series in the Food and Drug Administration (FDA) clinical trials database.

METHODS

A comprehensive literature search was performed using the Cochrane Collaboration methodology to identify PRCTs comparing LASIK and PRK for correction of myopia. A meta-analysis was performed on the results of PRCTs. In parallel, a systematic review of prospective data from FDA case series of LASIK and PRK for correction of myopia was undertaken.

MAIN OUTCOME MEASURES

Key efficacy outcomes (uncorrected visual acuity [UCVA] > or = 20/20, +/-0.50 diopters [D] of the target mean refractive spherical equivalent) and safety outcomes (loss of > or =2 lines of best spectacle-corrected visual acuity [BSCVA], final BSCVA > or = 20/40, and final BSCVA < 20/25 where preoperative BSCVA was > or =20/20).

RESULTS

Seven PRCTs were identified comparing PRK (683 eyes) and LASIK (403 eyes) for correction of myopia. More LASIK patients achieved UCVA > or = 20/20 at 6 months (odds ratio, random effects model [95% confidence interval], 1.72 [1.14-2.58]; P = 0.009) and 12 months (1.78 [1.15-2.75], P = 0.01). Loss of > or =2 lines of BSCVA at 6 months was less frequent with LASIK (2.69 [1.01-7.18], P = 0.05). Data from 14 LASIK (7810 eyes) and 10 PRK (4414 eyes) FDA laser approval case series showed that more LASIK patients achieved UCVA of 20/20 or better at 12 months (1.15 [1.03-1.29], P = 0.01), significantly more LASIK patients were within +/-0.50 D of target refraction at 6 months (1.38 [1.26-1.50], P<0.00001) and 12 months (1.21 [1.08-1.36], P = 0.0009) after treatment, and loss of > or =2 lines of BSCVA at 6 months was less frequent with LASIK (2.91 [2.22-3.83], P<0.00001).

CONCLUSIONS

LASIK appears to have efficacy and safety superior to those of PRK. However, the data examined are from studies conducted > or =5 years ago. It is therefore unclear how our findings relate to present-day methods and outcomes. Further trials comparing contemporary equipment and techniques are needed to reevaluate the relative merits of these procedures.

Photorefractive keratectomy (PRK) versus laser-assisted in-situ keratomileusis (LASIK) for myopia

BACKGROUND

Myopia (also known as short-sightedness or near-sightedness) is an ocular condition in which the refractive power of the eye is greater than is required, resulting in light from distant objects being focused in front of the retina instead of directly on it. The two most commonly used surgical techniques to permanently correct myopia are photorefractive keratectomy (PRK) and laser-assisted in-situ keratomileusis (LASIK).

OBJECTIVES

The aim of this review was to compare the effectiveness and safety of PRK and LASIK for correction of myopia.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library (2005, Issue 3), MEDLINE (1966 to September 2005), EMBASE (1980 to September 2005) and LILACs (1982 to 3 November 2005). We also searched the reference lists of the studies and the Science Citation Index.

SELECTION CRITERIA

We included randomised controlled trials comparing PRK and LASIK for correction of any degree of myopia. We also included data on adverse events from prospective multicentre consecutive case series in the Food and Drugs Administration (FDA) trials database (http//www.fda.gov/cdrh/LASIK/lasers.htm).

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data. Data were summarised using odds ratio and mean difference. Odds ratios were combined using a random-effects model after testing for heterogeneity.

MAIN RESULTS

This review included six randomised controlled trials involving a total of 417 eyes, of which 201 were treated with PRK and 216 with LASIK. We found that although LASIK gives a faster visual recovery than PRK, the effectiveness of these two procedures is comparable. We found some evidence that LASIK may be less likely than PRK to result in loss of best spectacle-corrected visual acuity.

AUTHORS' CONCLUSIONS

LASIK gives a faster visual recovery than PRK but the effectiveness of these two procedures is comparable. Further trials using contemporary techniques are required to determine whether LASIK and PRK are equally safe.