LASIK vs LASEK vs PRK: advantages and indications

Accuracy of the PEARL-DGS Formula for Intraocular Lens Power Calculation in Post-Myopic Laser Refractive Corneal Surgery Eyes

PURPOSE

To investigate the accuracy of the PEARL-DGS formula for intraocular lens (IOL) power calculation in post-myopic laser refractive corneal surgery eyes.

DESIGN

Retrospective case series.

METHODS

A total of 139 eyes of 139 patients (mean axial length: 27.4 ± 2.1 mm) who had prior myopic laser refractive corneal surgery and subsequent cataract surgery using Tecnis ZCB00 from March 2018 to February 2023 were included. Refractive outcomes of 5 formulas (Barrett True K, Haigis-L, Hoffer-QST, PEARL-DGS, and Shammas-PL) were evaluated. Prediction error was defined as the difference between the measured and predicted postoperative refractive spherical equivalent using the IOL power actually implanted. Mean prediction error (MPE), median absolute prediction error (MedAE), and mean absolute prediction error were calculated.

RESULTS

Without constant optimization, the PEARL-DGS resulted in a MPE of +0.05 ± 0.65 diopters (D), whereas the other formulas resulted in myopic shifts. The MedAEs of the formulas were 0.39, 0.53, 0.65, 0.85, and 1.11 D for the PEARL-DGS, Hoffer-QST, Barrett True K, Shammas-PL, and Haigis-L, respectively, in order of magnitude (P < .05). With constant optimization, there were no statistically significant differences in the MedAEs among the 5 formulas (P = .388).

CONCLUSIONS

In comparison to other IOL formulas, the PEARL-DGS resulted in better refractive outcomes after cataract surgery in post-myopic laser refractive corneal surgery eyes without constant optimization. We suggest that PEARL-DGS be considered as the first choice for IOL power calculation in these eyes when the clinicians do not have their optimized constants.

Refractive results of photorefractive keratectomy comparing trans-PRK and PTK-PRK for correction of myopia and myopic astigmatism

PURPOSE

To compare refractive outcomes after transepithelial photorefractive keratectomy (tPRK) and combined phototherapeutic keratectomy (PTK-PRK) procedure using two different excimer laser platforms for correction of myopia and myopic astigmatism.

METHODS

In this retrospective multicenter study, we compared the results of two different PRK methods. The first group received a tPRK treatment with the Amaris750 excimer laser (Schwind eye-tech solutions). The second group received a combined PTK-PRK treatment with the MEL90 excimer laser (Carl Zeiss). Only healthy eyes with no previous surgery and a spherical equivalent (SE) of -1 to -8 diopters (D) were included. Preoperative spherical equivalent (SE), age, and sex were matched among the two groups. All treatments were performed by the same surgeon in different clinics. This study was approved by the local Ethics Committee (No. 2022-1980).

RESULTS

We included 154 eyes of 86 patients in our study. There was no difference in predictability of SE between the two groups. Efficacy and safety indices were equally high in both groups. Similarly, no significant differences were seen in change of higher order aberrations (HOA) between the two groups (p > 0.05). No complications occurred.

CONCLUSION

Both investigated methods provide safe and effective refractive results. The combination of PTK with PRK may be a suitable option to the already used one-step tPRK for the correction of myopia.

Choice of refractive surgery types for myopia assisted by machine learning based on doctors' surgical selection data

In recent years, corneal refractive surgery has been widely used in clinics as an effective means to restore vision and improve the quality of life. When choosing myopia-refractive surgery, it is necessary to comprehensively consider the differences in equipment and technology as well as the specificity of individual patients, which heavily depend on the experience of ophthalmologists. In our study, we took advantage of machine learning to learn about the experience of ophthalmologists in decision-making and assist them in the choice of corneal refractive surgery in a new case. Our study was based on the clinical data of 7,081 patients who underwent corneal refractive surgery between 2000 and 2017 at the Department of Ophthalmology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences. Due to the long data period, there were data losses and errors in this dataset. First, we cleaned the data and deleted the samples of key data loss. Then, patients were divided into three groups according to the type of surgery, after which we used SMOTE technology to eliminate imbalance between groups. Six statistical machine learning models, including NBM, RF, AdaBoost, XGBoost, BP neural network, and DBN were selected, and a ten-fold cross-validation and grid search were used to determine the optimal hyperparameters for better performance. When tested on the dataset, the multi-class RF model showed the best performance, with agreement with ophthalmologist decisions as high as 0.8775 and Macro F1 as high as 0.8019. Furthermore, the results of the feature importance analysis based on the SHAP technique were consistent with an ophthalmologist's practical experience. Our research will assist ophthalmologists in choosing appropriate types of refractive surgery and will have beneficial clinical effects.

Cold bandage contact lens use reduces post-photorefractive keratectomy or corneal collagen-crosslinking pain perception in patients

Purpose

To compare post-operative pain perception using bandage contact lens (BCL) stored at 2-8°C (Cold BCL, CL-BCL) or room temperature (23 - 25°C, RT-BCL) after photorefractive keratectomy (PRK) or corneal collagen-crosslinking (CXL) and determine status of nociception associated factors.

Methods

In this prospective interventional study, 56 patients undergoing PRK for refractive correction and 100 keratoconus (KC) undergoing CXL were recruited following approval from the institutional ethics committee with informed consent. Patients undergoing bilateral PRK received RT-BCL on one eye and CL-BCL on the other. Pain was graded by Wong-Baker scoring on the first post-operative day (PoD1). Expression of transient receptor potential channels (TRPV1, TRPA1, TRPM8), calcitonin gene-related peptide (CGRP) and IL-6 was measured in cellular content from used BCLs collected on PoD1. Equal number of KC patients received RT-BCL or CL-BCL post-CXL. Pain was graded by Wong-Baker scoring on PoD1.

Results

Pain scores on PoD1 were significantly (P < 0.0001) reduced in subjects receiving CL-BCL (Mean ± SD: 2.6 ± 2.1) compared to RT-BCL (6.0 ± 2.4) post-PRK. 80.4% of subjects reported reduced pain scores with CL-BCL. 19.6% reported no change or increased pain scores with CL-BCL. TRPM8 expression was significantly (P < 0.05) increased in BCL of subjects reporting reduced pain with CL-BCL compared to those who did not. Pain scores on PoD1 were significantly (P < 0.0001) reduced in subjects receiving CL-BCL (3.2 ± 2.1) compared to RT-BCL (7.2 ± 1.8) post-CXL.

Conclusion

The simple approach of using a cold BCL post-operatively substantially reduced pain perception and could overcome post-operative pain-related limited acceptance of PRK/CXL.

Effects of atropine and tropicamide on ocular biological parameters in children: a prospective observational study

BACKGROUND

The effectiveness of cycloplegia in delaying the progression of myopia and its application in refractive examination in children have been extensively studied, but there are still few studies on the effects of atropine/tropicamide on ocular biological parameters. Therefore, the purpose of this study was to explore the effects of atropine/tropicamide on children's ocular biological parameters in different age groups and the differences between them.

METHODS

This was a prospective observational study in which all school children were examined for dioptres and ocular biological parameters in the outpatient clinic, and 1% atropine or tropicamide was used for treatment. After examination, we enrolled the patients grouped by age (age from 2 to 12 years treated by atropine, 55 cases; age from 2 to 10 years treated by tropicamide, 70 cases; age from 14 to 17 years treated by tropicamide, 70 cases). The ocular biological parameters of each patient before and after cycloplegia were measured, and the difference and its absolute value were calculated for statistical analysis using an independent-samples t test.

RESULTS

We compared the value and the absolute value of the differences in ocular biological parameters before and after cycloplegia in the same age group, and we found that the differences were not statistically significant (P > 0.05). There were significant differences in the corresponding values of AL, K1 and ACD among the different age groups (P < 0.05). Before cycloplegia, there were significant differences in AL, K, K1, K2 and ACD in different age groups (P < 0.05). However, the differences in AL, K, K1, K2 and ACD among different age groups disappeared after cycloplegia (P > 0.05).

CONCLUSIONS

This study demonstrated that atropine/tropicamide have different effects on cycloplegia in children of different ages. The effects of atropine/tropicamide on ocular biological parameters should be fully considered when evaluating the refractive state before refractive surgery or mydriasis optometry for children of different ages.

Clinical efficacy of Fluorometholone versus Loteprednol eye drops after photorefractive keratectomy: A triple-blinded randomized controlled trial

PURPOSE

This study aimed to compare the anti-inflammatory efficacy and safety of 0.1% Fluorometholone (FML) versus (vs.) 0.5% Loteprednol etabonate (LE) following photorefractive keratectomy (PRK).

METHODS

A triple-blinded randomized controlled trial was conducted on both eyes of 100 patients with stable refraction who were candidates for PRK. Both eyes in each subject were randomly allocated to the FML or LE groups. The product to be tested was 0.1% FML eye drops packaged in droppers vs. the 0.5% LE sterile ophthalmic suspension (Lotemax®) packaged in identical droppers. The main clinical outcomes were changes in best-corrected distance visual acuity (BCDVA) and corneal optical density. The second clinical outcomes were a change in intraocular pressure (IOP) after the intervention.

RESULTS

There was no significant difference regarding mean corneal optical density changes between the two groups, one (P = 0.55) and three months (P = 0.98) after the intervention. The mean ± SD BCDVA after one month of the intervention was 0.79 ± 0.11 and 0.84 ± 0.11 in LE and FML groups, retrospectively (P = 0.02). There was no significant difference regarding mean BCDVA between the two groups three months after intervention (P = 0.21). The IOP showed no significant difference between the two groups after one (P = 0.18) and three months (P = 0.53) of the intervention.

CONCLUSIONS

The results of this clinical trial demonstrate that LE and FML treatment was effective with no clinically meaningful effect on IOP following a short course of treatment.

Changes in ocular biological parameters after cycloplegia based on dioptre, age and sex

The effects of cycloplegia on ocular biological parameters in children have been extensively studied, but few studies have compared these parameters between different refractive states, ages, and sexes. Therefore, the purpose of this study was to investigate the changes in ocular biometry before and after cycloplegia in different groups based on dioptre, age and sex. We examined a total of 2049 participants in this cross-sectional study. A comprehensive eye examination was conducted before cycloplegia. Cycloplegia was implemented with the application of atropine or tropicamide. Ocular biological parameters were evaluated after cycloplegia, including axial length (AL), mean keratometry (K), flat keratometry (K1), steep keratometry (K2), central corneal thickness (CCT), anterior chamber depth (ACD) and white-to-white (WTW) distance. All the participants were categorized based on dioptre, age and sex. Statistical analysis was performed with paired t tests and Wilcoxon signed-rank tests. Regarding dioptre, AL was found to be increased significantly in the Fs, Ast and FA (p < 0.05) postcycloplegia groups. We observed significant increases in K, K1, K2 and ACD in the Fs group (p < 0.05) after cycloplegia. Regarding age, we found significant increases in AL, CCT and ACD in group 1 (p < 0.05), but AL decreased significantly in groups 2 and 3 (p < 0.05) postcycloplegia. There were no significant changes found in K, K1 and K2 in the three groups after cycloplegia (p > 0.05). Regarding sex, AL and WTW were found to decrease significantly among males and increase significantly among females (p < 0.05) postcycloplegia, while K, K1 and K2 showed the opposite trends. This study showed that there were differences in some ocular biological parameters after cycloplegia across different groups; in particular, there were significant differences in AL, CCT and ACD. Attention should be devoted to the influence of cycloplegia in clinical work.

Turner Syndrome: Ocular Manifestations and Considerations for Corneal Refractive Surgery

Turner Syndrome (TS) is the most common sex chromosome abnormality in females and is associated with physical changes, hormone deficiencies, increased risk of autoimmune disease, and ocular complications. In this article, we review the main ocular findings associated with TS and discuss their significance for the patient considering refractive surgery. We also present four cases of TS to highlight the clinical findings that may be present in these patients. The most common ocular manifestations include refractive errors, strabismus, and amblyopia. Less commonly, patients with TS may present with keratoconus, cataracts, glaucoma, uveitis, or other disorders of the posterior segment. When considering corneal refractive surgery in a TS patient, clinicians should perform a thorough ocular history, ask patients about hormone therapy and autoimmune conditions, and pay particular attention to any of the associated ocular symptoms of TS.

Quality of Vision After LASIK, PRK and FemtoLASIK: An Analysis Using the Double Pass Imaging System HD AnalyzerTM®

Purpose

Analyze and compare the quality of vision of Photorefractive keratectomy (PRK), LASER in situ keratomileusis with mechanical microkeratome (LASIK) and femtosecond-assisted LASIK (FS-LASIK) using the double-pass imaging system HD AnalyzerTM^®.

Setting

Ophthalmology department of Centro Hospitalar Universitário do Porto (CHUPorto).

Design

Retrospective, non-randomized, single center study.

Methods

Analysis of three equivalent groups of patients submitted to PRK, LASIK and FS-LASIK at our department. The objective quality of vision assessment included the objective scatter index (OSI), the modular transfer function cutoff frequency (MTF) and the predicted visual acuity within the 100% (PVA), 20% (PVA20) and 9% contrast levels (PVA9) that were evaluated at baseline, 1st week, 1 and 6 months after surgery.

Results

118 eyes were included: 40 underwent LASIK, 43 FS-LASIK and 35 PRK. The mean age was 30.6±4.6 years old and 56% were female. There was a significant impact concerning the type of procedure in the objective quality of vision analysis (Repeated measures ANOVA): the FS-LASIK group showed lower OSI values overtime [F(1,2)=4.566, p=0.012, OSI 0.83±0.53 (FS-LASIK) vs 0.87±0.47 (PRK) and 1.21±1.44 (LASIK)], higher MTF values [F(1,2)=6.569, p=0.002, MTF 40.17±8.33 vs 32.37±11.4 (PRK) and 30.26±10.28 (LASIK)], higher PVA 100% [F(1,2)=10.871, p<0.001], PVA 20% [F(1,2)=9.737, p<0.001] and PVA 9% [F(1,2)=6.335), p=0.003].

Conclusion

In our study, FS-LASIK showed an excellent optical performance through the HD AnalyzerTM technology, with significantly lower OSI and higher MTF, PVA100, PVA20 and PVA9 values. According to our results, this procedure seems to be superior to PRK and LASIK regarding visual quality objective parameters.

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

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

Changes of Subjective Symptoms and Tear Film Biomarkers following Femto-LASIK

Femtosecond laser-assisted in situ keratomileusis (Femto-LASIK) represents a common treatment modality in refractive surgery and shows excellent results in terms of safety, efficacy, predictability, and long-term stability. However, patients may be affected by dry eye symptoms. The aim of this study was to identify a potential association between subjective dry eye symptoms, objective dry eye markers, and possible changes in the tear film, which could be a target for future therapy development. Therefore, clinical (dry eye) examinations (OSDI, Schirmer test, lissamine green and fluorescein staining, BUT, visual acuity) were carried out before LASIK as well as 5 and 90 days post-OP. The dry eye marker MMP-9, cytokines (IL-1β, IL-8), and pain markers (NGF, CGRP) were quantified in tear samples with immunoassays. In addition, correlation analyses were performed. Clinical examinations revealed an upregulated OSDI score 5 days post-OP and an increased lissamine green staining score 90 days post-OP. Downregulated CGRP levels were noted 5 days post-OP, while other protein markers were not significantly altered after Femto-LASIK. Hence, Femto-LASIK surgery induced subjective symptoms like that of dry eye which could objectively rather be classified as Femto-LASIK-related discomfort. In the future, this could possibly be better detected and treated using pain markers such as CGRP.

Efficacy and safety of single-step transepithelial photorefractive keratectomy with the all-surface laser ablation SCHWIND platform without mitomycin-C for high myopia: A retrospective study of 69 eyes

BACKGROUND

Studies suggest that transepithelial photorefractive keratectomy (TransPRK) with the all-surface laser ablation (ASLA)-SCHWIND platform is effective and safe for both low-moderate myopia and high myopia. In most studies, mitomycin-C is administered immediately after surgery to prevent corneal opacification (haze), which is a significant complication of photorefractive keratectomy in general. However, there is evidence that adjuvant mitomycin-C induces endothelial cytotoxicity. Moreover, a recent study showed that omitting adjuvant mitomycin-C did not increase haze in low-moderate myopia. The present case-series study examined the efficacy, safety, and haze rates of eyes with high myopia that underwent ASLA-SCHWIND TransPRK without adjuvant mitomycin-C.

METHODS

All consecutive eyes with high myopia (≤-6 D) that were treated in 2018-2020 with the SCHWIND Amaris 500E® TransPRK excimer laser without adjuvant mitomycin-C in a tertiary-care hospital (France) and were followed up for 6 months were identified. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and spherical equivalent (SE) were recorded before and after surgery. Postoperative haze was graded using the 4-grade Fantes scale. Efficacy rate (frequency of eyes with 6-month UCVA ≤0.1 logMAR), safety rate (frequency of eyes that lost <2 BSCVA lines), predictability (frequency of eyes with 6-month SE equal to target SE±0.5 D), efficacy index (mean UCVA at 6 months/preoperative BSCVA), and safety index (BSCVA at 6 months/preoperative BSCVA) were computed.

RESULTS

Sixty-nine eyes (38 patients) were included. Mean preoperative and 6-month SE were -7.44 and -0.05 D, respectively. Mean 6-month UCVA and BSCVA were 0.00 and -0.02 logMAR, respectively. Efficacy rate and index were 95.7% and 1.08, respectively. Safety rate and index were 95.7% and 1.13, respectively. Predictability was 85.5%. Grade 3-4 haze never arose. At 6 months, the haze rate was zero.

CONCLUSIONS

ASLA-SCHWIND TransPRK without mitomycin-C appears to be safe as well as effective and accurate for high myopia.

Comparison of the effect of removing bandage contact lens on the days 3 and 5 following photorefractive keratectomy

AIM

To compare the outcomes of removing bandage contact lens (BCL) on days 3 and 5 after photorefractive keratectomy (PRK).

METHODS

One hundred patients who underwent PRK (a total of 200 eyes) were enrolled in the present study. The subjects were assigned to two groups. Group 1 consisted of the right eyes of subjects and bandage contact lenses removal were on the 3rd day; Group 2 consisted of the fellow eyes of same subjects and removed bandage contact lenses on the 5th day after PRK. Then, data obtained from both groups were compared. To evaluate complications, the subjects underwent a slit-lamp examination in all visits.

RESULTS

Filamentary keratitis was observed in one eye in both groups. The frequency of haze was higher in group 1; however, it was not significant between the two groups. Using mixed model analysis, significant differences were observed in the rate of complications as well as pain and eye discomfort scores between the groups (P < 0.05). No major complication was reported.

CONCLUSION

Majority of post-PRK corneal epithelial defect is healed on day 3. However, keeping BCL for 5 days postoperatively instead of the three days produces a slightly lower rate of total complication.

Usability of abattoir-acquired pig eyes for refractive excimer laser research

The purpose of this study was to elucidate, under which conditions abattoir-acquired pig eyes are suitable for refractive excimer laser experiments. Porcine eyes from tunnel-scalded (n = 5) and tank-scalded (n = 10) pigs were compared to unscalded eyes (n = 5) and to eyes scalded in the laboratory (n = 5). The corneal epithelium was removed before an excimer laser was used to perform a − 8.0 D photoablation. Corneal thickness was measured by optical coherence topography before and after photoablation. The ablation depth was determined with a contour measuring station, the morphology of the ablated areas was characterized by scanning electron microscopy and white-light profilometry. The scalded eyes showed an increase in corneal swelling which gained statistical significance in tank-scalded eyes showing a wedge-shaped opaque stromal lesion in the nasal corneal quadrant. A measurable deterioration of photoablation was only found in tank-scalded eyes that exhibited the opaque lesion. Ablated area morphology was smooth and regular in the unscalded and tunnel-scalded eyes. The tank-scalded eyes showed conspicuous wrinkles. While unscalded eyes should always be preferred for excimer laser laboratory experiments, the data suggest that the use of tunnel-scalded eyes may also be acceptable and should be chosen over tank-scalded eyes.

Computational study for temperature distribution in ArF excimer laser corneal refractive surgeries using different beam delivery techniques

Refractive errors are the most common causes of vision impairment worldwide and laser refractive surgery is one of the most frequently performed ocular surgeries. Clinical studies have reported that approximately 10.5% of patients need an additional procedure after the surgery. The major complications of laser surgery are over/under correction and dry eye. An increase in temperature may be a cause for these complications. The purpose of this study was to estimate the increase in temperature during laser refractive surgery and its relationship with the complications observed for different surgical techniques. In this paper, a finite element model was applied to investigate the temperature distribution of the cornea when subjected to ArF excimer laser at a single spot using various beam delivery systems (broad beam, scanning slit, and flying spot). The Pennes bio-heat equation was used to predict the temperature values at different laser pulse energies and frequencies. The maximum temperature increase by ArF laser ([Formula: see text] frequency and [Formula: see text] pulse energy) at a single spot was [Formula: see text] for [Formula: see text] diopter correction ([Formula: see text] of ablation of corneal stroma) using broad beam, scanning slit, and flying spot beam delivery approaches respectively. The peak temperature due to a single pulse was estimated to be [Formula: see text]. Although the peak temperature (sufficient energy to break intermolecular bonds) exists for a very short time ([Formula: see text]) compared to the thermal relaxation time ([Formula: see text]), there is some thermal energy exchange between corneal tissues during a laser refractive surgery. Heating may cause collagen denaturation, collagen shrinkage, and more evaporation and hence proposed to be a risk factor for over/under correction and dry eye.

Pain Control Following Photorefractive Keratectomy: A Prospective Clinical Trial Comparing Codeine Versus Oxycodone for the Management of Postoperative Pain

PURPOSE

To compare the efficacy of oral codeine plus acetaminophen versus oxycodone plus acetaminophen for severe pain control following photorefractive keratectomy (PRK).

METHODS

This single-center trial randomized 200 patients to receive codeine 30 mg/acetaminophen 325 mg (codeine group) or oxycodone 5 mg/acetaminophen 325 mg (oxycodone group)every 4 hours as needed for severe pain for 4 days following PRK. Patients recorded postoperative pain, tablet consumption, and tetracaine use. Patients were monitored at postoperative 1 day, 1 week, and 1, 3, and 6 months for visual acuity and follow-up. Study outcomes were mean postoperative pain, treatment and tetracaine use, and visual acuity.

RESULTS

Analysis of 197 patients who completed the trial (97 codeine group and 100 oxycodone group) showed mean pain scores were lower in the codeine group throughout the intervention period. Mean pain scores were higher in the oxycodone group than the codeine group on postoperative days 2 and 4 (P = .017 and P = .034, respectively). The oxycodone group consumed more tablets than the codeine group, with a difference on postoperative day 2 (P = .019), and used a greater number of tetracaine drops (P = .015). Repeated measures analysis of variance showed significant improvement in visual acuity in both groups with no difference in visual outcomes (P = .81).

CONCLUSIONS

Codeine/acetaminophen is as effective and safe as oxycodone/acetaminophen for pain control following PRK, with no clinical difference in overall pain control and long-term visual outcomes. This implies that treating postoperative pain after PRK with a Schedule III opioid (codeine) is effective and potentially decreases the risk of misuse by a higher regulated Schedule II opioid (oxycodone), lowering the potential for abuse and dependence. [J Refract Surg. 2021;37(9):582-589.].

Preferred practice patterns for photorefractive keratectomy surgery

Over the past two decades, excimer laser-based refractive surgery procedures have been successfully established for their safety and satisfactory visual outcomes. Surface ablation procedures or photorefractive keratectomy (PRK) are practised commonly for the correction of refractive errors including myopia, astigmatism and hyperopia. Satisfactory visual outcomes are achieved in majority of cases, although a very small percentage have issues related to corneal haze, regression, and its associated visual disturbances. To ensure optimal outcomes and to minimize complications, certain keys to success have been designed on the basis of the current review of literature on surface ablation procedures.

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.

Early clinical outcomes and comparison between trans-PRK and PRK, regarding refractive outcome, wound healing, pain intensity and visual recovery time in a real-world setup

PURPOSE

To compare early clinical outcomes of single-step transepithelial photorefractive keratectomy (tPRK) and photorefractive keratectomy (PRK) regarding refractive outcome, visual acuity, wound healing, pain intensity and visual recovery time.d.

METHODS

In this prospective clinical observational study 200 eyes of 100 consecutive patients with mild to moderate myopia with or without mild astigmatism were included. One hundred eyes each were either treated with StreamLight™ tPRK or PRK with the WaveLight® EX500 excimer laser. Visual acuity (Decimal) was assessed preoperatively and at day 4, 7 and 6 weeks postoperatively. Wound healing (hours between surgery and complete epithelial closure) was monitored at the slit lamp. At day 4, patients subjectively rated the maximum pain intensity within the last 4 days using a numerical pain rating scale (0-15).

RESULTS

Visual recovery was significantly faster in the tPRK group. At days 4 and 7, the mean monocular UCDVA was significantly better in the tPRK group than in the PRK group (p < 0.001). Four days after surgery 72 % of eyes in the tPRK group but no eye in the PRK had a UCDVA of 0.7 or better. At six weeks postoperatively, a UCDVA of 1.0 or better was achieved in both groups. Complete epithelial wound closure was achieved significantly faster in the tPRK group (p < 0.0001) and maximum pain level within the first 4 days after surgery was significantly lower in the tPRK group (p < 0.0001). No patient had lost a line of BCDVA and no complications or adverse effects were observed.

CONCLUSIONS

According to our early clinical results, both treatments options appear to be safe and effective methods for the correction of low to moderate myopia with and without astigmatism. However, in our study, StreamLight™ tPRK offered faster visual recovery and epithelial healing and was associated with less pain compared to PRK. It can therefore be considered a good treatment option for patients who refuse or are not eligible for Femto-LASIK, but at the same time demand a faster and more comfortable recovery time than PRK can offer.

Safety and efficacy of combination of suberoylamilide hydroxyamic acid and mitomycin C in reducing pro-fibrotic changes in human corneal epithelial cells

Corneal haze post refractive surgery is prevented by mitomycin c (MMC) treatment though it can lead to corneal endothelial damage, persistent epithelial defects and necrosis of cells. Suberanilohydroxamic acid (SAHA) however has been proposed to prevent corneal haze without any adverse effects. For clinical application we have investigated the short and long term outcome of cells exposed to SAHA. Human donor cornea, cultured limbal epithelial cells, corneal rims and lenticules were incubated with SAHA and MMC. The cells/tissue was then analyzed by RT-qPCR, immunofluorescence and western blot for markers of apoptosis and fibrosis. The results reveal that short term exposure of SAHA and SAHA + MMC reduced apoptosis levels and increased αSMA expression compared to those treated with MMC. Epithelial cells derived from cultured corneal rim that were incubated with the MMC, SAHA or MMC + SAHA revealed enhanced apoptosis, reduced levels of CK3/CK12, ∆NP63 and COL4A compared to other treatments. In SAHA treated lenticules TGFβ induced fibrosis was reduced. The results imply that MMC treatment for corneal haze has both short term and long term adverse effects on cells and the cellular properties. However, a combinatorial treatment of SAHA + MMC prevents expression of corneal fibrotic markers without causing any adverse effect on cellular properties.

Femtosecond laser assisted in situ keratomileusis (FS-LASIK) yields better results than transepithelial photorefractive keratectomy (Trans-PRK) for correction of low to moderate grade myopia

INTRODUCTION

The purpose of this study was to compare the outcomes of transepithelial photorefractive keratectomy (Trans-PRK) with femtosecond laser assisted in situ keratomileusis (FS-LASIK) for the correction of low to moderate myopia.

METHODS

A retrospective cohort study design was used. The study group included patients with myopia less than -6.0 D, with or without concomitant astigmatism under 2.0 D, who were treated with FS-LASIK or Trans-PRK in 2013 through 2014. Background, clinical and outcome data were collected from the patient files. A comparison between eyes treated with FS-LASIK or Trans-PRK was performed.

RESULTS

The Trans-PRK group was comprised of 1793 eyes and the FS-LASIK group of 666 eyes. Mean ± SD spherical equivalent (SE) refraction prior to surgery was -3.43 ± 1.27 D in the Trans-PRK group and -3.18 ± 1.34 D in the FS-LASIK group (p < 0.001). Efficacy index values were 0.95 ± 0.14 in the Trans-PRK group and 0.98 ± 0.12 in the FS-LASIK group (p < 0.001), and corresponding safety index values were 0.96 ± 0.13 and 0.99 ± 0.12 (p < 0.001). Distance from target refraction was 0.45 ± 0.42 D in Trans-PRK group and 0.43 ± 0.38 D in the FS-LASIK group (p = 0.537); 71.6% and 74.2% of eyes were within ±0.5 D of attempted correction, respectively (p = 0.193).

CONCLUSIONS

Both Trans-PRK and FS-LASIK demonstrated excellent results, mostly comparable with the current literature. FS-LASIK achieved better results than Trans-PRK surgery in the efficacy and safety parameters.

Refractive outcomes of high-magnitude astigmatism correction using femtosecond LASIK versus transepithelial PRK

PURPOSE

To compare the outcomes of femtosecond laser assisted in situ keratomileusis (FS-LASIK) with transepithelial photorefractive keratectomy (T-PRK) for the correction of high-grade astigmatism.

METHODS

Medical records of patients with astigmatism of 2 diopters (D) or higher, who were treated with FS-LASIK or T-PRK in 2013 through 2014 at a private practice laser clinic, were retrospectively analyzed. Efficacy, safety, predictability and vector analysis of astigmatism correction were compared between the treatment groups.

RESULTS

The study included 93 eyes treated with FS-LASIK and 186 eyes treated with T-PRK. No significant differences in postoperative spherical equivalent (-0.10 ± 0.7 D and -0.11 ± 0.7 D, respectively, p = 0.958) and postoperative refractive astigmatism (0.79 ± 0.54 D and 0.82 ± 0.63 D, respectively, p = 0.685) were demonstrated. A significant advantage of FS-LASIK over T-PRK was seen for the efficacy (1.00 ± 0.18 and 0.86 ± 0.22, respectively, p < 0.001) and safety (1.03 ± 0.17 and 0.89 ± 0.21, respectively, p < 0.001) indices. Results remain statistically significant in a multivariate analysis model. Vector analysis for the astigmatism correction showed no significant difference between the surgery methods in the surgically induced astigmatism, difference vector, correction index and index of success.

CONCLUSION

Both procedures demonstrated desirable post-operative SE outcomes for high-grade astigmatism correction. However, FS-LASIK achieved better results than T-PRK in the efficacy and safety parameters.

Photorefractive keratectomy (PRK) Prediction, Examination, tReatment, Follow-up, Evaluation, Chronic Treatment (PERFECT) protocol - A new algorithmic approach for managing post PRK haze

Purpose

The aim of this study was to discuss the possible risk factors predisposing to post photorefractive keratectomy (PRK) haze formation and develop and validate a risk scoring system, so that this could be applied to our clinical practice as an algorithmic approach.

Methods

Study was divided into 2 arms, in the retrospective arm we looked at 238 eyes of patients undergoing PRK where certain presumed risk factors from literature and clinical experience were identified and statistical significance of association was studied in the development of corneal haze. The risk scoring system was applied to the 450 eyes in the prospective arm for validation. This was then used to formulate an algorithmic approach to manage post-PRK haze.

Results

22 out of 238 eyes in the retrospective arm developed haze where risk factors such as contact lens intolerance, altered tear film break up time, meibomian gland drop out and vitamin d levels were significantly associated with post-PRK haze (p < 0.05) and these factors were identified in the prospective arm. Treatment of these modifiable factors led to a significant reduction in post-PRK haze.

Conclusion

Thus identifying and treating risk factors of haze in patients undergoing PRK could improve surgical outcomes and patient satisfaction.

Assessment of Factors Associated With Postoperative Pain After Photorefractive Keratectomy

PURPOSE

To define the factors that affect patient's self-assessed postoperative pain after photorefractive keratectomy (PRK).

METHODS

Patients who underwent PRK in 2016 were evaluated. Anonymized data collected included patient gender, age, and season at the time of surgery, ablation depth, surgeon status (attending vs. resident), topical tetracaine use, and subjective pain scores at postoperative days (PODs) 1 and 7. Average pain scores and amount of pain medication taken were analyzed for each of the previously mentioned variables.

RESULTS

Overall, 231 patients who underwent PRK were analyzed. The mean pain score and SD were 0.78 ± 1.87 on POD 1 and 0.03 ± 0.37 by POD 7. Patients who used topical tetracaine reported significantly higher pain on POD 1 and 7 compared with patients who did not use tetracaine (P < 0.001 and P = 0.038, respectively). No significant differences in pain scores were seen based on surgeon status, ablation depth, gender, and season. Patients who used topical tetracaine took a higher amount of oral pain medication (9.44 ± 6.01) compared with those who did not (7.02 ± 4.71) (P = 0.022).

CONCLUSIONS

Postoperative pain was significantly elevated in patients who used tetracaine on POD 1 and POD 7. These patients were also more likely to take oral pain medication than those who did not use topical tetracaine. Surgeon status, season, gender, and ablation depth showed no significant differences in subjective pain scores. Oral pain medication should be evaluated to assess efficacy and safety in inhibiting ocular pain after PRK.

Outcomes Comparison Between Wavefront-Optimized and Topography-Guided PRK in Contralateral Eyes With Myopia and Myopic Astigmatism

PURPOSE

To compare clinical outcomes between topography-guided customized ablation treatment (TCAT) and wavefront-optimized (WFO) photorefractive keratectomy (PRK) in fellow eyes of myopic patients.

METHODS

Forty-six eyes of 23 patients who underwent PRK were included. WFO ablation was performed in one eye (WFO group) and TCAT in the fellow eye (TCAT group). The customized treatment plan was based on the Topolyzer Vario topography system (Alcon Laboratories, Inc) data. The patients were observed for 12 months after the procedure.

RESULTS

One year after the surgery, there was no significant difference in the manifest refraction spherical equivalent, sphere, or cylinder variables between the two groups (P > .05). In both groups, 96% of eyes achieved an uncorrected distance visual acuity of 20/20 or better at 12 months postoperatively. Accuracy, safety, and efficacy of the refractive and visual outcomes were similar in the two groups. The postoperative higher order aberrations magnitude was lower in the TCAT group, but this was not statistically significant (P > .05). During the 12-month follow-up, no patient described any symptoms related to glare, halos, or starbursts in either eye. Other postoperative complications, such as infection or cor-neal infiltrates, did not occur in either group.

CONCLUSIONS

TCAT and WFO ablations provided similar outcomes after PRK for myopia and myopic astigmatism correction. There were no statistically significant differences in postoperative corneal wavefront analysis. [J Refract Surg. 2020;36(6):358-365.].

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.].

Comparison of the balafilcon A and samfilcon A lenses on postoperative pain control and epithelial healing time after photorefractive keratectomy: a contralateral eye study

To compare the effects of balafilcon A and samfilcon A silicone hydrogel bandage contact lenses on postoperative pain control and epithelial healing time after photorefractive keratectomy (PRK). Seventy-four eyes of 37 patients who underwent bilateral PRK were included in this randomized clinical trial study. In the end of the surgery, a balafilcon A lens was used in one eye and a samfilcon A lens was used in the fellow eye randomly. Pain, blurred vision, epiphora, photophobia, and foreign body sensation were assessed on the first and third postoperative day using a visual analogue scale (0 = no ocular pain or discomfort, 10 = highest level of ocular pain and discomfort). For balafilcon A and samfilcon A lenses, mean scores for pain were 6.22 ± 2.81 and 3.11 ± 2.90 on first postoperative day (p < 0.001) and 1.57 ± 1.65 and 0.68 ± 0.85 on third postoperative day (p = 0.001), respectively; mean scores for foreign body sensation were 6.11 ± 2.53 and 3.19 ± 2.72 on first postoperative day (p < 0.001) and 3.16 ± 1.92 and 1.35 ± 1.43 on third postoperative day (p < 0.001), also respectively; and mean scores for epiphora were 6.46 ± 2.64 and 5.46 ± 3.40 on first postoperative day (p = 0.007) and 1.68 ± 1.60 and 1.32 ± 1.31 on third postoperative day (p = 0.065), again respectively. No significant difference in blurred vision or photophobia emerged between the lenses on first and third postoperative day after PRK. On the third postoperative day, reepithelialization was complete in 83.7% of eyes with the balafilcon A lens and 89.1% of eyes fitted with the samfilcon A lens. Wearing samfilcon A lenses after photorefractive keratectomy can significantly manage pain, decrease foreign body sensation on first and third postoperative day, and reduce epiphora on first postoperative day.

Masked comparison of two silicone hydrogel bandage contact lenses after photorefractive keratectomy

PURPOSE

To compare the efficiency and safety of two bandage contact lenses after photorefractive keratectomy (PRK).

METHODS

In this double-blind study, 45 patients (90 eyes) received PRK in both eyes and wore bandage contact lenses (BCLs), PureVision (Bausch & Lomb, Rochester, NY, USA) in one eye and PureVision2 (Bausch & Lomb, Rochester, NY, USA) in the other eye, randomly assigned. The medication regimen after surgery was the same for both eyes. The epithelial defect's size, conjunctival hyperemia and lens centration were graded objectively using slit-lamp biomicroscopy on days 1, 3 and 5 after surgery. Also ocular symptoms of discomfort including tearing, photophobia, foreign body sensation and visual fluctuations were assessed subjectively at each visit.

RESULTS

The mean epithelial defect size on the first day after operation was similar in eyes fitted with PureVision (30.08 ± 5.30 mm²) and PureVision2 (30.25 ± 5.72 mm²) lenses. (p = 0.79) Contact lens deposits and bulbar hyperaemia on days 1 and 3 after PRK were similar between the two eyes, but were significantly greater on day 5 for PureVision2 lenses. (p = 0.02; p = 0.04 respectively) There was no difference in contact lens decentration, and discomfort symptoms including pain, tearing, foreign body sensation, photophobia and visual fluctuations between the eyes fitted with PureVision and PureVision2. (p > 0.05) CONCLUSIONS: PureVision and PureVision2 contact lenses are equivalent as bandage lenses in important aspects such as corneal re-epithelialization and subjective comfort., although PureVision2 led to a higher incidence of contact lens deposits and conjunctival hyperemia early post-PRK.

Explainable Machine Learning Approach as a Tool to Understand Factors Used to Select the Refractive Surgery Technique on the Expert Level

Purpose

Recently, laser refractive surgery options, including laser epithelial keratomileusis, laser in situ keratomileusis, and small incision lenticule extraction, successfully improved patients' quality of life. Evidence-based recommendation for an optimal surgery technique is valuable in increasing patient satisfaction. We developed an interpretable multiclass machine learning model that selects the laser surgery option on the expert level.

Methods

A multiclass XGBoost model was constructed to classify patients into four categories including laser epithelial keratomileusis, laser in situ keratomileusis, small incision lenticule extraction, and contraindication groups. The analysis included 18,480 subjects who intended to undergo refractive surgery at the B&VIIT Eye center. Training (n = 10,561) and internal validation (n = 2640) were performed using subjects who visited between 2016 and 2017. The model was trained based on clinical decisions of highly experienced experts and ophthalmic measurements. External validation (n = 5279) was conducted using subjects who visited in 2018. The SHapley Additive ex-Planations technique was adopted to explain the output of the XGBoost model.

Results

The multiclass XGBoost model exhibited an accuracy of 81.0% and 78.9% when tested on the internal and external validation datasets, respectively. The SHapley Additive ex-Planations explanations for the results were consistent with prior knowledge from ophthalmologists. The explanation from one-versus-one and one-versus-rest XGBoost classifiers was effective for easily understanding users in the multicategorical classification problem.

Conclusions

This study suggests an expert-level multiclass machine learning model for selecting the refractive surgery for patients. It also provided a clinical understanding in a multiclass problem based on an explainable artificial intelligence technique.

Translational Relevance

Explainable machine learning exhibits a promising future for increasing the practical use of artificial intelligence in ophthalmic clinics.

Myopic Laser-Assisted Subepithelial Keratectomy (LASEK) outcomes using three different excimer laser platforms: a retrospective observational study

Background

To compare the visual and refractive outcomes after myopic LASEK using three different excimer lasers and standardized surgical and mitomycin C (MMC) application protocols.

Methods

In this retrospective, observational cohort study, we examined 122 eyes treated with Allegretto, 135 eyes treated with Esiris and 137 eyes treated with Technolas excimer lasers. All eyes were treated under the same surgical protocol, and a standardized MMC dosage was used. The three groups were refraction-matched, and both visual and refractive outcomes were evaluated at 1 and 7 days and 1 and 3 months after surgery.

Results

At 3 months postsurgery, Allegretto provided significantly better outcomes than Esiris and Technolas in terms of postoperative uncorrected distance visual acuity (UDVA) (1.11 ± 0.2 vs 1.01 ± 0.2 vs 0.98 ± 0.2) (P = 0.0001), corrected distance visual acuity (CDVA) (1.13 ± 0.2 vs 1.10 ± 0.1 vs 1.04 ± 0.2) (P = 0.0001), residual sphere (− 0.01 ± 0.2 vs + 0.29 ± 0.7 vs + 0.27 ± 0.6) (P = 0.0001), and efficacy index (0.99 ± 0.2 vs 0.90 ± 0.2 vs 0.91 ± 0.2) (P = 0.0004).

Conclusions

We found slightly better visual and refractive outcomes in the Allegretto group at 3 months post-op after LASEK with MMC to correct myopia.

Presbyopia and the aging eye: Existing refractive approaches and their potential impact on dry eye signs and symptoms

Every part of the human body is subject to aging, including the eye. An increased prevalence of dry eye disease with age is widely acknowledged. Aging threatens ocular surface homeostasis, altering the normal functioning of the lacrimal functional unit and potentially leading to signs and symptoms of dry eye. Additional age-related processes take place within the crystalline lens, leading to presbyopia and cataractogenesis. Correction strategies for presbyopia and cataracts may directly or indirectly challenge the ocular surface. Contact lenses disturb the normal structure of the tear film and can interact negatively with the ocular surface, further deteriorating an already unbalanced tear film in presbyopes, however, newer contact lens designs can overcome some of these issues. Moreover, cataract and corneal refractive surgeries sever corneal nerves and disrupt the corneal epithelium and ocular surface, which can influence surgical outcomes and aggravate dryness symptoms in older age groups. This review summarises the current understanding of how the invasive nature of contact lens wear and cataract and refractive surgery influence signs and symptoms of ocular dryness in an aging population.

Corneal biomechanical properties after SMILE versus FLEX, LASIK, LASEK, or PRK: a systematic review and meta-analysis

BACKGROUND

The aim of this study was to compare the postoperative corneal biomechanical properties between small incision lenticule extraction (SMILE) and other corneal refractive surgeries.

METHODS

A systematic review and meta-analysis were conducted. Articles from January 2005, to April 2019, were identified searching PubMed, EMBASE, Web of Science, and International Clinical Trials Registry Platform. Studies that compared SMILE with other corneal refractive surgeries on adult myopia patients and evaluated corneal biomechanics were included. Multiple effect sizes in each study were combined. Random-effects model was conducted in the meta-analysis.

RESULTS

Twenty-two studies were included: 5 randomized controlled trials (RCTs), 9 prospective and 6 retrospective cohort studies, and 2 cross-sectional studies. Using the combined effect of corneal hysteresis (CH) and corneal resistance factor (CRF), which were obtained from ocular response analyzer (ORA), the pooled Hedges' g of SMILE versus femtosecond laser-assisted in situ keratomileusis (FS-LASIK) was 0.41 (95% CI, 0.00 to 0.81; p = 0.049; I² = 78%), versus LASIK was 1.31 (95% CI, 0.54 to 2.08; p < 0.001; I² = 77%), versus femtosecond lenticule extraction (FLEX) was - 0.01 (95% CI, - 0.31 to 0.30; p = 0.972; I² = 20%), and versus the group of photorefractive keratectomy (PRK) and laser-assisted sub-epithelial keratectomy (LASEK) was - 0.26 (95% CI, - 0.67 to 0.16; p = 0.230; I² = 54%). The summary score of Corvis ST (CST) after SMILE was comparable to FS-LASIK/LASIK with the pooled Hedges' g = - 0.05 (95% CI, - 0.24 to 0.14; p = 0.612, I² = 55%).

CONCLUSIONS

In terms of preserving corneal biomechanical strength after surgeries, SMILE was superior to either FS-LASIK or LASIK, while comparable to FLEX or PRK/LASEK group based on the results from ORA. More studies are needed to apply CST on evaluating corneal biomechanics after refractive surgeries.

Corneal indices following photorefractive keratectomy in children at least 5 years after surgery

PURPOSE

To evaluate long-term corneal outcomes in pediatric patients who underwent photorefractive keratotomy (PRK) for the treatment of refractive amblyopia.

METHODS

In this prospective interventional case series, children with refractive amblyopia underwent PRK between January 1, 2007, and December 31, 2011, at Texas Children's Hospital's Department of Ophthalmology, a single tertiary eye center, and were followed for at least 5 years after surgery. Main outcome measures were 5+ years postoperative indices of corneal thickness, keratometry, degree of corneal haze, and presence or absence of keratectasia.

RESULTS

Twelve eyes of 8 subjects aged 3-9 years who underwent PRK and were followed for at least 5 years were included. The mean PRK treatment dose was 8.46 D for the myopic cohort and 4.49 D for the hyperopic cohort, which removed an average of 72 μm of corneal stromal tissue in addition to the 50 μm of corneal epithelium that was removed prior to laser ablation. The mean corneal thickness was 563 μm preoperatively, which decreased to 441 μm immediately following the PRK. The mean corneal thickness 5+ years after PRK was stable, at 498 μm, because of epithelial regrowth. None of the subjects developed visually significant corneal haze or topographic evidence of keratectasia.

CONCLUSIONS

In this study cohort, there were no topographic signs of keratectasia or corneal haze in children treated with PRK for high refractive error 5 years or more after surgery.

Topography-Guided Custom Photorefractive Keratectomy for Myopia in Primary Eyes With the WaveLight EX500 Platform

PURPOSE

To evaluate the outcomes after topography-guided ablation treatment (T-CAT) for the correction of myopia and myopic astigmatism with photorefractive keratectomy (PRK).

METHODS

This was a retrospective, non-comparative case series study of 25 patients (40 eyes) with low to moderate myopia with or without astigmatism who underwent topography-guided custom PRK with the Wave-Light EX500 excimer laser platform (Alcon Laboratories, Inc., Fort Worth, TX). The customized treatment plan was based on Topolyzer Vario topography system (Alcon Laboratories, Inc.) data. The patients were observed for 6 months after the procedure.

RESULTS

The surgery significantly reduced the manifest refractive spherical equivalent (MRSE), sphere, and cylinder (P < .05) at 6 months of follow-up. Compared with the preoperative corrected distance visual acuity (CDVA), 8 (20%) and 10 (25%) of 40 eyes gained one or more lines of postoperative uncorrected distance visual acuity at 3 and 6 months, respectively. Only 1 eye presented loss of one line of CDVA at 6 months postoperatively, which was due to delayed epithelial healing. Ten patients (15 eyes) reported symptoms related to dry eye and the vision of 21 patients (17 eyes) fluctuated during the first month.

CONCLUSIONS

The T-CAT custom PRK procedure provided good early outcomes for treating patients with low to moderate myopia with or without astigmatism. [J Refract Surg. 2018;34(8):541-546.].

EpiLASIK with Mitomycin C

Purpose

Mitomycin C after photorefractive keratectomy (PRK) is used to reduce the development of haze and regression in higher intended corrections. The aim of this study was to investigate the safety, stability, and efficacy of EpiLASIK with mitomycin C.

Methods

Fifty eyes of 29 patients underwent EpiLASIK with the Gebauer EpiLift microkeratome. The mean preoperative spherical equivalent was −6.89 D (SD ±0.63, range −6.0 to −8.0 D). After the laser ablation, mitomycin C 0.02% was applied for 30 seconds on a sterile filter paper. Preoperatively and 1, 3, 6, and 12 months after surgery, a full ophthalmic examination was performed.

Results

In 42 of 50 eyes, the bandage contact lens was removed at day 3. Twelve months after surgery, 96% of all eyes were within ±1.0 D and 82% were within ±0.5 D of intended correction. Five percent of all patients lost 1 line of best-corrected Snellen visual acuity, 42% were stable, and 56% gained 1 or more lines. In most patients, the cornea was clear during the whole follow-up, and in 10% only trace haze was visible. The uncorrected visual acuity was at least 1.0 in 86% of all patients, and all patients reached 0.5.

Conclusions

EpiLASIK with mitomycin C with higher intended corrections seems to be an effective and safe procedure. With the application of mitomycin C, only minimal haze appears.

Wound healing in rabbit corneas after flapless refractive lenticule extraction with a 345 nm ultraviolet femtosecond laser

PURPOSE

To characterize corneal wound healing in a rabbit model after flapless refractive lenticule extraction with a 345 nm ultraviolet femtosecond laser.

SETTING

Departments of Ophthalmology and Anatomy II, University of Erlangen-Nürnberg and Wavelight GmbH, Erlangen, Germany.

DESIGN

Experimental study.

METHODS

Flapless refractive lenticule extraction was performed in 1 eye each of 20 New Zealand white rabbits (-5.0 diopters). Groups of 4 animals were euthanized after 48 hours, 1 week, 2 weeks, 4 weeks, and 3 months, respectively. Corneal samples were prepared for histology and fluorescence microscopy. To assess corneal cell death, proliferation, and myofibroblastic transdifferentiation, terminal uridine deoxynucleotidyl nick end-labeling (TUNEL) assay as well as immunostaining for Ki67 and α-smooth muscle actin (αSMA) were performed on sagittal cryosections.

RESULTS

Histology revealed a zone of keratocyte depletion with a thickness of approximately 50 μm around the extraction site. At 48 hours, pronounced TUNEL staining of keratocytes was detected around the interface (159.9 cells/mm ± 18.4 [SD]), which steadily decreased to 74.9 ± 19.8 cells/mm at 1 week and 5.7 ± 4.8 cells/mm at 2 weeks. Ki67 staining of keratocytes was evident at 48 hours (10.0 ± 3.8 cells/mm), which then decreased at 1 week (5.2 ± 1.7 cells/mm) and 2 weeks (0.4 ± 0.5 cells/mm). From 4 weeks onward, no TUNEL or Ki67 staining was detected. The corneal stroma was αSMA-negative at all timepoints.

CONCLUSION

Application of the 345 nm laser showed no signs of problematic repair processes in the cornea, which supports the initiation of the clinical phase.

Autologous serum eye-drops and enhanced epithelial healing time after photorefractive keratectomy

BACKGROUND

The aim of the study is to test whether use of autologous serum eye-drops can provide earlier epithelial healing following the application of photorefractive keratectomy.

METHOD

Sixty patients (60 eyes) underwent photorefractive keratectomy for myopia. Thirty eyes received autologous serum drops (Study group) while 30 eyes received conventional artificial tears (Control group) after photorefractive keratectomy. An 8 mm epithelial opening was prepared with the application of 18 per cent alcohol for 20 seconds. Photorefractive keratectomy was performed using ESIRIS excimer laser (SCHWIND, Kleinostheim, Germany) with an optic zone of 6.5 mm. Total duration of epithelial healing was monitored as the main outcome measure. The comparisons were done with chi-square test and independent samples t-test. Statistical significance was considered at p < 0.05.

RESULTS

Preoperative myopic spherical refraction and ablation depths were similar in the study and control groups. The mean duration for epithelial healing was about one day shorter in the eyes receiving autologous serum compared to the eyes receiving conventional treatment (2.2 ± 0.25 days versus 3 ± 0 days, p = 0.001). All eyes achieved 6/7.5 or better uncorrected visual acuity in six months. In both groups, more than 90 per cent of eyes were within ±0.50 D of emmetropia in 12 months. No significant difference was noted for the incidence of +1 haze.

CONCLUSION

Use of autologous serum drops reduces epithelial healing duration following surface ablation for two days.

Comparison of performances of femtosecond laser and microkeratome for thin-flap laser in situ keratomileusis

OBJECTIVE

To compare the clinical outcomes of femtosecond laser (FS) and microkeratome (MK) for thin-flap in situ keratomileusis (LASIK).

MATERIALS AND METHODS

Data from patients with moderate to high myopia (spherical equivalent, >-4 diopters [D]) who underwent thin-flap LASIK using FS (199 eyes/110 patients) and MK (157 eyes/86 patients) were analyzed in this retrospective study. Preoperative and postoperative data were recorded from day 1 and months 1 and 3, postoperatively. Visual and refractive outcomes were compared for efficacy, safety, predictability, stability, and the efficacy and safety indices.

RESULTS

Three months postoperatively, more eyes in the FS group had an uncorrected distance visual acuity (UCVA) of 20/40 or better compared to MK group (relative risk [RR] 1.01, 95% confidence interval [CI], 0.97-1.05, P = 0.58); significantly more eyes in FS group had an UCVA of 20/20 or better (RR, 1.26, 95%CI, 1.08-1.48, P = 0.003). Intraoperative bleeding occurred in 5% and 36.7%, respectively, of FS and MK groups. There were no significant differences in the refractive predictability within spherical equivalents of 0.5 D (FS, 72%; MK, 63%) and 1.0 D (FS, 90%; MK, 86%). Both groups showed good stability 3 months, postoperatively. The efficacy index in FS group was 113.4%; that in MK group was 102.5% at 3 months postoperatively (P < 0.05). The safety indices for FS and MK groups at 3 months postoperatively were 116.4% and 108.2%, respectively (P < 0.05).

CONCLUSIONS

Both methods of thin-flap created LASIK were effective, safe, predicable, and stable. FS group had significant improvements in efficacy and safety, confirmed by the efficacy and safety indices, compared to MK group. Lasers Surg. Med. 48:596-601, 2016. © 2016 Wiley Periodicals, Inc.

Laser-assisted subepithelial keratectomy (LASEK) versus photorefractive keratectomy (PRK) for correction of myopia

BACKGROUND

Myopia (near-sightedness or short-sightedness) is a condition in which the refractive power of the eye is greater than required. The most frequent complaint of people with myopia is blurred distance vision, which can be eliminated by conventional optical aids such as spectacles or contact lenses, or by refractive surgery procedures such as photorefractive keratectomy (PRK) and laser epithelial keratomileusis (LASEK). PRK uses laser to remove the corneal stroma. Similar to PRK, LASEK first creates an epithelial flap and then replaces it after ablating the corneal stroma. The relative benefits and harms of LASEK and PRK, as shown in different trials, warrant a systematic review.

OBJECTIVES

The objective of this review is to compare LASEK versus PRK for correction of myopia by evaluating their efficacy and safety in terms of postoperative uncorrected visual acuity, residual refractive error, and associated complications.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision group Trials Register) (2015 Issue 12), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to December 2015), EMBASE (January 1980 to December 2015), Latin American and Caribbean Health Sciences (LILACS) (January 1982 to December 2015), the ISRCTN registry (www.isrctn.com/editAdvancedSearch), ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 15 December 2015. We used the Science Citation Index and searched the reference lists of the included trials to identify relevant trials for this review.

SELECTION CRITERIA

We included in this review randomized controlled trials (RCTs) comparing LASEK versus PRK for correction of myopia. Trial participants were 18 years of age or older and had no co-existing ocular or systemic diseases that might affect refractive status or wound healing.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened all reports and assessed the risk of bias of trials included in this review. We extracted data and summarized findings using risk ratios and mean differences. We used a random-effects model when we identified at least three trials, and we used a fixed-effect model when we found fewer than three trials.

MAIN RESULTS

We included 11 RCTs with a total of 428 participants 18 years of age or older with low to moderate myopia. These trials were conducted in the Czech Republic, Brazil, Italy, Iran, China, Korea, Mexico, Turkey, USA, and UK. Investigators of 10 out of 11 trials randomly assigned one eye of each participant to be treated with LASEK and the other with PRK, but did not perform paired-eye (matched) analysis. Because of differences in outcome measures and follow-up times among the included trials, few trials contributed data for many of the outcomes we analyzed for this review. Overall, we judged RCTs to be at unclear risk of bias due to poor reporting; however, because of imprecision, inconsistency, and potential reporting bias, we graded the quality of the evidence from very low to moderate for outcomes assessed in this review.The proportion of eyes with uncorrected visual acuity of 20/20 or better at 12-month follow-up was comparable in LASEK and PRK groups (risk ratio (RR) 0.98, 95% confidence interval (95% CI) 0.92 to 1.05). Although the 95% CI suggests little to no difference in effect between groups, we judged the quality of the evidence to be low because only one trial reported this outcome (102 eyes). At 12 months post treatment, data from two trials suggest no difference or a possibly small effect in favor of PRK over LASEK for the proportion of eyes achieving ± 0.50 D of target refraction (RR 0.93, 95% CI 00.84 to 1.03; 152 eyes; low-quality evidence). At 12 months post treatment, one trial reported that one of 51 eyes in the LASEK group lost one line or more best-spectacle corrected visual acuity compared with none of 51 eyes in the PRK group (RR 3.00, 95% CI 0.13 to 71.96; very low-quality evidence).Three trials reported adverse outcomes at 12 months of follow-up or longer. At 12 months post treatment, three trials reported corneal haze score; however, data were insufficient and were inconsistent among the trials, precluding meta-analysis. One trial reported little or no difference in corneal haze scores between groups; another trial reported that corneal haze scores were lower in the LASEK group than in the PRK group; and one trial did not report analyzable data to estimate a treatment effect. At 24 months post treatment, one trial reported a lower, but clinically unimportant, difference in corneal haze score for LASEK compared with PRK (MD -0.22, 95% CI -0.30 to -0.14; 184 eyes; low-quality evidence).

AUTHORS' CONCLUSIONS

Uncertainty surrounds differences in efficacy, accuracy, safety, and adverse effects between LASEK and PRK for eyes with low to moderate myopia. Future trials comparing LASEK versus PRK should follow reporting standards and follow correct analysis. Trial investigators should expand enrollment criteria to include participants with high myopia and should evaluate visual acuity, refraction, epithelial healing time, pain scores, and adverse events.