Eighteen-year follow-up of excimer laser photorefractive keratectomy

Bibliometric and visualized analysis of myopic corneal refractive surgery research: from 1979 to 2022

Background

Myopic corneal refractive surgery is one of the most prevalent ophthalmic procedures for correcting ametropia. This study aimed to perform a bibliometric analysis of research in the field of corneal refractive surgery over the past 40 years in order to describe the current international status and to identify most influential factors, while highlighting research hotspots.

Methods

A bibliometric analysis based on the Web of Science Core Collection (WoSCC) was used to analyze the publication trends in research related to myopic corneal refractive surgery. VOSviewer v.1.6.10 was used to construct the knowledge map in order to visualize the publications, distribution of countries, international collaborations, author productivity, source journals, cited references, keywords, and research hotspots in this field.

Results

A total of 4,680 publications on myopic corneal refractive surgery published between 1979 and 2022 were retrieved. The United States has published the most papers, with Emory University contributing to the most citations. The Journal of Cataract and Refractive Surgery published the greatest number of articles, and the top 10 cited references mainly focused on outcomes and wound healing in refractive surgery. Previous research emphasized "radial keratotomy (RK)" and excimer laser-associated operation methods. The keywords containing femtosecond (FS) laser associated with "small incision lenticule extraction (SMILE)" and its "safety" had higher burst strength, indicating a shift of operation methods and coinciding with the global trends in refractive surgery. The document citation network was clustered into five groups: (1) outcomes of refractive surgery: (2) preoperative examinations for refractive surgery were as follows: (3) complications of myopic corneal refractive surgery; (4) corneal wound healing and cytobiology research related to photorefractive laser keratotomy; and (5) biomechanics of myopic corneal refractive surgery.

Conclusion

The bibliometric analysis in this study may provide scholars with valuable to information and help them better understand the global trends in myopic corneal refractive surgery research frontiers. Two stages of rapid development occurred around 1991 and 2013, shortly after the innovation of PRK and SMILE surgical techniques. The most cited articles mainly focused on corneal wound healing, clinical outcomes, ocular aberration, corneal ectasia, and corneal topography, representing the safety of the new techniques.

Unexpected ocular morphological changes after corneal refractive surgery: A review

Corneal refractive surgery (CRS) currently is widely used to correct refractive errors because of its efficacy and reliability. Several studies dealt with the corneal modification induced by this type of surgery, but it is still debated if CRS can induce unexpected changes namely anterior chamber depth (ACD) and axial length (AL). A literature review was performed, including all articles regarding CRS and eye-variations from 1999 to December 2021. Excluding articles about specific systemic conditions (e.g., pregnancy), pathological conditions, post-surgical complications or about only corneal flattening and thinning post CRS, we found nine studies that met the search criteria. We divided the found articles according to the type of surgery performed (radial keratotomy, PRK/LASEK, lasik) and analyzed the results about ACD and AL. Finally, according to the literature, we can conclude that CRS not only gives a corneal flattening, thinning and biomechanical changes, but also induces AL and ACD decrease. This makes the AL and ACD measurements obtained before CRS uselessness in case of IOL power calculation.

Ten-Year Outcome of Topography-Guided Transepithelial Surface Ablation for Refractive Myopia Treatment

BACKGROUND

To evaluate 10-year long-term refractive visual stability and participants' satisfaction in the refractive treatment of myopic eyes undergoing topography-guided transepithelial surface ablation using a 1KHz excimer laser.

PATIENTS AND METHODS

This single-center prospective survey assessed participants' satisfaction 10 years after the treatment using a non-validated questionnaire with regards to visual outcome, dry eye, and visual disturbance symptoms. Pre- and postoperative visual and refractive data were evaluated.

RESULTS

Of 106 participants (54% females) with a mean patient age of 36 (± 8.6) years, 166 eyes were included. Mean preoperative spherical equivalent (SE) was - 4.23 (± 2.48) diopters (D). Uncorrected distant visual acuity (UCVA) after 10 years was ≥ 1.0 (Snellen) in 92% of the eyes. Manifest SE was within ± 1.0 D of the desired refraction in 86% of the eyes after 10 years. Mean quality of life (QOL) improvement was high (9.15 out of 10 points). Dry eye symptoms were reported by 35 out of 104 (34%) patients. Visual symptoms like halos or starbursts were reported by 24 out of 101 (24%) and 12 out of 100 (12%) patients, respectively.

CONCLUSIONS

Topography-guided transepithelial surface ablation for myopia provided stable long-term results in terms of UCVA and SE. Participant satisfaction was high, with only low rates of dry eye or visual symptoms.

Surface ablation outcomes in high myopia with different epithelium removal techniques

PURPOSE

To study the outcomes of alcohol-assisted photorefractive keratectomy (PRK) when compared with transepithelial PRK (TransPRK) using 2 software programs, with or without SmartPulse Technology (SmartSurfACE), in high myopia.

SETTING

Vissum Miranza, University Miguel Hernandez, Alicante, Spain.

DESIGN

Retrospective, consecutive, case series.

METHODS

High myopic eyes undergoing surface ablation were included. The main inclusion criteria were preoperative spherical equivalent (SE) above -5.50 diopters (D) and no other ocular surgeries. Mitomycin-C was used in all the surgeries. The outcomes were analyzed using the 6-month follow-up visit data.

RESULTS

135 eyes were included. Alcohol-assisted PRK was performed in 65 eyes, transepithelial PRK (TransPRK1) in 32 eyes, and TransPRK2 in 38 eyes. The mean all groups preoperative sphere, cylinder, and SE were -6.00 ± 0.87 D, -1.13 ± 1.03 D, and -6.57 ± 0.69 D, respectively. The mean efficacy index in the alcohol-assisted PRK group was 0.91 ± 0.18 compared with 0.98 ± 0.1 and 0.98 ± 0.12 in the TransPRK1 and TransPRK2, respectively (P = .027). The mean safety index in alcohol-assisted PRK was 0.99 ± 0.05, whereas it was 1 ± 0.06 in the TransPRK1 and 0.99 ± 0.08 in the TransPRK2 (P = .780). A final SE of ± 0.50 D was achieved in 96.9% of eyes in the TransPRK1 group and in 100% eyes in the TransPRK2 group compared with 73.8% in the alcohol-assisted PRK group (P < .001).

CONCLUSIONS

Surface ablation with the Amaris 500 excimer laser with flying spot pattern and mitomycin C use showed adequate refractive outcomes in high myopia correction in the 3 groups. TransPRK with or without SmartPulse Technology achieved statistically significant better outcomes than alcohol-assisted PRK in refractive predictability and efficacy.

[Long-term outcomes of PRK, LASIK and SMILE]

BACKGROUND

Patients and refractive surgeons have a legitimate interest in the long-term results of the most commonly used laser procedures for correction of ametropia.

OBJECTIVE

To assess the safety, predictability, stability and late complications according to the current recommendations of the committee for refractive surgery (KRC).

METHODS

Literature search in PubMed with the search term "long-term outcome" combined with either "PRK", "LASIK" or "SMILE". Articles about PRK and LASIK with a minimum follow-up of 10 years and SMILE with a minimum follow-up of 5 years were evaluated and duplications were eliminated.

RESULTS

From a total of 440 articles that matched these search terms 15 articles were selected and analyzed. The results of PRK were described in 4 studies with a total of 666 eyes, 7 studies (566 eyes) described the results of LASIK and 5 studies (188 eyes) the results after SMILE.

CONCLUSION

Long-term studies with follow-up periods of at least 10 years have shown that PRK and LASIK treatment carried out in the early days of medical excimer lasers have a very high level of safety and late complications occurred only rarely. The effectiveness of particularly high corrections declined over time. In contrast, there was no clinically significant regression within the indications recommended by the KRC. The results of SMILE were not inferior to those of PRK and LASIK. In direct long-term comparisons no procedure showed a clear superiority. Due to technological improvements in hardware and software for both preoperative diagnostics and lasers, treatment performed nowadays is presumably even safer, more efficient and also more stable over a long period of time.

[Regression and ablation profiles in corneal refractive surgery]

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

Biological effects of mitomycin C on late corneal haze stromal fibrosis following PRK

This review details the current understanding of the mechanism of action and corneal effects of mitomycin C (MMC) for prophylactic prevention of stromal fibrosis after photorefractive keratectomy (PRK), and includes discussion of available information on dosage and exposure time recommended for MMC during PRK. MMC is an alkylating agent, with DNA-crosslinking activity, that inhibits DNA replication and cellular proliferation. It acts as a pro-drug and requires reduction in the tissue to be converted to an active agent capable of DNA alkylation. Although MMC augments the early keratocyte apoptosis wave in the anterior corneal stroma, its most important effect responsible for inhibition of fibrosis in surface ablation procedures such as PRK is via the inhibition of mitosis of myofibroblast precursor cells during the first few weeks after PRK. MMC use is especially useful when treating eyes with higher levels of myopia (≥approximately 6 D), which have shown higher risk of developing fibrosis (also clinically termed late haze). Studies have supported the use of MMC at a concentration of 0.02%, rather than lower doses (such as 0.01% or 0.002%), for optimal reduction of fibrosis after PRK. Exposure times for 0.02% MMC longer than 40 s may be beneficial for moderate to high myopia (≥6D), but shorter exposures times appear to be equally effective for lower levels of myopia. Although MMC treatment may also be beneficial in preventing fibrosis after PRK treatments for hyperopia and astigmatism, more studies are needed. Thus, despite the clinical use of MMC after PRK for nearly twenty years-with limited evidence of harmful effects in the cornea-many decades of experience will be needed to exclude late long-term effects that could be noted after MMC treatment.

Twenty-Year Follow-Up of Excimer Laser Photorefractive Keratectomy: A Retrospective Observational Study

Introduction

Photorefractive keratectomy (PRK) was introduced in the late 1980s to correct myopia. The purpose of this study was to assess its long-term efficacy and safety, analyzing patients with at least 20-year follow-up.

Methods

This retrospective observational study was carried out on 85 eyes of 54 patients (33 females) that underwent PRK between 1991 and 1998 (mean age 32.62 ± 9.74, range 18–55 years). Both preoperatively and postoperatively, patients underwent a complete ophthalmological evaluation, including uncorrected and corrected distance visual acuity, slit-lamp, intraocular pressure, dilated fundus, and corneal topographic examinations. The outcome assessment was made by comparing the preoperative refraction, as spherical equivalent, with the postoperative ones, taking into account the planned refractive correction. Safety and efficacy indices were also calculated. All the data were evaluated with a paired t test.

Results

The mean attempted correction as spherical equivalent was – 5.64 ± 3.01 D (range – 1.00 to – 15.00 D), while the mean achieved correction after 20 years was – 4.30 ± 3.13 D (range – 1.88 to – 14.25 D), with a significant statistical difference (p < 0.01).

The mean expected refractive outcome was – 0.27 ± 0.81 D (range – 4.00 to + 1.25 D). The mean difference between achieved and attempted treatment was 1.33 ± 1.92 D (range – 4.25 to + 6.25 D), with a significant difference (p < 0.01).

The safety index was 1.00 and the efficacy index was 0.63.

Conclusion

The results provided by this study highlight that the procedure could be considered safe, with no long-term sight-threatening complications such as late ectasia or haze.

10-Year Results of FLEx Refractive Surgery

PURPOSE

To evaluate the 10-year results of femtosecond lenticule extraction (FLEx) for treatment of myopia and myopic astigmatism.

METHODS

This long-term follow-up of a prospective clinical trial was conducted at HELIOS Klinikum Erfurt and Phillips University of Marburg, Germany. In 2006, 108 eyes underwent the FLEx procedure. All patients were invited for reexamination 10 years after FLEx treatment for myopia and astigmatism. Visual acuity, objective and manifest refraction, intraocular pressure, and slit-lamp examination and side effects were documented. Main outcome measures were uncorrected (UDVA) and corrected (CDVA) distance visual acuity, objective and manifest refraction, and slit-lamp examination and side effects.

RESULTS

A total of 77 eyes of 40 patients of the original treatment group volunteered for a reexamination 10 years after surgery. The mean age of the patients was 45.9 years; 26 were women and 14 were men. UDVA was 0.09 ± 0.19 logMAR and CDVA was stable at -0.1 ± 0.09 logMAR. More than half of the eyes gained one or two Snellen lines, and none of the eyes lost two or more lines. Over the 10-year period, regression was 0.18 D.

CONCLUSIONS

FLEx has stable results 10 years after treatment for myopia and astigmatism. [J Refract Surg. 2019;35(11):707-711.].

Safety and complications after three different surface ablation techniques with mitomycin C: a retrospective analysis of 2757 eyes

BACKGROUND

To evaluate the safety and spectrum of complications of three excimer laser surface ablation techniques (SATs) with an intraoperative application of mitomycin C (MMC) 0.02%. A retrospective, non-comparative large case series.

METHODS

SATs were performed on 2757 eyes with a preoperative spherical equivalent (SE) of - 4.41 ± 2.44 and a Wavelight Allegretto 200 platform. Ablation zone diameters between 6.0 and 7.0 mm were used according to mesopic pupil size. All patients were treated with an intraoperative application of MMC for 30 to 90 s depending on refractive error. The mean follow-up time was > 3 months (107 ± 24 days). Complication range and incidence were analyzed retrospectively and safety index was calculated.

RESULTS

Two thousand seven hundred and fifty-seven eyes met the inclusion criteria for surface ablation. Two thousand five hundred and seventy-three eyes were assigned to alcohol-assisted photorefractive keratectomy (APRK), 135 eyes to transepithelial photorefractive keratectomy (TPRK), and 49 eyes to off-flap epithelial laser in situ keratomileusis (EpiLASIK/EpiK). Overall, the safety index was 1.06 ± 0.28. Haze was graded according to the Fantes scale. Haze incidence rates were highest in the TPRK group (14.81%) and comparably low in APRK (2.95%) and EpiK (4.08%) groups.

CONCLUSIONS

Intraoperative topical application of MMC (0.02%) results in good safety and no severe side effects. However, highest incidence of haze was observed after TPRK. The more frequent peripheral localization of haze might be attributed to large ablation zones and the wavefront optimized ablation profile especially in the PTK modus of the laser platform.

Outcomes of photorefractive keratectomy in patients with atypical topography

Background

Photorefractive keratectomy (PRK) is at risk of serious complications such as corneal ectasia, which can reduce corrected distance visual acuity. The rate of complications of PRK is higher in patients with atypical topography.

Objective

To determine the outcomes of photorefractive keratectomy in patients with atypical topography.

Methods

This cross-sectional study was done in 2015 in Shiraz in Iran. We included 85 eyes in this study. The samples were selected using a simple random sampling method. All patients were under evaluation for uncorrected distance visual acuity, corrected distance visual acuity, manifest refraction, corneal topography, central corneal thickness using pentacam, slit-lamp microscopy, and detailed fondus evaluation. The postoperative examination was done 1–7 years after surgery. Data were analyzed using IBM SPSS 21.0 version. To analyze the data, descriptive statistics (frequency, percentage, mean, and standard deviation), chi-square, and independent samples t-test were used.

Results

We studied 85 eyes. Among the patients, 23 (27.1%) were male and 62 (72.9%) were female. Mean age of the participants was 28.25±5.55 years. Mean postoperative refraction was – 0.37±0.55 diopters. Keratoconus or corneal ectasia was not reported in any patient in this study. There was no statistically significant difference between SI index before and after operation (p=0.736). Mean preoperative refraction was −3.84 ± 1.46 diopters in males and −4.20±1.96 diopters in females; thus there was not statistically significant difference (p = 0.435).

Conclusion

PRK is a safe and efficient photorefractive surgery and is associated with low complication rate in patients with atypical topography.

Advances in Refractive Surgery: June 2014 to July 2015

PURPOSE

The objective of this study was to review the advances in the field of refractive surgery as reported in the peer-reviewed literature during the previous year.

DESIGN

A literature review.

METHODS

In this review, we highlight the most pertinent articles in the field from June 2014 to the end of July 2015.

RESULTS

This past year has seen a growing body of research on small-incision lenticule extraction, presbyopic inlays, and phakic intraocular lenses, as more clinicians are adopting these techniques into their armamentarium.

CONCLUSIONS

Laser-assisted in situ keratomileusis and photorefractive keratectomy continue to dominate the keratorefractive literature, as they remain the most frequently performed refractive surgeries.