Mitomycin C Application After Corneal Cross-linking for Keratoconus Increases Stromal Haze

Refractive surgical approaches to keratoconus: A systematic review and network meta-analysis

Advancements in diagnostic methods and surgical techniques for keratoconus (KC) have increased non-invasive treatment options. Successful surgical planning for KC involves a combination of clinical science, empirical evidence, and surgical expertise. Assessment of disease progression is crucial, and halting the progression should be the focus if it is progressive. While surgeons used to rely on experience alone to decide the surgical method, comparing the network of primary factors, such as visual acuity, across studies can help them choose the most appropriate treatments for each patient and achieve optimal outcomes. Meticulous tabulation methods facilitate interpretation, highlighting the importance of selecting the correct surgical and rehabilitation approach based on each patient's condition and stage of the disease. We detail the outcomes of a comprehensive network meta-analysis comparing the effectiveness of various combined therapeutic refractive treatments for KC at identical stages of the disease, spanning four distinct follow-up intervals. Additionally, the comprehensive analysis suggests that for corneas with optimal best corrected visual acuity (BCVA) preoperatively (classified as regular), combining phakic intraocular lenses with intracorneal ring segments (ICRS) and corneal cross-linking (CXL) could offer the best therapeutic approach provided the disease stage does not exceed stage 3. For irregular corneas, although initial follow-ups show a significant difference in BCVA with surface ablation, longer-term follow-ups recommend combining surface ablation with ICRS and CXL, especially at higher stages.

Ray-Tracing Transepithelial Excimer Laser Central Corneal Remodeling Plus Pachymetry-Guided Accelerated Corneal Crosslinking for Keratoconus

PURPOSE

The aim of this study was to report the 12 to 96 months results of a tissue-preservation algorithm based on ray-tracing-guided transepithelial excimer laser central corneal ablation (RT t-PRK) combined with individualized pachymetry-guided accelerated crosslinking (M nomogram ACXL) in young adult patients with stable keratoconus (KC).

METHODS

This was a prospective interventional study including 38 eyes of 38 young adult patients (stage II KC) with a mean age of 35 years (range 26-46 years) who underwent simultaneous RT with t-PRK plus pachymetry-based ACXL in the worst eye. The treatments were performed using the iViS Suite iRES Excimer Laser (Ligi, Taranto, Italy). Ray-tracing-guided treatments were planned using the customized interactive programmed transepithelial ablation (CIPTA) 2 web software and diagnostic data were assessed by the Precisio 2 tomographer (Ligi, Taranto, Italy) and Sirius tomographer (C.S.O., Florence, Italy). The main outcome measures included uncorrected distance visual acuity, best spectacle-corrected visual acuity, Kmax, high-order aberrations, minimum corneal thickness, and posterior elevation, with a mean follow-up of 52 months (range 12-96 m).

RESULTS

The mean UDVA improved + 3.5 ±1.28 Snellen lines (SL); 38% gained ≥ 4 ±1.34 SLs, 35% ≥ 3 ±1.21 SLs, 22% ≥ 2 ±1.12 SLs, and 5% ≥ 1 ±0.75 SLs. The mean best spectacle-corrected visual acuity increased by + 4.3 ±1.3 SL. Sixty-eight percent gained ≥ 4 ±0.88 SLs and 30% ≥ 3 ±0.78 SL. No SLs were lost.

CONCLUSIONS

RT t-PRK plus ACXL significantly improved the quality of vision in patients with KC, preventing overcorrection and minimizing tissue consumption.

Keratoconus: exploring fundamentals and future perspectives - a comprehensive systematic review

Background

New developments in artificial intelligence, particularly with promising results in early detection and management of keratoconus, have favorably altered the natural history of the disease over the last few decades. Features of artificial intelligence in different machine such as anterior segment optical coherence tomography, and femtosecond laser technique have improved safety, precision, effectiveness, and predictability of treatment modalities of keratoconus (from contact lenses to keratoplasty techniques). These options ingrained in artificial intelligence are already underway and allow ophthalmologist to approach disease in the most non-invasive way.

Objectives

This study comprehensively describes all of the treatment modalities of keratoconus considering machine learning strategies.

Design

A multidimensional comprehensive systematic narrative review.

Data sources and methods

A comprehensive search was done in the five main electronic databases (PubMed, Scopus, Web of Science, Embase, and Cochrane), without language and time or type of study restrictions. Afterward, eligible articles were selected by screening the titles and abstracts based on main mesh keywords. For potentially eligible articles, the full text was also reviewed.

Results

Artificial intelligence demonstrates promise in keratoconus diagnosis and clinical management, spanning early detection (especially in subclinical cases), preoperative screening, postoperative ectasia prediction after keratorefractive surgery, and guiding surgical decisions. The majority of studies employed a solitary machine learning algorithm, whereas minor studies assessed multiple algorithms that evaluated the association of various keratoconus staging and management strategies. Last but not least, AI has proven effective in guiding the implantation of intracorneal ring segments in keratoconus corneas and predicting surgical outcomes.

Conclusion

The efficient and widespread clinical translation of machine learning models in keratoconus management is a crucial goal of potential future approaches to better visual performance in keratoconus patients.

Trial registration

The article has been registered through PROSPERO, an international database of prospectively registered systematic reviews, with the ID: CRD42022319338.

A Novel Procedure for Keratoconus/Corneal Ectasia Treating Epithelial Compensation of Higher-Order Aberrations, Topographic Guided Ablation, and Corneal Cross Linking - The CREATE+CXL Protocol

Purpose

To present the outcomes of a retrospective study in keratoconus/corneal ectasia patients of treating the higher order aberrations compensated for the corneal epithelium in addition to topographic guided ablation followed by corneal cross linking.

Methods

Twenty-seven eyes of 14 patients were treated for keratoconus/corneal ectasia utilizing trans-epithelial topographic guided ablation photorefractive keratectomy (PRK) for treatment of corneal higher order aberrations and lower order astigmatism followed immediately by 15-minute cross linking were examined retrospectively. Six-month results were analyzed via measurement of vision, refraction, residual higher-order aberrations (HOAs), residual lower-order and higher-order aberrations, as well as for loss or gains of lines of best corrected visual acuity.

Results

All eyes save one had reduction in K1, K2, K Max, and K Mean. All eyes had reduction in manifest astigmatism, Contoura measured astigmatism, 57% reduction of higher-order aberrations (HOA), and 53% reduction of higher-order aberrations grouped with lower-order aberrations (Grouped). Nearly all (96.3%) eyes achieved 20/40 vision or better, 20 eyes had 1-7 lines gained of vision, and no eyes had any loss of lines of vision.

Conclusion

Use of the CREATE+CXL protocol combined with 15-minute corneal cross linking results in a significant increase in HOA reduction, as well as a significant improvement in corrected distance visual acuity over past procedures.

Long-term results of hyperopic ablations using alcohol-assisted PRK and FS-LASIK: comparative study

PURPOSE

To evaluate the long-term visual and refractive outcomes of hyperopic excimer ablation using alcohol-assisted photorefractive keratectomy (PRK) and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK).

SETTING

American University of Beirut Medical Center, Beirut, Lebanon.

DESIGN

Retrospective, matched comparative study.

METHODS

Eyes that underwent alcohol-assisted PRK were compared to matched eyes that underwent FS-LASIK. All patients were followed up for at least 3 years after surgery. The refractive and visual outcomes of each group were compared at different postoperative time points. The main outcome measures were spherical equivalent deviation from target (SEDT), manifest refraction, and visual acuity.

RESULTS

83 eyes underwent alcohol-assisted PRK and 83 matched eyes underwent FS-LASIK. Preoperative manifest refraction spherical equivalent was 2.44 ± 1.18 diopters (D) and 2.20 ± 0.87 D ( P = .133) in the PRK and FS-LASIK groups, respectively. Preoperative manifest cylinder was -0.77 ± 0.89 D and -0.61 ± 0.59 D ( P = .175) for the PRK and LASIK groups, respectively. 3 years postoperatively, SEDT was 0.28 ± 0.66 D and 0.40 ± 0.56 D for the PRK and LASIK groups, respectively ( P = .222), whereas manifest cylinder was -0.55 ± 0.49 D and -0.30 ± 0.34 D for PRK and LASIK, respectively ( P < .001). The mean difference vector was 0.59 ± 0.46 for PRK and 0.38 ± 0.32 for LASIK ( P < .001). 13.3% of PRK eyes and 0% of LASIK eyes had >1 D of manifest cylinder ( P = .003).

CONCLUSIONS

Both alcohol-assisted PRK and FS-LASIK are safe and effective for the treatment of hyperopia. PRK induces slightly more postoperative astigmatism than LASIK. Larger optical zones and recently introduced ablation profiles that lead to a smoother ablation surface might improve the clinical results of hyperopic PRK.

Management of keratoconus: an updated review

Keratoconus is the most common corneal ectatic disorder. It is characterized by progressive corneal thinning with resultant irregular astigmatism and myopia. Its prevalence has been estimated at 1:375 to 1:2,000 people globally, with a considerably higher rate in the younger populations. Over the past two decades, there was a paradigm shift in the management of keratoconus. The treatment has expanded significantly from conservative management (e.g., spectacles and contact lenses wear) and penetrating keratoplasty to many other therapeutic and refractive modalities, including corneal cross-linking (with various protocols/techniques), combined CXL-keratorefractive surgeries, intracorneal ring segments, anterior lamellar keratoplasty, and more recently, Bowman's layer transplantation, stromal keratophakia, and stromal regeneration. Several recent large genome-wide association studies (GWAS) have identified important genetic mutations relevant to keratoconus, facilitating the development of potential gene therapy targeting keratoconus and halting the disease progression. In addition, attempts have been made to leverage the power of artificial intelligence-assisted algorithms in enabling earlier detection and progression prediction in keratoconus. In this review, we provide a comprehensive overview of the current and emerging treatment of keratoconus and propose a treatment algorithm for systematically guiding the management of this common clinical entity.

Evaluation of the effects of ethanol and mitomycin on survival of rat limbal stem cells: an in vitro study

PURPOSE

Ethanol and mitomycin C (MMC) are clinically used to treat corneal diseases such as LASEK and LASIK surgery. In this study, we investigated the effects of time-dependent alcohol and MMC in cultured rat limbal stem cells (LSCs) to determine the appropriate time for the use of this compound in the clinical setting.

METHODS

LSCs (N = 10 eyes) isolated from male Wistar rats were cultured and characterized; then, isolates were divided into three groups. One group was exposed to a 20% concentration of ethanol for 5, 10, 15, 20, 25, and 30 s, and cell viability was assessed one, three, and five days following ethanol exposure using an MTT assay. To investigate the effect of MMC, cells in the second group were treated with 0.02% MMC in various periods (i.e., 15 s, 30 s, 60 s, 90 s, and 120 s) and time-dependent responses of cultured LSCs were recorded. Cells in the third group were co-treated with ethanol and MMC; then, dose and time dependency was evaluated.

RESULTS

In comparison with the viable cells in the control group, ethanol markedly decreased the viability of cells in a time-dependent manner in days one and three. On day five, the viability of LSCs was improved significantly (p < 0.05) in comparison with day one. The number of viable progenitor cells was significantly decreased after MMC treatment in a time-dependent manner, as determined by the MTT assay (p < 0.001). The use of mitomycin, along with alcohol, decreased cell viability in all groups treated with ethanol + MMC compared to the control on days one, three, and five (p < 0.0001).

CONCLUSIONS

Our findings suggest that ethanol and MMC reduced cell viability in cultured LSCs in a time-dependent manner. In addition, when LSCs were exposed to alcohol alone, they had a better recovery process within 5 days in comparison to when exposed to mitomycin alone or mitomycin + alcohol.

Effect of fluence levels on prophylactic corneal cross-linking for laser in situ keratomileusis and transepithelial photorefractive keratectomy

PURPOSE

The purpose of this study is to assess the effect of various fluence levels on prophylactic corneal cross-linking (CXL) combined with femtosecond laser in situ keratomileusis (FS-LASIK-Xtra) or transepithelial photorefractive keratectomy (TransPRK-Xtra) on biomechanics, demarcation line (DL), and stromal haze.

METHODS

Prospective analysis where two prophylactic CXL protocols (lower/higher fluence [LF/HF]: 30 mw/cm² , 60/80 s, 1.8/2.4 J/cm² ) were performed as part of either an FS-LASIK-Xtra or TransPRK-Xtra procedure. Data were collected preoperatively and at 1 week and 1, 3, and 6 months postoperatively. Main outcome measures were (1) dynamic corneal response parameters and the stress-strain index (SSI) from Corvis, (2) actual DL depth (ADL), and (3) stromal haze on OCT images analysed by a machine learning algorithm.

RESULTS

Eighty-six eyes from 86 patients underwent FS-LASIK-Xtra-HF (21 eyes), FS-LASIK-Xtra-LF (21 eyes), TransPRK-Xtra-HF (23 eyes), and TransPRK-Xtra-LF (21 eyes). SSI increased similarly by around 15% in all groups 6 months postoperatively (p = 0.155). All other corneal biomechanical parameters were statistically significant worsening postoperatively, but the change was similar in all groups. At 1 month postoperatively, there was no statistical difference in mean ADL among four groups (p = 0.613), mean stromal haze was similar between the two FS-LASIK-Xtra groups, but higher in the TransPRK-Xtra-HF group compared with the TransPRK-Xtra-LF group.

CONCLUSIONS

FS-LASIK-Xtra and TransPRK-Xtra lead to a similar ADL and improve SSI equally. Lower fluence prophylactic CXL might be recommended as it achieves similar mean ADL with potentially less induced stromal haze, especially in TransPRK. The clinical relevance and applicability of such protocols remains to be assessed.

Combined photorefractive keratectomy and corneal collagen cross-linking for treatment of keratoconus: a 2-year follow-up study

Background:

Corneal collagen cross-linking (CXL) is considered an effective procedure for slowing down or eliminating the progression of keratoconus. New techniques, in combination with CXL, have been proposed to stop the evolution of keratoconus and improve the visual function.

Objective:

To evaluate the effectiveness of combined photorefractive keratectomy (PRK) with mitomycin-C (MMC) application and CXL in the management of grade 1–2 keratoconus over a 2-year follow-up.

Methods:

Fifteen eyes underwent topography-guided PRK with 0.02% MMC application immediately followed by standard CXL.

Results:

Best corrected visual acuity improved from 0.15 ± 0.11 logMAR to 0.08 ± 0.09 logMAR at 24 months (p < 0.0001) in treated eyes. Mean steepest meridian keratometry reduced from 48.79 ± 3.22 D at baseline to 46.16 ± 3.11 D at 24 months (p < 0.0001). Mean flattest meridian keratometry reduced from 45.18 ± 2.17 D preoperatively to 44.35 ± 2.19 D at 24 months (p < 0.0001).

Conclusion:

Simultaneous topography-guided PRK with MMC 0.02% application and standard CXL is a safe, promising and effective procedure in the treatment of mild and moderate keratoconus.

Treatment of Keratoconus with WaveLight Contoura and Corneal Cross-Linking Combined

Purpose

To investigate the outcomes of the treatment of keratoconus/corneal ectasia utilizing topographic-guided ablation (WaveLight Contoura) followed by corneal cross-linking.

Methods

Thirty-six eyes of 21 patients were treated for keratoconus/corneal ectasia utilizing topographic guided ablation photorefractive keratectomy (PRK) for treatment of corneal higher-order aberrations and refractive error followed immediately by 15-minute cross-linking were examined retrospectively. Six-month results were analyzed via measurement of vision, refraction, residual higher-order aberrations (HOAs), residual lower-order and higher-order aberrations, as well as for loss or gains of lines of best-corrected visual acuity.

Results

All eyes save one had reduction in K1, K2, K Max, K Mean. All eyes had reduction in manifest astigmatism, Contoura-measured astigmatism, higher-order aberrations, higher-order aberrations grouped with lower-order aberrations (Grouped). Four eyes had lost 1-2 lines of vision, mainly to corneal haze formation, 17 eyes gained lines of vision, and 15 eyes equaled their pre-op best-corrected visual acuity. Eight eyes from four sample patients have their data included in this manuscript to demonstrate the procedure and the outcomes.

Conclusion

Treatment with WaveLight Contoura combined with 15-minute corneal cross-linking is an effective and safe treatment for keratoconus and should be considered a primary treatment to prevent corneal transplant as well as improve vision and corneal irregularity.

Severe long-term progressive corneal remodeling after bilateral simultaneous prophylactic crosslinking and topography-guided surface ablation with mitomycin

To report a case of a 20-year-old woman who developed massive and progressive corneal remodeling in both eyes after bilateral PRK with mitomycin and CXL as an elective refractive procedure for mild keratoconus. The patient had 6 years of follow up, initially presenting with focal steepening of up to 20 diopters on both eyes one-and-a-half- years postoperatively that spontaneously reversed over the next five years while the high order aberrations worsened. At the present time, the patient depends on bilateral scleral contact lenses for her day-to-day activities. The use of combined elective PRK with mitomycin and prophylactic CXL could lead to progressive corneal deformation. Additional reports would help to establish the role of this combination procedure among the armamentarium to visually rehabilitate patients with keratoconus.