Accelerated (45 mW/cm2) Transepithelial Corneal Cross-Linking for Progressive Keratoconus Patients: Long-Term Topographical and Clinical Outcomes

Long-term outcomes of corneal crosslinking

PURPOSE OF REVIEW

This manuscript summarizes contemporary research from 2018 to 2023 evaluating long-term (≥2 years) outcomes of corneal crosslinking (CXL) for progressive keratoconus (KCN).

RECENT FINDINGS

The standard Dresden protocol (SDP) has been utilized clinically since the early 2000 s to treat ectatic disorders, primarily progressive KCN and postrefractive ectasia. Various modifications have since been introduced including accelerated and transepithelial protocols, which are aimed at improving outcomes or reducing complications. This review summarizes data demonstrating that the SDP halts disease progression and improves various visual and topographic indices (UDVA, CDVA, Kmax, K1, K2) up to 13 years postoperatively. Accelerated and transepithelial protocols have been found to be well tolerated alternatives to SDP with similar efficacy profiles. Studies focusing on pediatric populations identified overall higher progression rates after CXL. All protocols reviewed had excellent safety outcomes in adults and children.

SUMMARY

Recent studies revealed that SDP successfully stabilizes KCN long term, and a variety of newer protocols are also effective. Pediatric patients may exhibit higher progression rates after CXL. Further research is required to enhance the efficacy and ease of these protocols.

Accelerated corneal cross-linking (18mW/cm2 for 5 min) with HPMC-riboflavin in progressive keratoconus - 5 years follow-up

PURPOSE

To evaluate long-term results of accelerated corneal cross-linking (ACXL) in patients with progressive keratoconus, seventy-four eyes of 53 patients with progressive keratoconus (documented Kmax progression > 1D/a) who underwent ACXL (18mW/cm2 for 5 min) were included in a retrospective observational clinical study. The investigation focused on tomographic and keratometric parameters, refractive data, and visual outcomes at 5 years follow-ups.

METHODS

Corrected distance visual acuity (CDVA), slit lamp, and Pentacam® examinations were conducted, including assessments of thinnest corneal point (TP), minimum radius (Rmin), corneal astigmatism, and maximum anterior keratometry (Kmax). These examinations were performed two weeks before the surgery and, on average, 56 months after the surgery. In a subgroup of 24 eyes, Pentacam® examination data from an intermediate visit at 12 months until the final visit was evaluated to confirm continuous stability. The ACXL protocol included corneal abrasion, hydroxypropylmethylcellulose (HPMC)-riboflavin eye drops administered every 5 min for a total duration of 30 min, and irradiation with 18mW/cm2 for 5 min using riboflavin eye drops applied every minute during the irradiation process. Intraoperatively, minimal corneal pachymetry of > 400 µm was ensured in every patient.

RESULTS

After 56 months, all values exhibited statistically significant changes (paired t-test; CDVA p = 0.002; Kmax p < 0.001; Rmin p < 0.001; astigmatism p = 0.03; TP p < 0.001). In the subgroup analysis of 24 eyes, which included tomographical and keratometric parameters, no statistically significant changes were observed during the last 12 months of observation (paired t-test; Kmax p = 0.72; Rmin p = 0.67; astigmatism p = 0.72). Treatment failure was strictly defined as an increase in Kmax (> 1D) during the 5-year follow-up and was observed in only 3 eyes (4%).

CONCLUSIONS

ACXL is an effective and safe treatment for patients with progressive keratoconus. Our results demonstrate improvements in functional and tomographical outcomes even after high-energy ACXL (18mW/cm2 for 5 min) over a long-term period of 56 months. Our analysis indicates stable conditions in previously progressive keratoconus, particularly during the final year of the observation period. The treatment failure rate was 4%.

Transepithelial Accelerated Crosslinking for Progressive Keratoconus: A Critical Analysis of Medium-Term Treatment Outcomes

Purpose

To report the 4-year outcomes of transepithelial accelerated corneal collagen crosslinking (TE-ACXL) in the treatment of eyes with progressive keratoconus (KC).

Methods

Eyes of patients who underwent TE-ACXL (6mW/cm2 for 15 minutes) for progressive KC and presented 48 months of follow-up were included. Corrected distance visual acuity (CDVA), keratometry measurements (Kmax, maximum keratometry, Kmean, mean keratometry and Astg, corneal astigmatism), thinnest corneal thickness (PachyMin), and topographic, and tomographic indices (specifically the posterior radius of curvature from the 3.0 mm centered on the thinnest point of the cornea (PRC), and the D-index) were analysed preoperatively and every 12 months after TE-ACXL, up to 48 months. Progression after TE-ACXL was considered when eyes presented ≥1 criteria: (1) increase of ≥1D in Kmax or increase of ≥0.75D in Kmean or increase of ≥1D in Astg; (2) reduction of ≥0.085 mm in PRC; (3) decrease ≥5% in PachyMin.

Results

41 eyes from 30 patients were included, with a mean age at crosslinking of 20.90±4.69 years. There was a significant increase in Kmean (+0.64±1.04 D, p<0.001; +0.98 ± 1.49 D, p<0.001; +1.27±2.01 D, p<0.001; +1.13±2.00 D, p=0.006) and a significant decrease in PRC throughout follow-up (-0.12±0.22, p=0.002; -0.15±0.24, p<0.001; -0.17±0.43, p=0.021; -0.16±0.43, p=0.027). PachyMin decreased significantly at 36 and 48 months (-8.50±15.93 μm, p=0.004; -7.82±18.37, p=0.033). According to our progression criteria, there was a major progression rate throughout follow-up (57.1%, 61.1%, 58.8%, and 67.9%, respectively). Surgery and follow-up were uneventful in all subjects. Eleven eyes (26.8%) required further procedures, ≥36 months after the initial TE-ACXL, due to persistent progressive disease.

Conclusion

TE-ACXL proved to be a safe therapeutic option for progressive KC. However, its efficacy is deemed unsatisfactory, as a notable proportion of affected eyes may continue to advance within a 4-year timeframe, necessitating additional procedures to halt the disease's course.

Corneal biomechanical stiffness and histopathological changes after in vivo repeated accelerated corneal cross-linking in cat eyes

Corneal cross-linking (CXL) has been proved efficiency for treating progressive keratoconus and other corneal ectasia diseases by stabilizing corneal geometry and biomechanics. However, the necessity of repeated CXL treatment in patients is unknown. This study aimed to investigate corneal biomechanical stiffness and change in corneal histopathological characteristics after repeated accelerated CXL (A-CXL) in cat eyes. A-CXL was performed with 0.1% riboflavin applied for 10 min, followed by ultraviolet A irradiation at 30 mW/cm² for 3 min at 365 nm in 15 domestic cats. Corneas (n = 30) were divided into three groups: one-time accelerated corneal cross-linking (A-CXL*1 group), repeated accelerated corneal cross-linking (A-CXL*2 group), and an untreated control group. In A-CXL*2 group, A-CXL was repeated at 1-month intervals. In vivo ocular examinations were performed pre- and postoperatively. Biomechanical analysis was performed using a biotester biaxial testing system. We used the Mooney-Rivlin strain-energy function to describe corneal material properties. No infection in any case after A-CXL was observed. Biomechanical tests showed that the stress-strain curves of the two A-CXL groups were significantly different from those of the control group (P < 0.01), whereas stress-strain curve of the A-CXL*2 group was similar to that of the A-CXL*1 group (P > 0.05). Delayed epithelial healing and haze were observed 1 month after surgery. Stromal demarcation line depth measured with anterior spectral-domain optical coherence tomography was 187.6 ± 20.4 and 197.1 ± 11.5 μm for the A-CXL*1 and A-CXL*2 groups, respectively (P > 0.05). These results show that A-CXL can increase corneal biomechanics in cat eyes. The biomechanical enhancement of cat corneas treated with repeated A-CXL at 1-month intervals was similar to that of performing a one-time A-CXL. Repeated cross-linking procedures at short intervals may increase the risk of adverse reactions, and more caution should be taken in clinical applications.

Three-year results of accelerated transepithelial cross-linking (30 mW/cm2 × 3 min) for keratoconus: a prospective study

Objective

To assess the long-term efficacy and safety of accelerated transepithelial corneal cross-linking (ATE-CXL) with 30 mW/cm2 × 3 min.

Methods and Analysis

Thirty-four eyes of 23 patients with progressive keratoconus (KCN) recruited within a single centre were enrolled in this prospective interventional study. Exclusion criteria included: history of Descemet’s membrane rupture, glaucoma, uveitis, severe dry eye, concurrent corneal infections, and systemic disease that could affect corneal healing. ATE-CXL was performed with 3 min of ultraviolet-A continuous irradiation (30 mW/cm2). Follow-up examinations were scheduled on postoperative day 1; 1 and 2 weeks; 1, 3 and 6 months; and 1, 2 and 3 years. Main outcome measures were maximum corneal power (Kmax), average corneal power (AvgK), steepest corneal power (Ks), central corneal thickness, thinnest corneal thickness, uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BCVA) and endothelial cell density.

Results

Mean Kmax, AvgK, Ks, UCVA, BCVA and endothelial cell density did not significantly change over 3 years. The speed of progression obtained by linear regression analysis on corneal parameters (Kmax, AvgK, Ks) improved after ATE-CXL. All baseline parameters correlated with the postoperative Kmax slope. Two eyes underwent ATE-CXL redo because of continued progression after the primary CXL.

Conclusion

This is the first report of 3-year results of ATE-CXL with 30 mW/cm2 × 3 min. ATE-CXL (30 mW/cm2 × 3 min) was safe and effective for slowing down KCN progression.

Trial registration number

This study was registered with ID UMIN000009372 in UMIN-Clinical Trials Registry.

Long-Term Follow-Up of Accelerated Transepithelial Corneal Crosslinking for Post-LASIK Ectasia: A Pilot Prospective Observational Study

Background: Keratectasia after corneal refractive surgery is a rare but serious postoperative complication, and reports on accelerated transepithelial corneal crosslinking (ATE-CXL)-based treatment of patients with post-laser-assisted in situ keratomileusis (LASIK) ectasia are limited. Therefore, this study evaluated the long-term efficacy and safety of ATE-CXL for progressive post-LASIK ectasia.

Methods: This prospective observational study was conducted at the Eye and ENT Hospital, Fudan University, Shanghai, China, and 25 eyes from 25 patients with post-LASIK ectasia undergoing ATE-CXL were examined. Clinical examinations were conducted preoperatively and postoperatively to assess parameters such as manifest refraction, corrected distance visual acuity (CDVA), endothelial cell density; keratometry, corneal thickness, posterior elevation and topometric indices were measured using Pentacam; sectoral pachymetry and epithelial thickness were evaluated using optical coherence tomography. A paired t-test, Wilcoxon rank-sum test, Kruskal-Wallis test, and repeated measures analysis of variance were used for statistical analysis.

Results: Participants were examined for an average of 46 months. No severe complications occurred during or after ATE-CXL. CDVA improved from 0.25 ± 0.31 preoperatively to 0.15 ± 0.17 postoperatively (p = 0.011). Maximum keratometry decreased from 55.20 ± 8.33 D to 54.40 ± 7.98 D, with no statistical significance (p = 0.074), and the central corneal thickness increased from 414.92 ± 40.96 μm to 420.28 ± 44.78 μm (p = 0.047) at the final follow-up. Posterior elevation, pachymetry, and epithelial thickness remained stable (p > 0.05) throughout the follow-up. No significant differences were noted in topometric indices, except the central keratoconus index, which decreased significantly (p < 0.001) at the final follow-up.

Conclusion: Improvements in CDVA and stabilization in corneal keratometry and posterior elevation after ATE-CXL were noted at the 46-months follow-up, demonstrating that ATE-CXL is a safe and effective treatment for progressive post-LASIK ectasia.

Update on corneal collagen crosslinking for ectasia

PURPOSE OF REVIEW

Corneal collagen crosslinking (CXL) is a minimally invasive treatment that can stabilize corneal ectatic disorders including keratoconus, pellucid marginal degeneration, or postrefractive surgery ectasia. The benefits of CXL have been well documented. New research is focused on modifying current treatment protocols with the goals of maximizing corneal stability while also shortening overall procedure time.

RECENT FINDINGS

Accelerated CXL protocols have the goal of delivering the same ultraviolet A intensity as conventional protocols, but over a shorter time period. Accelerated protocols have shown success to date, but there are concerns for long-term corneal stability. Pulsed protocols may increase the long-term efficacy of the accelerated designs. In addition, transepithelial crosslinking protocols have been designed with the goal of reducing postoperative pain and lower the risk of infectious complications of epithelial-off conventional protocols.

SUMMARY

Newer CXL protocols attempt to make the procedure safer and more effective. Current research is promising, but long-term studies are essential to understand how the new protocols may affect corneal stability.