Accelerated versus standard corneal collagen cross-linking in pediatric keratoconus patients: 24 months follow-up results

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.

Long-term results of accelerated corneal collagen crosslinking in paediatric patients with progressive keratoconus: 10-year follow-up

OBJECTIVES

To evaluate the 10-year visual, refractive, and tomographic outcomes of epithelium-off accelerated corneal collagen cross-linking (ACCL) in paediatric patients with progressive keratoconus (KC) and to compare the stages in terms of re-progression.

METHODS

Patients under 18 years of age with progressive KC who underwent ACCL between 2010 and 2012 and completed at least 10 years of follow-up were included in this retrospective study. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refractive errors, and corneal tomography parameters were evaluated preoperatively and at 1, 5, and 10 years postoperatively. The effect of stage and age on re-progression was analysed.

RESULTS

The study included 175 eyes of 97 patients (mean age: 14.46 ± 2.17 years). Improvement in UDVA and CDVA was observed in all postoperative periods compared to the preoperative period (each p-value < 0.05). The increase in spherical equivalent (SE), flattening of keratometry values, and decrease in thinnest corneal thickness (TCT) were statistically significant in the tenth year compared to preoperatively (each p-value < 0.05). Re-progression was observed in 16 eyes (9.14%). Haze was observed in 13 eyes (7.43%), 4 of which were permanent. Deep anterior lamellar keratoplasty was performed in 3 eyes (1.7%) and a second ACCL in 3 eyes (1.7%).

CONCLUSIONS

ACCL is an effective and safe long-term strategy to prevent progression of KC in paediatric patients. In the light of this study with a 10-year follow-up re-progression rate of 9.14%, long-term follow-up of patients after ACCL for possible re-progression and the need for re-CCL or keratoplasty may be recommended.

Outcomes of accelerated corneal cross-linking for pediatric and adult keratoconus: a comparative study

PURPOSE

To compare the visual, refractive, and topographic outcomes of a high irradiance accelerated corneal crosslinking (ACXL) protocol after a 12-month follow-up between pediatric and adult patients with progressive keratoconus (KC).

METHODS

Retrospective, comparative, cohort study. Patients with KC were divided into two groups: pediatric (≤ 18 years) and adult (> 18 years). All of them were managed with epi-OFF ACXL (30 mW/cm2, 8 min, pulsed 1:1 on and off = 7.2 J/cm2). Visual, refractive, and topographic values were measured preoperatively and at 1, 3, 6, and 12 months postoperative. KC progression, defined as a Kmax increase of  ≥ 1D during follow-up, was recorded.

RESULTS

Eighty-nine eyes (53 patients) were included for analysis; 45 (50.6%) eyes were from pediatric patients and 44 (49.4%) from adults. At one-year follow-up, pediatric patients experienced significantly higher rates of progression (22.2% vs. 4.5%, p = .014). Contrariwise, female gender (Beta = - 3.62, p = .018), a baseline uncorrected visual acuity of Snellen ≥ 20/60 (Beta = - 5.96, p = .007), and being ≥ 15 years at ACXL treatment (Beta = - 0.31, p = .021) were associated with non-progressive disease. A significant improvement in best-corrected visual acuity, Kmin, Km, and Kmax was recorded in both groups. Overall, 86.5% of eyes from both groups showed Kmax stabilization or improvement.

CONCLUSIONS

Despite the similarity in visual, refractive, and topographic outcomes in both groups, younger age was associated with KC progression after ACXL at one year of follow-up.

High-Fluence Epithelium-off Accelerated Pulsed Corneal Cross-linking (15 mW/cm2; 7.2 J/cm2) for Pediatric Keratoconus: A 3-Year Retrospective Analysis

PURPOSE

To assess the safety and efficacy of treatment and secondarily determine the topographic changes, visual outcomes, and demarcation line depth after high-fluence pulsed light accelerated cross-linking (ACXL) in pediatric patients (younger than 18 years) with progressive keratoconus.

METHODS

This retrospective analysis included 32 eyes (25 children, aged 11 to 18 years), with progressive keratoconus treated with high-energy epithelium-off pulsed light ACXL (7.2 J/cm2, 15 mW/cm2, 12 minutes, 2 seconds on/1 second off). Corrected distance visual acuity (CDVA), Scheimpflug tomography, and anterior optical coherence tomography measurements were recorded preoperatively and 1, 2, and 3 years postoperatively.

RESULTS

A total of 32 eyes were included. Significant CDVA improvement, pachymetry, and maximum keratometry reduction were found at all follow-up visits. Mean keratometric values remained stable, and astigmatism showed a mild worsening (< 0.25 D) with statistical significance at 1 and 3 years. Total aberration showed discordant results and coma aberration had a slight improvement without statistical significance. The demarcation line depth was 265 ± 26 μm. Three patients developed mild haze without visual acuity loss. None of the patients underwent a second CXL procedure.

CONCLUSIONS

In pediatric patients, high-fluence epithelium-off pulsed light ACXL appears to be a safe and effective procedure to halt the progression of keratoconus, slightly improving the CDVA and keratometric values. [J Refract Surg. 2024;40(3):e148-e155.].

Analysis of the outcomes of three different cross-linking protocols for treatment of paediatric keratoconus: A multicentre randomized controlled trial

PURPOSE

To analyse long-term outcomes of standard cross-linking (SCXL), accelerated cross-linking (ACXL) and transepithelial cross-linking (TCXL) in the treatment of progressive paediatric keratoconus regarding stability, safety and efficacy.

METHODS

This prospective multicentre randomized controlled trial included 97 eyes of 97 paediatric patients with stages I-III ABCD keratoconus grading system, who were randomized into three groups; SCXL group (control group, n = 32; 3 mW/cm2  × 30 min/5.4 J/cm2 ), ACXL (n = 33; 18 mW/cm2  × 5 min/5.4 J/cm2 ) and TCXL (n = 32; 18 mW/cm2  × 5 min/5.4 J/cm2 ). Subjective refraction, uncorrected and corrected visual acuity, keratometry and pachymetry measurements using corneal topography were recorded preoperatively and 1, 2 and 3 years postoperatively.

RESULTS

SCXL group exhibited significant successive improvements in the mean visual, refractive and keratometric parameters throughout the entire postoperative 3 years while ACXL group exhibited significant improvements in visual and keratometric parameters in the first postoperative year that remained stable in second and third postoperative years. TCXL group exhibited significant progressive deterioration in all mean parameters compared to SCXL and ACXL (p < 0.0001). Both SCXL and ACXL revealed final 100% success rate with good stability while TCXL revealed final 22% failure rate with keratoconus progression (p < 0.0001).

CONCLUSION

SCXL and ACXL were comparable in halting keratoconus progression and achieved good stability and safety; however, SCXL was more efficient than ACXL as it yielded greater significant postoperative mean visual, refractive and keratometric improvements achieving smoother corneal remodelling. Both SCXL and ACXL were much superior to TCXL. SCXL is the best CXL treatment option for paediatric keratoconus while ACXL is a good and effective alternative.

Accelerated Corneal Cross-linking in Pediatric Patients with Progressive Keratoconus: 12-Month Follow-up Results

PURPOSE

To evaluate effectiveness and safety of accelerated corneal cross-linking (CXL) in the treatment of keratoconus in pediatric patients.

SETTING

Tertiary care hospital.

DESIGN

Retrospective observational study.

METHODS

In this study, case series of patients 18 years old or younger with progressive keratoconus who underwent accelerated CXL were observed. All consecutive patients underwent accelerated CXL with setting of 9 mW/cm2 for 10-minute Ultraviolet-A radiation, corresponding to a total dose of 5.4 J/cm2. Preoperative and 12-month postoperative data including uncorrected distance visual acuity (UDVA), best-corrected distance visual acuity (BDVA), keratometry (K) measurements, mean spherical, and cylindrical refraction were evaluated.

RESULTS

The group consisted of 28 eyes from 14 patients (10 males and 4 females). Mean age of the patients was 16.9 years (11-18 years). UDVA did not change significantly from 0.71 ± 0.54 to 0.65 ± 0.43 logMAR (P = 0.41). BDVA improved significantly from 0.30 ± 0.35 to 0.21 ± 0.34 (P = 0.006). The steep K-value decreased from 48.4 ± 4.3 to 48.0 ± 4.6 diopters, but there was no significant change in steep K-value (P = 0.35). There was no significant change in flat and mean K-value (P > 0.05). Mean spherical and cylindrical refraction were not significantly altered (P > 0.05). One patient with vernal keratoconjunctivitis showed sterile peripheral corneal infiltrates. Patient was treated with topical corticosteroids, antibiotics, and artificial tears.

CONCLUSION

The findings revealed that accelerated CXL is an effective and safe procedure that halts the progression of keratoconus in pediatric patients.

Outcome indicators for cross linking in pediatric keratoconus

Purpose

To evaluate the predictive factors for successful corneal collagen cross-linking (CXL) in pediatric patients with Keratoconus (KC).

Methods

This retrospective study was conducted using a prospectively built database. Patients (18 years old or younger) underwent CXL for KC between 2007 and 2017, with a 1-year follow-up period or longer. The outcomes included changes in Kmax (delta [Δ] Kmax = Kmax_last - Kmax_pre) and LogMAR visual acuity (ΔLogMAR = LogMAR_last - LogMAR_pre).The effects of CXL type (accelerated or non-accelerated), demographics (age, sex, background of ocular allergy, ethnicity), preoperative LogMAR visual acuity, maximal corneal power (Kmax), pachymetry (CCT_pre), refractive cylinder, and follow-up (FU) time on the outcomes were analyzed.

Results

One hundred thirty-one eyes of 110 children were included (mean age, 16 ± 2 years; range, 10-18 years). Kmax and LogMAR improved from baseline to last visit: from 53.81 D ± 6.39 D to 52.31 D ± 6.06 D (p < 0.001) and from 0.27 ± 0.23 LogMAR units to 0.23 ± 0.19 LogMAR units (p = 0.005), respectively. A negative ΔKmax (meaning corneal flattening) was associated with a long FU, low CCT_pre, high Kmax_pre, high LogMAR_pre, and non-accelerated CXL on univariate analysis. High Kmax_pre and non-accelerated CXL were associated with negative ΔKmax in the multivariate analysis.A negative ΔLogMAR (meaning vision improvement) was associated with a high LogMAR_pre in univariate analysis.

Conclusion

CXL is an effective treatment option in pediatric patients with KC. Our results showed that the non-accelerated treatment was more effective than the accelerated treatment. Corneas with advanced disease had a greater effect on CXL.

Outcomes of accelerated collagen cross linking in progressive paediatric keratoconus

Purpose

To determine the efficacy and safety of pediatric accelerated cross linking (CXL).

Methods

A prospective study on progressive keratoconus (KC) cases under ≤18 years of age. Sixty four eyes of thirty nine cases underwent epithelium-off accelerated CXL protocol. Visual acuity (VA), slit-lamp examination, refraction, pentacam reading of keratometry (K), corneal thickness, and thinnest location pachymetry were noted. Cases were followed up on days 1, 5, and at 1^st, 3^rd, 6^th, and 12th-month post procedure.

Results

Statistically, significant improvement of the mean aided VA, K, and mean corneal astigmatism (p < 0.0001) was noted. Mean Kmax reading reduced from 55.5 ± 5.64 (47.4-70.4) diopter (D) preoperatively to 54.41 ± 5.51 (46-68.3) D at 12 months postaccelerated CXL. Two cases had progression. Complications encountered were sterile infiltrate and persistent haze.

Conclusion

Accelerated CXL is effective and efficacious in pediatric KC.

Paediatric cornea crosslinking current strategies: A review

Background

In the general population, 1 in 2000 people has keratoconus. Indians and other people from Southeast Asia have a higher incidence of keratoconus. Children with keratoconus typically present earlier in life and with a more severe disease. Rubbing the eyes has been identified as a risk factor. Children have a higher incidence and a faster rate of keratoconus progression. Visual rehabilitation in children with keratoconus is challenging. They have a low compliance with contact lens use. Many of these children require penetrating keratoplasty at an early age. Therefore, stopping the progression of keratoconus in children is of paramount importance.

Main text

Compared to treatment, keratoconus progression prophylaxis is not only preferable, but also easier. Corneal collagen cross-linking has been shown to be safe and effective in stopping its progression in children. The Dresden protocol, which involves central corneal deepithelization (7-9 ​mm), saturation of the stroma with riboflavin (0.25%), and 30 ​min UV-A exposure, has proven to be the most successful. Two significant disadvantages of the typical Dresden regimen are the prolonged operating time and the significant post-operative pain. Accelerated-CXL (9 ​mW/cm2 x 10 ​min) has been studied to reduce operative time and has been shown to be equally effective in some studies. Compared to accelerated CXL or traditional CXL, epi-off procedures, transepithelial treatment without the need for de-epithelialization and without postoperative discomfort, have been shown to be safer but less effective. Corneal crosslinking should only be performed after treating children with active vernal keratoconjunctivitis. Corneal opacity, chronic corneal edema, sterile infiltrates, and microbial keratitis have been reported after cross-linking of corneal collagen.

Conclusions

The "Dresden protocol", also known as the conventional corneal cross-linking approach, should be used to halt the progression of keratoconus in young patients. However, if the procedure needs to be completed more rapidly, accelerated corneal crosslinking may be considered. Transepithelial corneal cross-linking has been proven to be less effective at stabilizing keratoconus, although being more safer.

Three-year follow-up of accelerated versus standard corneal cross-linking in paediatric Keratoconus

PURPOSE

Standard corneal collagen cross-linking (S-CXL) is an effective treatment to arrest Keratoconus (KC) progression in children. Less is known on the long-term efficacy of accelerated CXL (A-CXL) in paediatric populations.

METHODS

A historical cohort analysis of paediatric patients (≤18 years) with KC who underwent S-CXL and A-CXL at two tertiary referral centres in Israel between 2010-2017. Preoperative and 3-year postoperative evaluation included changes in visual acuity (best spectacle corrected [BSCVA]) and uncorrected [UCVA]), refractive errors, and keratometric data.

RESULTS

Ninety-three eyes of 93 patients were analysed (A-CXL: n = 39; S-CXL: n = 54). Baseline characteristics were similar between groups. Both groups showed a significant improvement in visual acuity compared to baseline (S-CXL: 0.810-0.602 LogMAR UCVA; A-CXL: 0.890-0.306 LogMAR UCVA, p < 0.05 for both). Improvement in BSCVA and UCVA following A-CXL was non-inferior to S-CXL (< ± 0.2 LogMAR). Kmax decreased by a mean of 0.98 ± 5.56 dioptres following S-CXL (p = 0.02) and by 1.48 ± 8.4 dioptres following A-CXL (p = 0.015). Thinnest pachymetry decreased following both treatments (S-CXL: by 26.8 ± 40.7 µm, p = 0.001, A-CXL: by 10.2 ± 13.4 µm, p = 0.028), the difference between groups was within the non-inferiority margin (< ± 10 µm).

CONCLUSIONS

Paediatric patients followed for three years after A-CXL showed improved visual function, reduced corneal astigmatism and Kmax, and decreased thinnest corneal thickness. A-CXL was non-inferior to S-CXL at three years in terms of best-corrected and uncorrected visual acuity, thinnest pachymetry, and astigmatism. For Kmax, non-inferiority could not be concluded.

Long-term Safety and Efficacy of Corneal Collagen Crosslinking in a Pediatric Group With Progressive Keratoconus: A 7-year Follow-up

PURPOSE

To assess effectiveness and safety of corneal crosslinking (CXL) to reduce keratoconus (KC) progression and improve visual acuity among children with progressive KC and to analyze the use of 20% dextran-based (Dextran) and 1% hydroxypropyl methylcellulose-based (HPMC) riboflavin.

DESIGN

Prospective, clinical cohort study METHODS: Standard CXL (SCXL) was performed in 74 eyes (58 patients, 45 males, mean age 13.0 ± 2.1 years): 53 eyes with HPMC and 21 with Dextran. Examinations were performed at baseline, 3 and 6 months, and 1, 2, 3, 4, 5, and 7 years of follow-up, including uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), a complete ophthalmologic examination, anterior segment ocular coherence tomography, Scheimpflug corneal tomography, and specular microscopy.

RESULTS

UDVA and CDVA improved at all periods with statistically significant differences in CDVA at 1, 2, and 3 years. Compared with baseline, maximum K (Max K) reduced throughout the 7-year follow-up. Mean thinnest pachymetry (Th Pachy) decreased significantly at 3 months and remained low; in the Dextran group, the Th Pachy mean value returned to baseline 6 months postoperatively. After CXL, 1.5 diopter progression in max K was 1.4% to 14.6% of eyes; worsening was found at 4 to 7 years postoperatively.

CONCLUSION

SCXL reduced KC progression in children up to 7 years of follow-up and revealed improvement and stability of UDVA and CDVA in 82% of eyes. For visual acuity and KC stability, no statistically significant difference was observed between Dextran-HPMC. The HPMC group showed persistent cornea thinning, raising concerns about its use in SCXL.

Accelerated corneal collagen cross-linking in progressive keratoconus: Five-year results and predictors of visual and topographic outcomes

Purpose:

To analyze the 5-year results of accelerated corneal collagen crosslinking (CXL) for progressive keratoconus and identify preoperative characteristics predictive of visual and topographic outcomes.

Methods:

A prospective interventional case series. Nineteen eyes of 19 patients receiving accelerated CXL with settings of 18 mW/cm² for 5 min were included. Clinical and topographic parameters were assessed. Linear regression and logistic regression were used to compare the R² and odds ratio (OR), respectively, between baseline characteristics and postoperative outcomes.

Results:

Corrected distance visual acuity (CDVA) remained stable from 0.28 ± 0.21 to 0.25 ± 0.18 logMAR (P = 0.486). The mean cylindrical refraction was stable (P = 0.119). The maximal keratometry (Kmax) decreased from 61.99 ± 10.37 to 59.25 ± 7.75 D (P < 0.001), flattening in the flattest and steepest meridians and mean keratometry were also observed (P ≤ 0.040). The mean anterior elevation at the apex reduced from 21.42 ± 16.69 to 18.53 ± 12.74 mm (P = 0.013) and changes in posterior elevation were non-significant (P = 0.629). Preoperative Kmax best predicted the postoperative change in Kmax (R² = 0.55, P < 0.001) compared to the other baseline characteristics (P ≤ 0.028), whereas preoperative CDVA was the only significant predictor of postoperative change in CDVA (R² = 0.41, P = 0.003). Accelerated CXL is less likely to fail in eyes with a steeper preoperative Kmax (OR = 0.74, P = 0.040) or greater posterior elevation at the apex (OR = 0.91, P = 0.042).

Conclusion:

Kmax significantly decreased following accelerated CXL. Eyes with worse preoperative CDVA and higher Kmax were more likely to have an improvement in visual acuity and corneal flattening.

Progression of Pediatric Keratoconus After Corneal Cross-Linking: A Systematic Review and Pooled Analysis

PURPOSE

Corneal collagen cross-linking (CXL) is an effective treatment to slow down keratoconus (KC) progression in adults. Several studies have also shown efficacious outcomes in pediatric populations, yet no systematic analysis has been performed and no accepted definition for progression is available in children after CXL. This study aimed to establish the most commonly used criteria for progression and to conduct a systematic review of the literature with pooled analysis to assess children's keratoconus progression after CXL.

METHODS

A systemic literature review combined with pooled analysis was performed on full-length studies of KC after CXL treatment in a pediatric population and the methods used to report progression were analyzed.

RESULTS

Thirty-seven studies (2078 eyes) were identified on the rates of KC progression after CXL. The most common method to report progression was increased Kmax, Kmean, or Ksteep by ≥1.0 diopter (78.3% of studies). Using these criteria, the mean pooled progression rate after epithelium-off CXL was 9.9% (95% confidence interval: 6.1% -14.6%, total pooled sample size: 1508 eyes) with high heterogeneity between studies [I 2 = 86.48% (95% confidence interval: 80.98 - 90.39), P < 0.0001].

CONCLUSIONS

When considering KC progression after CXL in children, with an increase in Kmax, Kmean, or Ksteep ≥ 1.0 diopter, the progression risk was roughly 10%. We encourage clear quantitative reporting of KC progression in future studies evaluating CXL efficacy in pediatric populations.

Pediatric Crosslinking: Current Protocols and Approach

Keratoconus (KC) is likely to be more aggressive in the pediatric population, with a higher risk of progression and visual loss. Several techniques have been proposed for corneal crosslinking (CXL) so far. The standard CXL (SCXL) technique, or the Dresden Protocol, originally developed by Wollensak et al., has been shown to be safe and effective in the pediatric KC group. With similar efficacy to the conventional method, the accelerated CXL (ACXL) protocols proposed a reduced UVA exposure time by increasing the intensity of UVA irradiation. Transepithelial CXL (TCXL), considered an "epithelium-on" method, emerged as a strategy to improve safety and reduce postoperative complications and discomfort. For thinner corneas, we can highlight the use of hypoosmolar riboflavin and new studies, such as contact lens-assisted CXL (CACXL), the epithelial-island CXL (EI-CXL), and the Sub400 protocol. In addition to the different protocols used, another factor that changes CXL results is the type of carrier used: dextran-based or hydroxypropyl methylcellulose-based (HPMC) riboflavin solutions. There are several ways to perform a CXL surgery, and it is still unclear which method is the safest and most effective in the pediatric group. This review of the literature in English, available in PubMed, provides an update on corneal CXL in the pediatric KC group, exploring the data on the techniques currently used and under investigation, including their advantages, efficacy, safety profiles, risks, and cost analyses.

Comparison of Efficacy and Safety Between Standard, Accelerated Epithelium-Off and Transepithelial Corneal Collagen Crosslinking in Pediatric Keratoconus: A Meta-Analysis

Purpose

The purpose of the study is to compare the efficacy of standard epithelium-off CXL (SCXL), accelerated epithelium-off CXL (ACXL), and transepithelial crosslinking CXL (TECXL) for pediatric keratoconus.

Methods

A literature search on the efficacy of SCXL, ACXL, and TECXL [including accelerated TECXL (A-TECXL)] for keratoconus patients younger than 18 years was conducted using PubMed, Cochrane Library, ClinicalTrials.gov, and EMBASE up to 2021. Primary outcomes were changes in uncorrected visual acuity (UCVA) and maximum keratometry (Kmax) after CXL. Secondary outcomes were changes in best-corrected visual acuity (BCVA), mean refractive spherical equivalent (MRSE), and central corneal thickness (CCT). Estimations were analyzed by weighted mean difference (WMD) and 95% confidence interval (CI).

Results

A number of eleven identified studies enrolled 888 eyes (SCXL: 407 eyes; ACXL: 297 eyes; TECXL: 28 eyes; A-TECXL: 156 eyes). For pediatric keratoconus, except for a significant greater improvement in BCVA at 24-month follow-up in SCXL (WMD = –0.08, 95%CI: –0.14 to –0.01, p = 0.03, I² = 71%), no significant difference was observed in other outcomes between the SCXL and ACXL groups. SCXL seems to provide greater changes in UCVA (WMD = –0.24, 95% CI: –0.34 to –0.13, p < 0.00001, I² = 89%), BCVA (WMD = –0.09, 95% CI: –0.15 to –0.04, p = 0.0008, I² = 94%), and Kmax (WMD = –1.93, 95% CI: –3.02 to –0.85, p = 0.0005, I² = 0%) than A-TECXL, with higher incidence of adverse events.

Conclusion

For pediatric keratoconus, both SCXL and ACXL appear to be comparable in the efficacy of visual effects and keratometric outcomes; SCXL seems to provide greater changes in visual and pachymetric outcomes than A-TECXL.

36-Month Outcomes of Mechanical and Transepithelial PTK Epithelium Removal Techniques Prior to Accelerated CXL for Progressive Keratoconus

PURPOSE

To compare the 36-month visual, refractive, and topographic results and the optical quality of the cornea between mechanical and transepithelial phototherapeutic keratectomy (PTK) epithelium removal techniques prior to the accelerated corneal cross-linking (CXL) procedure in patients with progressive keratoconus.

METHODS

Keratoconic eyes that received either mechanical epithelium removal or transepithelial PTK epithelium removal prior to accelerated CXL with 36 months of follow-up were included. The uncorrected (UDVA) and corrected (CDVA) distance visual acuity, spherical equivalent (SE), manifest astigmatism, flat keratometry (K1), steep keratometry (K2), maximum keratometry (Kmax) readings, thinnest corneal thickness (TCT), topographic astigmatism, point spread function (PSF), and aberrometric parameters including root mean square higher order aberrations (RMS HOAs), vertical coma, and spherical aberration (SA) were assessed preoperatively and 12, 24, and 36 months postoperatively.

RESULTS

One hundred ten eyes of 110 patients with keratoconus were included (mechanical epithelium removal group: 69 eyes, transepithelial PTK epithelium removal group: 41 eyes). After the CXL procedure, the mean UDVA, CDVA, manifest astigmatism, RMS HOAs, SA, vertical coma, and PSF improved significantly throughout the follow-up visits in both groups (P < .05 for all variables). The improvement in the mean UDVA, CDVA, manifest astigmatism, K1, K2, Kmax, RMS HOAs, SA, vertical coma, and PSF were significantly better in eyes that underwent transepithelial PTK epithelium removal when compared to eyes that underwent mechanical epithelium removal during the follow-up period (P < .05 for all variables).

CONCLUSIONS

Transepithelial PTK-assisted accelerated CXL seems to be more efficient in improving the visual acuity and the optical quality while stabilizing the cornea compared to the accelerated CXL with mechanical epithelium removal in patients with progressive keratoconus. [J Refract Surg. 2022;38(3):191-200.].

Corneal Cross-Linking as Treatment in Pediatric Keratoconus: Comparison of Two Protocols

Introduction

Keratoconus is a progressive corneal disease commonly treated by collagen cross-linking (CXL). Accelerated protocols have recently become common. This study sought to compare the outcomes of accelerated and standard CXL in terms of visual acuity, keratometry, and tomographic parameters in pediatric population.

Methods

We retrospectively reviewed the files of pediatric patients who underwent standard and accelerated CXL for keratoconus in our hospital, between October 2014 and March 2018. Changes in uncorrected distance visual acuity (UCDVA), best corrected distance visual acuity (BCDVA), tomographic keratometry parameters (K_max, K_steep, K_flat, K_mean), and endothelial density count (EDC) were assessed before and at 6 and 12 months following treatment. The analysis included intergroup and intragroup comparisons.

Results

This study included 53 eyes (44 patients). Fourteen eyes were treated with standard CXL (S-CXL, 3 mW/cm², 30 min), while 39 underwent accelerated CXL (A-CXL, 9 mW/cm², 10 min). Intergroup comparison found insignificant differences between groups, with the exception of better results for UCDVA in the S-CXL group after 12 months (P = 0.03). In this study, there was no significant difference between the two protocols postoperatively in BCDVA, K_max, K_mean, pachymetry, or corneal astigmatism.

Conclusion

A-CXL is as safe and effective as S-CXL for stabilizing progressive keratoconus in pediatric population. Larger-sample-size studies with a longer follow-up time are required. Considering the long-term results of 9 mW A-CXL and its safety and efficacy profile, it should be preferred to S-CXL for reducing treatment time and improving patients' comfort.

Comparative Results Between "Epi-Off" Accelerated and "Epi-Off" Standard Corneal Collagen Crosslinking-UVA in Progressive Keratoconus - 7 Years of Follow-Up

Purpose

The purpose of the present study was to assess the long-term efficiency and safety of the “epi-off” accelerated CXL (9 mW/cm² for 10 minutes) in comparison to the standard “epi-off” CXL (3 mW/cm² for 30 minutes) in terms of topographical and keratometric parameters, refractive data and visual outcomes at 7 years of follow-up, in progressive keratoconus.

Material and Method

A retrospective and comparative study was performed. A total of 183 eyes from 183 patients with documented progressive keratoconus were included in the study. The patients were divided in two groups: 93 eyes from 93 patients underwent “epi-off” standard cross-linking technique (3 mW/cm² for 30 minutes) (S-CXL group) and 90 eyes from 90 patients underwent accelerated “epi-off” corneal CXL technique (9 mW/cm² for 10 minutes) (A-CXL group).

Results

Improvements in uncorrected distance visual acuity (UDVA) were statistically significant compared to baseline values in both groups at each time-point visit (p=0.0421 at 1 year, p=0.0411 at 7 years for A-CXL and p=0.0375 at 1 year, p=0.0389 at 7 years for S-CXL). At 7 years there was a statistically significant increase in CDVA (p=0.039 in the A-CXL group and p=0.0343 in the S-CXL group at 7 years). Statistically significant reduction was noticed in Ksteep (p=0.0411 in A-CXL group and p=0.0224 in S-CXL group), Kflat (p=0.0198 in A-CXL group and p=0.008 in S-CXL group), K mean (p=0.0106 in A-CXL group and p=0.0193 in S-CXL group) and Kmax (p=0.0413 in A-CXL group and p=0.054 in S-CXL group) at 7 years, compared to baseline values, in both groups, but without any statistically difference between the two procedures, at all time-point visits (p>0.05).

Conclusion

The long-term outcomes of “epi-off” accelerated corneal collagen crosslinking-UVA (9 mW/cm² for 10 minutes) are similar to standard “epi-off” corneal collagen crosslinking procedure in the treatment of progressive keratoconus.

Corneal collagen cross-linking epithelium-on vs. epithelium-off: a systematic review and meta-analysis

BACKGROUND

The purpose of the study was to determine the advantages and disadvantages of epi-on corneal cross-linking (CXL) techniques compared with standard epi-off CXL.

METHODS

We searched MEDLINE and EMBASE for randomized controlled trials (RCTs) and non-randomized studies of interventions (NRSIs) and we evaluated the selected papers according to the Cochrane risk of bias tool. We considered, as primary outcomes, average Kmax flattening, changes in uncorrected and corrected distance visual acuity (UDVA and CDVA); as secondary outcomes, we considered changes in pachymetry values and endothelial cell density (ECD). We also investigated adverse events related to the treatments and treatment failure. Meta-analysis was conducted with a fixed or random-effects model using weighted mean difference (MD) with 95% confidence interval (CI) as the effect size.

RESULTS

A total of 15 studies were included and among these 15 trials, 9 were RCTs and 6 were NRSIs, but only 4 studies showed no high risk of bias and were included in this meta-analysis. Our analysis revealed significant postoperative differences in CDVA (MD = 0.07; 95% CI 0.04 to 0.10; P < 0.001), and no significative differences in UDVA, Kmax, central corneal thickness (CCT) and ECD (P > 0.05). Epi-on CXL protocol was found to be significantly less prompt to have risks of delay in epithelial healing (P = 0.035) and persistent stromal haze (P = 0.026).

CONCLUSION

Epi-on CXL is as effective as epi-off CXL. Except for a higher significant improvement in CDVA with current epi-on protocols, our meta-analysis demonstrates that epi-on and epi-off CXL have comparable effects on visual, topographic, pachymetric, and endothelial parameters. Epi-on CXL has clinical advantages in terms of comfort and avoidance of complications as it reduces the risk of developing delay in epithelial healing and persistent stromal haze.

One-Year Follow-Up of Corneal Biomechanical Changes After Accelerated Transepithelial Corneal Cross-Linking in Pediatric Patients With Progressive Keratoconus

Aims: This study aimed to investigate the corneal biomechanical changes and topographic outcomes of accelerated transepithelial corneal cross-linking (ATE-CXL) in pediatric progressive keratoconus.

Methods: In this prospective longitudinal study, 31 eyes of 28 pediatric patients with keratoconus (21 boys and 7 girls; mean age, 14.35 ± 2.68 years) undergoing ATE-CXL (epithelium-on procedure with 45 mW/cm² for 320 s) were included. Corvis ST was used to measure dynamic corneal response parameters at baseline and at 12 month after ATE-CXL. Corneal keratometry and corneal thickness were measured using Pentacam pre-operatively and 1, 6, and 12 month post-operatively.

Results: No serious complications occurred during or after ATE-CXL. The maximum keratometry values were 60.10 ± 7.51 D pre-operatively and 61.42 ± 8.92, 61.17 ± 7.96, and 60.02 ± 7.58 D at 1, 6, and 12 month after ATE-CXL (P > 0.05), respectively. Corneal thickness remained stable during the 12-month follow-up (P > 0.05). At post-operative 12 month, first applanation time (P < 0.001), first applanation length (P = 0.004), second applanation velocity (P = 0.014), highest concavity time (P = 0.022), and radius of curvature at highest concavity (P = 0.031) increased significantly. The value of stiffness parameter at first applanation was significantly increased from 57.70 ± 27.57 pre-operatively to 63.36 ± 27.09 at 12 months after ATE-CXL (P = 0.018).

Conclusions: ATE-CXL is safe and effective in stabilizing the progression of pediatric keratoconus. Changes in corneal biomechanical response consistent with stiffening following ATE-CXL were observed in pediatric patients with keratoconus.

Long term results of accelerated corneal collagen cross-linking in pediatric keratoconus

PURPOSE

To evaluate the long term visual, refractive, and corneal tomographic outcomes of epithelium-off accelerated corneal collagen cross-linking (ACXL) in the management of pediatric keratoconus (KC).

METHODS

This retrospective study included patients under 18 years old with progressive KC who underwent ACXL between 2012 and 2019 at Dicle University Hospital. Complete ophthalmic examination was performed including uncorrected distance visual acuity (UDVA), best spectacle-corrected distance visual acuity (CDVA), manifest refraction, and corneal tomography. Evaluations were performed preoperatively and at 6 months intervals postoperatively.

RESULTS

Forty-nine eyes of 49 patients were included in the study. The mean age of patients at the time of ACXL was 14.2 ± 1.8 (range: 9.5-17.3) years. Mean follow up was 4.61 ± 1.90 (range: 2.0-8.1) years. The mean LogMAR UDVA improved from 0.94 ± 0.41 to 0.81 ± 0.43, 0.69 ± 0.41, and 0.67 ± 0.33 after 1, 3, and 5 years respectively (p = 0.001). The mean LogMAR CDVA improved from 0.58 ± 0.36 to 0.46 ± 0.31, 0.34 ± 0.23, and 0.39 ± 0.27 after 1, 3, and 5 years respectively (p = 0.015). The mean refractive cylinder improved significantly from 6.01 ± 2.07 diopters (D) to 5.46 ± 1.87, 5.38 ± 2.18, and 5.02 ± 2.31 D after 1, 3, and 5 years respectively (p = 0.005). As compared to preoperative values, steep keratometry and maximum keratometry were not significantly different (p = 0.805 and 0.448, respectively) following ACXL, while flat keratometry significantly improved after ACXL (p = 0.012). Although central corneal thicknesses decreased significantly (p = 0.029), the decrease in thinnest corneal thickness was not statistically significant (p = 0.205).

CONCLUSION

Epithelium-off ACXL seems to be effective for halting KC progression with long term clinical benefits in pediatric patients.

Accelerated corneal crosslinking in children with keratoconus: 5-year results and comparison of 2 protocols

PURPOSE

To evaluate long-term clinical results of 2 different accelerated corneal crosslinking (CXL) protocols in pediatric patients with keratoconus.

SETTING

Beyoğlu Eye Training and Research Hospital, Istanbul, Turkey.

DESIGN

Retrospective case-control study.

METHODS

Patients who were younger than 18 years were included in the study. Group 1 received 4 minutes of illumination at 30 mW/cm, and Group 2 received 5 minutes of illumination at 18 mW/cm. Uncorrected and corrected distance visual acuities, manifest refraction, corneal topographic parameters, and corneal higher-order aberrations (HOAs) were evaluated at baseline and during 1-, 3-, and 5-year follow-up visits.

RESULTS

A total of 143 eyes from 86 patients were included in the study. There were 30 eyes in Group 1 and 113 eyes in Group 2. The mean follow-up time was 4.15 ± 0.99 years. Mean keratometry (K) and/or maximum K progressed ≥1.00 diopter (D) in 7 eyes (23.3%) in Group 1 and 19 eyes (16.8%) in Group 2 (P = .411). Mean K and/or maximum K decreased ≥2.00 D in 2 eyes (6.7%) in Group 1 and 24 eyes (21.2%) in Group 2 (P = .06). In Group 1, there were no statistically significant differences in topographic parameters during follow-up. In Group 2, there was a statistically significant reduction in total HOA and coma during the 5-year visit when compared with the preoperative visit (P = .005 and P = .045, respectively).

CONCLUSIONS

Accelerated CXL is beneficial in terms of halting the progression of keratoconus in pediatric patients throughout 5 years of follow-up examinations. An increased irradiance with a reduced application time reduces the topographic effects of CXL.

Corneal collagen cross-linking in pediatric keratoconus with three protocols: a systematic review and meta-analysis

BACKGROUND

Keratoconus is a bilateral progressive noninflammatory degenerative disease of the cornea characterized by corneal thinning, irregular astigmatism, and subsequent visual impairment. It has an aggressive course in children. This systematic review evaluates the efficacy of available corneal collagen cross-linking (CXL) protocols for stabilizing the cornea in pediatric patients with keratoconus.

METHODS

We searched all peer-reviewed publications from 2000 to 2019 indexed in PubMed, Google Scholars, Web of Science, and Cochrane's Database for the terms keratoconus and cross-linking. The following data were extracted from eligible studies: study design, type of intervention, number of the eyes and mean age of patients for each study, duration of follow-up period, mean pre- and postoperative uncorrected and corrected visual acuity, keratometric and aberrometric indices, were analyzed with RevMan 5.3 software. Intra-and intergroup post hoc analyses of outcome variables were performed using t tests.

RESULTS

A total of 28 studies, including 1,300 eyes, were reviewed. In conventional and accelerated epithelium-off techniques, there was a significant improvement in uncorrected and corrected visual acuities. Similarly, the keratometric indices improved significantly after CXL. Uncorrected visual acuity did not alter after CXL using transepithelial method.

CONCLUSIONS

Both conventional and accelerated collagen CXL of the cornea are effective therapeutic options in management of keratoconus in children.

Long-Term Visual, Refractive and Topographic Outcomes of "Epi-off" Corneal Collagen Cross-Linking in Pediatric Keratoconus: Standard versus Accelerated Protocol

PURPOSE

To compare the visual, refractive and topographic outcomes of standard and accelerated corneal collagen cross-linking (CXL) in pediatric keratoconus patients.

METHODS

Prospective, comparative observational study on 68 eyes of 35 pediatric keratoconus patients (<18 years). Patients were classified into two groups, group (I) included 34 eyes and received standard "Epi-Off" CXL (3 mW/cm², 30 min.) and group (II) included 34 eyes and received accelerated "Epi-Off" CXL (9 mW/cm², 10 min.). Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), spherical equivalent (SE), simulated keratometry (Sim K-1, Sim K-2, K-max, K-mean), cylindrical (CYL), pachymetry and Q-value were evaluated preoperatively and for 3 years postoperatively.

RESULTS

Postoperative UDVA and CDVA did not significantly change in both groups after 3 years. Postoperative SE was increased significantly in accelerated CXL (p=0.012) with no significant change in the postoperative cylinder in both procedures. Standard CXL had greater "significant" effect in decreasing Sim K-1, K-max and K-mean. The mean reduction in postoperative corneal pachymetry (at thinnest location) was significant in standard CXL (18.4 μm) (p=0.001). No significant change was noticed in postoperative Q-value.

CONCLUSION

Standard and accelerated CXL protocols are efficient in pediatric keratoconus management with better outcomes in the standard procedure.

Accelerated Epithelium-off Corneal Cross-linking With High Ultraviolet Energy Dose (7.2 J/cm2) for Progressive Keratoconus: 2-Year Results in a Chinese Population

PURPOSE

To evaluate the results of epithelium-off continuous light accelerated corneal cross-linking (CXL) with a total dose of 7.2 J/cm² for treating progressive keratoconus in a Chinese population during 24 months of follow-up.

METHODS

In this retrospective, interventional case series, 45 eyes of 31 consecutive patients with progressive keratoconus were evaluated. All patients underwent accelerated CXL with settings of 30 mW/cm² for 4 minutes, corresponding to a total dose of 7.2 J/cm². Visual acuity, manifest refraction, epithelial thickness, topography, tomography, aberrometry, endothelial cell count, and intraocular pressure were evaluated at baseline and at 1, 3, 6, 12, 18, and 24 months postoperatively.

RESULTS

Progressive keratoconus was stabilized in 91.11% and 93.33% of the patients at 12 and 24 months, respectively. The improvement in corrected distance visual acuity was significant throughout the postoperative follow-up period (P < .05), excluding month 1. A significant decrease in the maximum keratometric values (0.67 ± 1.68, 0.92 ± 1.78, and 0.97 ± 1.73 D) was observed at months 12, 18, and 24, respectively (P < .05 for all). Corneal irregularity improved, particularly total root mean square and higher order aberrations at 12 to 24 months after CXL. In bilateral CXL, the progression of the first eye was highly predictive of the outcome of the second eye.

CONCLUSIONS

CXL with a total dose of 7.2 J/cm² maintains long-term results in halting the progression of keratoconus, with significant improvement in the corrected distance visual acuity and stability of keratometric values. Further clinical studies with longer follow-up periods and larger samples are necessary to confirm these results. [J Refract Surg. 2020;36(11):731-739.].

Intrastromal Corneal Ring Segments Implantation And Corneal Cross-Linking For Keratoconus In Children With Vernal Keratoconjunctivitis - Three-Year Results

Purpose

To assess the 3-year safety and efficacy of femtosecond laser-assisted intrastromal corneal ring segments' (ICRS) implantation followed or accompanied by transepithelial accelerated corneal collagen cross-linking (TE-ACXL) as a treatment of keratoconus in children with vernal keratoconjunctivitis (VKC).

Patients and methods

Fifty two eyes of 28 children with keratoconus and vernal VKC were included in this study. Cases were divided into 2 groups; the first group had been treated with femtosecond laser-assisted ICRS (Keraring) implantation accompanied or followed by TE-ACXL, while the second group had been treated by TE-ACXL only and all cases completed a follow-up period of 3 years.

Results

In group 1: the mean uncorrected (UCVA) and best-corrected (BCVA) visual acuity, spherical equivalent, K-max and Q-value improved markedly from 0.97 ± 0.19, 0.67 ± 0.18, −8.75 ± 4.55, 60.41 ± 4.98, and −1.18 ± 0.54 preoperatively to 0.61 ± 0.27, 0.39±0.21, −3.25 ± 3.56, 55.22 ± 5.72, and −0.44 ± 0.68 postoperatively respectively. While in group 2: the preoperative mean UCVA, BCVA, spherical equivalent, K-max and Q-values were 0.68 ± 0.28, 0.38 ± 0.24, −2.84 ± 2.59, 50.29 ± 4.04, and-0.58 ± 0.23 respectively while their corresponding postoperative values were 0.58 ± 0.34, 0.19 ± 0.17, −2.35 ± 2.07, 49.58 ± 3.26, and −0.57 ± 0.25. Only one case in group 1 required repeat cross-linking.

Conclusion

Although the long-term safety and efficacy of femtosecond laser-assisted ICRS implantation accompanied or followed by TE-ACXL in children with keratoconus and VKC is high, some cases still may need repeat cross-linking.

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Keratoconus Screening in Elementary School Children

Keratoconus is a degenerative structural disease of the cornea. Progression leads to poor acuity that is not easily correctable by standard means. New treatments, such as collagen cross-linking, lead to better long-term outcomes if performed early in the disease course. Currently, children in the USA are screened for acuity in school, but not for keratoconus. Due to the severity of the disease in children, we recommend topographic screening in elementary schools as a way to provide early detection and treatment.Funding Research to Prevent Blindness provided funding for the Rapid Service Fees.

Effectiveness and safety of accelerated (9 mW/cm2) corneal collagen cross-linking for progressive keratoconus: a 24-month follow-up

OBJECTIVES

To examine the effectiveness and safety of accelerated corneal collagen cross-linking (CXL) for keratoconus over a 24-month period and to explore potential prognostic factors for post-treatment visual outcome and progression.

METHODS

A retrospective, non-comparative, interventional case series. All patients who underwent accelerated epithelium-off CXL, using 9 mW/cm² ultraviolet-A irradiation for 10 min, for progressive keratoconus in Sunderland Eye Infirmary, UK, between May 2014 and July 2016 were included. All patients completed 24 months' post-CXL follow-up. Significant post-CXL progression of keratoconus was defined as >1 D increase in Kmax from preoperative to 24-month visit.

RESULTS

Fifty-two eyes of 48 patients were included. At 24-month post-CXL, there was a significant improvement in corrected-distance visual acuity (CDVA; -0.05 LogMAR; p = 0.026), Kmax (-1.68 D; p < 0.001), K1 (-0.64 D; p = 0.002) and Kmean (-0.50 D; p = 0.009). The proportion of eyes with CDVA ≥ 0.3 LogMAR significantly improved from 43 (82.7%) eyes preoperatively to 50 (96.2%) eyes at 24 months (p = 0.026). Corneal haze (12, 23.1%) was the only postoperative complication and no adverse event was noted. Final CDVA was associated with lower CDVA (p = 0.002) and greater Kmax (p = 0.018) at baseline. Post-CXL progression of keratoconus was associated with greater preoperative Kmax (p = 0.12) and Kmean (p = 0.11), though statistical significances were not achieved.

CONCLUSIONS

Accelerated CXL (9 mW/cm²) serves as an effective and safe treatment for halting the progression of keratoconus and stabilising the vision over a 24-month period. Our observation suggests that accelerated CXL might be more effective in stabilising keratoconus of milder severity; however further larger studies are required to elucidate this finding.

Analysis of the Outcomes of Combined Cross-Linking with Intracorneal Ring Segment Implantation for the Treatment of Pediatric Keratoconus

PURPOSE

To analyze the visual and refractive outcomes of combined accelerated cross-linking with femtosecond laser intracorneal ring segment implantation for the treatment of pediatric keratoconus.

MATERIALS AND METHODS

This retrospective multicenter noncomparative clinical study included 63 eyes of 37 patients (age, 9-17 years) who underwent between August and September 2016 combined cross-linking with intracorneal ring segment implantation for keratoconus. Preoperative and postoperative (6, 12, and 18 months) uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA), subjective refractions, keratometry (K), and pachymetry measurements were compared.

RESULTS

The postoperative spherical equivalent refraction was within ±1 D, ±2 D, and ±3 D in 19 (30.2%), 27 (42.9%), and 37 (58.8%) eyes, respectively. Only 27 eyes achieved the attempted preoperative spherical equivalent refraction. The mean spherical equivalent refraction significantly improved from -6.01 ± 2.97 to -3.13 ± 2.78 D postoperatively (P < 0.0001). The mean K average reading significantly decreased from 48.75 ± 4.25 to 46.65 ± 3.89 D postoperatively (P < 0.0001). The mean postoperative myopic, astigmatic, and spherical equivalent corrections were -2.17 ± 2.19, -1.52 ± 2.03, and -2.93 ± 2.35 D, respectively. The mean UDVA and CDVA showed significant improvements (0.89 ± 0.33 to 0.40 ± 0.28, P < 0.0001; 0.35 ± 0.31 to 0.25 ± 0.24, P = 0.004; respectively) at 18 months postoperatively. Keratoconus progression, segment migration, and segment extrusion were seen in four (6.4%), one (1.6%), and three (4.7%) eyes, respectively, probably contributing to the lower mean postoperative CDVA.

CONCLUSION

Cross-linking plus is only partially effective for pediatric keratoconus. Despite some improvements in vision and keratometry measures, it resulted in complications such as keratoconus progression, segment extrusion, and segment migration that affected the vision in some patients. These findings suggest an assessment of standard epithelium-off collagen cross-linking as a sole procedure to treat pediatric keratoconus in future studies.