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.

Crosslinking with UV-A and riboflavin in progressive keratoconus: From laboratory to clinical practice - Developments over 25 years

Changes in the biomechanical and biochemical properties of the human cornea play an important role in the pathogenesis of ectatic diseases. A number of conditions in primarily acquired (keratoconus or pellucid marginal degeneration) or secondarily induced (iatrogenic keratectasia after refractive laser surgeries) ectatic disorders lead to decreased biomechanical stability. Corneal collagen cross-linking (CXL) represents a technique to slow or even halt the progression of ectatic pathologies. In this procedure, riboflavin is applied in combination with ultraviolet A radiation. This interaction induces the production of reactive oxygen species, which leads to the formation of additional covalent bonds between collagen molecules and subsequent biomechanical corneal strengthening. This procedure is so far the only method that partially interferes etiopathogenetically in the treatment of ectatic diseases that slows or stops the process of corneal destabilization, otherwise leading to the need for corneal transplantation. Besides, CXL process increases markedly resistance of collagenous matrix against digesting enzymes supporting its use in the treatment of corneal ulcers. Since the discovery of this therapeutic procedure and the first laboratory experiments, which confirmed the validity of this method, and the first clinical studies that proved the effectiveness and safety of the technique, it has been spread and adopted worldwide, even with further modifications. Making use of the Bunsen-Roscoe photochemical law it was possible to shorten the duration of this procedure in accelerated CXL and thus improve the clinical workflow and patient compliance while maintaining the efficacy and safety of the procedure. The indication spectrum of CXL can be further expanded by combining it with other vision-enhancing procedures such as individualized topographically-guided excimer ablation. Complementing both techniques will allow a patient with a biomechanically stable cornea to regularize it and improve visual acuity without the need for tissue transplantation, leading to a long-term improvement in quality of life.

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.

Update on corneal crosslinking for keratoconus and corneal ectasia

PURPOSE OF REVIEW

To review corneal crosslinking for keratoconus and corneal ectasia, and recent developments in the field. This study will review the mechanism of crosslinking, clinical approaches, current results, and potential future innovations.

RECENT FINDINGS

Corneal crosslinking for keratoconus was first approved by U.S. FDA in 2016. Recent studies have confirmed the general long-term efficacy of the procedure in decreasing progression of keratoconus and corneal ectasia. New types of crosslinking protocols, such as transepithelial treatments, are under investigation. In addition, adjunctive procedures have been developed to improve corneal contour and visual function in these patients.

SUMMARY

Crosslinking has been found to be well tolerated and effective with the goal of decreasing progression of ectatic corneal diseases, keratoconus and corneal ectasia after refractive surgery. Studies have shown its long-term efficacy. New techniques of crosslinking and adjunctive procedures may further improve treatments and results.

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.

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.

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.

Management Outcomes in Pediatric Keratoconus: Childhood Keratoconus Study

Introduction. The Global Delphi Panel of Keratoconus (KC) and Ectatic Diseases formulated management guidelines for KC in 2015. The aim of this study was to evaluate management outcomes in pediatric KC. Materials and Methods. Prospective, interventional study was conducted at a tertiary care hospital including KC patients aged <18 years. Based on disease severity and progression of disease, patients were prescribed either glasses or contact lenses (CLs) or underwent corneal collagen crosslinking (CXL), deep anterior lamellar keratoplasty (DALK), or penetrating keratoplasty (PK). Main Outcome Measures. Best corrected visual acuity (BCVA), manifest cylinder, maximum keratometry, thinnest corneal thickness, total higher order aberrations, and corneal hysteresis at baseline and 12 and 24 months. Results. 116 eyes of 62 patients with a mean age of 14.76 ± 2.77 years were included. 32.8% of the eyes (n = 38) achieved satisfactory BCVA with glasses/CLs only. Corneal collagen crosslinking (CXL) was performed in 43.1% of the eyes (n = 50) with progressive KC and halting of progression was noted in 83.3% (n = 35) of the eyes at 2 years. 7.7% of the eyes (n = 9) were managed for acute hydrops. DALK and PK were successfully performed in 9.5% (n = 11) and 6.9% (n = 8) of the eyes with BCVA of 0.14 ± 0.09 and 0.08 ± 0.12 at 2 years, respectively. Conclusions. Pediatric KC cases with progression show good visual and aberrometric outcomes and halting of progression after CXL. DALK and PK have good outcomes. The global consensus guidelines showed good clinical utility in pediatric patients. Presence of VKC did not have an impact on the outcomes of CXL in pediatric patients.

Pain mechanisms and management in corneal cross-linking: a review

Though corneal collagen cross-linking (CXL) is an increasingly available and effective treatment for keratoconus, few reports have considered its impact on pain-related physiology in depth. This comprehensive narrative review summarises mechanisms underlying pain in CXL and clinical care possibilities, with the goal of future improvement in management of CXL-related pain. Postoperative pain associated with CXL is largely due to primary afferent nerve injury and, to a smaller extent, inflammation. Chronification of pain after CXL has not been reported, even as long-term nerve damage without regeneration following standard CXL treatment is frequently observed. The lack of pain chronification may be due to the minimally invasive nature of the procedure, with its rapidly recovering superficial corneal wound, and to the positive anti-inflammatory changes of the tear film that have been described after CXL. Different CXL approaches have been developed, with the transepithelial epithelial-on technique (epi-on) associated with less postsurgical pain than the gold standard, epithelial-off technique (epi-off). After the first few days, however, the difference in pain scores and need for analgesics between epi-on and epi-off disappear. Patients experience relatively high-intensity pain the first few days post-CXL, and many strategies for acute pain control following CXL have been studied. Currently, no method of pain management is considered superior or universally accepted. Acute pain following CXL is a recognised and clinically significant side effect, but few CXL studies have systematically investigated postoperative pain and its management. This review aims to improve patient pain outcomes following this increasingly common procedure.

Risk factors for progression following corneal collagen crosslinking in keratoconus

PURPOSE

To assess risk factors for progression following corneal collagen crosslinking (CXL) in eyes with keratoconus.

METHODS

Charts of patients who developed progression following conventional CXL treatment (Dresden protocol) were retrospectively evaluated in two centers (Center 1 and Center 2). 871 eyes of a total of 676 patients were analyzed. Progression was defined as > 1 diopter (D) increase in maximum keratometry (Kmax) readings compared to baseline.

RESULTS

Progression was noted in 20 eyes of 20 patients (progression rate 3%). The mean age of the patients was 17.65 ± 5.76 (11-34)-years-old, and the mean follow-up following CXL was 36.70 ± 25.72 (12-84)-months-old. The gender distribution was 13 (65%) females and seven (35%) males. Four eyes (20%) had mild, 13 eyes (65%) had moderate, and three eyes (15%) had severe keratoconus at baseline. Fifteen eyes (75%) had allergic conjunctivitis, and 20 eyes (100%) reported eye-rubbing. Cone location was central in 17 (85%) eyes, and peripheral in 3 (15%) eyes. A mean of 2.21 ± 1.30 D (1.00-5.30 D) steepening was determined at Kmax 6 to 82 months following CXL treatment.

CONCLUSIONS

Progression rate was found to be higher in the patients under the age of 17 years, female gender, allergic conjunctivitis, high preoperative Kmax (> 57 D), thin corneas (< 430 µm). The majority of progressive patients were central cone and moderate keratoconus.

Intracorneal Ring Segment Implantation for the Management of Keratoconus in Children

The short-term safety and efficacy of intracorneal ring segment (ICRS) implantation in keratoconus eyes of children are investigated in this study. A retrospective interventional case series study including a total of 33 keratoconus eyes (age 8 to 17 years) that had undergone ICRS (Keraring segments, Mediphacos) implantation was conducted. Information about visual, refractive, pachymetric, corneal topographic and aberrometric, and corneal endothelial changes during a 3-month follow-up were extracted and analysed. A significant improvement was observed in logMAR corrected distance visual acuity (p = 0.005), combined with a statistically significant reduction in keratometric readings (p < 0.001). A reduction in the magnitude of corneal astigmatism of ≥1 D was observed in 52.8% of eyes. No significant changes were observed in corneal endothelial density (p = 0.317). Significant changes were found in the anterior vertical coma component (p = 0.002) as well as in the spherical aberration of the posterior corneal surface (p = 0.004). Only two relevant complications were described: one corneal microperforation with penetration of the ring segment into the anterior chamber (1 eye, 2.8%), and a case of ring extrusion (1 eye, 2.8%). ICRS implantation in children keratoconus eyes allows a reduction of corneal astigmatism, irregularity, and aberrations, leading to a significant visual improvement.

Corneal Cross-Linking for Keratoconus: Current Knowledge and Practice and Future Trends

Corneal collagen cross-linking (CXL) with riboflavin is an accepted universal standard of care for our keratoconus patients with progressive disease. It has been a game changer in how we manage keratoconus. Early diagnosis and treatment is essential in paediatric patients as younger patients progress more rapidly and have poorer transplant outcomes. There is an ongoing debate around standard, accelerated, and transepithelial protocols of CXL, the role of CXL, and the combination of laser refractive surgery. Future developments will improve CXL safety and efficacy and the scope of utilization, but we must be careful not to leap too far ahead with clinical applications before publication of basic science research and good clinical results with standardized protocols.

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.

Accelerated and Standard Corneal Cross-Linking Protocols in Patients with Down Syndrome: A Non-inferiority Contralateral Randomized Trial

Introduction

To compare the results of an accelerated corneal cross-linking (CXL) protocol (9 mW/cm², 10 min) with the standard CXL protocol (3 mW/cm², 30 min) in patients with Down syndrome (DS) who have keratoconus (KC).

Methods

Twenty-seven 10- to 20-year-old patients with DS who had bilateral progressive KC were enrolled in a contralateral randomized trial and completed 2 years of follow-up examinations. Fellow eyes were randomly allocated to the accelerated CXL group or the standard CXL group. The main outcome measure was change in maximum keratometry (K_max) centered on the steepest point (zonal K_max − 3 mm) with a non-inferiority margin of 1.0 diopter (D). Vision and refraction tests, ophthalmic examinations, and corneal tomography were performed at baseline and at 6, 12, and 24 months after CXL. Failure was defined as an increase of ≥ 1.0 D in zonal K_max − 3 mm within a 12-month period.

Results

The mean age (± standard deviation) of the patients was 15.71 ± 2.40 years. The within-group change in zonal K_max − 3 mm was not significant after 2 years in either group, and within-group zonal K_max − 3 mm remained stable. At 2 years after CXL, the mean change in the zonal K_max − 3 mm was – 0.02 ± 0.81 D and – 0.31 ± 0.86 D in the accelerated CXL and standard CXL groups, respectively (P = 0.088). At 1 year of follow-up, three patients in the accelerated CXL group showed treatment failure (mean change in zonal K_max − 3 mm + 2.12 ± 0.11 D); no patients in the standard CXL group showed treatment failure. At 2 years of follow-up, these three patients showed a decrease of – 0.43 ± 0.18 D in zonal K_max − 3 mm from a baseline value of 55.11 ± 0.32 D. The 2-year trends of the inferior–superior asymmetry and vertical coma were statistically significantly different between the two groups, with the accelerated CXL protocol showing superiority in patients with higher baseline values.

Conclusion

In young patients with Down syndrome, the accelerated CXL protocol was able to halt disease progression and may be an alternative for the standard CXL protocol. In advanced KC, the efficacy of the accelerated approach was delayed and appeared later in the follow-up. In asymmetric cornea, the accelerated CXL resulted in centralization of the corneal cone.

Trial Registration

Iranian Registry of Clinical Trials, IRCT20100706004333N3

Electronic supplementary material

The online version of this article (10.1007/s40123-020-00303-4) contains supplementary material, which is available to authorized users.

Comparative Results of "Epi-Off" Conventional versus "Epi-Off" Accelerated Cross-Linking Procedure at 5-year Follow-Up

Purpose

The aim of our study was to compare the long-term efficacy and safety of “epi-off” conventional and “epi-off” accelerated corneal cross-linking (CXL) in patients with progressive keratoconus.

Methods

“Epithelial-off” (“Epi-off”) CXL using the conventional technique (3 mW/cm², 30 minutes) was performed in 93 eyes of 93 patients (S-CXL group) and “epi-off” accelerated method (9 mW/cm², 10 minutes) in 76 eyes of 76 patients with progressive KCN (A-CXL group). Cases with different stages of keratoconus and topographic evidence of progression were included. Main outcomes comprised refraction, keratometry measurements, uncorrected (UCVA) and best-corrected visual acuity (BCVA), and topographical indices. Micromorphological analysis was assessed by anterior segment ocular coherence tomography (AS-OCT). The follow-up period was 5 years.

Results

In both groups, Kflat presented similar results: decrease at 1 year (p=0.465), at 2 years (p=0.672), at 3 years (p=0.198), at 4 years (p=0.32), and at 5 years (p=0.864). In both groups, Ksteep presented a similar decrease at 1 year (p=0.709), at 2 years (p=0.455), at 3 years (p=0.43), at 4 years (p=0.57), and at 5 years (p=0.494), with no statistically significant difference. Decrease in Kavg was similar in both groups at all analyzed time points (p=0.18 at 1 year, p=0.093 at 2 years, p=0.57 at 3 years, p=0.154 at 4 years, and p=0.247 at 5 years). Kmax had a similar decrease in both groups at 1 year (p=0.06), at 2 years (p=0.09), at 3 years (p=0.126), at 4 years (p=0.113), and at 5 years (p=0.114). There was no statistically significant difference between the cylinder decrease in both groups (p=0.349 at 1 year, p=0.6782 at 2 years, p=0.299 at 3 years, p=0.0943 at 4 years, and p=0.144 at 5 years). The BCVA values were statistically significantly higher than the preoperative values in both groups at all time points (p < 0.05). Topographical indices such as thinnest corneal point (TP), corneal volume (CV), index vertical asymmetry (IVA), index of vertical asymmetry (ISV), index of height asymmetry (IHA), index of height decentration (IHD), Belin/Ambrosio Enhanced Ectasia Display (BAD_D), and Ambrosio retinal thickness (ART Max) were significantly statistically decreased compared with baseline at all time points, in both groups.

Conclusion

“Epi-off” accelerated and conventional CXL have the same efficacy in terms of improvement in visual and topographic outcomes.

Baseline factors predicting the need for corneal crosslinking in patients with keratoconus

INTRODUCTION

The primary purpose of crosslinking is to halt the progression of ectasia. We retrospectively assessed the condition of keratoconus patients who were followed-up at least twice after the initial examination to evaluate keratoconus progression, to identify definitive factors to predict a later need for corneal crosslinking (CXL).

METHODS

The medical charts of 158 eyes of 158 keratoconus patients (112 males and 46 females; mean age, 27.8 ± 11.7 years), who were followed up at the Department of Ophthalmology, Keio University School of Medicine at least twice after the initial examination to evaluate keratoconus progression were retrospectively reviewed. Best-spectacle corrected visual acuity, intraocular pressure, steepest corneal axis on the anterior float (Ks), thinnest corneal thickness according to Pentacam® HR, and corneal endothelial cell density were assessed. Gender, age, onset age of keratoconus, history of atopic dermatitis, and Pentacam® indices were also recorded. CXL was performed when the eye showed significant keratoconus progression, an increase in the steepest keratometric value, or an increase in the spherical equivalent or cylinder power of the manifest refraction by more than 1.0 D versus the respective values 2 years prior. Predictor variables and the requirement for CXL were analyzed using logistic regression.

RESULTS

Fifty-eight eyes required CXL treatment. The best predictor of the requirement for CXL was patient age, followed by the Pentacam® Rmin (the minimum sagittal curvature evaluated by Pentacam®) value. The incidence of CXL was 86.4% in the < 20 years age group, with an Rmin of ≤ 5.73 mm, whereas 10.8% in the ≥ 27 years age group with an Rmin > 5.73 mm underwent treatment.

CONCLUSIONS

An age of < 20 years and an Rmin value of ≤ 5.73 mm predicted keratoconus progression and the requirement for CXL treatment in the near future.

Differential Regional Stiffening of Sclera by Collagen Cross-linking

Purpose: Corneal collagen cross-linking by ultraviolet light activation of riboflavin has been used clinically to enhance corneal stiffness. We sought to determine if cross-linking differentially affects scleral regions.Methods: Adjacent, parallel strips of sclera were cut from superolateral, superomedial, inferolateral, and inferomedial quadrants of posterior and equatorial sclera of 12 human cadaver eyes. One of each pair served as control while the other was cross-linked by immersion in 0.1% riboflavin and 365 nm exposure at 6 mW/cm² irradiance for 30 min. Behavior of strips was characterized using a microtensile load cell. Preloaded strips were imaged using orthogonally mounted cameras and optical coherence tomography to determine specimen dimensions including cross-sectional area. Tension was measured during 0.1 mm/s constant rate elongation.Results: Young's modulus (YM), the slope of the relationship relating tensile stress to strain, was calculated at 8% strain, and increased significantly after cross-linking (P < .001). In posterior sclera, mean (± standard error of mean, SEM) YM is increased in the superolateral, superomedial, inferolateral, and inferomedial quadrants by 46 ± 15%, 32 ± 11%, 67 ± 20%, and 53 ± 11%, respectively. In equatorial sclera, YM is increased by 139 ± 43%, 68 ± 27%, 143 ± 92%, and 68 ± 14%, respectively. The YM of pooled equatorial quadrants increased significantly more than that of the pooled posterior quadrants.Conclusions: Scleral collagen cross-linking by ultraviolet activation of riboflavin differentially increases scleral YM more in the equatorial than posterior sclera, and most in the lateral, equatorial sclera. Cross-linking might be used to arrest progressive myopia or to prevent staphyloma formation.

Corneal Collagen Cross-Linking Under General Anesthesia for Pediatric Patients With Keratoconus and Developmental Delay

PURPOSE

To report the clinical characteristics and outcomes of pediatric patients with keratoconus (KCN) who underwent corneal collagen cross-linking (CXL) under general anesthesia for developmental delay or inability to cooperate with topical anesthesia.

METHODS

In this retrospective case series, we reviewed the medical charts of pediatric patients with KCN who had CXL under general anesthesia from January 2018 to April 2019. Baseline disease characteristics of patients with and without developmental delay were compared using the Pearson χ test and the t test. Main outcomes were anesthesia or surgical complications and postoperative best corrected visual acuity (BCVA), keratometry (K) values, and caregiver report of eye-rubbing behavior.

RESULTS

Fourteen eyes of 9 patients were reviewed. All were habitual eye rubbers at baseline. Six (66.7%) were developmentally delayed. Compared with patients without developmental delay, developmentally delayed patients were diagnosed and treated at older ages (16.0 vs. 13.9 years), experienced longer delays from diagnosis to surgery (20.7 vs. 8.8 weeks), and had lower BCVA (20/70 vs. 20/40), higher steep K values (54.0 vs. 50.9), and a higher incidence of corneal scarring (75.0% vs. 33.3%) and monocular vision loss (50.0% vs. 0.0%) at baseline, although these differences were not statistically significant. No anesthesia or surgical complications occurred. BCVA and K values were stable at postoperative month 6, with no clinically or statistically significant change observed for either measure. Eight patients decreased or stopped eye rubbing.

CONCLUSIONS

We demonstrate the efficacy and safety of CXL under general anesthesia in halting the progression of KCN for pediatric patients with developmental delay or an inability to cooperate with the procedure until topical anesthesia.

Different accelerated corneal collagen cross-linking treatment modalities in progressive keratoconus

Background

To compare the outcomes of two different protocols of accelerated corneal crosslinking (CXL) on visual, corneal high order aberrations (HOA) and topographic parameters in patients with progressive keratoconus.

Methods

In this prospective comparative study, sixty-six eyes of 66 patients with progressive keratoconus were divided into two groups; 37 eyes in Group 1 received 18 mW/cm² for five minutes, and 29 eyes in Group 2 were treated with 9 mW/cm² for 10 min. The uncorrected distant visual acuity (UCVA), best-corrected distant visual acuity (BCVA), corneal HOAs and topography parameters were measured preoperatively and postoperatively at the end of 12 months. The data for the two groups were compared statistically.

Results

The mean UCVA and BCVA were significantly improved at the postoperative 12 months compared with the preoperative values in both groups (P < 0.05 for all). A significant improvement in corneal HOAs was observed in both groups (P < 0.05 for all). The change in corneal coma value was significantly higher in Group 2 (P < 0.05). The change in keratometric values K1, K2, AvgK and maximum keratometry (AKf) were significantly higher in Group 2 (P < 0.05 for all). The regression model showed that the most important factor predicting the change in AKf was the type of CXL (β = − 0.482, P = 0.005).

Conclusions

Accelerated CXL using 10 min of UVA irradiance at 9 mW/cm² showed better topographic improvements and coma values than five minutes of UVA irradiance at 18 mW/cm² independent of keratoconus severity.