Efficacy of Customized Corneal Cross-linking vs. Standard Corneal Cross-linking (C-CROSS)

Efficacy of Customized Corneal Cross-linking Versus Standard Corneal Cross-linking in Patients With Progressive Keratoconus

The standard or Dresden protocol was established in 2003 and treats the entire cornea. However, recent ultra-structural research showed that keratoconus is localized. Therefore, treating only the affected zone and minimalizing the risk of damaging surrounding tissues would be beneficial.

The objective of this study is to evaluate whether the effectiveness of customized cross-linking (cCXL) is non-inferior to standard accelerated cross-linking (sCXL) in terms of flattening of the cornea and halting keratoconus progression.

Study Overview

• Status: Completed
• Conditions: Keratoconus
• Intervention / Treatment: Procedure: Customized crosslinking; Procedure: Standard crosslinking

Detailed Description

In 2003 Wollensak et al used corneal cross-linking (CXL) in humans to halt the progression of keratoconus. During the procedure the top layer of the cornea, the epithelium, is debrided. Then the cornea is soaked with riboflavin, a photosensitizer. Hereafter a 9.0 mm diameter Ultraviolet-A (UVA) beam radiates the cornea for 30 minutes with a fluence of 3 mW/cm2 resulting in a total energy of 5,4 J/cm2. This protocol is called the Dresden protocol. Currently, accelerated versions of the Dresden protocol are used in common practice. There are different accelerated protocols with fluences of 9mW/cm2, 10mW/cm2 and 15 mW/cm2. The higher the fluence, the shorter the treatment time, however according to the Bunsen-Roscoe reciprocity law the total amount of energy stays the same.During the procedure oxygen radicals are formed that interact with the surrounding molecules, leading to the formation of new chemical bounds between the collagen fibrils (i.e. corneal crosslinks). The final goal of the procedure is to cause the cornea to stiffen and achieve flattening of the treated region.

For any treatment, it is imperative that the unaffected region of the tissue is not unnecessarily treated by an intervention or drug application. To minimalize the risk of damage to surrounding tissues it would be beneficial that the UVA beam is restricted to the affected, keratoconic zone in the patient's cornea. This can be achieved by customizing the beam shape and size in a way that only the degenerated zone is treated, i.e. by customized cross-linking (cCXL). Recently published studies provide clinical evidence that similar clinical outcomes (amount of corneal flattening) can be achieved when only the cone is treated instead of the entire cornea.They also show the potential benefits of cCXL, e.g. the treatment is patient-specific, a smaller surface of the cornea is irradiated, lower incidence of corneal haze, a faster reepithelialisation and a shorter procedure time. However, none of these studies are randomized and study results are limited by using small sample sizes. Therefore, we feel that there is a great need for a randomized controlled trial with an appropriate design and sample size to confirm these findings.

The aim of this study is to investigate if cCXL is non-inferior to sCXL (10 mW/cm2) in terms of flattening of the corneal surface and halting the disease progression.

• Study Type: Interventional
• Enrollment (Actual): 124
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Netherlands
  • Groningen, Netherlands, 9713 GZ
    • University Medical Center Groningen
  • Utrecht, Netherlands, 3584 CX
    • University Medical Center Utrecht
  • Limburg
    • Maastricht, Limburg, Netherlands, 6229 HX
      • Maastricht University Medical Center (MUMC+)

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 16 years to 45 years (Child, Adult)
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Progressive keratoconus based on an increase of maximum keratometry (Kmax) of 1 diopter (D) over a time period of 12 months

Exclusion Criteria:

• Corneal scarring
• Corneal disease other than keratoconus
• History of corneal surgery (e.g. refractive surgery, corneal transplantation, intracorneal ring segments)
• Patient unwilling or unable to give informed consent, unwilling to accept randomization or inability to complete follow-up (e.g. hospital visits) or comply with study procedures
• Insufficient corneal thickness including epithelium < 375 µm
• Pregnancy
• Among patients in whom both eyes are eligible only the first eye which is undergoing corneal cross-linking is enrolled in the study
• Participation in another clinical study

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Customized crosslinking; In the customized corneal cross-linking protocol (cCXL) a patient-specific treatment pattern, based on the patient's Pentacam images, will be used to treat the cornea. The CXL pattern exists out of 3 concentric circles and is centered on the cone. To estimate the cone location a combination of the thinnest corneal point, maximum anterior elevation and maximum posterior elevation is used. The epithelium is debrided with alcohol within the marked zone. After the application of riboflavin each circle receives a different amount of energy, which gradually decreases with increasing circle size. The procedure is done with the Avedro Mosaic CXL device (Avedro, Inc. Waltham, Massachusetts, United States).	Procedure: Customized crosslinking; In the customized corneal cross-linking protocol (cCXL) a patient-specific treatment pattern, based on the patient's Pentacam images, will be used to treat the cornea. The CXL pattern exists out of 3 concentric circles and is centered on the cone. To estimate the cone location a combination of the thinnest corneal point, maximum anterior elevation and maximum posterior elevation is used. The epithelium is debrided with alcohol within the marked zone. After the application of riboflavin each circle receives a different amount of energy, which gradually decreases with increasing circle size. The procedure is done with the Avedro Mosaic CXL device (Avedro, Inc. Waltham, Massachusetts, United States).
Active Comparator: Standard crosslinking; In the standard corneal cross-linking protocol (sCXL) the epithelium is debrided with alcohol over a region with a diameter of 9.0 mm. After the application of riboflavin the cornea is irradiated with UVA with a fluence of 10 mW/cm2 during 9 minutes with a diameter of 9.0 mm, resulting in a total energy of 5.4 J/cm2. The procedure is done with the Avedro Mosaic CXL device (Avedro, Inc. Waltham, Massachusetts, United States).	Procedure: Standard crosslinking; In the standard corneal cross-linking protocol (sCXL) the epithelium is debrided with alcohol over a region with a diameter of 9.0 mm. After the application of riboflavin the cornea is irradiated with UVA with a fluence of 10 mW/cm2 during 9 minutes with a diameter of 9.0 mm, resulting in a total energy of 5.4 J/cm2. The procedure is done with the Avedro Mosaic CXL device (Avedro, Inc. Waltham, Massachusetts, United States).

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in maximum keratometry (Kmax)	Kmax is measured with Scheimpflug photography (Pentacam® HR, OCULUS Optikgeraete GmbH, Wetzlar, Germany)	12 months postoperatively

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Visual acuity	Measured with ETDRS	at baseline, 4 weeks, 3 months, 6 months and 12 months postoperatively
Refraction	Change in spherical equivalent	at baseline and 12 months postoperatively
Depth and size of demarcation line	Measured with AS OCT	at 4 weeks and 12 months postoperatively
Pachymetry	Measured with the Pentacam HR	at baseline, 4 weeks, 3 months, 6 months and 12 months postoperatively
Zonal Kmax	The analysis of a 3.0 mm zone centered on Kmax measured with the Pentacam HR	at baseline, 4 weeks, 3 months, 6 months and 12 months postoperatively
DUCK score	Dutch Crosslinking for Keratconus Score is based on changes in 5 clinical parameters that are routinely assessed: age, visual acuity, refraction error, keratometry, and subjective patient experience. Each items is scored from 0 to 2 and cutoffs are determined by clinical experience.	at baseline, 4 weeks, 3 months, 6 months and 12 months postoperatively
ABCD grading system	Anterior radius of curvature (A), Posterior radius of curvature (B), Corneal pachymetry at thinnest point (C), Distance best corrected vision (D), and a modifier (-) for no scarring, (+) for scarring that does not obscure iris details and (++) for scarring that obscures iris details	at baseline, 4 weeks, 3 months, 6 months and 12 months postoperatively
Success/failure rate	Failure is defined as progression of the disease after CXL. Progression is defined as an increase in Kmax >1D over 12 months, an increase in K1 and/or K2 >1D over 12 months and thinning and/or an increase in the rate of corneal thickness change from the periphery to the thinnest point >10% over 12 months	at 12 months postoperatively
Mean endothelial cell loss	Measured using specular microscopy photography	at 6 and 12 months postoperatively
Rate of reepithelialisation	evaluated with fluorescein and blue light, a slit lamp image is taking to perform quantitative morphometric surface analysis	4 days postoperatively
Patient Reported Outcomes Measures (PROMs)	Health-related quality of life as measured by HUI3 (Health Utility Index Mark 3) questionnaire	at baseline, 3 months, 6 months and 12 months postoperatively
Patient Reported Outcomes Measures (PROM)	Patient satisfaction and vision-specific quality of life as measured by National Eye Institute Visual Function Questionnaire (NEI VFQ-25)	at baseline, 3 months, 6 months and 12 months postoperatively
Patient Reported Outcomes Measures (PROM)	Patient satisfaction and vision-specific quality of life as measured by Keratoconus Outcome Research Questionnaire (KORQ)	at baseline, 3 months, 6 months and 12 months postoperatively
Pain after crosslinking	measured with the short form of the McGill Pain Questionnaire (SF-MPQ)	4 days postoperatively
Quality Adjusted Life Years (QALYs)	Calculated based on generic health-related quality of life, using the EQ-5D-5L questionnaire	baseline until 12 months postoperatively
Quality Adjusted Life Years (QALYs)	Calculated based on generic health-related quality of life, using the HUI-3 questionnaire	baseline until 12 months postoperatively
Costs per patient	Cost per patient, including valuation of resource use by using the Dutch guidelines for cost-analyses or cost prices provided by the medical center.	baseline until 12 months postoperatively
Incremental cost-effectiveness ratios (ICERs): QALY	Evaluation of cost-effectiveness by using calculated costs per quality-adjusted life years (QALYs)	baseline until 12 months postoperatively
Incremental cost-effectiveness ratios (ICERs): NEI VFQ-25	Calculated costs per clinically improved patient on the NEI VFQ-25 questionnaire	baseline until 12 months postoperatively
Incremental cost-effectiveness ratios (ICERs): Kmax	incremental healthcare costs per patient with a reduction in Kmax of ≥ 1D after crosslinking	baseline until 12 months postoperatively
Incremental cost-effectiveness ratios (ICERs): visual acuity	incremental healthcare costs per patient with clinical improvement in (un-) corrected distance visual acuity	baseline until 12 months postoperatively
Budget impact	Reported as a difference in costs. Different scenario's will be compared to investigate the impact of various levels of implementation (e.g. 25%, 50%, 75% of eligible patients)	baseline until 12 months postoperatively

Collaborators and Investigators

• Sponsor: Maastricht University Medical Center
• Collaborators: ZonMw: The Netherlands Organisation for Health Research and Development
• Investigators: Principal Investigator: R.M.M.A. Nuijts, MD, PhD, Department of Ophthalmology, Maastricht University Medical Center (MUMC+)

Study record dates

Study Major Dates

• Study Start (Actual): March 1, 2021
• Primary Completion (Actual): June 1, 2024
• Study Completion (Actual): June 5, 2024

Study Registration Dates

• First Submitted: August 20, 2020
• First Submitted That Met QC Criteria: August 26, 2020
• First Posted (Actual): August 31, 2020

Study Record Updates

• Last Update Posted (Actual): June 11, 2024
• Last Update Submitted That Met QC Criteria: June 10, 2024
• Last Verified: March 1, 2023

More Information

Terms related to this study

• Keywords: Keratoconus; Crosslinking; Customized
• Additional Relevant MeSH Terms: Eye Diseases; Corneal Diseases; Keratoconus
• Other Study ID Numbers: NL73003.068.20

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No