Biomechanical Properties of Keratoconic Eyes

In keratoconus (KC) corneal thinning and protrusion can cause myopia and irregular astigmatism, affecting vision. The biomechanical properties of the cornea is maintained by an intricate collagen network, which is responsible for its shape and function. In KC this collagen network is disrupted resulting in the cornea losing its shape and function. Keratoconic changes are focal and localised to certain regions of the cornea and the early detection of these changes is challenging. Screening methods include corneal topography (evaluation of anterior corneal surface curvature), tomography (assessing the morphological features of the anterior segment) and aberrometry (measuring the optical aberrations of the eye). More recent research suggests that the biomechanical destabilization of the cornea may precede topographic and tomographic evidence of KC. Management of KC depends on disease severity with severe cases being treated with keratoplasty and less severe cases with cornealcollagencrosslinking (CXL). CXL is an emerging technique, which aims to increase the biomechanical strength of the keratoconic cornea. Despite strong evidence of changes in the biomechanical properties in human corneas following CXL, there is a significant need for accurate measures of biomechanical changes in vivo pre and post CXL. Until recently technical limitations have restricted the ability to assess the biomechanical properties of the whole cornea in vivo. With the introduction of the CorvisST (Oculus) it is now possible to assess regional biomechanical behaviour of the cornea. The output from the device provides a variety of parameters to indicate the cornea's biomechanical strength. To date, the association between the deflection behaviours in various regions of the cornea in keratoconic eyes preand post CXL has not been studied. In order to effectively assess the clinical benefits of CXL such information is vital. The primary goal of this investigation is to investigate regional biomechanical properties of the keratoconic eye before and after CXL.

Study Overview

• Status: Unknown
• Conditions: Keratoconus
• Intervention / Treatment: Procedure: Corneal Cross-linking

• Study Type: Observational
• Enrollment (Anticipated): 35

Contacts and Locations

Study Locations

• United Kingdom
  • Devon
    • Plymouth, Devon, United Kingdom, PL6 8BH
      • Recruiting
      • Plymouth University
      • Contact: Hetal Buckhurst; Phone Number: 01752 588886; Email: hetal.buckhurst@plymouth.ac.uk

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

• Sampling Method: Non-Probability Sample

Study Population

Potential participants will be identified as those patients who are due to undergo corneal collagen crosslinking treatment

Description

Inclusion Criteria:

• Adult subjects over the age of 18 with keratoconus who are enrolled for collagen crosslinking treatment

Exclusion Criteria:

• Any patient who has had surgical complications will also be excluded from participation in the study.

Determination during enrolment:

• Pregnancy or breastfeeding during the study
• Any kind of systemic disease which affect collagen and the body water regulation system (Marfan syndrome, osteogenesis imperfect, pseudozanthoma elasticum, EhlersDanlos, diabetes, rosacea, acne, cardiovascular disease, thyroid disease)

Study Plan

How is the study designed?

Design Details

• Observational Models: Cohort
• Time Perspectives: Prospective

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change of the corneal hysteresis following corneal crosslinking (mmHg)	Corneal hysteresis as measured using the CorvisST	Up to 3 months prior to corneal collagen crosslinking treatment and at 3-6 months after treatment

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change of refractive error following corneal crosslinking (LogMAR)	Refractive error measured using objective refraction	Up to 3 months prior to corneal collagen crosslinking treatment and at 3-6 months after treatment
Axial Length prior to corneal crosslinking (mm)	Axial length determined with the LenStar	Up to 3 months prior to corneal collagen crosslinking treatment
Axial Length axial length following corneal crosslinking (mm)	Axial length determined with the LenStar	At 3-6 months after treatment
Change in corneal curvature following corneal crosslinking (mm)	Corneal curvature assessed with the Pentacam HR	Up to 3 months prior to corneal collagen crosslinking treatment and at 3-6 months after treatment
Tear break up time prior to corneal crosslinking (s)	Tear break up time determined using the Oculus K5	Up to 3 months prior to corneal collagen crosslinking treatment
Tear break up time following corneal crosslinking (s)	Tear break up time determined using the Oculus K5	At 3-6 months after treatment

Collaborators and Investigators

• Sponsor: University of Plymouth

Study record dates

Study Major Dates

• Study Start (Actual): June 1, 2015
• Primary Completion (Anticipated): December 1, 2019
• Study Completion (Anticipated): January 1, 2020

Study Registration Dates

• First Submitted: June 14, 2015
• First Submitted That Met QC Criteria: June 18, 2015
• First Posted (Estimate): June 19, 2015

Study Record Updates

• Last Update Posted (Actual): January 23, 2019
• Last Update Submitted That Met QC Criteria: January 22, 2019
• Last Verified: January 1, 2019

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Eye Diseases; Corneal Diseases; Keratoconus
• Other Study ID Numbers: 15/SW/0107