Those eligible for the study are children and young people aged 10 to 16 with progressive KC in one or both eyes (as measured by Pentacam scans at least 3 months apart). Not eligible for the study are youngsters who have corneal scarring, have a corneal apex thickness of less than 400 microns or K max (corneal curvature) of more than 62 dioptres or have other corneal conditions as well as KC. The study also excludes any rigid contact lens wearers who are not able to leave their contact lenses out for 7 days before a topography measurement (i.e. cope with glasses only for 7 days) and Down’s syndrome patients with KC (because KC tends to be different in these patients).
Those taking part in the study are randomly assigned to either the group that will have CXL treatment or to the group receiving ‘standard care’ i.e. spectacles or contact lenses, this second group being the ‘control’ group for the study. The optometrists carrying out the Pentacam scans will not know which group a child is in.
The main outcome measure of the study is the Pentacam scan i.e. measuring any changes in corneal curvature in both groups. Secondary outcome measures are progression of KC, best corrected visual acuity (BCVA), refraction, apical corneal thickness and quality of life (as measured by questionnaires). All patients in the study are followed up every 3 months for 18 months (although the hope is that funding will eventually be available for longer follow up).
Mr Larkin stressed the significance of this study, which is the first randomised trial of CXL in children in the world, and its importance in view of the recent large increase in diagnosis and referrals from community optometrists of children with KC. Challenges for the trial are that parents’ preconceived belief in the effectiveness of CXL could hinder recruitment to the trial (although so far no eligible families have declined to participate in the study) and the possibility that some children in the standard care group might show significant progression of KC during the study. Ethical considerations mean these will be looked at individually to see if further treatment should be offered.
One question this study is not looking at is whether CXL should be performed at the point of diagnosis, without confirmation that KC is progressing. Mr Larkin’s view is that it shouldn’t, as some patients even in this age group have spontaneous stabilisation without any intervention, and, as mentioned above, CXL is not safe in all patients.
The Keralink trial is being funded by the National Institute for Health Research (NIHR) and is happening in three centres – Moorfields, St Paul’s Eye Unit in Liverpool and the Royal Hallamshire Hospital in Sheffield though children for the study need not already be patients of those hospitals. Recruitment to the study is still continuing.
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