First Author: J.Jolly UK
Co Author(s): M. Groppe R. MacLaren 0 0 0 0 0 0 0 0 0
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Autofluorescence (AF) is a valuable tool to monitor disease progression in choroideremia and other inherited retinal degenrations. The area of AF is a biomarker of presumed surviving retinal tissue. This work aims to establish the repeatability of qualitative measurements obtained from autofluorescence (AF) imaging using Heidelberg Eye Explorer software (Heidelberg Engineering, Germany).
Oxford University Hospitals NHS Trust, UK. Outpatients department.
AF images from ten eyes of ten patients were obtained. Images were obtained with a field of view of 30 degrees and 55 degrees for each patient. Each eye had two images from a single visit. The area of healthy retina was measured using Heidelberg Eye Explorer software. Two different images from a single visit were measured for each eye. For 30 degree images, the measurement focussed on the area of the central island of healthy retina. For 50 degree images, all sections of healthy retina were measured and total area calculated. A percentage area of healthy retina was then established.
A Bland Altman analysis was conducted on both sets of images. The coefficient of repeatability for 30 degree images was 0.24. Mean difference between the two images was 0.01 ± 0.30mm2. The 95% limits of agreement were -0.23 to 0.25mm2. The coefficient of repeatability for 55 degree images was 0.75. Mean difference between the two images was 0.09 ± 0.38%. The 95% limits of agreement were -0.83 to 0.66%.
Establishing coefficient of repeatability is important for understanding what level of change constitutes a significant change from previous measurements. Patients can then be advised whether the disease is progressing and an indication can be provided as to how quickly any change is occurring over time. The ability to qualitatively analyse change is becoming more important with the introduction of new treatment modalities, such as gene therapy.