MRI in Retinal Degeneration
Research type
Research Study
Full title
Changes in Visual Cortex In Patients With Visual Field Loss Secondary to Inherited Retinal Degeneration
IRAS ID
226399
Contact name
Holly Bridge
Contact email
Duration of Study in the UK
3 years, 0 months, 0 days
Research summary
Research summary
The retina is located at the back of the eye and contains light-sensitive cells called photoreceptors that convert light energy to electrical signals. The electrical signals are transmitted to the brain and processed by the visual cortex. If these cells are damaged, the light arriving at the eye can no longer lead to stimulation of the visual system. Inherited retinal degenerations are a group of genetic conditions that affect the way the retina works and cause progressive visual loss leading to blindness by middle age. The study aims to investigate whether longterm loss of visual function has an impact on the structure and function of the visual cortex (the part of the brain that processes visual information) and whether it would be possible to use fMRI brain imaging in assessing the outcomes of clinical trials. Multiple types of MRI scans will be conducted whilst participants are looking at visual simuli to assess structure and function of the visual cortex in patients with reduced visual fields. A feasibility survey will be conducted following the scanning sessions in order to provide information about the acceptability of the procedure to patients. Additionally the practicalities of visual testing in vision loss will be assessed. The information from this study will allow sample size calculations to be performed for future studies.Summary of results
Thank you for taking part in the study at the University of Oxford and Oxford Eye Hospital a few years ago. We have now completed the study. At visit one, 20 people with choroideremia, 17 people with Stargardt disease and 22 age-matched comparison participants completed the MRI scan and all the vision tests. Approximately 2 years later, 12 people with choroideremia, 8 with Stargardt disease and 18 control participants returned for follow-up assessments.
The key findings that have been analysed across the different groups thus far are as follows:
Visual function:
1. Using our microperimetry measure of visual fields, we found that the central visual fields decreased in size over the 2 year period, particularly in the choroideremia group.
2. The number of letters read on the chart did not change over time
Measurements of retinal structure:
The scans of the back of the eye (optical coherence tomography) were used to measure the thickness of different layers of the retina. The main layers that we are interested in are the photoreceptors, which are the light sensitive cells necessary for vision. While this layer was thinner in both choroideremia and Stargardt disease compared to those without eye disease, the thickness did not change over time.
Visual pathway:
We used one of the MRI scans to investigate the structure of the visual pathway from the eyes to the brain. In particular we were interested in the optic radiation that carries information to the primary visual cortex that processes all the information arriving from the eye.
Both choroideremia and Stargardt disease groups showed a change in the pathway to the brain, compared to control participants, indicating that the vision loss at the eye also affects the brain. However, initial results suggest that this did not change very much over the 2 year period, implying that these changes are likely very slow.
Over the next few months, we will continue to analyse the remaining data to understand more details about how the brain changes in these two inherited retinal diseases.
We hope to build on this work in the future to work out how we can use understanding of these changes to develop therapies that harness the adaptability of the brain to make the most of the remaining vision.REC name
London - Bromley Research Ethics Committee
REC reference
17/LO/1540
Date of REC Opinion
27 Sep 2017
REC opinion
Further Information Favourable Opinion