Age-related macular degeneration (AMD) Eye Diseases Degeneration of macula and posterior pole
Conditions
Interventions
The purpose of the pilot study is to develop quantitative methods to assess brain structure and function in participants with macular degeneration in order to predict the success and measure the effec
Sponsors
University of York
Eligibility
Sex/Gender
All
Inclusion criteria
Inclusion criteria: Participants for our study will be drawn only from participants in the Argus II Retinal Prosthesis System Dry AMD Feasibility Study led by Prof Paulo Stanga in Manchester (https://clinicaltrials.gov/show/NCT02227498). Therefore, participants must meet the inclusion criteria specified for this study. Broadly, this includes adult participants with the 'dry' form of macular degeneration without other eye problems that would preclude retinal prosthetic implantation.
Exclusion criteria
Exclusion criteria: Participants will be subject to the exclusion criteria outlined in the linked study 'Argus II Retinal Prosthesis System Dry AMD Feasibility Study Protocol' (https://clinicaltrials.gov/show/NCT02227498). In addition, participants with contraindications for magnetic resonance imaging (MRI) will not be included in this study. Contraindications for MRI include the following: 1. A cardiac pacemaker 2. Operations involving implantation of metal or other implants that may not be MRI compatible 3. A programmable hydrocephalus shunt 4. Cochlear implant 5. Fixed dental braces 6. Injuries involving metal fragments or shrapnel 7. Metal piercings that cannot be removed 8. Certain medicinal patches incompatible with MRI 9. Close relatives of the investigators 10. Epilepsy/seizures 11. Severe claustrophobia or discomfort maintaining a supine position in the MRI scanner
Design outcomes
Primary
| Measure | Time frame |
|---|---|
| The purpose of this study is the feasibility for conducting a larger study in the future. To determine this, the following primary outcomes will be evaluated: 1. Participant's tolerance, comfort and safety during each measure (to be noted down in writing by researcher during debriefing at the end of each visit) 2. Which neural measures are most reliable and least affected by implant artifacts and other noise sources? (by evaluating each neural measure outside of the main regions of interest) 3. Which neural measures are most predictive of successful vision restoration following retinal implantation? (by correlation with visual improvement as assessed by Prof Stanga with clinical vision tests) 4. Which neural measures are most effective for assessing visual cortical changes following retinal implantation? (based on outcome of secondary, scientific measures) Neural measures refer to the amount of brain activation measured with MRI in response to visual stimulation. Measured before retinal implantation and once about 12 months after implantation. | — |
Secondary
| Measure | Time frame |
|---|---|
| Secondary outcome measures will be the scientific assessment of neural characteristics of visual cortex within each participant before and after retinal implantation. 1. Structural measures will include grey and white matter volume, cortical thickness and myelination fraction (macromolecular tissue volume), which will gauge the potential changes in myelinated input to primary visual cortex. 2. Functional measures will include the blood oxygenation level dependent (BOLD) response level to simple and complex stimuli, and the position of stimulation within the visual field that yields the highest response (retinotopic mapping), and the level of the inhibitory neurotransmitter GABA. 3. To control for variability across participants and sessions, a ratio will be used to compare each the neural measures at the lesion projection zone (part of the brain receiving inputs from the macular, lesioned retina) and the intact projection zone (part of the brain receiving inputs from the peripheral, intact retina) within each participant and each session (before and after treatment). Measured before retinal implantation and once about 12 months after implantation. | — |
Countries
United Kingdom
Outcome results
None listed