Abstract
Purpose: :
To use functional MRI as an objective, fixation-independent measure of topographic visual function and assess cortical responsivity in patients undergoing anti-angiogenic treatment for wet age-related macular degeneration (AMD).
Methods: :
Patients with bilateral neovascular AMD were scanned using functional MRI before and at regular intervals while undergoing treatment with intravitreal anti-angiogenic injections (primarily LucentisTM). Blood oxygenation level-dependent (BOLD) signals were measured in the brain while patients viewed a visual stimulus consisted of a full-field flickering (6 Hz) white light alternating with a uniform gray background (18 sec on, 18 sec off). Topographic distribution and magnitude of activation in visual cortex were compared within individuals longitudinally throughout the treatment period (<1 year) and with control patients not currently undergoing treatment.
Results: :
The area of visual cortex activated increased significantly after the first treatment to include more posterior cortex that normally receives inputs from lesioned parts of the retina. Subsequent treatments yielded no significant further increase in activation area; however, activation magnitude continued to increase. Untreated patients showed a consistent lack of significant response in the cortex representing retinal lesions.
Conclusions: :
Retinal treatments may improve vision but also result in a concomitant improvement in fixation stability. Current clinical behavioural measures (e.g. acuity, perimetry) are largely dependent on fixation stability, and therefore cannot separate improvements of visual function from fixation improvements. Functional MRI, which provides an objective and sensitive measure of visual function independent of fixation, reveals a significant increase in visual cortical responses in wet AMD patients following treatment with anti-angiogenic injections. Despite recent evidence that visual cortex degenerates subsequent to retinal lesions, our results indicate that it remains responsive as its inputs are restored.
Keywords: age-related macular degeneration • neuro-ophthalmology: cortical function/rehabilitation • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)