Abstract
Purpose :
Retinotopic maps acquired by fMRI provide a valuable adjunct in the assessment of macular dysfunction at the level of the visual cortex. The present study quantitatively assesses the performance of different visual stimulation approaches for mapping visual field coverage.
Methods :
Twelve patients with geographic atrophy (GA) secondary to age-related macular degeneration were examined using high-resolution 7 Tesla fMRI (Siemens Magnetom 7T[CW1] ) and microperimetry (MP, Nidek MP-3). We compared pRF-based coverage maps obtained with two stimulus variants (moving bars; rotating wedges and expanding rings) with the results of MP. Correspondence between MP and pRF mapping was quantified by calculating the simple matching coefficient (SMC).
Results :
We find that stimulus choice biases the spatial distribution of pRF centres. In addition, eccentricity values and pRF sizes obtained from wedge/ring or bar stimulation runs show systematic differences. Wedge/ring stimulation results show lower eccentricity values and strongly reduced pRF sizes compared to bar stimulation runs. Statistical comparison shows significantly higher pRF centre numbers in the foveal 2.5° region of the visual field for wedge/ring compared to bar stimuli. However, these differences do not have an effect on SMC values when compared to MP (bar below 2.5° : 0,88 plusminus 0,13 bar above 2.5°: 0,88 plusminus 0,11; wedge/ring below 2.5°: 0,89 plusminus 0,12 wedge/ring above 2.5° 0,86 plusminus 0,10) for the peripheral visual field.
Conclusions :
Both visual stimulation designs examined in this study can be applied successfully in GA patients. Although the two designs show systematic differences in the distribution of pRF centre locations, this variability has no impact on the SMC when compared to MP outcome.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.