SU-F-I-18: Altered Visual Cortex Responses by Wide-View FMRI in Primary Open Angle Glaucoma Patients.

PURPOSE: Primary open-angle glaucoma (POAG) is a common ocular disorder with progressive retinal ganglion cell loss. This study explored the application of wide view fMRI to evaluate neural activity of the whole visual cortex and its relation with visual field functions in POAG patients.

METHODS: Nine subjects with diagnosed POAG (age: 59.9±10.9 y.o., 4 males) and nine age-matched healthy volunteers (age: 58.0±4.6 y.o., 6 males) were scanned on a 3T Siemens scanner. For each subject, wide view (110°) visual stimulation of a rotating wedge was performed during fMRI acquisition. T1-MPRAGE was used to acquire anatomical images as a reference. fMRI signal percent change was calculated for quadrant areas of the visual field for each subject. Group comparison was performed using non-parametric Mann-Whitney test with Bonferroni correction. In POAG patients, indices of visual field score and retina layer thickness from each quadrant were correlated with the corresponding fMRI percent changes by Spearman's method. P<0.05 was the threshold for statistical significance.

RESULTS: The fMRI signal percent changes of moderate (0.65±0.10, N=9) and advanced (0.44±0.05, N=2) POAG quadrant visual cortex showed significant decrease (moderate: P<0.05; severe: P<0.01) compared with normal (1.02±0.05, N=36). Slightly reduced fMRI signal in early POAG (0.97±0.07, N=25) was observed but not statistically significant. For POAG patients, the fMRI responses per quadrant activation were positively correlated with the clinical visual field scores (ρ=0.48, P<0.005); no correlation was found between fMRI response and retinal nerve layer thickness (ρ=0.01, P>0.05).

CONCLUSION: fMRI revealed a functional decrease of the neural activity in the visual cortex in moderate and advanced POAG. The correlation of fMRI signal with visual field test results indicate fMRI could be used as an objective tool to quantify visual field defects for glaucoma patients.