This study used fMRI to measure functional activity in the lateral geniculate nucleus (LGN) of 10 subjects with primary open-angle glaucoma (POAG). Subjects underwent visual stimulation scans alternating between left/right and superior/inferior visual fields. Large clusters of correlated activity were found in primary visual cortex (V1) but not in the LGN of POAG subjects. A healthy control subject showed detectable LGN activity, providing evidence that the LGN undergoes functional degeneration in POAG.