Altered spontaneous cortical activity in mild glaucoma: A quantitative EEG study.

Functional neuroimaging studies have reported alterations in cortical activity indicating glaucoma as a progressive neurodegenerative disease. Hence the current study aimed to assess the cortical activity using high-density EEG in patients with mild glaucoma during resting state. Treatment-naive 37 patients with primary open angle glaucoma (POAG), 34 patients with primary angle closure glaucoma (PACG), and 32 healthy controls were included in the study. Resting state EEG i.e., eyes closed (EC) and eyes open conditions (EO) were acquired using 128-channel for 3 min. After preprocessing, the current density of 6239 voxels of the data was estimated using sLORETA. In comparison to healthy controls, PACG had higher activity at cingulate gyri, medial and superior frontal gyri during EO only. POAG had significantly higher activity at precentral gyrus and middle frontal gyrus during EC, whereas at cingulate gyri, frontal gyri, precentral gyri, paracentral lobule, sub-gyral region, postcentral gyrus, and precuneus during EO. POAG had significantly higher activity at precuneus and cuneus compared to PACG during EO. Intraocular pressure and mean-deviation of visual fields had a positive correlation with cortical activity. Results of the study indicate physiological alterations not only at the level of retina but also at brain even in the early stages of the disease. These alterations in the cortical activity were more in POAG than PACG. Controlling the IOP alone might be insufficient in glaucoma because of widespread alterations in cortical activity. These findings might enhance the current understanding of cortical involvement in glaucoma.