Abstract
PurposeTo investigate the altered intrinsic functional connectivity (iFC) of the primary visual cortex (V1) in primary angle-closure glaucoma (PACG) patients before and after surgery using resting-state functional MRI.Materials and MethodsTwenty-five preoperative PACG (pre-PACG) patients and 25 well-matched healthy controls (HCs) were included in this study, and 9 PACG patients were assessed again at least 3 months after treatment (post-PACG). We generated the iFC maps of the seed regions in the centers of the left and right V1 and conducted group comparisons. Then, the relationships between the altered iFC coefficients and clinical variables were investigated in the pre-PACG patients.ResultsCompared with the HCs, the pre-PACG patients showed decreased iFC between the left V1 and right V2 (covering the cuneus, calcarine and lingual gyrus) and increased iFC between the left V1 and left temporal-parietal region, left frontal opercula-insula-basal ganglia region, right insula-basal ganglia region, and right inferior parietal lobule (P < 0.01, corrected). Compared with the pre-PACG patients, the post-PACG patients showed increased iFC between the left V1 and bilateral V2, and between the left V1 and left or right postcentral gyrus; in addition, they showed decreased iFC between the left V1 and the dorsal-attention and frontoparietal-control networks. In the pre-PACG patients, visual activity (VA) was positively correlated with increased iFC between the left V1 and the left temporal-parietal region or the right inferior parietal lobule. Similar patterns of alterations were observed in the right V1-iFC in both the pre- and post-PACG patients.ConclusionsThe primary findings have demonstrated a gradual decrease in visual information integration in the left V1-V2 pathway and VA-related functional compensation in the pre-PACG patients, generating further evidence of functional restoration in post-PACG patients.
Highlights
Primary glaucoma, the second leading cause of blindness worldwide, will have affected 79.6 million people by 2020 [1]
The primary findings have demonstrated a gradual decrease in visual information integration in the left V1-V2 pathway and visual activity (VA)-related functional compensation in the pre-primary angle-closure glaucoma (PACG) patients, generating further evidence of functional restoration in post-PACG patients
Several recent studies have shown that glaucoma patients possess abnormalities such as decreased intrinsic functional connectivity, both within the visual network [13] and beyond the visual system [9], as well as alterations in amplitude of low-frequency fluctuations (ALFFs) [14] or regional homogeneity (ReHo) [15]
Summary
The second leading cause of blindness worldwide, will have affected 79.6 million people by 2020 [1]. Several recent studies have shown that glaucoma patients possess abnormalities such as decreased intrinsic functional connectivity (iFC), both within the visual network [13] and beyond the visual system [9], as well as alterations in amplitude of low-frequency fluctuations (ALFFs) [14] or regional homogeneity (ReHo) [15]. These results have been reported for patients with primary open-angle glaucoma (POAG), which is most prevalent in Western societies. DC is a measure of the topology of the architecture of the brain functional connectome [22], but it does not reflect the temporal correlation between spatially remote neurophysiological events. iFC, which is amenable to simple and straightforward interpretation, allows for measurement of connectivity between brain regions that share functional properties [23]
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