Pilotto E, et al. - Researchers conducted this prospective study in order to better understand the pathophysiology of geographic atrophy (GA), secondary to age-related macular degeneration. For this purpose, they evaluated eyes affected by unilateral GA (and CNV in the fellow eye; U-GA group) or by bilateral GA (B-GA group) using an integrated morpho-functional approach and quantifying biomarker of retinal macroglial activity. Among 40 eyes of 40 patients (18 in the U-GA group and 22 in the B-GA group), the groups were noted to differ regarding retinal thicknesses (RT), GA area, best-corrected visual acuity, contrast sensitivity, multifocal electroretinography, and microperimetry (at both background luminances). U-GA group had significantly thinner CT compared to B-GA group. The B-GA vs U-GA group showed significantly worse low-luminance VA and low-luminance deficit. The B-GA group had significantly higher glial fibrillary acidic protein intraocular concentration. These findings suggest the role of different pathophysiologic mechanisms for GA in unilateral (with CNV in the fellow eye) compared to bilateral GA cases. A thinner choroid seems to play a key role in unilateral cases, whereas, Müller cells and their supported photoreceptors may be primarily involved in bilateral cases.