Abstract
Evidence has shown that the spatial extent of crowding increases with age (Liu & Kwon, 2017). It is also known that aging brings about approximately 15% to 25% loss of retinal ganglion cells (RGCs) even in the healthy eyes (Curcio & Drucker, 1993; Gao & Hollyfield, 1992). While RGCs, the output neurons of the retina, are likely to impose a fundamental limit on spatial integration properties, little is known about the role of RGCs in age-related changes in the extent of spatial integration. Here we investigated whether the age-related loss of RGCs is associated with the age-related increase in crowding zone and in Ricco's area (if any). The study included 15 young (mean age=23.4±4.2 years) and 7 older adults (mean age=59.9±5.8 years) with normal or corrected-to-normal vision. For each subject, the thickness of the macular RGC plus inner plexiform (RGC+) layer, known to be related to RGC density, was measured with Spectral-Domain Optical Coherence Tomography within the central 20 degrees visual field. Crowding zone (i.e., the minimum target-flanker spacing required for reliable target recognition) and Ricco's area (i.e., the area of complete spatial summation for reliable luminance detection) were also measured at various retinal locations within the central 20 degrees visual field. Our results showed that, compared to young adults, older adults exhibited a significant reduction in macular RGC+ layer thickness, but a significant increase in crowding zone and Ricco's area (all p< 0.05). Furthermore, macular RGC+ layer thickness was significantly correlated with both crowding zone (r=−0.50, p=0.02) and Ricco's area (r=−0.44, p=0.04). Taken together, our findings suggest that age-related loss of RGCs may in part explain age-related increase in spatial integration zone.
Meeting abstract presented at VSS 2018