The retina is a major sensory processing circuit for humans and as the overall nervous system, it is a complex and hierarchical large network of cells consisting of different types of neurons. These cells communicate with each other through biochemical and bioelectrical signals that, at the circuit level, lead to the encoding of different features of the visual inputs. To understand this process many studies based on electrophysiological recordings have been conducted on single-cells or a restricted pool of cells. Only with the recent technological developments, as the new generations of high-density microelectrodes arrays (HD-MEA) that exploit CMOS (Complementary Metal-Oxide-Semiconductor) technology, we have reached the capability of monitoring the light-evoked responses of several thousands of retinal ganglion cells (RGCs) in individual retinas.