One common feature of diseases causing photoreceptor loss is that inner retinal neurons are preserved long after photoreceptor apoptosis occurs. Some degree of vision may potentially be restored if these remaining neurons could directly respond to light and transmit meaningful information to visual centers. Recently, light-sensitive cation channels (Channelrhodopsins) and anion pumps (Halorhodopsins) were shown to effectively excite and inhibit neural activity in response to visible light. By targeting these rhodopsins appropriately in a diseased retina, a virtual ON or OFF signaling pathway may potentially be generated. The human retina contains at least 30 morphologically distinct bipolar and ganglion cell subtypes, however ON and OFF-center signal detection is the most significant division among visual features extracted by ganglion cells. Imparting light sensitivity specifically to ON or OFF-center bipolar and ganglion cells with excitatory or inhibitory rhodopsins may yield new insights into signal processing and could allow light perception in the absence of rod and cone-mediated vision. Using patterned light stimuli with electrophysiological recording techniques, we are attempting to understand the quality of vision that could be restored using this prosthetic approach.