Researchers at the University of Pennsylvania School of Medicine have estimated the data transmission rate between the human eye and the brain according to a news release. They hope their findings will "inform the design of artificial vision systems". As it turns out, they say the human retina transmits data to the brain at roughly 10 millions bits per second. Technically, the retina is actually part of the brain but the information processed their is carried to higher centers of the brain. To reach their estimates, the researchers measured the rate of spikes occuring in several different cell types in a guinea pig retina esposed to video of object motion. For more information, an earlier paper from the same researchers is available: Efficiency of Information Transmission by Retinal Ganglion Cells (PDF format).