The Biophysics of Visual Photoreception

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Abstract
Vision is awe inspiring. The wondrous nature of this sensory process becomes clear when we consider just a few of its features. In the terminology of today's technology, the human visual system has a set of stereoscopic foreoptics that are instantly and automatically focusable to a few centimeters and are fully corrected for geometric aberrations, a servo‐controlled two‐axis scanning mechanism, a millisecond framing rate, sensitivity to brightnesses varying by a factor of 100 billion, the ability to detect a single photon, nearly 100% quantum efficiency and a spatial as well as temporal image processor that could not be matched by the fastest supercomputer. The absorption of a single photon by a pigment molecule called rhodopsin in a photoreceptor cell in the retina initiates a process of amplification that ends in a neural response.