Human Retina

The human retina is an amazing structure.

The retina is part of the brain, having been sequestered from it early in development but having kept its connections with the brain through a bundle of fibers   the optic nerve

It consists of three layers of nerve cell bodies separated by two layers containing synapses

The tier of cells at the back of the retina contains the light receptors, the rods and the cones

Rods, which are far more numerous then cones, are responsible for our vision in dim light (scotopic vision) and do not work in bright light

Cones do not respond to dim light but are responsible for our ability to see fine detail and color light (scotopic vision)

Figure: Relative positions of the three retinal layers (from Hubel, 1988)


The number of rods and cones vary markedly over the surface of the retina. In the very centre (fovea) , where our vision is best, we have only cones. The fovea is about 0.5mm in diameter Figure Distribution of rods and cones in the retina (from Gonzalez and Woods, 1992)


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Last modified on April 05, 1999, G. Scott Owen,