retina2The retina is the light-sensitive membrane on the inside back of the eye that converts the image focused on it into neural impulses that travel along the optic nerve to the brain to create sight.

retina3The retina itself is made up of several layers– those most toward the back of the eye contain the rods and cones which are responsible of our black and white and color vision respectively. Additional layers contain Horizontal, Bipolar, Amacrine and Ganglion cells that combine the impulses of the individual rods and cones before they travel along the optic nerve fibers to the brain.

The Macula

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The macula is at the very center of the retina. It contains the highest concentration of cones which provide both color and detail vision.The macula is “ground zero.” When we look at things we look with our macula.

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Image of a Normal Retina

The macula represents the central 10 degrees of one’s visual field (of almost 180 degrees diameter) and is the part of the retina that provides our 20/20 vision.

As we move further away from the macula, the remaining retina, even when healthy, does not provide the clear, detail vision that we are accustomed to using. In fact, 10 degrees from the center of the macula, even healthy eyes are only capable of seeing about 20/100.

FIG-FOVEA

10 degrees from the center of the macula (fovea), even healthy eyes are only capable of seeing about 20/100.

As we go more peripherally on the retina, the concentration of cones decreases while the concentration of rods increases. The rods work most well in low light and are most sensitive to motion rather than detail.