This month’s How Things Work feature focuses on the retina. When light passes through a healthy eye, the tissues in front of the eye adjust the light so that it comes to a focal point at the back of your retina, called the macula (or fovea). This visual information is then transmitted by our optic nerve (last month’s feature) up to the brain.

The retina is the neurological lining on the inside curvature of the eye. Like a miniature, bowl-shaped projector screen, the retina receives and maps the images our eyes are viewing. The purpose of the cornea and lens are to focus light onto the retina. The retina has numerous microscopic layers.

Many people recall studying in school about the “rods and the cones” of the retina. The rods are retinal cells that aid in the processing of low-light (night) vision, and the cones are the retinal cells that help process vision in normal light. The rods do not contribute to color vision, hence the inability to discern colors in dim illumination, and the cones provide the color vision we are accustomed to under normal lighting.


The retina is a complex tissue made up of intertwining nerves, cellular structural support systems, arteries, and veins. The information from the retina is collected and then “packaged” and sent to the brain for further processing. The optic nerve is the two-way “highway” that connects the retina and brain. Information carried via nerves, and oxygen carried through arteries and veins are all transported in and out of the retina via the optic nerve highway.

Numerous bodily diseases can severely, and sometimes irreversibly, damage the retina, including diabetes, high blood pressure, and high cholesterol. Because the retina is so rich in blood supply, the functioning of the arteries and veins are critical. The eye itself can even have a “stroke” if the arteries and veins are not functioning normally.

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