Parts of the Eye: The Retina

If you’re reading this blog, then you have your retinas to thank for it. Located at the back of the eye, the retina plays an essential role in vision by converting light into neural signals, which our brains process as images. Take a look below to learn more about the retina and how it functions!

Structure

The retina consists of several layers of tissue and neurons that line the back of the eye and that are linked together by synapses, or structures that transmit electrical and chemical signals to the brain. While there are five types of neurons in the retina, only three are directly sensitive to light: rods, which process dim or less intense light; cones, which are responsible for daylight and color vision; and photosensitive ganglion cells that handle reflexive responses to light. The retina is a part of the central nervous system, and it accounts for 65% of the eye’s interior surface.

Functions

When light enters your eye, the retina’s photosensitive cells—primarily rods and cones—send electrical and chemical signals that travel along synapses to the optic nerve. These signals are then transmitted to the brain, which processes the light into the images that we see.

In other words, think of the retina as a camera. When light enters a camera’s lens—in this case, the cornea, or the outermost layer of the eye—it imprints an image onto film, similarly to how the rods and cones in the retina convert light into electrical and chemical signals before transmitting them to the brain. Film is then developed into a photograph, just like how the brain processes signals from the retina into an image.

Problems

As the key link in the chain between the eye and the brain, damage to the retina can lead to vision loss or even permanent blindness. Common disease or conditions that affect the retina include:

  • Macular Degeneration, which occurs when the macula—a point in the center of the retina that is responsible for detailed vision—deteriorates, creating a blind spot in the middle of your visual field.
  • Detached Retinas can cause permanent vision loss and result from small tears or splits in the retina. Some vision loss may be unavoidable, but generally speaking, surgeries to treat detached retinas have a 95% success rate.
  • Diabetic Retinopathy is a condition that occurs when blood cells in the retina are damaged as a result of high blood sugar from diabetes. As a result, the cells may become distorted or even bleed, which interrupts the regular transmission of light from the eye to the brain.

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