How Your Retina Works
The eye is one of the most amazing organs in the body. To understand how artificial vision is created, it's important to know about the important role that the retina plays in how you see. Here is a simple explanation of what happens when you look at an object:
- Scattered light from the object enters through the cornea.
- The light is projected onto the retina.
- The retina sends messages to the brain through the optic nerve.
- The brain interprets what the object is.
The retina is complex in itself. This thin membrane at the back of the eye is a vital part of your ability to see. Its main function is to receive and transmit images to the brain. These are the three main types of cells in the eye that help perform this function:
- ganglion cells
There are about 125 million rods and cones within the retina that act as the eye's photoreceptors. Rods are the most numerous of the two photoreceptors, outnumbering cones 18 to 1. Rods are able to function in low light (they can detect a single photon) and can create black-and-white images without much light. When enough light is available, cones give us the ability to see color and detail of objects. Cones are responsible for allowing you to read this article, because they allow us to see at a high resolution.
Click the play button to see what happens when light strikes the eye.
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The information received by the rods and cones are then transmitted to the nearly 1 million ganglion cells in the retina. These ganglion cells interpret the messages from the rods and cones and send the information on to the brain by way of the optic nerve.
There are a number of retinal diseases that attack these cells, which can lead to blindness. The most notable of these diseases are retinitis pigmentosa and age-related macular degeneration. Both of these diseases attack the retina, rendering the rods and cones inoperative, causing either loss of peripheral vision or total blindness. However, it's been found that neither of these retinal diseases affect the ganglion cells or the optic nerve. This means that if scientists can develop artificial cones and rods, information could still be sent to the brain for interpretation.