Scientists Figure Out Retinal Code

In the Western world, the two most common degenerative diseases of the eye are Retinitis Pigmentosa (RP) and Age-Related Macular Degeneration (AMD). These can be very debilitating conditions and, in their worst forms, these eye diseases can cause the sufferer to gradually go blind. These diseases target the super-fine layer of cells at the back of our eyes which help us to see, the retinal ganglion cells (RGC) of the retina.

A person who lives with with either of these eye conditions gradually loses the use of these RGCs and without them, slowly goes blind. But recently, scientists and ophthalmologists across the globe believe that they have cracked the retinal code and, with the use of some nifty neuroengineering and ophthalmic genetics, are on the way to restoring the sight to tens of millions of people who have lost their vision in this way.

How Does the Eye Work?

Our eyes see by using a complex pathway of different types of cells which fire off nerve signals to each other in rapid succession. To demonstrate how fast these signals fire, imagine that you switch on a light bulb. How quickly do you see the light? It is the time taken for the light to reach your eye, and for that signal to travel along cells in the retina, optic nerve, into the brain and then to the back of your head where the visual system is found. That’s fast!

The retina is made up of around 15 million RGCs and other types of cells which all feed in to the optic nerve. The optic nerve is a long insulated pipe of about a million cells, which constantly sends the signals from all the different types of cells which are responsible for vision.  Think of the optic nerve as a big electricity cable which is insulated. Inside, the copper wires conducting the electricity are like the long axons of the optic nerve fibres, except that there are about a million in each eye.

Now think about the different types of information about our environment that these cells send to our brains. Look around for a second, you take in information about:

• Light and darkness in the environment
• Colors
• Visual textures
• Hues and shades
• Movement
• Distance and spatial relationships
• Patterns

This is just the beginning of the story. A visual scientist could list many more factors the eye has to be able to see for a person to perceive their environment entirely.

AMD and RP

The area of the macula in the retina is where we see fine detail. When we focus our vision on something, we are using the macula and this has the highest number of retinal cells. With AMD, degeneration of these cells can occur with age and it means that we can no longer focus on things, but retain our peripheral vision. Some scientists believe that this may be due to ‘light toxicity’, and many types of medicines are available to slow down this change.

RP is the name given to a collection of inherited diseases of the retina which begin with the loss of peripheral vision and night blindness, but can end with a loss of even central vision. Inherited genetic defects affect at least 40 different genes which are responsible for making sure that the cells in the eye and retina function properly.