The retina is part of our central nervous system and is the crucial conduit between the eye and the brain. It is essentially light sensitive tissue at the back of the eye and covers about 65% of its total interior surface.
Within the retina are photosensitive (light sensitive) cells, which transform light energy into signals conveyed to the brain via the optic nerve fibres.
The retina delivers information to the brain, which puts all of these signals together to determine what we see.
The retina is a structure with several layers of neurons interconnected by synapses. This refers to a structure that allows a neuron (or nerve cell) to pass electrical or chemical signals, thus allowing messages to pass along the nerve.
The only neurons directly sensitive to light are known as photoreceptor cells. There are two main types of these, known as rods and cones. Essentially, the rods deal with dim lighting conditions and are not sensitive to colour.
The cones mainly look after daytime vision and colour perception. There is a third photoreceptor (photosensitive ganglion cell) that is primarily responsible for reflex response to bright daylight.
Overall, each human eye contains about 120 million rods and six or seven millions cones, while there are only about 1 million or so ganglion cells.
The retina is an essential component of the eye and any disorders tend to be serious and can cause vision loss. They include:
In recent times, there have been several new strategies for dealing with diabetic retinopathy and, generally, it can be treated, but successfully maintaining vision in the long-term relies on managing the underlying diabetes and blood glucose levels.
The best way to describe the role that the retina plays in vision – and therefore how important it is to diagnose and treat any problems as soon as possible – is to explain how the eye works:
So, you could say the retina is the eye’s essential communication tool. Without that vital information, we simply wouldn’t know what we are looking at.