Your eye works similarly to a camera. By focusing images through a series of lenses, our eyes allow us to see the world around us.
Basically, sight is the result of light passing through the lens and being ‘encoded’ on the back of your eye by a light-sensitive membrane called the retina. The retina sends on that image as electrical impulses to your brain. At the front of the eye is a transparent structure called the cornea. The corneas job is to help focus the incoming light. Just Behind the cornea is a coloured, ring-shaped membrane called the iris. The iris has an adjustable circular opening called the pupil that can expand or contract to control the amount of light coming in. Ciliary muscles surround the eyes lens. These muscles hold the lens in place, but they also play an important role in how we see. When the ciliary muscles relax, they pull on and ﬂatten the lens, allowing your eye to see objects that are far away. To see closer objects clearly, the ciliary muscles have to contract to thicken the lens.
The interior chamber of your eyeball is ﬁlled with a jelly-like tissue called the vitreous humour. After passing through your lens, light has to travel through this humour before striking the sensitive layer of cells called the retina.
The retina is made up of millions of two types of specialised cells known as rods and cones. Rods are used for monochrome vision in poor light, while cones are used for colour and the detection of ﬁne detail. Cones are packed into a part of the retina directly behind the retina called the fovea, responsible for sharp central vision. The retina transforms the image it gets into electrical messages to the brain in the form of electrical impulses. These impulses are sent to the optic disk on the retina where they get transferred by a further set of electrical impulses along the optic nerve, to be processed by your brain.
Check out each part of the eye and its function in more detail below.
The four most common problems with vision:
- Astigmatism: A defect in the eye caused by non-spherical curvature
- Myopia: Short Sightedness
- Hyperopia: Long Sightedness
- Presbyopia: Age-related Long Sightedness
Most people will develop presbyopia in their 40s or 50s, and start needing reading glasses. The reason is that with age, the lens of the eye gets denser, making it harder for the ciliary muscles to bend it.