Refractive

The eye is almost round in shape and is made up of layers, all of which serve a purpose in focusing images. The eye has two parts, which professionals call 'chambers'. The anterior chamber is everything in front of the pupil. This part is small, but very important because it is both curved as well as clear or transparent. This structure is called the cornea, and is responsible for focusing 80% of light.

The back of the eye is called the posterior chamber and is made up of everything behind the pupil. The lens is responsible for approximately 20% of focusing and when correcting a 'REFRACTIVE ERROR' it is the strength or focusing power of the cornea (Lasik, Lasek, PRK) or the lens (CLE - Clear Lens Extraction) that is altered.

With age it is common for the lens to harden and become less clear (also known as opacification). The hardening of the lens makes it difficult for it to change shape and therefore fine focusing becomes difficult without spectacles. This is known as PRESBYOPIA and affects almost everyone over the age of 45. Cloudy lenses are known as CATARACTS and these affect many people from the age of 65, but can affect younger people too.

The eye is filled with a gel like substance and this is maintained at a constant pressure. A disturbance in the balance between the formation and excretion of fluid can cause an increase in pressure, which is known as GLAUCOMA

Cataract and presbyopia, are unfortunately not the only age related conditions to affect the eye. The gel like substance that maintains the shape of the eye (vitreous) can shrink slightly and come away from the wall of the eye (the retina). In minor cases this can cause FLOATERS whilst in severe cases the retina detaches too and results in a RETINAL DETACHMENT/TEAR.

We blink every 2-10 seconds

We see upside-down the brain inverts the image

New born babies see upside-down until the brain learns to invert the image

Those with 1 eye can only see two dimensionally (cannot replicate by closing 1 eye)

A chameleon can look in two directions at the same time

An owl can see a moving object at 150 feet away in light no better than candle light

The cornea has 5 layers, the upper layers self heal if injured.

The middle of the cornea is 0.5mm thick

The eye muscles are the most active mucles in the body

The eye is composed of more than 2 million working parts

The cornea and the nails do not have a blood supply