Normal - Normal Sight
Normal sight is achieved when light rays entering the eye through the cornea (the clear domed front surface of the eye) and the lens, are focused onto a single point on the retina.
Short Sight or Myopia
Short sight is due to the cornea being too steeply curved or the eye is longer than normal. Therefore, light rays fall in front of the retina, resulting in blurred distance vision.
Long Sight or Hyperopia
Long sight occurs if the cornea is too flat or the eye too short.
Therefore light rays focus on a point behind the retina causing near vision to become blurred.
On reaching mid to late forties, most people find they need reading glasses, this is due to the natural ageing process of the eye, Presbyopia. The crystalline lens inside the eye loses its flexibility, so it can’t change focus from distance to near vision. Laser treatment can correct an individual’s distance vision however they will continue to need reading glasses.
is caused by the cornea being shaped rather like a rugby ball instead of being spherical.This produces two different focal points which can blur images at all distances. Astigmatism can occur with both long and short-sight.
If the problem is due to the size or shape of the eye, this is often called REFRACTIVE ERROR. There are four main types, these being MYOPIA, HYPEROPIA, PRESBYOPIA and ASTIGMATISM. Refractive Error can be corrected with contact lenses or spectacles it can also be treated with surgery.
It is possible to have a combination of errors, which can be subject to change over time, particularly in later years when the eye becomes less able to 'fine focus' (presbyopia) or if the lens within the eye becomes cloudy (cataract).
Like most organs, the eye is quite complex. To see well, the eye needs to be the right shape and size and all structures that make up the eye should work well. In reality very few of us have perfect vision but the brain compensates for slight imperfections. More pronounced imperfections may effect different structures.