Refractive errors result in a blurred retinal image and, if uncorrected at higher levels, cause vision impairment and blindness. Refractive errors affect people of all ages and backgrounds. Common forms of refractive error include:
Myopia – light from distant objects is focussed ‘in front’ of the retina, making it difficult to clearly see objects in the distance. Myopia is usually due to an excessive elongation of the eye ball. High Myopia is a major risk factor for severe conditions such as Glaucoma, Cataract, retinal detachment and Macular Degeneration.
Astigmatism is mostly caused by an irregular-shaped cornea and/or lens which give rise to multiple images that are not focussed on the retina. Both distance and near objects appear blurred and distorted.
Spectacles are the most common and the least expensive method of correcting refractive errors.
The two other options are contact lenses (more expensive and not suitable in all settings) and refractive laser surgery.
Presbyopia – in the younger eye the lens is elastic and can change shape as the ciliary muscles supporting the lens contract or relax, enabling images of objects at any distance to be focussed on the retina. This is known as accommodation, but as part of the ageing process the lens becomes harder and less elastic, making accommodation more difficult.
Most people over the age of 40 will have a degree of Presbyopia and cannot see near objects clearly.