Refractive Errors

The Normal Eye

Light from a distant object is focused by the cornea at the front of the eye and the lens inside the eye, to a sharp point of focus on the retina at the back of the eye.

Refractive Errors

Patients in which the light is not accurately focused on the retina are said to have a REFRACTIVE ERROR. There are 4 main types of refractive errors that produce a blurred image, resulting in the need for glasses or contact lenses.

		MYOPIA or Short Sightedness Light is focused in front of the retina to a large eye
		HYPEROPIA or Long Sightedness Light is focused behind the retina due to a small eye
		ASTIGMATISM Light is not focused to a point but rather over a blurred distance in front or behind the retina due to an oval shaped eye.

PRESBYOPIA (Need for Reading Glasses)

People who had previously normal vision find it increasingly harder to focus on near objects. Light from near objects is focused behind the retina due to the natural aging process of the lens. This usually becomes noticeable from around 40 years of age. Some people may be suitable for monovision, which is an alternative to reading glasses. Monovision involves laser refractive surgery to correct one eye for distance and one for near vision. Monovision is not suitable for everyone and therefore a trial using contact lenses can provide a good indication whether this is a suitable option for you. Alternative treatments include multifocal lens implants.

EXCIMER LASER

The EXCIMER laser can reshape the corneal surface in suitable patients with myopia, hyperopia and astigmatism, to allow light to come to focus on or near the retinal surface. This improves distance vision. The laser does not correct presbyopia. Reading glasses will still be required in middle age.