Far-sightedness, also known as long-sightedness, hypermetropia, or hyperopia, is a condition of the eye where distant objects are seen clearly but near objects appear blurred. This blurred effect is due to incoming light being focused behind, instead of on, the retina wall due to insufficient accommodation by the lens. Small amount of hypermetropia in young patients is usually corrected by their accommodation, without any defects in vision. But, due to this accommodative effort for distant vision, people may complain asthenopic symptoms while constant reading. Some hypermetropes can see clear at distance, but near vision may be blurred due to insufficient accommodation. For this reason, this defect is referred as far-sightedness. If the hypermetropia is high, there will be defective vision for both distance and near. People may also experience accommodative dysfunction, binocular dysfunction, amblyopia, and strabismus.Newborns are almost invariably hypermetropic, it will gradually decrease as the age increase.
There are many causes for this condition. It may occur when the axial length of eyeball is too short, or if the lens or cornea is flatter than normal. Changes in refractive index of lens, alterations in position of the lens or absence of lens are the other main causes. Risk factors include a family history of the condition, diabetes, certain medications, and tumors around the eye.It is a type of refractive error. Diagnosis is based on an eye exam.
There are also surgical treatments for far-sightedness:
- Photorefractive keratectomy (PRK): This is a refractive technique that is done by removal of a minimal amount of the corneal surface. Hyperopic PRK has many complications like regression effect, astigmatism due to epithelial healing, and corneal haze.Post operative epithelial healing time is also more for PRK.
- Laser assisted in situ keratomileusis (LASIK): Laser eye surgery to reshape the cornea, so that glasses or contact lenses are no longer needed. Excimer laser LASIK can correct hypermetropia up to +6 diopters.LASIK is contraindicated in patients with lupus and rheumatoid arthritis.
- Laser epithelial keratomileusis (LASEK): Resembles PRK, but uses alcohol to loosen the corneal surface.
- Epi-LASIK: Epi-LASIK is also used to correct hyperopia. In this procedure, use of epikeratome eliminates the use of alcohol.
- Laser thermal keratoplasty (LTK): Laser thermal keratoplasty is a laser based non-destructive refractive procedure used to correct hyperopia and presbyopia. It uses Thallium-Holmium-Chromium (THC): YAG laser.