Hyperopia lens correction
|Classification and external resources|
Hyperopia or hypermetropia, commonly known as farsightedness (American English) or longsightedness (British English), is a defect of vision caused by an imperfection in the eye (often when the eyeball is too short or the lens cannot become round enough), causing the eye to not have enough power to see close or nearby objects. Correction is usually achieved by the use of convex corrective lenses. For near objects, the eye has to accommodate even more. Depending on the amount of hyperopia and the age of the person which directly relates to the eye's accommodative ability, the symptoms can be different.
- Simple hyperopia
- Pathological hyperopia
- Functional hyperopia
The signs and symptoms of farsightedness are blurry vision, headaches, and eyestrain. The common symptom is 'tiring' of the eyes (asthenopia). Difficulty seeing with both eyes (binocular vision) may occur, as well as, difficulty with depth perception.
The defect of hyperopia is the result of the visual image being focused behind the retina, hyperopia is mainly caused by two reasons:
- Low converging power of eye lens because of weak action of ciliary muscles.
- Abnormal shape of the cornea
Farsightedness is often present from birth, but children have a very flexible eye lens, which helps make up for the problem. In rare instances hyperopia can be due to diabetes, and problems with the blood vessels in the retina.
The diagnosis of farsightedness (hyperopia) can be done via the silt-lamp test which examines the cornea, conjunctiva, and iris, a yellow dye is used to help examine the cornea. Other test done include the following:
In severe cases of hyperopia from birth, the brain has difficulty in merging the images that each individual eye sees. This is because the images the brain receives from each eye are always blurred. A child with severe hyperopia can never see objects in detail. If the brain never learns to see objects in detail, then there is a high chance of one eye becoming dominant. The result is that the brain will block the impulses of the non-dominant eye. In contrast, the child with myopia can see objects close to the eye in detail and does learn at an early age to see detail in objects.[medical citation needed]
- PRK: removal of a minimal amount of the corneal surface 
- LASIK: laser eye surgery can fix an individuals vision,by reshaping the cornea, therefore glasses or contact lenses are not needed anymore.
- Refractive Lens Exchange: is a variation of cataract surgery, the difference is the existence of abnormal ocular anatomy which causes a high refractive error.
- LASEK resembles PRK, but uses alcohol to loosen the corneal surface.
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