|Synonyms||hypermetropia, hyperopia, longsightedness|
|Far-sightedness lens correction|
|Classification and external resources|
Far-sightedness, also known as long-sightedness and hyperopia, is a condition of the eye in which light is focused behind, instead of on, the retina. This causes close objects to be blurry, while far objects may appear normal. As the condition worsens, objects at all distances may be blurred. Other symptoms may include headaches and eye strain. People with hyperopia can also experience accommodative dysfunction, binocular dysfunction, amblyopia, and strabismus,
Correction is usually achieved by the use of convex corrective lenses. For near objects, the eye has to accommodate even more. Depending on the degree of hyperopia and the age of the person, which directly relates to the eye's accommodative ability, the symptoms can be different.
Far-sightedness primarily affects young children, with rates of 8% at 6 years and 1% at 15 years.
Signs and symptoms
The signs and symptoms of far-sightedness are blurry vision, headaches, and eye strain. The common symptom is eye strain. Difficulty seeing with both eyes (binocular vision) may occur, as well as difficulty with depth perception.
As hyperopia is the result of the visual image being focused behind the retina, it has two main causes:
- Low converging power of eye lens because of weak action of ciliary muscles
- Abnormal shape of the cornea
Far-sightedness 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.
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]
- Simple hyperopia
- Pathological hyperopia
- Functional hyperopia
- PRK: the removal of a minimal amount of the corneal surface
- LASIK: laser eye surgery to reshape the cornea, so that glasses or contact lenses are no longer needed.
- Refractive Lens Exchange: 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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