Hyperopia

For the fictional goddess created by Terry Pratchett, see Discworld gods § Hyperopia.

Hyperopia
Hyperopia lens correction
Classification and external resources
Specialty	Ophthalmology
ICD-10	H52.0
ICD-9-CM	367.0
DiseasesDB	29644
MedlinePlus	001020
Patient UK	Hyperopia
MeSH	D006956

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.

People with hyperopia can experience blurred vision, asthenopia, accommodative dysfunction, binocular dysfunction, amblyopia, and strabismus,

Classification

Hyperopia is typically classified according to clinical appearance, its severity, or how it relates to the eye's accommodative status.

• Simple hyperopia
• Pathological hyperopia
• Functional hyperopia

Signs/symptoms

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.

Causes

Human eye cross-section

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.

Mechanism

Refractive errors occur when the shape of the eye keeps you from focusing well.Human vision occurs when light is refracted as it passes through the cornea (and lens). The retina adjusts the light into information that is sent via the optic nerve to the individuals brain which creates an image.

Diagnosis

Retina section

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:

• Glaucoma test
• Refraction testing
• Retinal exam
• Eye movement
• Visual acuity

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.

Treatment

Treatment of farsightedness includes contact lenses and eyeglasses, and can also be done via the following methods:

• 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.

Complications

Farsightedness can have rare complications such as strabismus and amblyopia, at a young age severe long-sightedness can cause the child to have double vision as a result of over-focusing

See also

• Myopia
• Presbyopia