Hyperopia

Hyperopia, also known as farsightedness, longsightedness or hypermetropia, 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 difficulty focusing on near objects, and in extreme cases causing a sufferer to be unable to focus on objects at any distance. As an object moves toward the eye, the eye must increase its optical power to keep the image in focus on the retina. If the power of the cornea and lens is insufficient, as in hyperopia, the image will appear blurred.

Hyperopia, and restoring of vision with convex lens.

People with hyperopia can experience blurred vision, asthenopia, accommodative dysfunction, binocular dysfunction, amblyopia, and strabismus.^[1]

Hyperopia is often confused with presbyopia,^[2][3] another condition that frequently causes blurry near vision.^[4] Presbyopes who report good far vision typically experience blurry near vision because of a reduced accommodative amplitude brought about by natural aging changes with the crystalline lens.^[4] It is also sometimes referred to as farsightedness, since in otherwise normally-sighted persons it makes it more difficult to focus on near objects than on far objects.^[5]

The causes of hyperopia are typically genetic and involve an eye that is too short or a cornea that is too flat, so that images focus at a point behind the retina. People with hyperopia can usually see distant objects well, but have trouble focusing on nearby objects.

Classification of hyperopia

Hyperopia is typically classified according to clinical appearance, its severity, or how it relates to the eye's accommodative status.^[1]

Classification by clinical appearance

• Simple hyperopia
• Pathological hyperopia
• Functional hyperopia

Diagnosis

Visual acuity is affected according to the amount of hyperopia, as well as the patient's age, visual demands, and accommodative ability.^[1]

In severe cases of hyperopia from birth the brain has difficulty to merge the images that each individual eye see. This is because the images the brain receives from each eye is always blurred. A child with sever hyperopia has never seen objects in detail and might present with amblyopia or strabismus. If the brain never learns to see objects in detail, then there is a high chance that one eye will become dominant. The result is that the brain will block the impulses of the non-dominant eye with resulting amblyopia or strabismus. 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.

The child with hyperopia will typically stand close, in front of a television. One would have expected that the child will stand far to see, but because the brain has never learned to see objects in detail and the child with hyperopia from birth presents with the picture of decreased visual perception.

The parents of a child with hyperopia do not always realize that the child has a problem at an early age. A hyperopic child might have problems with catching a ball because of blurred vision and because of a decreased ability to see three dimensional objects. The child will typically perform below average at school. As soon as a child starts identifying images a parent might find that the child cannot see small objects or pictures.

Treatment

Various eye care professionals, including ophthalmologists, optometrists, orthoptists, and opticians, are involved in the treatment and management of hyperopia. At the conclusion of an eye examination, an eye doctor may provide the patient with an eyeglass prescription for corrective lenses.

Minor amounts of hyperopia are sometimes left uncorrected. However, larger amounts may be corrected with convex lenses in eyeglasses or contact lenses. Convex lenses have a positive dioptric value, which causes the light to focus closer than its normal range.

Hyperopia is sometimes correctable with various refractive surgery procedures (LASIK). It can also be corrected with special convex lenses.

A child with severe hyperopia from birth will not see better with glasses when first fitted. This is because the brain must still learn to process the new detailed images received from the eyes and this learning process takes time.

See also

• Myopia (shortsightedness)
• Presbyopia

NOTES

External links

• Vision - Learn how Hyperopia happens by pupilEyes
• Scottish Sensory Centre - Medical Info on Hypermetropia
• LASIK - Medical Info on refractive disorders by eMedicine
• Farsightedness by EyeTopics