Farsightedness or Longsightedness or Hypermetropia or Hyperopia

A person suffering from hypermetropia can only see distant objects clearly but cannot see clearly an object lying closer than a certain distance. In other words, the distance of the near point 'N' of a hypermetropic eye from it is greater than least distance of distant vision. The rays of light from object at least distance of distinct vision are brought to focus behind retina at the point O as shown in fig alongside. This defect occurs when either:

i] the eye ball becomes shorter than the normal size, i.e distance between the eye lens and the retina becomes less.

ii] the focal length of the eye lens, when the eye is fully relaxed, become large.

Remedy:

Such a defect will be cured, if the eye can see clearly objects placed at near point 'N' i.e. at least distance of distinct vision. To correct for this defect, a convex lens of suitable focal length is placed close to the eye so that the rays of light from the object at least distance of distinct vision after refraction through the  lens appear to come from the near point 'N' of the hypermetropic eye as shown in fig below.

What causes long-sightedness?

The causes of hypermetropia are usually genetic (hereditary). Long-sightedness can occur at any age but it tends to become more noticeable above the age of 40 years. 

In rare cases, hypermetropia is caused by other conditions such as diabetes, small eye syndrome (microphthalmia), cancers around the eye and problems with the blood vessels in the retina. 

A particular type of age-related long-sightedness called presbyopia occurs because the lens of the eye becomes more stiff with age. (See separate leaflet called 'Presbyopia' for more information.)

What are the symptoms?

The main symptom is a difficulty with near vision. 'Tiring' of the eyes (asthenopia) is common and long-sighted people may have headaches and uncomfortable vision. 

There may be difficulties with seeing with both eyes (binocular vision) as the brain will tend to ignore signals coming from the most long-sighted eye. Amblyopia (lazy eye) or strabismus (squint) can also occur in hypermetropia. Long-sighted people may have difficulty with depth perception (3-dimensional vision).