In a hypermetropic eye, the light is not bent sufficiently so that it focuses at a point behind the retina. Here a person sees well for distance but near vision is difficult and causes strain. Hence hypermetropic people are called long-sighted.
What are the types of hypermetropia?
There are three types: congenital hypermetropia, simple hypermetropia and acquired hypermetropia.
What is congenital hypermetropia?
This is hypermetropia which occurs due to an abnormally short or small eye. Usually it is accompanied by poor vision. It is quite rare.
What is simple hypermetropia?
This type of hypermetropia is commonly seen. It is usually a continuation of the childhood hypermetropia which has not regressed with time.
Most normal infants when they are born have a hypermetropia of plus 4 dioptres. This is due to a variety of factors though the main reasons are a shorter eye and a forward-placed lens. As the child grows older, the length of the eyeball increases to normal and the hypermetropia usually goes away by the age of 5 years.
Thus, simple hypermetropia, more often than not, is just a case of an eye that has not grown in length sufficiently.
The power rarely increases beyond 4 or 5 dioptres.
The importance of this type of refractive error is that it often leads to, and is combined with, squint, and hence early recognition is important.
What is acquired hypermetropia?
The commonest cause of this condition is removal of the crystalline lens after the operation of cataract. Since the lens has been removed it has to be replaced by another plus spectacle lens.
Acquired hypermetropia can also occur after injury or even by itself in certain disorders when the lens dislocates and slips backwards.
The condition in which the crystalline lens is no longer in its place is termed aphakia. The management of aphakia is complex.
How do you control hypermetropia?
To correct the hypermetropic eye, a plus lens is required so that the light can now focus on the retina.
It is important to give the exact amount of plus correction as any excess will again lead to problems.
Often the simple correction of hypermetropia may cure squint if detected at an early stage.
What are the symptoms of hypermetropia?
In the young, because of the reserve capacity of the eye, there may be no symptoms.
At a later age, the main complaints are of continuously nagging headache and strain. The main problems are burning of the eyes during close work, especially in the evenings by artificial illumination. The eye tends to become red and the front of the head pains. The eye may also ache and feel dry.
In older people, usually after the age of 38 years, as the capacity to accommodate for near work fails, the reading material has to be held farther away from the eye than comfort or good vision dictates, and the condition is then called presbyopia.
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