What is hypermetropia?
Hypermetropia or farsightedness is a deviation of the eye where one sees less clearly or experiences blurred vision at close range or at short distances, while far off objects often remain clear.
Like myopia, hypermetropia is not a disease but a refraction abnormality (refractive error) in the optical system. A farsighted or hypermetropic eye is shorter than the normal eye or has a cornea which is too flat, so that the focal point of the broken rays of light falls beyond the retina. This creates an out of focus image and blurred vision.
Young people with hypermetropia are strongly accommodative when looking into the distance. Being accommodative in this sense of the word means making the lens more rounded so that distant images that fall behind the retina are moved forward through natural lens adjustment (‘zooming’). As a result, a distant object can often be in focus.
This extra effort involves excessive eye muscle movement and uses energy, sometimes leading to fatigue, headache, loss of concentration and a burning sensation in the eyes.
With age, the accommodative power of the lens slowly decreases. This makes an image look blurry when viewed close-up. As the years progress, visual acuity decreases not only for close range but also for distant objects.
In comparison with myopia (short-sightedness), a strong degree of hypermetropia is rare. However, a large number of people are slightly farsighted.
Farsightedness is less likely to be diagnosed in young people because they have sufficient accommodative power and can therefore focus on distant objects.
Those who are at an early stage of farsightedness see less clearly at shorter distances. Objects at a greater distance can often be seen very clearly. The first signs of farsightedness are fatigue and a burning sensation in the eyes, loss of concentration and headache. A farsighted person sometimes tends to read a book by holding it further from the face or will choose to sit further from the TV or computer screen.
Older people with hypermetropia first notice symptoms when reading; letters become blurred because they can no longer compensate through lens accommodation.
It is suspected that refractive errors, such as short-sightedness and farsightedness, arise from a complex interaction between environmental and hereditary factors. Genetic variants within certain genes play a role in hypermetropia.
A slight degree of hypermetropia does not need to be treated, thanks to the permanent accommodative action of the eye muscles.
With higher degrees, hypermetropia can be corrected by glasses or contact lenses with positive lenses.
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