Hypermetropia or long (far) sightedness is a common eye defect where a person faces difficulty in seeing objects that are kept nearby clearly but has no trouble seeing the distant objects. Hypermetropia is common in new-born babies as they have small eyeballs. Gradually, it gets corrected with time as the eyeball grows to its normal size. The most common symptoms of Hypermetropia or Hyperopia are blurry vision while focusing on close objects, eye strain, tiredness of the eye, and frontotemporal headaches. Young children with severe far-sightedness may suffer from double vision as a result of over-focusing.
A person with hypermetropia may develop rare complications such as strabismus and amblyopia. There is a high risk for hypermetropic patients with a short axial length of developing primary angle-closure glaucoma. Therefore, a routine check-up of eyes should be regularly done for all hypermetropic patients.
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The causes of hypermetropia or hyperopia are listed below.
Hypermetropia occurs when there is a shortening of the eyeball along the axis. As a result, the light rays that enter the eyes fall behind the retina instead of falling on the retina which creates blurry vision.
An increase in the focal length of the eye lens also causes hypermetropia.
Hypermetropia occurs when the cornea of the eye is not curved enough, i.e., the lens or cornea is flatter than normal.
The stiffening of ciliary muscles is another cause of hypermetropia.
The types of hypermetropia are listed below.
Simple Hypermetropia - Simple hypermetropia includes axial hypermetropia (i.e. hypermetropia caused when the axial length of the eyeball is too short) and curvature hypermetropia (i.e. hypermetropia caused when the curvature of cornea or lens is flatter than normal). It is the most common type of hypermetropia.
Pathological Hypermetropia - Pathological Hypermetropia is caused either due to congenital or due to acquired conditions. There are four types of pathological hypermetropia. They are senile or acquired hypermetropia, positional hypermetropia, aphakic hypermetropia, and consecutive hypermetropia.
Functional Hypermetropia - It is commonly seen in patients suffering from third intracranial nerve palsy and internal ophthalmoplegia where paralysis of the eye’s ability to accommodate occurs.
Hypermetropia is classified into three types based on severity:
Low: Power up to +2 D.
Moderate: Power ranging from +2.2 - 5 D.
High: Power more than 5 D. Rare cases include power exceeding 6 - 7 D.
Hypermetropia can be simply corrected by using corrective glasses or contact lenses. A convex lens is used in correcting hypermetropia.
Hypermetropia can be treated surgically. The various surgical treatments are as follows.
Photorefractive Keratectomy (PRK): Photorefractive Keratectomy is a refractive technique in which a minimal amount of corneal surface is removed. It may have complications like astigmatism and regression effect due to epithelial healing, and corneal haze.
Laser Epithelial Keratomileusis: It is similar to PRK. In this method, alcohol is used to loosen the corneal surface.
Laser-Assisted in Situ Keratomileusis (LASIK): Reshaping of the cornea is done in LASIK so that usage of contact lenses or eyeglasses is no longer needed.
Vision defects are diagnosed by using an eye chart known as the Snellen Chart. It is an eye chart that is used to measure the clarity of vision and visual acuity. It was developed by Dutch ophthalmologist Herman Snellen in 1862 and hence, the chart is named after him. Nowadays, the Log MAR chart is used by many ophthalmologists and vision scientists.
1. How is Hypermetropia Different From Presbyopia?
Ans. Presbyopia is an eye defect that is generally found in elderly people whereas hypermetropia is found in young people. People with presbyopia and people with hypermetropia face the same problem, i.e., they cannot see nearby objects clearly but a presbyopic patient cannot see the distant objects as well. Presbyopia occurs due to the stiffening of ciliary muscles and thus the eye loses its ability to accommodate. Generally, the onset of Presbyopia happens, once the person reaches the age group of the 40s. Hence, it may happen with everyone regardless of whether they are myopic, hypermetropic, or have normal vision. Bifocal lens (lens having two different sections, i.e., an upper section for distance vision and a lower section for close vision) is used to correct Presbyopia.
2. What is Astigmatism?
Ans. Astigmatism is a common eye problem that is caused due to the irregular shape of the cornea or the eye lens. This is a refractive error in which the eye fails to focus light evenly on the retina. As a result, the person sees fuzzy or distorted images at all distances. The symptoms of astigmatism include difficulty seeing at night, eyestrain, eye irritation, trouble driving at night, etc. Astigmatism can be of two types, i.e., corneal astigmatism or lenticular astigmatism. Corneal astigmatism occurs due to the irregular curvature of the cornea. Lenticular astigmatism occurs due to the irregular shape of the eye lens.