[Physics Class Notes] on Eye Defects Hypermetropia or Hyperopia Pdf for Exam

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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What Causes Hyperopia?

The causes of hypermetropia or hyperopia are listed below.

1. 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.

2. An increase in the focal length of the eye lens also causes hypermetropia.

3. Hypermetropia occurs when the cornea of the eye is not curved enough, i.e., the lens or cornea is flatter than normal.

4. The stiffening of ciliary muscles is another cause of hypermetropia.

Types of Hypermetropia

The types of hypermetropia are listed below.

1. 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.

2. 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.

3. 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.

Severity of Hypermetropia

Hypermetropia is classified into three types based on severity:

How to Correct Hypermetropia?

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.

Did You Know?

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.