Difference Between Myopia and Hypermetropia

The difference between myopia and hypermetropia is that a myopic person is only able to see the near or short distance objects clearly whereas a hypermetropic person is only able to see the far or distant objects clearly.

Both myopia and hypermetropia are the type of eye diseases that are based on the distance to see the object. These two are the “Refractive or Vision error”, where the image is formed at different sites (either in front or behind the retina) due to change in the size of an eyeball. In a myopic eye, the image forms in front of the retina and in a hypermetropic eye, the image forms behind the retina but not ‘on the retina’ as the normal eye.

Content: Myopia Vs Hypermetropia

  1. Comparison Chart
  2. Definition
  3. Diagram
  4. Correction
  5. Classification
  6. Complications
  7. Key Differences
  8. Conclusion

Comparison Chart

PropertiesMyopiaHypermetropia
Alternative nameNear or Short sightednessFar or distant sightedness
NatureClear visibility to the nearby objectsClear visibility to the far objects
Image formationImage is formed in front of the retinaImage is formed behind the retina
Effect on eye ballSize of the eye ball increasesSize of the eye ball decreases
Focal length of the lensDecreasesIncreases
EffectsRetinal detachment, cataract, glaucoma etc.Retinal detachment, glaucoma, amblyopia, strabismus etc.
CausesHeredity, exposure to sunlight, body’s circadian rhythms etc.Heredity, high blood pressure, weak functioning of ciliary muscle
SymptomsBlurred image of distant objectBlurred image of near object
Treatment By concave lensBy convex lens

Definition of Myopia and Hypermetropia

Myopia: It also refers to “Nearsightedness”. It is a refractive error by which a person can only see the nearby objects clearly but the visibility to the distant object is not clear.

Hypermetropia: It also refers to “Farsightedness”. It is a refractive error by which a person can only see the far objects clearly but the visibility to the near object is not clear.

Diagram

The difference between the myopic and hypermetropic eye is as follows:

  • In a myopic eye, the image forms in front of the retina.
  • In the hypermetropic eye, the image forms behind the retina.

Whereas, in a normal eye, the image forms on the retina.

diagram of myopia and hypermetropia

Correction

The correction of myopia is through the concave lens (diverging lens) which has a negative refractive power which increases with the severity of myopia.

correction of myopic eye

And the correction of hypermetropia is through the convex lens (converging lens) which has a positive refractive power which also increases with the severity of hypermetropia.

correction of hypermetropic eye

Classification of Myopia and Hypermetropia

Based on the refractive error, myopia and hypermetropia classify into the following three types:

  1. Low
  2. Moderate
  3. High

Classification of myopia:

Low myopia: In this, the refractive error is ≥ -3.00 D.
Moderate myopia: In this, refractive error is ˂ -3.00 to -6.00 D.
High myopia: In this, refractive error is ˂ -6.00 D.

Classification of hypermetropia:

Low hypermetropia: In this, the refractive error is ≥ +2.00 D.
Moderate hypermetropia: In this, refractive error is ˂ +2.00 to +5.00 D.
High hypermetropia: In this, refractive error is ˂ +5.00 D.

Complications of Myopia and Hypermetropia

Complications of myopia: These complications are based on the types of myopia, which are as follows:

High myopia: It is the severe condition which has following complications like retinal detachment, cataract and glaucoma

Degenerative myopia: Also refers to “Malignant myopia” which is a critical condition in which the size of eyeball increases very quickly. It has complications like retinal detachment, choroid neovascularization, glaucoma, strabismus and amblyopia.

Complications of hypermetropia: It includes retinal detachment, strabismus, amblyopia etc.

Terminologies for the complications caused by both myopia and hypermetropia are discussed below:

Retinal detachment: It is the condition, by which the retinal membrane separates or detaches from the back of the eye.

Cataract: It is a disease which causes clouding of the eye lens.

Glaucoma: It is a major problem that damages the optic nerve which plays a crucial role in transferring the signals that convert from images by the retina.

Choroid neovascularization: It defines as the condition which causes the growth of abnormal blood vessel in the eye.

Strabismus: It is the condition, where an eye cannot move in the same direction while looking onto the object. This disease also refers to “Crossed eye”.

Amblyopia: Strabismus leads to amblyopia which is a medical condition also term as “Lazy eye” which cause diminished vision.

Key Differences Between Myopia and Hypermetropia

  1. Myopia and hypermetropia are sometimes referred to by their alternative names “Nearsightedness” and “Farsightedness” respectively.
  2. The nature of myopia and hypermetropia is one where a myopic person can see the objects clearly that are near to the eye, and a hypermetropic person can look at the objects clearly that are far from the eye.
  3. The characteristic difference between the two is the image formation wherein myopic eye, the image forms in front of the retina and in a hypermetropic eye, the image forms behind the retina.
  4. The major effect is on the size of the eyeball, which increases in a myopic eye by which the focal length decreases. And, the size of eyeball decreases in a hypermetropic eye which increases the focal length. The focal length of a lens is inversely proportional to the size of eyeball i.e. when the size of eyeball increases, the focal length will decrease and vice versa.
  5. Both myopia and hypermetropia is a refractive error whose correction requires a different lens to correct these two conditions. Concave lens and convex lens recommends for the treatment of myopia and hypermetropia.

Conclusion

Therefore, both myopia and hypermetropia are the refractive errors i.e. an error, where due to change in the size of the eyeball, the light or the image not focus on the retina unlike a normal eye (where image focuses on the retina). These two conditions can be caused due to heredity, muscle dysfunctioning of an eye, trauma etc.

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