Myopia and Hypermetropia are two vision conditions of eye in which objects at a certain range of distance appear blur to the person suffering from them.
A normal eye forms the image of the object on the retina but a myopic eye and a hypermetropic eye forms the image of the object in front of the retina and behind the retina respectively.
Myopia vs Hypermetropia
The main difference between Myopia and Hypermetropia is that in Myopia, a person can see the short distance objects clearly and not the distant objects. In hypermetropia, a person can see distant objects clearly but not the short distance objects.
The distant objects appear to be blurred in the case of myopia. On the other hand, the nearby objects appear to be blurred in the case of hypermetropia.
Comparison Table Between Myopia and Hypermetropia
| Parameters of Comparison | Myopia | Hypermetropia |
| Definition | The person suffering from Myopia can see only the near or short distance objects clearly. | The person can suffering from Hypermetropia see only the far or distant objects clearly. |
| Another Name | Near or Short sightedness | Far or distant sightedness |
| Size of Eye Ball | The size of the eye ball increases. | The size of the eye ball decreases. |
| Formation of Image | The image of the object is formed in front of the retina. | The image of the object is formed behind the retina. |
| Causes | The two major reasons for myopia are: 1) Heredity 2) Exposure to sunlight | The three major reasons for Hypermetropia are: 1) Heredity 2) High blood pressure 3) Weak functioning of ciliary muscle |
| Symptoms | Blurred image of the distant objects. | Blurred image of the near objects. |
| Treatment | With the help of concave lens (diverging lens) of a negative refractive power. | With the help of convex lens (converging lens) of a positive refractive power. |
| Focal length of the eye lens | The focal length decreases of the eye lens. | The focal length increases of the eye lens. |
What is Myopia?
Myopia or also called as ‘Near sightedness’ is a vision condition where the person is able to see only the nearby objects clearly. In this case, the distant objects appear to be blur. The image is formed in front of the retina for a myopic eye.
It can be caused due to heredity, exposure to sunlight, body’s circadian rhythms and many more. It can be identified by the blurred image of the distant objects. In case of a myopic eye, the size of eye ball increases.
The focal length of the eye lens decreases. The other effects of hypermetropia are retinal detachment, cataract, glaucoma and etc.
The condition of Myopia can be divided into three types:
- Low myopia: The Refractive error is greater or equal to -3.00 D.
- Moderate myopia: The refractive error is less than -3.00 to -6.00 D.
- High myopia: The refractive error is less than -6.00 D.
A myopic eye can be corrected with the help of concave lens (diverging lens). It has a negative refractive power that increases according to the severity of myopia.
What is Hypermetropia?
Hypermetropia or also called as ‘Far sightedness’ is a vision condition where the person is able to see only the distant objects clearly. In this case, the nearby objects appear to be blur. The image is formed behind the retina for a myopic eye.
It can be caused due to heredity, high blood pressure, weak functioning of ciliary muscle, excessive curvature of eye lens or elongation of eye ball and many more. It can be identified by the blurred image of the nearby objects. In case of a hypermetropic eye, the size of eye ball decreases.
The focal length of the eye lens increases. The other effects of hypermetropia are retinal detachment, glaucoma, amblyopia, strabismus and etc.
The condition of Hypermetropia can be divided into three types:
- Low hypermetropia: The refractive error is greater than or equal to +2.00 D.
- Moderate hypermetropia: The refractive error is less than +2.00 to +5.00 D.
- High hypermetropia: The refractive error is less than +5.00 D.
A hypermetropic eye can be corrected with the help of convex lens (converging lens). It has a positive refractive power that increases according to the severity of myopia.
Main Differences Between Myopia and Hypermetropia
- A person suffering from Myopia can see only short distance objects clearly. On the other hand, a person suffering from Hypermetropia can see only the far or distant objects clearly.
- Myopia is also known as the Near or Short sightedness whereas Hypermetropia is also known as the Far or distant sightedness.
- In case of a Myopic eye, the size of the eye ball increases. In case of a Hypermetropic eye, the size of the eye ball decreases.
- In Myopia, the focal length of the eye lens decreases whereas, in Hypermetropia, the focal length of the eye lens increases.
- In Myopia, the image of the object is formed in front of the retina whereas in Hypermetropia, image of the object is formed behind the retina.
- The Myopia is caused due to heredity, exposure to sunlight and body’s circadian rhythms. On the other hand, the Hypermetropia is caused due to heredity, high blood pressure and weak functioning of ciliary muscle.
- In Myopia, the distant objects appear to be blurry whereas in Hypermetropia, the nearby objects appear to be blurry.
- Myopia can be treated with the help of concave lens of a negative power. On the other hand, Hypermetropia can be treated with the help of convex lens of a positive power.
Conclusion
The nature of the Myopia is that the person suffering from it can only see the objects clearly that are near to the eye. The nature of the Hypermetropic is that the person suffering from it can only look at the objects clearly that are far from the eye.
Both the eye conditions require a different type of lens to correct them. Myopia requires a concave lens with a negative refractor power that increases as the severity of myopia increases. Hypermetropia requires a convex lens with a positive refractor power that increases as the severity of hypermetropia increases.
References
- https://www.ajo.com/article/0002-9394(55)91283-6/pdf
- https://www.sciencedirect.com/science/article/pii/S004269890900457X