The human eyes can concentrate on objects at a distance or in near vicinity because of their abilities. The eye’s lens has a small focal length, allowing it to observe and focus on surrounding things. The lens can concentrate on closer objects if it has a large curvature. If the curvature is slight, it can focus on objects further away. The effects of the defect typically appear at the extreme ends of the visual spectrum. Myopia, which is also known as nearsightedness, is a common vision problem in which objects in the near vicinity are clear, but objects farther away are blurry. This happens when the shape of the eye causes light rays to bend (refract) wrongly, focusing images in front of rather than on the retina.
By using a diverging lens, we can solve the problem of nearsightedness or myopia. The beneficial formula of the focal length of combined lenses that can be used to find the power of the correcting lens for myopia, and the formula is:
where f = effective focal length, f1 = focal length of the lens required and f2 = focal length of the human eye.
Read More: Myopia
Important Questions with Answers
1. What are the causes of myopia?
- Hereditary is one of the natural factors for a person to have the defect of myopia. Assume that one of the parents has the defect. In such cases, the child will likely inherit the same problem when they reach adulthood.
- Myopia is more common in young people and is caused by elongation of the eyeball or bulging of the cornea. Light rays are refracted when the cornea’s regular curvature bulges, forming an image in front of the cornea.
- When the image is focused, the rods and cones of our eyes have areas where the image has the best clarity. As a result, the image of distant objects is detected as hazy since it is not created at the correct location.
- Uncontrolled hyperglycemia is another major cause of this sort of eye impairment. Some uncontrolled cataract growths can also cause myopia.
2. Who is most affected by myopia?
Myopia usually appears in school-age children. The eye continuously grows during childhood, that is, in the age group of 1–2 to 12–13. It generally goes until about age 20. However, myopia can develop in adults due to visual stress or medical diseases such as diabetes.
3. Which lens is used in myopia?
- concave mirror
- concave lens
- convex mirror
- convex lens
Answer – b. concave lens
Explanation – To correct myopia/nearsightedness, a concave lens is used. The concave lens separates the light rays, so they arrive in proper focus at the back of the eye. The focus of a nearsighted person is on the back of the eyeball.
4. Does myopia improve with age?
Myopia usually appears in school-age children. So myopia worsens in childhood and adolescence and stabilizes by early adulthood. Despite that, we do have options! An optometrist may suggest techniques known as myopia control to protect children’s vision.
5. Define myopia.
Myopia, also known as nearsightedness, is an eye disorder that occurs when the eye loses its ability to focus on far-off objects.
6. Is myopia a disease?
Myopia is not a disease. It is a refractive error, an optical condition that prevents the eye from adequately bending (refracting) light. Hence, it correctly focuses on the retina for clear vision.
7. Where is an image formed in a myopic eye?
In a myopic eye, the image is formed in front of the retina.
8. Does the curvature of the lens decrease or rise in a myopic eye? Why?
Myopia develops when the eyeball is too long in comparison to the focusing capacity of the cornea and lens. As a result, light rays concentrate in front of the retina rather than on its surface. Nearsightedness can also be induced by the cornea and lens being bent too far for the length of the eyeball. Myopia can be caused by a combination of these variables in some circumstances.
9. How could we correct nearsightedness?
By using a diverging lens, nearsightedness can be corrected. The image appeared hazy because the light rays were not diverging at the correct position, resulting in a focused image. Before reaching the retina, the rays are concentrated. Because the cornea creates an image on the retina, the light rays concentrate.
10. How often does myopia lead to blindness?
The prevalence of visual impairment grew with increasing axial length and spherical equivalent. Hence, the cumulative risk of visual impairment among persons with higher myopia is 5.7% at 60 and 39% at 75 years.
Practice Questions
1. What formula calculates the power of the correcting lens for myopia?
2. What are the symptoms of myopia?
3. What is the limit of myopia?
4. Short-sighted people may suffer from tired eyes and severe headaches by overstraining their eyes.
- True
- false
5. How can we prevent myopia?
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