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प्रश्न
What is presbyopia? Write two causes of this defect. Name the type of lens which can be used to correct presbyopia.
उत्तर
Presbyopia is a defect of the eye because of which a person cannot see nearby objects clearly. This defect occurs because of the loss of the power of accommodation of the eye. Presbyopia usually occurs in old age.
The two causes of this defect are as follows.
1. Weakening of the ciliary muscles in old age.
2. Reduction in the flexibility of the eye lens.
Presbyopia, which is a special kind of hypermetropia, can be corrected by using spectacles with convex lenses.
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संबंधित प्रश्न
Write the function of the following part of the human eye: ciliary muscles
How does the eye regulate the amount of light that falls on the retina?
Distinguish between: aqueous humor and vitreous humor
Explain the mechanism of vision.
A person got his eyes tested by an optician. The prescription for the spectacle lenses to be made reads :
Left eye : +2.50 D
Right eye : +2.00 D
State whether these lenses are thicker in the middle or at the edges.
Fill in the following blank with suitable words:
When light is dim, the pupil becomes................
Fill in the following blank with suitable word:
To bring light from a near object to a focus on the retina of the eye, the convex eye-lens need to be made....................
With reference to the functioning of the eye, answer the question that follow:
Name the cells of the retina and its respective pigments which get activated in the dark.
State the main functions of the following:
Seminal Vesicles
From where the following nerves arise.
Optic nerve
