Question

what is presbyopia? write two causes of this defect.

Answer 1

Presbyopia is a common defect of vision, which generally occurs at old age. A person suffering from this type of defect of vision cannot see nearby objects clearly and distinctively. A presbyopic eye has its near point greater than 25 cm and it gradually increases as the eye becomes older.

Presbyopia is caused by the

1. Weakening of the ciliary muscles

2. Reduction in the flexibility of the eye lens

Answer 2

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Old people cannot see near by object clearly due to power of accomodation of eye.The ner point of old person having presbyopia gradually resist much more than 25 cm.

Two causes of this defect are:-

1 - Presbyopia is caused by an age-related process. This differs from astigmatism, nearsightedness and farsightedness, which are related to the shape of the eyeball and are caused by genetic and environmental factors. 

2 - Presbyopia generally is believed to stem from a gradual thickening and loss of flexibility of the natural lens inside your eye.

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