Explanation
The least distance up to which we can see the objects clearly without any strain is called least distance of distinct vision. Least distance of distinct vision for a normal human being is 25cm. For young people, the least distance of distant vision will be within 25cm which however it varies with age. For infants, the least distance of distinct vision is about 5 to 8 cm. As the person grows old, their culinary muscles responsible for adjusting the eye lens get weakened. As a result, the power of accommodation reduces and hence the least distance of distinct vision for old people (55years) generally increases. This defect is called Presbyopia.
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