For near point of 20 cm, a hypermetropic of +4D has to exercise accommodation of –
**Core Concept**
The **near point** is the closest point at which an object can be seen clearly, and **hypermetropia** (also known as farsightedness or long-sightedness) is a condition where distant objects are seen clearly but nearby objects appear blurred due to the eyeball being too short or the cornea being too flat. **Accommodation** is the process by which the eye changes optical power to maintain a clear image or focus on an object as its distance varies.
**Why the Correct Answer is Right**
For a hypermetropic person with a refractive error of +4D, the eye has difficulty focusing on near objects due to the reduced optical power. To focus on an object at 20 cm, the eye must increase its optical power through **accommodation**. The amount of accommodation required can be calculated by adding the **dioptric power** needed to focus at the near point (which is the reciprocal of the distance in meters, 1/0.2 = 5D for 20 cm) to the hypermetropic correction (+4D), resulting in a total of 5D + 4D = 9D.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it underestimates the total accommodation required.
**Option B:** This option is also incorrect as it does not accurately reflect the calculation of total accommodation needed.
**Option D:** Similarly, this option is wrong because it does not correctly account for the hypermetropic correction and the dioptric power for the near point.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that the **amplitude of accommodation** decreases with age, which is why presbyopia (age-related decline in near vision) typically starts in the early to mid-40s. Understanding how to calculate the required accommodation for different refractive errors and near points is crucial for clinical practice.
**Correct Answer:** Correct Answer: C. 9D.