Answer :
Final answer:
The ADD required for a patient with an accommodative power of 6.00 D to see clearly at a distance of 20 cm would be -1.00 D, suggesting that their existing accommodation already exceeds what is necessary, and no further addition would be required.
Explanation:
The question involves the calculation of the additional lens power, referred to as the addition (ADD), that the patient needs to see clearly at a close range (20 cm). To find the ADD required, one must know the lens formula which is P = 1/f, where P is the power in diopters (D) and f is the focal length in meters (m). Given that accommodation (acc) is the ability of the eye to change its focus from distant to near objects, and the patient already has a certain accommodative power (6.00 D), we need to calculate the difference between the power required to see clearly at 20 cm and the patient's existing accommodation.
To see clearly at 20 cm, the power required is given by P = 1/f, or P = 1/0.20 (since 20 cm = 0.2 m), which equals +5.00 D. Since the patient already has an accommodating power of 6.00 D, the additional power needed (ADD) is the difference between +5.00 D and their existing accommodation of 6.00 D. Thus the ADD required would be -1.00 D, but since negative power lenses for close work are not usual, it suggests that the existing accommodation already exceeds what is necessary, and no additional positive lens power is required.
If there's a misunderstanding and the current accommodation should be subtracted from the needed power, then ADD would be +5.00 D - 6.00 D = -1.00 D. However, this is not among the provided options.
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