In the example case, what was the tentative ADD?

In the example case, what was the tentative ADD?

• A. +0.75D
• B. +1.25D
• C. +2.50D
• D. +3.00D

Answer: (B)

The tentative ADD is the extra plus power needed to allow clear near vision given the person’s available accommodation while wearing the distance correction. For a typical reading distance of 40 cm, the near dioptric demand is 1/0.40 = 2.50 D. If, with the distance correction in place, the patient still has about 1.25 D of focusing ability left, the remaining power needed to focus at near is 2.50 D minus 1.25 D, which equals 1.25 D. That difference is the tentative ADD. So the best choice is the one that provides +1.25 D of addition. If the remaining accommodation were different, or if a different reading distance were assumed, the ADD would change accordingly.

The tentative ADD is the extra plus power needed to allow clear near vision given the person’s available accommodation while wearing the distance correction. For a typical reading distance of 40 cm, the near dioptric demand is 1/0.40 = 2.50 D. If, with the distance correction in place, the patient still has about 1.25 D of focusing ability left, the remaining power needed to focus at near is 2.50 D minus 1.25 D, which equals 1.25 D. That difference is the tentative ADD. So the best choice is the one that provides +1.25 D of addition. If the remaining accommodation were different, or if a different reading distance were assumed, the ADD would change accordingly.