A patient has FCC of +1.00, NRA +1.50, PRA -1.00. What is the patient's tentative ADD?

A patient has FCC of +1.00, NRA +1.50, PRA -1.00. What is the patient's tentative ADD?

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

Answer: (B)

The idea is to estimate near add by combining the distance baseline with the patient’s accommodative reserves. In this approach, the tentative ADD is calculated as ADD = FCC + (NRA + PRA)/2. Here, NRA is +1.50 and PRA is −1.00, so NRA + PRA = +0.50. Half of that is +0.25. Adding this to FCC = +1.00 gives +1.25 diopters. So the patient’s tentative near add is +1.25D. This matches why the other numbers don’t fit: using the full NRA would overestimate near add, and using only FCC would underestimate it. The halfway adjustment from the combined NRA/PRA reserves brings the value to the correct level.

The idea is to estimate near add by combining the distance baseline with the patient’s accommodative reserves. In this approach, the tentative ADD is calculated as ADD = FCC + (NRA + PRA)/2.

Here, NRA is +1.50 and PRA is −1.00, so NRA + PRA = +0.50. Half of that is +0.25. Adding this to FCC = +1.00 gives +1.25 diopters.

So the patient’s tentative near add is +1.25D.

This matches why the other numbers don’t fit: using the full NRA would overestimate near add, and using only FCC would underestimate it. The halfway adjustment from the combined NRA/PRA reserves brings the value to the correct level.