Using the balancing formula Add = (NRA + PRA)/2 + BCC, if NRA = +2.25 and PRA = -1.25 measured through a +0.50 add, what is the calculated add?

Using the balancing formula Add = (NRA + PRA)/2 + BCC, if NRA = +2.25 and PRA = -1.25 measured through a +0.50 add, what is the calculated add?

• A. +0.50
• B. +1.00
• C. +1.50
• D. +0.75

Answer: (B)

The calculation combines the accommodative responses with a balancing convergence correction to determine the near add. First, add NRA and PRA: 2.25 + (-1.25) = 1.00. Take half of that: 1.00 / 2 = 0.50. Then include the balancing convergence correction (BCC), which is +0.50 when measured through a +0.50 add. Add these together: 0.50 + 0.50 = 1.00. So the calculated near add is +1.00 diopter.

The calculation combines the accommodative responses with a balancing convergence correction to determine the near add. First, add NRA and PRA: 2.25 + (-1.25) = 1.00. Take half of that: 1.00 / 2 = 0.50. Then include the balancing convergence correction (BCC), which is +0.50 when measured through a +0.50 add. Add these together: 0.50 + 0.50 = 1.00. So the calculated near add is +1.00 diopter.