**AC/A ratio (accommodative convergence/accommodation ratio)
can be measured using either the gradient method or the heterophoria method.**
**A patient has a 12**^{D} esophoria
with a -2.00D lenses R and L and 4^{D }exophoria
with +2.00D lenses R and L.

**a. Which method can be used to calculate the AC/A ratio?**

**b. What is the AC/A ratio in this patient?**