- Both eyes adduct independent with each other
- Accompanies accommodation (AC/A ratio)
- Used to maintain fixation on near targets
- Quantified by measuring convergence amplitudes and near point of convergence
- Dysfunctional convergence is seen in Exophoria and Exotropia
- When accompanies exophoria, sensory fusion may be able to be strengthened by convergence exercises
- Convergence insufficiency can occur without strabismus
- Testing requires sensory fusion
- With a fixation target at near and distance, look through progressively larger base out prisms until diplopia occurs.
- The break point is the prism value where diplopia occurs
- The recovery point is the prism value where sensory fusion is re-established
- Normal measurements for break point:
- Near: 30Δ to 40Δ
- Distance: 20Δ to 30Δ
- Point in space directly in front of the eyes where maximal convergence is used
- Practically defined as the distance from nose where diplopia occurs
- Can use a Prince rule or any ruler with an accommodative target to measure
- Normal near point:
- 4cm to 10cm
Photo courtesy AAO
oculoman