====== Convergence ======
  * Both eyes adduct independent with each other
  * Accompanies accommodation ([[accommodative_convergence_to_accommodation_ratio|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|Convergence insufficiency]] can occur without strabismus

===== Convergence Amplitudes =====
  * 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

===== Near Point of Convergence =====
  * 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
==== Prince Rule ====
{{::aao_prince_rule.jpg?direct&400|https://www.aao.org/image/new-mediabeacon-item-65}}\\
Photo courtesy [[https://www.aao.org/image/new-mediabeacon-item-65|AAO]] 
{{tag>strabismus}}