This document discusses accommodation and convergence in the eye. It defines accommodation as the ability of the eye to focus on near objects and convergence as the inward movement of the eyes. It describes how accommodation and convergence are measured in diopters and meters respectively. The document also explains that accommodation and convergence are linked (accommodative convergence) and how the ratio between the two (AC/A ratio) is important for diagnosing certain eye conditions.

1. Accommodation &
convergence
Lecture NO ( # )

2.  Accommodation:
•Definition
•Association with convergence
•The far point of accommodation
•The near point of accommodation
•Amplitude of accommodation

3.  Measurement:
• Measured in diopters
• Calculated in reciprocal of fixation
distance
• RAF rule
• Monocularly and binocularly measured
• Push up method
• Trial lenses method
• The effect of age

4.  Convergence:
• Inward disjugate movement of the two eyes
• Types:
1) Tunic
2) Accommodative
3) Fusional
4) Proximal
• Meter angle is the unit for measurement
• The formula:1/d X IPD

5.  Measurement:
•NPC is assessed using RAF rule
•The target jump , blur , or become
doubled
•Recorded in centimeters
•Pupil dilation may occur indicating
convergence break

6.  AC/A ratio:
• The amount of accommodative convergence
induced by each amount of accommodation
exerted
• Measured in prism diopter
• It depends on the IPD and the distance of the
object from the eyes
• It can be modified permanently by surgery to
the extra ocular muscles or temporarily by
drugs and lenses that change the
accommodation

7.  Methods of measuring :
• Gradient method
• Graphic method
• Hetrophoric method

8.  Uses of AC/A ratio:
• Diagnosis of convergence excess type
intermittent esotropia
• Differential diagnosis of true and
simulated intermittent distant exotropia