convergence
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Transcript of convergence
Measurement of Convergence
Measurement of Convergence
It is essential that assessment of vergence is made during an eye examination
There are many aspects to the vergence response
Near Point of Convergence (NPC)
NPC
Subjective NPC: Patient reports diplopia
Objective NPC: Clinician observes point when one eye turns out
NPC
Less than 12cm is normalBetween 12 and 15cm is suspectGreater than 15cm is
anomalous: orthoptic training is indicated
Jump Vergence
A more natural testPatient changes fixation from
distance to nearIf task is difficult patient will
attempt to look away
Fusional Vergence
Phorias are kept latent by the fusion reflex
Large phorias may need a large fusional effort to maintain binocularity
Important to know how much fusional vergence is being used
Positive Fusional Reserves
Negative Fusional Reserves
Measurements
Break Point
Recovery Point
Blur Point
Base In
Base Out
Relative Vergence
When eyes converge accommodation is stimulated
The target will become blurredThe amount of ∆ to the blur
point is known as the relative convergence
Relative Vergence
Negative Relative Convergence: amount of BI ∆ to blur
Positive Relative Convergence: amount of BO ∆ to blur
Vertical Fusional Reserves
Measured with Base up or down ∆
Fusional range small
Normal Values
Clinical Value
Distance phoria: 8XOPPositive reserve: 16 ∆Total +ve vergence: 8 + 16 =241/3 of total being used to over
come phoria
Accommodation and Vergence
Relative Accommodation
Amount of accommodation which can be exerted while vergence remains constant
Measured by using +ve and -ve lenses
Zone of Clear Vision
Zone of Clear Vision
Zone of Clear Vision
Summary
Consider all aspects of vergenceNPC a routine measurePhoria a routine measureFusional reserves should be
considered in diagnosis and management of BV problems