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