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convergence

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convergence

  1. 1. Measurement of Convergence
  2. 2. Measurement of Convergence <ul><li>It is essential that assessment of vergence is made during an eye examination </li></ul><ul><li>There are many aspects to the vergence response </li></ul>
  3. 3. Near Point of Convergence (NPC)
  4. 4. NPC <ul><li>Subjective NPC: Patient reports diplopia </li></ul><ul><li>Objective NPC: Clinician observes point when one eye turns out </li></ul>
  5. 5. NPC <ul><li>Less than 12cm is normal </li></ul><ul><li>Between 12 and 15cm is suspect </li></ul><ul><li>Greater than 15cm is anomalous: orthoptic training is indicated </li></ul>
  6. 6. Jump Vergence <ul><li>A more natural test </li></ul><ul><li>Patient changes fixation from distance to near </li></ul><ul><li>If task is difficult patient will attempt to look away </li></ul>
  7. 7. Fusional Vergence <ul><li>Phorias are kept latent by the fusion reflex </li></ul><ul><li>Large phorias may need a large fusional effort to maintain binocularity </li></ul><ul><li>Important to know how much fusional vergence is being used </li></ul>
  8. 8. Positive Fusional Reserves
  9. 9. Negative Fusional Reserves
  10. 10. Measurements <ul><li>Break Point </li></ul><ul><li>Recovery Point </li></ul><ul><li>Blur Point </li></ul>
  11. 11. Base In
  12. 12. Base Out
  13. 13. Relative Vergence <ul><li>When eyes converge accommodation is stimulated </li></ul><ul><li>The target will become blurred </li></ul><ul><li>The amount of ∆ to the blur point is known as the relative convergence </li></ul>
  14. 14. Relative Vergence <ul><li>Negative Relative Convergence: amount of BI ∆ to blur </li></ul><ul><li>Positive Relative Convergence: amount of BO ∆ to blur </li></ul>
  15. 15. Vertical Fusional Reserves <ul><li>Measured with Base up or down ∆ </li></ul><ul><li>Fusional range small </li></ul>
  16. 16. Normal Values
  17. 17. Clinical Value <ul><li>Distance phoria: 8XOP </li></ul><ul><li>Positive reserve: 16 ∆ </li></ul><ul><li>Total +ve vergence: 8 + 16 =24 </li></ul><ul><li>1/3 of total being used to over come phoria </li></ul>
  18. 18. Accommodation and Vergence
  19. 19. Relative Accommodation <ul><li>Amount of accommodation which can be exerted while vergence remains constant </li></ul><ul><li>Measured by using +ve and -ve lenses </li></ul>
  20. 20. Zone of Clear Vision
  21. 21. Zone of Clear Vision
  22. 22. Zone of Clear Vision
  23. 23. Summary <ul><li>Consider all aspects of vergence </li></ul><ul><li>NPC a routine measure </li></ul><ul><li>Phoria a routine measure </li></ul><ul><li>Fusional reserves should be considered in diagnosis and management of BV problems </li></ul>

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