O3A 6 Vergence

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Author:
sookylala
ID:
225079
Filename:
O3A 6 Vergence
Updated:
2013-06-26 07:30:56
Tags:
vergence
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Description:
vergence
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  1. crossed disparity
    • when you are fixating on a distant object
    • near object will have crossed disparity
  2. What is uncrossed disparity?
    • when you are fixating on a near object
    • dx object will have uncrssed disparity
  3. What is a measure of vergence?
    metre angle
  4. how do you calculate metre angle?
    • 1/dx in metres
    • object at 50cm? need 2 MA
  5. Vergence demand formula?
    pd (cm)X100 / d+2.7
  6. How is gradient AC/A ratio calculated?
    • phoria 1 - phoria 2 / lens 2 - lens 1 
    • exo: add negative
    • Eso: positive
  7. What is AC/A?
    amount that vergence changes for a specific change in accommodation
  8. What is the calculated AC/A?
    • change in vergence that results per dioptric change in fixation dx
    • change due to both accommodation and proximal cues
  9. What are the 4 vergence components of the Maddox model?
    • tonic
    • accom verg
    • proximal
    • fusional
    • assumes all 4 are additive
    • ignores convergence stimulating accom
  10. gradient vs calculated AC/A ratio?
    • gradient measured both at 40cm so proximal vergence is the same
    • calculated is measured at dx and near so proximal is affection one reading
  11. How to calculate CALCULATED AC/A?
    CHANGE IN VERGENCE / CHANGE IN ACC DEMAND

    CHANGE IN VERGENCE: Vd - phoria dx + phoria near

    CHANGE IN ACC: Near - dx
  12. What to prescribe: ortho at 6m, 10 eso at 40cm
    CHANGE IN VERGENCE/CHANGE IN ACC

    15 - 0 + 10 / 2.5 - 0

    25/2.5= 10:1

    +1.00D required plus lens because of eso
  13. PRA NRA
    • keeps accomm stable
    • once vergence runs out
    • use accom
    • blurs

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