# O3A 6 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
• 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
 Author: sookylala ID: 225079 Card Set: O3A 6 Vergence Updated: 2013-06-26 11:30:56 Tags: vergence Folders: Description: vergence Show Answers: