Vergences

Question 0

.Calc PRV, NRV vs. PFV, NFV

Answer 0

PRV, NRV
First #, L -> R, Rel to 0
= Fusional reserve verg (leftover after compensating for phoria)

PFV, NFV
Rel to phoria

[visualize on number line BI (exo) - BO (eso)

Question 1

.Morgan’s norms for vergences

Answer 1

D. BI. x/5/3. BO. 7/15/8
N. BI. 11/19/10. 14/18/7

Minimum expected
OR
if not X

Question 2

.Prism to Rx, based on Sheard’s criterion

Answer 2

Function comfortably if 1/3 or less of compensating fusional verg is used to offset phoria, so 2/3 = Fusional reserve verg

If not meet R > or = to 2D, where R is in compensating direction

Prism = 2D - R / 3

Eso
Increase new verg by prism amount

Exo
Decrease new verg by prism amount

Question 3

.Reason for BLUR

Answer 3

When limit of fusional vergence has been reached, so acc vergence kicks in to maintain single vision (get blur due to change in acc)

Question 4

.Reason for BREAK

Answer 4

When limit of fusion is reached, so eyes return to phoric position (get two clear images)

Question 5

.Types of vergences

Answer 5

1) Tonic
2) Accommodative
3) Proximal
4) Fusional