BV tests

Question 1

What is fixation disparity

Answer 1

Amount of associated phoria
Retinal images fall on non-corresponding points but within panums fusional area so single

Leads to over/under convergence

Question 2

Fusional reserves

Answer 2

Measures amount of stress on BV system
Determine if compensated/decompensated
Larger = more likely to be compensated
1/3-2/3 FR can be used to overcome phoria

Question 3

Positive FR

Answer 3

Simulate convergence

BO Prism

Question 4

Negative FR

Answer 4

Stimulate divergence

BI prism

Question 5

Which FR should you measure first

Answer 5

The one opposing the phoria first

E.g. if XOP then measure +ve (BO) FR first

Question 6

What is the blur point

Answer 6

Accom error exceeds depth of focus

Question 7

Break point

Answer 7

Eyes can’t produce motor response to overcome diplopia

Question 8

NPC

Answer 8

Max convergence effort whilst maintaining BSV
Norm: 8-10cm
>10cm - CI may be present

Question 9

What can suppression indicate

Answer 9

Anisometropia
Amblyopia
Aniseikonia
Strabismus

Question 10

Tests for suppression

Answer 10

W4D
TNO
Titus fly
Mallet unit 
Bagolini lenses