Development of BSV

Question 1

What is essential for normal BSV development?

Answer 1

Normal anatomical development of globes, orbit, visual pathway.
Overlapping of VFs.
Decussation of retinal fibres at chiasm.
Normal retinal correspondence.E

Question 2

What is simultaneous perception?

Answer 2

Can see two images (one on each retina)

Question 3

What is motor fusion?

Answer 3

Ability to maintain sensory fusion via vergence movements.
Tested with 20^ BO test, prism fusion range or synoptophore.

Question 4

What is sensory fusion?

Answer 4

Ability to interpret two images as one fused image.
Tested with bagolini, worth 4 dot, synoptophore.

Question 5

What is a normal response to the 20^ BO test?

Answer 5

Both eyes move together, then fellow eye corrects (neither eye suppressing)

Question 6

What are the abnormal responses to the 20^ BO test?

Answer 6

Suppression:
Fellow eye - doesn’t move back in due to no diplopia noticed
Eye behind prism - doesn’t move initially as no change in image

Question 7

What is the normal fusional reserves at near?

Answer 7

45BO-18BI

Question 8

What is the normal fusional reserves at distance?

Answer 8

20BO-8BI

Question 9

How many seconds of arc does the Lang test?

Answer 9

1200-200

Question 10

How many seconds of arc does the Wirt (fly) test?

Answer 10

800-440

Question 11

How many seconds of arc does the TNO test?

Answer 11

240-15

Question 12

How many seconds of arc does Frisby test?

Answer 12

600-15

Question 13

What are the common obstacles to BSV?

Answer 13

Sensory, i.e. poor VA in one eye
Fusional, e.g. insufficient fusional reserves to cope with phoria, or hyperopia causing excessive accomm or conv
Extraneous, e.g. ptosis, over occlusion
Cortical, i.e. failure of binocular cells in V1 (usually due to trauma, tumour or infection)