lecture 3 - sensory fusion

Question 1

What is sensory fusion?

Answer 1

Integration of two similar images, one formed on each retina into one image within the brain, and images must be of similar brightness, size and form

Question 2

How do you design a test for measuring sensory fusion?

Answer 2

control: both eyes being used

RE and LE are slightly different

Question 3

who do you measure sensory fusion for?

Answer 3

Px’s with manifest strabismus
(suppression, ARC, pathological diplopia, confusion)
for the DVLA

Question 4

when you investigate suppression what do you measure>

Answer 4

size of scotoma (area suppression)
position of scotoma
density of suppression

Question 5

how do you measure area suppression/suppression scotoma

Answer 5

• use prisms
• place prism before the deviated eye
• increase prism until px notes double
• recorded for base in out up down

Question 6

how do you measure density of suppression

Answer 6

sbisa and NDF bar

• put the bar of varying density of red filters
• placed in front of the fixing eye
• hold torch at 1/3 m
• px asked to view light and what colour
• increase bar strength
• px informs examiner when the light changes from red to white or diplopia or examiner has seen fixation swap
• record the density the bar above the one they report

Question 7

weak suppression

Answer 7

if suppression is less than 10

danger of intractable diplopia

Question 8

why does the light switch from red to white

Answer 8

px finds it difficult to use their fixing eye so the other eye Strats and the light becomes white

Question 9

DVLA rules

Answer 9

• can’t drive
• fined £100,000
• can only drive if DVLA has confirmation that diplopia is controlled (glasses or patch) or ophthalmologist has signed it off

Question 10

what is BV like in ARC

Answer 10

normally weaker than Normal BSV

they have abnormal BSV (ABSV)

Question 11

synoptophre

Answer 11

test for sensory fusion
total dissociation
different targets for each eye

Question 12

tests for total dissociation

Answer 12

synoptophre

Question 13

tests for partial dissociation

Answer 13

single target- only part seen by one eye
Worth’s lights - red/green glasses
Bagolini Lenses - diffraction
Mallet unit- polarisation

Question 14

how many lights are in worth’s lights, and what colour are they

Answer 14

4
2- green
1 - red
1- white

Question 15

Normal BSV response with worth’s lights

Answer 15

1 red light (control )
2 green lights (control)
the fused white light at the bottom is a mixture of red and green (rivalry)

Question 16

what size does worth’s lights come in

Answer 16

for use at 6m and 1/3 m viewing distance

Question 17

result of worth’s lights with esotropia

Answer 17

uncrossed diplopia
will see 5 lights in total (3 green and 2 red)
image hits nasal retina which projects temporally

Question 18

do you use red/green glasses with worth’s lights

Answer 18

yes

Question 19

how do you manage esotropia (4 points)

Answer 19

• maximum plus
• base out prisms (fresnel or incorporated)
• exercises stereograms, lend prism bar
• refer to hospital eye service for surgery or second opinion

Question 20

result of worth’s lights with exotropia

Answer 20

crossed diplopia
therefore 5 circles - 2 red and 3 green
image hits temporal retina which projects nasally

Question 21

how do you manage exotropia (4 points)

Answer 21

• maximum minus
• base in prims (fresnel or incorporated)
• exercises stereograms, lend prism bar
• refer HES for second opinion or surgery

Question 22

when using red/green glasses which eye does the red lens go in front of ?

Answer 22

right

Question 23

result of worth’s lights with left suppression

Answer 23

2 red lights

Question 24

result of worth’s lights with right suppression

Answer 24

3 green lights

Question 25

how to manage constant suppression

Answer 25

leave it alone

Px may want cosmetic surgery

Question 26

how to manage central suppression

Answer 26

• they may have a microtropia
• usually don’t need treatment
• BSV may be slightly worse

Question 27

result of worth’s lights with ARC

Answer 27

normal BSV

Question 28

how to manage ARC

Answer 28

monitor BSV (may be slightly worse than normal)
do not treat

Question 29

what are Bagolini Lenses also known as..

Answer 29

striated lenses

Question 30

what do Bagolini Lenses do

Answer 30

they disperse light to form a street perpendicular to striations

Question 31

what do the striations in Bagolini Lenses form?

Answer 31

partial dissociation

Question 32

how do you use Bagolini Lenses?

Answer 32

• fixate a spot light (pen torch)
• place lenses perpendicular to each other at 45 and 135
• ask px how many lights they can see
• ask px to draw pattern they see
• ask if there are any gaps near the centre of the light

Question 33

result of esotropic px using Bagolini lenses

Answer 33

image hits nasal retina which projects temporally

- they see 2 lights with this pattern /\

Question 34

result of exotropic px using Bagolini lenses

Answer 34

image hits temporal retina which projects nasally

- they see 2 lights with this pattern \/

Question 35

results of suppression when using Bagolini lenses

Answer 35

will only see 1 light and 1 lines

Question 36

results of central suppression when using Bagolini Lenses

Answer 36

they may see gaps around the centre in one direction so you NEED to ask them about gaps

Question 37

result of Bagolini Lenses with ARC

Answer 37

same as normal BSV