lecture 4- motor fusion cont.

Question 1

if motor fusion is present, what is the prognosis?

Answer 1

good prognosis

- aim to restore straight eyes with BSV

Question 2

if motor fusion is absence, what is the prognosis?

Answer 2

poor prognosis,

• can’t restore BSV completely
• aim to make cosmetically acceptable

Question 3

how do you measure motor fusion

Answer 3

you measure fusional vergence

Question 4

fusional vergence is also known as..

Answer 4

fusional reserves
fusional amplitudes
prism fusion range
prism vergences

Question 5

how does prism fusion range measure the strength of teamwork?

Answer 5

normal Px uses fovea of both eyes to view the tree

• place base out prism in front and the image will be displaced towards the apex
• now the normal px will see double and move their eye towards the nose so the fovea will be looking at the tree to avoid diplopia
• when the eye moves in towards the nose, the other eye will move temporal then moves nasal to resolve it
• this is convergence as both eyes move in towards the nose
• the larger the prism they can overcome the better the motor fusion therefore the less likely they are to break down into heterophoria

Question 6

PFR can be determined objectively at distance or near?

Answer 6

near

Question 7

the better your BSV or PFR the less likely you are to….

Answer 7

decompensate

Question 8

base out prism measures …

Answer 8

positive fusion range

Question 9

base in prism measures…

Answer 9

negative fusion range

Question 10

base up measures

Answer 10

infravergence

Question 11

base down measures …

Answer 11

supravergence

Question 12

how to carry out prism fusion range

Answer 12

Patient sits head erect —
Looks at 6/60 —
Prism bar placed before one eye (either eye) —
Strength prism bar increased slowly —
Continue increasing strength until patient reports diplopia —
Ask them if they can make the image single keep going if they can —
Continue to increase prism —
Note maximum amount of prism before diplopia is recorded - Break point —
Once fusion lost decrease strength until patient can regain fusion —
Carry out at near ( 1/3m & 6m ) working distance

note the blur point, break and recovery

Question 13

during the PFR test the patient may complain of blur. why ?

Answer 13

blur point of accommodation is achieved

Question 14

when accommodation increases, what happens to convergence?

Answer 14

increaases

Question 15

when accommodation decreases, what happens to divergence?

Answer 15

increases

Question 16

normal range for distance base IN for PFR test

Answer 16

5-7 prism dioptres

Question 17

normal range for distance base OUT for PFR test

Answer 17

15 prism dioptres

Question 18

normal range for near base IN for PFR test

Answer 18

15 prism dioptres

Question 19

normal range for near base OUT for PFR test

Answer 19

35-40 prism dioptres

Question 20

recover is usually how many prism dioptres before break

Answer 20

4

Question 21

blur is how many prism dioptres before break

Answer 21

6-8

Question 22

how to measure vertical fusion rnage

Answer 22

Look at 6/60 letter —
Place prism bar base-down in front of one eye —
Record prism power as the one just before the break point —
Repeat with either
— - Prism base-up in front of same eye or
— - Prism base-down in front of other eye —
Carry out at near (1/3m & 6m ) working distance

Question 23

Percival’s analysis of prism fusion range…

Answer 23

convergent and divergent fusional reserves should be balanced, one should not be less than half of the other

Question 24

according to Percival’s anaylsis of PFR, would normals be considered normal?

Answer 24

no

Question 25

Sheard’s analysis of PFR

Answer 25

opposing fusional reserve to blue point should be twice the degree of phoria

Question 26

insufficient fusional reserves may result in motor fusion breaking down which means Px will get…

Answer 26

diplopia and asthenopic symptoms

Question 27

what is orthophoria

Answer 27

no phoria

Question 28

what is the base in fusional reserve for orthophoric px

Answer 28

14

Question 29

what is the base out fusional reserve for orthophoric px

Answer 29

14

Question 30

who do you carry out the 20 base out test for?

Answer 30

young infants
adults with learning difficulties
short time in practice
don’t have a prism bar

Question 31

disadvantage of the 20 base out test

Answer 31

doesn’t quantify the amount of prism- essentially a screening test

Question 32

how to carry out the 20 base out test

Answer 32

Single base-out prism placed before one eye & then the other —
Child fixates toy/picture at 33cm —
Work quickly —
If a 20Δ base-out prism is not overcome encourage patient to fuse images —
Also important to note recovery movement as prism is removed, speed, accuracy —
If does not overcome try 15 or 10 diopter prism

Question 33

the 20 diopter test useful in proving presence of BSV in…

Answer 33

Suspected pseudostrabimus

— Child with inconclusive cover test —

Question 34

what is the 4 base out test used for?

Answer 34

testing macula suppression (suspected microtropia)

Question 35

how to carry out the 4 base out test

Answer 35

Patient fixates letter target at distance or near —
Fixate a tiny/letter target —
Consider bringing prism down from above —
Prism placed before right eye, image displaced outside macula area
—Both eyes make a versional movement towards apex of prism to left —
Left eye then converges to re-establish foveal fixation

Question 36

if all 3 movements are seen with the 4 base out test then the px has…

Answer 36

confirmed bifoveal fusion

Question 37

if the px has central suppression, on the 4 base out prism test, will the affected eye move behind the prism?

Answer 37

no

Question 38

for 4 base out test, base out is used in..

Answer 38

suspected microtropia

Question 39

for 4 base out test, base in is used in..

Answer 39

micro-exotropia

Question 40

what does the synoptophore measure

Answer 40

horizontal fusional reserves
vertical fusional reserves
torsional reserves

Question 41

Which test would you use to measure central suppression?

Answer 41

4 dioptre

Question 42

Which test would you use to measure bifoveal fixation?

Answer 42

4 dioptre