binocular vision

Question 1

duane’s retraction syndrome cause

Answer 1

caused by inner action of the lateral rectus by extra branches of CN3 due to an absent/ atrophic CN6

Question 2

3 types of duane’s

Answer 2

type 1 - limitation of abduction
type 2 - limitation of adduction
type 3 - limitation of abduction + adduction

Question 3

duane’s adduction

Answer 3

narrowing of palpebral aperture, upshoots and globe retraction

Question 4

duane’s abduction

Answer 4

limitation of abduction and widening of palpebral aperture

Question 5

Brown’s syndrome cause

Answer 5

mechanical restriction of superior oblique caused by inflammation or trauma to trochlear region

Question 6

Brown’s syndrome

Answer 6

• usually unilateral
• mechanical restriction of SO (inflammation or trauma)
• little deviation in primary position
• overaction of contralateral SR
• clicking if nodule gets through tendon and becomes stuck

Question 7

incomitant

Answer 7

angle of deviation changes in different positions of gaze

Question 8

neurogenic

Answer 8

relates to problem with nerve supply to a muscle

Question 9

myogenic vs mechanical

Answer 9

myogenic = weakness of muscle itself

mechanical = physical limitation/ restriction

Question 10

contralateral synergist

Answer 10

muscles in different eyes which move eyes in the same direction

e.g., R lateral rectus + L medial rectus

Question 11

ipsilateral antagonist

Answer 11

muscles in same eyes which move in different directions

e.g., R lateral rectus + R medial rectus

Question 12

ipsilateral synergist

Answer 12

muscles in same eyes which move in same direction

e.g., superior oblique + inferior rectus both depress eyes

Question 13

herrings law of equal innervation

Answer 13

when increased innervation is sent to a muscle to contract it, a simultaneous and equal impulse is sent to the contralateral synergist

Question 14

sherringtons law of reciprocal innervation

Answer 14

when increased innervation is sent to a muscle to contract it, decreased innervation goes to the direct antagonist (same eye) which is therefore relaxed

Question 15

RADSIN

Answer 15

recti adduct (obliques abduct)

superior intort (inferior extort)

Question 16

muscle sequelae steps

Answer 16

1. underaction of primary muscle
2. overaction of contralateral synergist
3. overaction of ipsilateral antagonist
4. secondary inhibition palsy of contralateral antagonist

Question 17

deviation in primary positions
mechanical vs neurogenic

Answer 17

mechanical - little or no deviation in PP

neurogenic - depending on extent of palsy, deviation can be marked

Question 18

diplopia in mechanical vs neurogenic

Answer 18

mechanical - reversal of diplopia (e.g., between upgaze + downgaze)

neurogenic - except in 3rd, nature of diplopia remains the same in all POG

Question 19

pain on movement mechanical vs neurogenic

Answer 19

pain on movement in mechanical whereas no pain in neurogenic

Question 20

muscle sequelae mechanical vs neurogenic palsy

Answer 20

mechanical = steps 1+2 only

neurogenic = if complete, full sequelae

Question 21

CN3 signs

Answer 21

dilated pupil, ptosis, headache, pain around eye

PP - eye down + out (XOT + hypotropia) - larger at near

cannot adduct, elevate or depress

Question 22

CN3 management

Answer 22

emergency referral - phone ARC

Question 23

CN3 causes

Answer 23

pupil involvement = suspect aneurysm of posterior communicating artery

pupil spared = suspect underlying vascular cause (diabetes)

trauma, compression

Question 24

CN4

Answer 24

trochlear nerve affected which supplies superior oblique muscle

Question 25

CN4 causes

Answer 25

- trauma (longest nerve so more susceptible) - decompensating congenital palsy - microvascular causes

Question 26

CN4 signs

Answer 26

- vertical diplopia (worse at near + looking down) - hypertropia in PP - size of deviation worsens when head tilted to affected side

Question 27

CN6 palsy

Answer 27

abducens nerve affected which supplies the lateral rectus

Question 28

CN6 causes

Answer 28

usually microvascular - diabetes, trauma, intracranial hypertension

Question 29

CN6 signs

Answer 29

- px presents with horizontal diplopia (worse at distance) - deviation in PP (SOT)

Question 30

amblyopia

Answer 30

developmental condition characterised by reduced vision in one eye VA worse than 6/9 not due to uncorrected refractive error/ pathology due to presence of sensory impediment to visual development

Question 31

different types of amblyopia

Answer 31

1. stimulus deprivation - due to ptosis or congenital cataract 2. strabismic 3. anisometropic 4. ametropia 5. meridonial

Question 32

critical period

Answer 32

when visual development is most vulnerable and plastic vision - birth to 3yrs BSV - birth to 5yrs

Question 33

sensitive period

Answer 33

visual development is vulnerable to damage but may still respond to correction + treatment vision 3-8yrs old BSV 5-8yrs old

Question 34

px presents with unequal VAs but no strabismus

Answer 34

prescribe full rx FT then 3/12 review then referral if no improvement in amblyopic eye

Question 35

ESOPHORIA REFRACTIVE MANAGEMENT

Answer 35

needs hyperopic/ max plus correction max plus relaxes accommodates -> relaxes convergence -> reduces SOP SOP at near only may need bifs so DVA still clear

Question 36

EXOPHORIA REFRACTIVE MANAGEMENT

Answer 36

needs full myopic correction / over minus more minus = px accommodates over that to correct XOP i.e., more accommodate more convergence to reduce XOP

Question 37

BIX BOS

Answer 37

EXO = neutralised by base in prism ESO = neutralised by base out prism

Question 38

sheards criterion

Answer 38

if more than half the fusional reserves need to be used to control the phoria then the visual system will be under stress and phoria decompensates

Question 39

maddox rod vs fixation disparity

Answer 39

maddox rod measures full size of deviation fixation disparity measures degree of prism relief required to neutralise any FD present i.e., amount of phoria not being controlled by fusional reserves

Question 40

fusional reserves

Answer 40

amount of divergence or convergence that can be induced before fusion compromised / blurred or double vision occurs

Question 41

jump exercises

Answer 41

used for convergence insufficiency move pen to nose until goes double - look at distance object until goes clear then look back at pen

Question 42

when is prisms used?

Answer 42

when eye exercises inappropriate due to age/ ill health/ lack of time/ lack of incentive power prescribed is minimum that just allows phoria to become compensated

Question 43

when may referral be considered for diplopia?

Answer 43

factor contributing to decompensation that requires attention of another practitioner cause of anomaly suspected to be pathological/ recent head injury anomaly not responded to refractive correction, exercises or prisms

Question 44

fusion amplitude

Answer 44

phoria becomes decompensated when fusion amplitude insufficient poor positive fusion amplitude on XOP, poor negative in SOP

Question 45

recession vs resection

Answer 45

recession weakens the muscles whereas resections strengthens muscles

Question 46

risk of squint

Answer 46

no strabismic relative = 1% chance 1 parent or sibling = 15% risk 2 or more parents/siblings = >20%

Question 47

BHHT

Answer 47

allows differentiate of SO palsy from one affecting contralateral SR head tilt to affected side - if hypertropia increases = SO palsy