Unit 7 Visual Function/ BV

Question 1

what type of drop is cyclopentolate

Answer 1

antimuscarinic drop relaxing the iris sphincter muscle (creating a light resistant dilated pupil) and cycloplegia by relaxing the ciliary body

Question 2

indications for cyclo

Answer 2

o U16’s with symptoms; headaches
o 1st eye tests
o Presenting strabismus in children
o Family history of squints
o Unequal or reduced VA in children
o Variable refraction
o Suspect latent hyperopes

Question 3

therapeutic uses of cyclo

Answer 3

o To break synechiae – used when dilating anterior uveitis px Anterior/Posterior Uveitis and Posterior Synechiae breakdown: 1-2 drops of 1%
every 6-8 hours
o To reduce ciliary spasm – reduces pain if px has had trauma to the eye e.g., corneal abrasion
* Alleviation of ciliary spasm: 1 drop of 1% 2-3 times a dayc

Question 4

dosage for cyclo in relation to age

Answer 4

 3 months – 12 years; 1 drop of 1%
 12 years – adult; 1 drop of 0.5%

Question 5

contraindications of cyclo

Answer 5

 Hypersensitivity to cyclo or any component of preparation
 Px with confirmed or suspected angle closure ( not contraindicated in downs syndrome, but greater risk of angle closure)
 Baby < 3 months (due to high systemic absorption)
 History of neurological disorder e.g., organic brain syndrome
Cyclopentolate should only be used during pregnancy when clearly needed, and it’s unknown if it passes into breast milk

Question 6

side effects of cyclo

Answer 6

 Transient stringing, blurring
 Photophobia
 Raised IOP
 Conjunctival hyperaemia, oedema
 Hypersensitivity may occur – facial & upper body rash 4-6 hours post instillation
 Transient stinging may also occur due to pH5 (acidic)
 Symptoms of adverse reaction:
o Pain/redness in or around eyes
o Disorientated (CNS reaction) 5-10mins after instillation
o Incoherent speech
o Visual disturbances
o Racing pulse or palpitations
 If any of the above, advise px’s parent to contact you or seek medical advice ASAP

Question 7

unwanted side effect of atropine

Answer 7

ventricular tachycardia.

Question 8

what prism corrects exo

Answer 8

base in

Question 9

what prism corrects eso

Answer 9

base out

Question 10

does plus rx make XOT worse?

Answer 10

yes

Question 11

what rx makes an esotropia worse

Answer 11

minus

Question 12

Cardiff cards

Answer 12

 Useful for very young, non-verbal children
 Vanishing optotype’s which measure resolution acuity – the ability of the eye to detect/resolve target (can’t resolve = whole target looks grey)
 Cards are held at 50cm or 1m
 Examiner uses child’s eye movements to determine if they see the target
 Not very sensitive to amblyopic deficits
 There are three cards at each acuity level, an endpoint is reached when 2 out of 3 are correct. Range is 6/60 to 6/6 at 1m, 6/120 to 6/12 at 50cm

Question 13

Kays Pictures

Answer 13

 Patient names or matches pictures
 Available as crowded or single
 Range 6/60 to 6/6
 3-meter version used in practice
 Before beginning, to practice run at close distance to check understanding

Question 14

1mm displacement from central cornea - what does it mean

Answer 14

 Displaced temporally in SOT, nasally in XOT
 1mm displacement from central cornea = 7 degrees = ~15 prism dioptres

Question 15

Lea symbols

Answer 15

o Tested at 3m.
o 3 symbols used: house, apple and square
o VAs range from 6/4.8 to 6/24
o Can say outloud what they see or point to the same shape on the near card
o Flipperbook

Question 16

Lang 2

Answer 16

 Easy to use, screening test
 No dissociating glasses used to it is useful in young children
 Dissociation is provided by the vertical cylinders on the front of the card
 Each card shows three objects which assess three different levels of stereo
 Lang 2 contains a elephant, car and moon – as well as a star which can be seen monocularly
 It measures 600 to 200 seconds of arc.

Question 17

Randot

Answer 17

 Random dots & polarised vectographs to present different images to each to allow for stereoscopic testing
 Generally used in adults, but animal portion can be used for paediatric patients
 Quantitative = 800 – 40 seconds of arc using shapes, animals and circles

Question 18

titmus

Answer 18

 Cross polaroid’s partially dissociate the eyes
 Qualitative assessment = gross stereo = fly (3000 sec of arc)
 Quantitative assessment = animals = 500 – 100 sec arc, circles = 500 – 40 sec arc of stereopsis.
 Some monocular cues

Question 19

TNO

Answer 19

 Most challenging
 Random dot stereogram – random dots are viewed with the aid of stereopsis; the disparity between eyes produces a sensation of depth
 Red/green filters partially dissociated the eyes
 3 screening plates (1980 sec arc) and 3 quantitative plates (480 – 15 sec arc)

Question 20

Frisby

Answer 20

 Only test which uses real depth, with the image printed on the other side of the plastic to the other print
 Used at any age
 Child has to indicate which of the 4 has the circle sticking out
 3 plates at 9 distances allows for 27 disparities between 600 – 5 seconds of arc
 However, if the child moves motion parallax cues can reveal the correct answer

Question 21

OKN drum

Answer 21

 OKN response - physiological reflex nystagmus caused by the attempt to maintain fixation on a moving set of black and white bars
 Combination of saccade as smooth pursuit eye movements, which develops around 6 months
 Crude assessment to show the visual system is intact
 Optokinetic drum is spun in front of the px at about 30cm and their eye movements are observed (head is still, eyes track movement of object)

Question 22

4^ prism test (or prism reflex with 20^)

Answer 22

 Access presence of bifoveal fusion, and prove the presence of absence of BSV
 Principle the same as prism reflex, but 4^ prism is used
 Base out used initially

1. Prism placed in front of eye – eye under prism moves in (adducts) to regain fixation
2. Other eye makes conjugate movement out, Herring’s law, and then moves back in to take up fixation

• Size of prism keeps image within the central retinal area, elicits the smallest movement reliably detected by experienced observers
• All 3 movements = bifoveal fusion

Question 23

amount of accommodation expected for 4y/o

Answer 23

14D

Question 24

amount of accommodation expected for 12 y/o

Answer 24

12D

Question 25

amount of accommodation expected for 20 y/0

Answer 25

10D

Question 26

Optokinetic Nystagmus (OKN)

Answer 26

– Combination of a saccade and smooth pursuit eye movement which develops around 6 months.
Crude assessment to show that the visual system is intact.
Using an optokinetic drum, spin it in front of the Px and watch their eye movements. - f asymmetrical movements then neurological cause
normal response is symmetrical and conjugate, with no abnormalities:
Slow phase: The eye moves smoothly in the direction of the stimulus.
Fast phase: The eye moves quickly in the opposite direction of the stimulus.
* Drum is rotate 12-18 inches in front of the px’s eyes and the response is observed

Question 27

preferential looking (keeler/teller cards)

Answer 27

way of estimating VA in infants and non-verbal Px.
Child is shown two circles. Principle is that the child will look towards the patterned circle
instead of the blank stimulus.
Pattern is a square wave grating (alternate black and white lines of equal thickness).
* Present the grating and record the looking response
* highest SF that gives correct looking response used to estimate VA.

Question 28

what is a heterophoria

Answer 28

 Latent strabismus in which the visual axes are normally directed to the fixation of the object but deviate when the eyes are dissociated
 The fusion reflex maintains correct alignment of the 2 eyes - if this fusion reflex is suspended; the eyes will adopt the ‘fusion free’ position & a measurable deviation of the visual axes will occur
 During cover-uncover: the covered eye deviates (under the cover) if heterophoria is present
 In compensated heterophoria, motor fusion is maintained - therefore sensory fusion and stereopsis should occur

Question 29

sheards criterion

Answer 29

 Sheards - if more than half the fusional reserves need to be used to control the phoria, the visual system will be under stress & the phoria decompensates
 Increasing degrees of decompensation = increase in symptoms
 Phoria becomes decompensated when it is too large / fusional reserves too small
o Poor + in EXO
o Poor – in ESO

Question 30

convergence excess esophoria

Answer 30

 Convergence excess (deviation greatest at near) – frontal HA, ocular fatigue, distance focus reduced after prolonged near work – more common

Question 31

divergence weakness esophoria

Answer 31

 Divergence weakness (deviation greater at distance) – worse @ end of day, distance difficulties
o Generally due to high myopia because eye is too big, relaxed state eyes naturally diverge
o Possibly due to 6th
o only option is prism or surgery

Question 32

stereogram - 3 cats

Answer 32

o Demonstrate physiological dip with 2 pens
o Make the 3rd cat through physiological diplopia
o Distance stereogram (SOP) - card held @30cm – px fixates on distance target just over the top of the card
o Near stereogram (XOP) – card @ 40cm problems at near: look at near object in front of stereogram, appreciated 3rd image
o Flat fusion = eyes ability to produce a composite picture from two images which you are looking at

Question 33

normal fusional reserves

Answer 33

near: positive 26 break, recovery 16
negative 16 break 8 rec

Distance: positive 20 break, 10 recovery
negative 10 break 8 rec

Question 34

what does myogenic mean

Answer 34

when there is a weakness in the muscle itself

Question 35

Herrings law of equal innervation

Answer 35

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

Question 36

Sherrington’s law of reciprocal innervation

Answer 36

increased innervation is sent to a muscle to contract, decrease innervation goes to the direct antagonist which is therefore caused to relax

Question 37

BHHT

Answer 37

Allows differentiation of SO palsy from one affecting the contralateral SRo

Theres a Positive result = 5^ difference from tilted R to L

Question 38

muscle sequelae

Answer 38

1. Under action of the primary affected muscle
2. Overaction of the contralateral synergist – Hering’s Law
3. Overaction of the ipsilateral antagonist – Sherrington’s Law
4. Inhibition palsy of the contralateral antagonist
    Recent onset = only 1st & 2nd
    Longstanding = full sequelae established