Amblyopia pt.1

Question 1

what is amblyopia

Answer 1

When we are born the visual pathway not complete, causing abnormal visual development

Question 2

what is the amblyopia caused by

Answer 2

Abnormal visual development caused by:
refractive error - blur
pathology
strabismus

Question 3

when does amblyopia occur

Answer 3

During critical period (birth to 7-8 years old)

Question 4

what is the critical period

Answer 4

the period where the visual pathway is still forming

if give an abnormal picture during critical period then the visual pathway grows to be used to that

Question 5

what is the outcome of amblyopia

Answer 5

permenantly reduced Vision/Visual-Acuity

Question 6

what is the prevalence on amblyopia

Answer 6

approximately 3% of the population

Question 7

list the 3 periods of visual acuity

Answer 7

• developmental period
• critical period
• sensitive period

Question 8

what does the developmental period of visual acuity relate to

Answer 8

The period from birth where vision is developing

Question 9

what does the critical period of visual acuity relate to

Answer 9

The period where vision is susceptible to abnormal visual input

Question 10

what does the sensitive period of visual acuity relate to

Answer 10

The period where treatment for amblyopia is effective

usually up to the age of 8, but recently found that on older age groups/teenagers it can work

Question 11

when does the sensitive period of visual acuity occur

Answer 11

• From time of deprivation to teenage/adult years

- 0-18 years old

Question 12

when does the critical period of visual acuity occur

Answer 12

After birth to 7/8 years

Question 13

when dos the developmental period of visual acuity occur

Answer 13

Birth to 3/5 years

Question 14

at which period of visual acuity is the prognosis for improvement better

Answer 14

the critical period, 7/8 years old

Question 15

when is the first eye test for a child and how is it done

Answer 15

• at the hospital after birth or within the first 6 weeks of life
• doctor checks a rough rx and checks for a red reflex

Question 16

what is the red reflex appearance of unequal refraction and what will you do if this is found

Answer 16

• non symmetrical
• one red reflex is brighter than the other
• do a cyclo refraction and check the fundus

Question 17

what is the red reflex appearance of a patient with cataracts

Answer 17

• there is no red reflex in the eye with the cataract or is very dim
• as the presence of the opacity block the fundus

Question 18

what is the red reflex appearance of a patient with a foreign body abrasion on the cornea

Answer 18

• the red reflection from the pupil will back light the corneal defects or foreign body
• movements of the examiner’s head in one direction will appear to move the corneal defects in the opposite direction

Question 19

what is the red reflex appearance of a patient with a strabismus

Answer 19

the red reflection is more intense from the deviated eye

Question 20

what did research on the critical period suggest about, Induced unilateral strabismus (Hubel and Wiesel)

Answer 20

• Eye with strabismus amblyopic
• Few binocular driven cell - no potential for BSV or stereo (due to squint)
• this is the worst to have

Question 21

what did research on the critical period suggest about, Induced alternating strabismus (Hubel and Wiesel)

Answer 21

• Neither eye has strabismus
• Few binocular driven cells
• The alternation prevents amblyopia

Question 22

what type of pathology is worst to have during the critical period and why, and what is done when treating this pathology to avoid amblyopia

Answer 22

• unilateral cataract
• as severe amblyopia may happen and binocular cells may go
• patch the good eye in-between cataract surgery if doing cataract one eye at a time
• for bilateral cataract - simultaneous occlusion should be used, where you patch the good eye when waiting to remove the cataract from the other eye to preserve the binocular cells

Question 23

where is the damage that causes amblyopia found

Answer 23

• Cortical deficit in V1 measured via (fMRI)

- Higher order areas are now also thought to be affected

Question 24

for what 2 reasons is amblyopia difficult to assess

Answer 24

• Patient cannot determine what it is like NOT to have amblyopia
• Difficult to separate what is due to e.g:
  • Cosmetic aspect of the strabismus
  • Treatment (bullying)
  • Amblyopia:
    Reduced V-A
    Reduced S-A (stereo-acuity) and binocularity

Question 25

list 4 examples of effects of reduced stereo-acuity

Answer 25

``` - Driving e.g. Breaking distances No. of accidents - Navigating around obstacle course - Threading beads on a string - Reaching and grasping ```

Question 26

what does amblyopia double the risk of

Answer 26

binocular visual impairment

Question 27

list the 5 types of functional amblyopia

Answer 27

- strabismic amblyopia - stimulus deprivation amblyopia - anisometropic amblyopia - meridional amblyopia - ametropic amblyopia

Question 28

strabismic amblyopia occurs....

Answer 28

monocularly only

Question 29

what form of strabismus prevents bilateral amblyopia

Answer 29

alternating strabismus

Question 30

what type of deviation/tropia does strabismic amblyopia occur in and which type is it more likely to occur in

Answer 30

- a constant manifest deviation - more likely in an esotropia (as its more likely to be constant) - XOT often remains intermittent during childhood = sometimes the child gets normal vision which prevents amblyopia from developing

Question 31

what is stimulus deprivation and list 4 possible causes of this

Answer 31

some sort of pathology which causes obstruction to the clear passage of light, preventing clear formation of an image for example: - ptosis - cataract - retinal problems - corneal scar

Question 32

what is important to note with stimulus deprivation

Answer 32

note how much pathology prevents clear image | at the macula and is causing the amblyopia e.g. with ptosis, how much of it is covering the pupil etc

Question 33

anisometropic amblyopia occurs...

Answer 33

monocularly always

Question 34

what is anisometropic amblyopia

Answer 34

- Difference in refractive error - one eye receives better visual input at all distances (the one with the higher ref error = amblyopia) - The refractive error may be spherical and/or astigmatic difference

Question 35

when does meridional (astigmatic) amblyopia occur monocularly and binocularly

Answer 35

- monocularly with anisometropic amblyopia (if big difference) - binocularly with ametropic amblyopia (if big asthmatic error in both eyes)

Question 36

ametropic amblyopia occurs...

Answer 36

bilaterally

Question 37

what causes ametropic amblyopia

Answer 37

High degree of uncorrected bilateral refractive error

Question 38

how can high hyperopia cause ametropic amblyopia

Answer 38

cannot be compensated for with accommodation

Question 39

list 4 things you will ask in history when investigating amblyopia

Answer 39

- What is the problem - What age did the problem start - How long has it been there - Strabismus, is it: constant/intermittent or alternating

Question 40

why will you carry out ophthalmoscopy when investigating amblyopia

Answer 40

to see if its down to pathology, causing the stimulus deprivation type of amblyopia

Question 41

what does the RCO, state that the risk values for developing amblyopia isometropic (both eyes) in hyperopia and myopia are and what age are these values appropriate for and why

Answer 41

- Hypermetropia: +4.50D - Myopia: -3.00D - values are appropriate for 3 years old and upwards - as the younger you are, you will accept higher refractive errors as normal

Question 42

what does the RCO, state that the risk values for developing amblyopia anisometropic (one eye) in hyperopia , astigmatism and myopia are and what age are these values appropriate for and why

Answer 42

- Hyperopia: +1.50D - Astigmatism: 2.00D - Myopia: -2.00D - values are appropriate for 3 years old and upwards - as the younger you are, you will accept higher refractive errors as normal

Question 43

when do you need more refractive error before considering a child is at risk of developing amblyopia, and what do you do if your not sure

Answer 43

- the younger the patient is, the more refractive error you need before considering - if never sure, always bring the child back after a few months to check their vision, if there are changes then give glasses - monitoring is good in a borderline case

Question 44

when will you only consider giving treatment for a hyperopic px with an esotropia and what will you always give

Answer 44

- if their refractive power is +2.00D or more - but always give plus at any power as its good for an esotropia - it can only make an esotropia better

Question 45

what is the normal range of visual acuity in logmar crowded and uncrowded for 4-5 year old children

Answer 45

0. 087 (approx 6/7.5) +/- 0.10 log units for crowded - 0.010 (approx 6/6) +/- 0.10 log units for uncrowded LogMAR tests Always write the type of test chart singles or logMAR

Question 46

list the 5 things you must do whilst carrying out visual acuity when investigating amblyopia

Answer 46

- Near and Distance - Use Log MAR - Due to crowding phenomenon - Name test type - With and without compensatory head posture (CHP) - If manifest latent nystagmus may want to use spielman occluder

Question 47

what test is a more sensitive measure than visual acuity

Answer 47

constrast sensitivity

Question 48

what are the effects of someones contrast sensitivity dependent on

Answer 48

the type of amblyopia they have

Question 49

what test will you do on a child if a visual acuity test is not possible and why

Answer 49

- cover test - it can tell you what the vision will be like e. g. if the child doesn't use their fovea to begin with, then the vision will be significantly reduced. the child will use an extra foveal point (eccentric fixation) whereby the visual acuity will not be as good

Question 50

list the 4 things you must note/observe when doing a cover test on a child

Answer 50

- Note whether alternating unilateral deviation - Will the amblyopic eye hold fixation to blink - Central fixation versus eccentric fixation via corneal reflections (gross only) - Is the deviation constant or intermittent

Question 51

why is it important to note whilst doing a cover test, if the amblyopic eye will hold fixation to blink

Answer 51

if the child can hold their fixation with their squinting eye straight after the cover is removed from the fixing eye until they blink, then that means they have stronger vision, compared to if the eye moves straight back to their squinting position straight after the cover has been removed from the fixing eye

Question 52

what can an ocular motility test show you when carried out on a patient with incomitancy (child has slight muscle weakness)

Answer 52

may be more likely to decompensate when you start occlusion

Question 53

what 3 tests can you do to check binocular status when investigating amblyopia

Answer 53

- Prism Fusion Range - Stereopsis - Cover test (recovery)

Question 54

how will you confirm that your strabismic amblyopic patient does not have binocular functions

Answer 54

by seeing whether they got suppression

Question 55

a strabismic amblyopic patient will not have binocular functions, but name a type of amblyopic patient that should have some binocular functions and what can you use to measure this

Answer 55

- anisometropic amblyopes - will have some binocular functions - measured using: prism fusion range, stereopsis, recovery in cover test

Question 56

how will you measure the deviation when investigating amblyopia, and what must you ensure does not happen and why

Answer 56

- Prism cover test (if possible) - Ensure that occlusion is not increasing the size of the deviation - because of risk of decompensation - so if the deviation increases = sign they will decompensate e.g. if you find that when you started to patch and their fusional reserves thwarted to reduce as well as stereo acuity and recovery from cover test became poor, you will have to stop the patching treatment. this is because you are more likely to decompensate them. so don't do this on anisometropic amblyopes as you don't want to decompensate them

Question 57

which type of patients is the sbisa bar used on

Answer 57

- Patients with suppression - In all strabismic amblyopes over the age of 5 years old - To prevent intractable diplopia

Question 58

which type and age group of patients will you use a sbisa bar on to measure suppression and why

Answer 58

- In all strabismic amblyopes over the age of 5 years old | - To prevent intractable diplopia

Question 59

why is there a risk of patching a patient with strabismic amblyopia

Answer 59

although you may increase their visual acuity, but you can reduce their suppression and cause diplopia, which is the most risky on 5 years old and under

Question 60

what does the sbisa bar measure

Answer 60

the density of suppression

Question 61

list the steps of how the sbisa bar is used to measure the density of suppression

Answer 61

- Graded bar of varying density of red filters - Placed in front of the fixing eye - Patient requested to view light and asked what colour - Filters slowly increased in strength - Patient informs examiner: When light changes from red to white or Diplopia appreciated or Fixation swaps - Record density - Density less than 10 consider not patching

Question 62

which density value on the sbisa bar will you consider NOT to patch and why

Answer 62

- density value less than 10 | - as don't want to risk contractable diplopia

Question 63

which group of amblyopes should ophthalmoscopes or visuscopes be carried out on and what for

Answer 63

- On all strabismic amblyopes - Determine whether eccentric fixation present or not - Determine the location of the eccentric point - Further away from the fovea the worse the V-A - To monitor progress with time If treating via occlusion may find the eccentric point changes with time on a px with a strabismic amblyope

Question 64

what may you find will change as well as va, on treating a patient with occlusion on a patient with strabismic amblyopia

Answer 64

the eccentric point changes with time

Question 65

list the steps of how you will use an ophthalmoscope or visuscope to detect subtle eccentric fixation and what can this tell you about a person's visual acuity

Answer 65

- Occlude untested eye. - Examiner projects the fixation target onto the fundus close to the fovea. - Patient is instructed to look directly at the centre of the circle - The position of the fixation target on the fundus is then noted. e.g. fovea, parafovea, further away etc - There is a decrease in visual acuity with increasing distance from the fovea

Question 66

what 3 things in an eye exam can misinterpret a child from having amblyopia and therefore what 4 things must you do to rule amblyopia out and avoid mis-diagnosing

Answer 66

- incorrect v-a (no co-operation on that day) - incorrect refraction - mild pathology Therefore, reduced visual acuity does not equal amblyopia - Repeat V-A assessment - Repeat BV assessment (cover test) - Repeat refraction - Repeat fundus and media examination if you find no problems then refer them to hospital only start patching is there is a amblyogenic risk factor i.e. px has to be anisometropia, ametropia, pathology or a constant strabismus

Question 67

In which type of amblyopic patient would you measure the density of suppression (3 marks)? Name the piece of equipment that you would use to measure it (2 marks).

Answer 67

- strabismic amblyope over 5 years old | - using a sbisa bar