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Strabismus 106 > Functional Visual Loss > Flashcards

Functional Visual Loss Flashcards

1
Q

What is functional (non-organic) visual loss?

A

Is a condition in which a patient complains of visual disturbances not explained by pathology of ocular structures and the visual system

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2
Q

What is organic (non-functional) visual loss?

A

Visual loss due to ocular pathology

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3
Q

How do we differentiate between functional and organic (non-functional) visual loss?

A
  • Difficult
  • No objective pathology
  • Not a diagnosis of exclusion
  • Need positive findings of ‘functional’ to support diagnosis
  • Diagnosis = Possible functional element/ functional overlay

Need to ensure not meeting a subtle, treatable organic pathology

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4
Q

What are the 3 forms of functional visual loss?

A
  • Malingering
  • Factitious disorders
  • Somatoform disorders
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5
Q

What is Malingering?

A
  • Purposeful feigning of symptoms
  • Usually for clear secondary gain
    e.g. Student claiming visual loss to get out of exams or have time off school
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6
Q

How often is Malingering seen and who is it more common in?

A
  • 1-5% children
  • 5.25% adults
  • Most common in females
  • More common aged 11 - 20yo
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7
Q

What is Factitious Disorder?

A
  • Intentionally produced symptoms
  • Assuming the sick role
    e.g. person claiming visual loss and wanting to be registered blind
  • No specific gain
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8
Q

Why might someone pretend to have visual loss (Factitious Disorder)?

A
  • High incidence of concomitant psychosocial events >1/3 (Lim et al, 2005)
  • Cry for help
  • Attention
  • Other problems
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9
Q

What is Somatoform Disorder?

A
  • Occurs outside the persons conscious awareness
  • Not intentional
  • Psychological / psychiatric problems (Hysteria)
  • Psychogenic visual loss (often complex psychiatric and medical conditions)

Person unaware of why they have visual symptom, no secondary gain, not wanting to be ‘ill’, suspicion of psychological disorder and/or underlying psychiatric problem. Can be subconscious expression of stress, emotional or psychological problems.

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10
Q

What is Functional Overlay?

A

True visual loss as a result of an organic disease/process but is exaggerated or intentionally claims symptoms are worse often to be believed or to provoke investigations

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11
Q

What are common claims of someone with functional visual loss?

A
  • Reduced Vision or blind in either or both eyes
  • Visual Field Loss
  • Loss of stereopsis
  • Convergence or Accommodation Defect
  • Difficulty Reading
  • Colour Vision Defects
  • Photophobia
  • Polyopia or Diplopia
  • Strabismus
  • Night Blindness
  • Flashes
  • Headache
  • Eye Pain
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12
Q

What must we consider when testing for functional visual loss?

A
  • Order of Tests & Test Selection
  • Observation
  • Phrasing
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13
Q

What should you observe for in a patient with functional visual loss?

A

Observe the patient before you call them in…
- Are they on their phone, Facebook? Whatsapp?
- Standard web print on a mobile device is 14px/10.5pt

When you call their name how do they respond?
- Do they look up and make eye contact?
- Pick up their jacket? Water bottle? Put their phone in away?
- Fold up the newspaper?

In The Clinic:
Do they navigate to your clinic room and find the chair?
- Is this overly dramatic?
- How are their relatives reacting?
A truly blind patient will move cautiously and bump into objects naturally. A functionally blind patient will deliberately bump into objects or exaggerate movements.

Put your hand out to shake their hand
- Do they see and find your hand easily?

Pass them something, do they take it?

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14
Q

What is the sunglasses sign in functional visual loss?

A

The “sunglasses sign” in a patient without an obvious ophthalmic reason to wear sunglasses is highly suggestive of nonorganic visual loss.

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15
Q

How do you investigate functional visual loss during a case history?

A
  • Plausible
  • Realistically fit e.g. Trauma
  • Current circumstances and past events e.g. Delve deeper
  • FH
  • Previous medical records
  • OH e.g. amblyopia, cataracts, myopia

They may say that they have always had a ‘weaker eye’

Prescription in each lens identical? May indicate a balance lens and so longstanding poor VA (as the poorer eye is blind or too weak/not used so put in a balanced lens)

Can ring opticians and ask re previous VAs

Check for retinal detachment signs or age-related macular degeneration (e.g. a sudden drop in vision and/or distortion meaning straight lines will appear bent)

Need to check glasses are correct, up-to-date, their own and made-up correctly

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16
Q

What Proprioceptive tests can we use for investigating functional visual loss?

A
  • Finger Touch Test
  • Signature Test

The fingertip touching test is performed by asking the patient to bring their index fingers together. A truly blind patient can easily touch the tips of the fingers together. Those who are functionally blind tend not to. Do it BEO and monocularly.

Similarly, the signature test is also a non-visual task. A patient with organic visual loss can easily sign his/her name without difficulty, but a FVL patient may produce a bizarre signature.
Can be done both eyes open or if uniocular VA loss each eye at a time – compare the two.

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17
Q

What is the Startle test when investigating functional visual loss?

A
  • Flick fingers
  • Flash brightest light

See patient’s reaction to see if they can see the target coming towards them

18
Q

What is the Mirror Test in Functional Visual Loss?

A

Surprise them with a mirror and then rock it back and forwards to see if their eyes track in line with the mirror movement

19
Q

How can we use colour vision to test for functional visual loss?

A

Ishihara screening plate - Would expect even people with colour deficiency to do the screening plate well

20
Q

What does Optokinetic response tell us in functional visual loss?

A

OKN Drum, Flag, mobile app
Saccade to fix and then track slow pursuit and then saccade – if you see a OKN response you can expect the vision to be in the region of: 20/200 (6/60)

21
Q

If a patient claims not to see the top line of a VA chart what can we do to test for functional visual loss?

A
  • Changing test distance (x2 or ½)
  • Changing charts
  • Numbers & letters
  • Monocular & binocular
  • Encouragement
  • Extra time
  • Bribery
  • Wait
22
Q

How can we use VA tests to investigate functional visual loss?

A

We can use the Keeler Crowded (3m) to repeat their vision (without the ETDRS chart present)

  • No frame of reference
  • Different testing distance
  • Start at -0.300 and work up

Is the result the same?
If the vision has been tested on the same chart it is quite easy to stop in the same place each time i.e. 3rd row down.

If non-functional = no difference between the two tests i.e. this and an ETDRS
If functional = difference between them

23
Q

How do you approach testing VA again in a patient suspected of functional visual loss?

A

That they should now be able to see it –
“This test is closer, so it should make it easier for you”
“that was a bit hard let me try an easier test closer up”.

Start from the highest acuity (smallest letters) and work backwards
When approach normal/expected level of vision
“These are getting larger now you’ll probably be able to make them out”

Encouragement!
“You’re doing extremely well, keep trying”

24
Q

How can we use VA testing in functional visual loss that isn’t just VA charts?

A

Also can use neutralising lenses, rotating high cyl lenses and small vertical prism

For Unilateral VA loss use the:
- Cylinder Test
- Fogging Test
Say: “I think this lens could be of some help to you, can you now read this line of letters”

25
Q

How do we do the Cylinder Test for Functional Visual Loss?

A

Watch the patient and make sure they aren’t closing one eye at a time to compare images & use big lenses

1) A plus cylinder and minus cylinder lens of the same power are lined up in parallel over each eye. This alignment produces a lens with no refractive power.

2) The examiner then rotates the lenses 90° causing blurry vision in both eyes.
The patient is instructed to view a line on the vision chart that would normally be visible with the eye with good vision, but not the eye with bad vision.

3) The examiner slowly rotates the lenses back to position, moving the lens in front of the eye with good vision more slowly. If the patient successfully reads the line, it can be attributed to vision from their eye with bad vision

26
Q

How do we do the Fogging Test in Functional Visual Loss?

A

Fogging test – don’t let them close the ‘bad’ eye!

This works by blurring or “fogging” the vision in the patient’s “good” eye.

1) A plus spherical lens is placed in front of the “good” eye and a lens with minimal power over the “bad” eye. The visual acuity is tested with both eyes.

2) Then, the strength of the plus lens is gradually increased without the patient’s knowledge. Eventually, the fogging effect of the plus lens over the “good” eye will reduce the visual acuity and the visual acuity generated will represent vision in the “bad” eye.

27
Q

How can we use Neutralising Lenses in Functional Visual Loss?

A

Don’t remove both at once, to give them the comparison with nothing

Here we create blur with a convex (+) lens and then add its equivalent concave (-) completely neutralising the blur.

We then use increased strengths of lenses each time checking the visual acuity.

28
Q

Why are stereo-tests useful for assessing functional visual loss?

A

Good VA in both eyes is required for fine stereopsis!

29
Q

Which stereotest is best for testing for functional visual loss?

A
  • Frisby: their inclusion was to permit the detection of stereopsis even if non-severe amblyopia is present so not good for FVL
  • Titmus/Wirt: Ability to see 40” suggested to correlate to 0.00 VA
  • TNO: Detection of stereo targets on TNO requires good visual acuity to discriminate fine textures – if the patient achieves a normal level of stereoacuity on TNO they must have a good level of visual acuity
30
Q

What other orthoptic tests can we use to investigate functional visual loss?

A
  • 20∆: (peripheral fusion) overcome?
  • 4∆: (bifoveal fusion) overcome?
    4D (foveal fusion) - easy to overcome if vision is good. Sub-consciously very difficult not to.
    Ensure the patient is fixing and not staring through the prism
  • Bar reading: achieved? (requires physiological diplopia)

Bar reading Used in Orthoptic testing to overcome suppression and increase fusional endurance, but here it is used to simply prove vision.
The subject will be able to read continuously if the acuity of both eyes is good, whereas the vertical bar will block the better eye and interrupt reading if the fellow eye has poor vision.
Use text of increasingly smaller sizes to see what they can achieve in the ‘reduced vision eye’.

  • Synoptophore: what can they see?
  • CT: fixation? Speed? Target size?
  • Saccades: accurate? fast?
  • Pupils: equal? Responsive? RAPD?
  • Stereoacuity: Fits with VA?
  • Lees screen: binocular test
31
Q

What can Visual Fields tell us about functional visual loss?

A
  • See more on Goldmann / Octopus
  • Central Scotomas - high suspicion of pathology
  • Testing for funnel (not tunnel) vision. The VF should be larger at a further distance i.e. from 1m to 2m so need to check if it’s the same or if it constricts in the distance
  • Spiralling
  • Overlapping Isopters
    Isopters should be falling cleanly of each other so if they overlap = functional element
  • ‘Staring’
    If the stimulus is presented along random isopters this causes ‘staring’ to occur.
32
Q

How do we test for uniocular VA loss?

A
  • Nasal field extends 60 degrees nasally
  • Test their visual fields binocularly by confrontation
  • Do they wait till the midline?
33
Q

What does spiralling on VF testing mean in functional visual loss?

A

Spiralling occurs when the patient reports the first observation of the target at points that are progressively closer to fixation as the test proceeds.

To demonstrate a spiral the clinician must test uniformly in the same direction with equal spacing.

34
Q

How can fatigue affect results on VF testing that means it’s not always functional visual loss?

A

Spiral fields, star-shaped fields and overlapping isopters are actually the result of poor reproducibility and can therefore also be seen in association with fatigue.

35
Q

How can refraction indicate functional visual loss?

A

Subjective
Cyclo
May want glasses!

Duochrome (reading letters with R & G glasses)

Responses to + & - lenses
VA
Accommodation
Dynamic retinoscopy – objective accommodation measure
Subjective claims of accommodation / RAF rule

36
Q

What Ophthalmological investigations can we do into functional visual loss?

A

Ocular structure
- Anterior segment
- Media
- Fundus

  • Pupils
  • Blink response
  • Response to near/unexpected objects
  • Ophthalmic imaging
37
Q

What Electro-Diagnostic Testing (EDTs) investigations can we do into functional visual loss?

A
  • Normal – reassuring
    Doesn’t exclude the presence of all diseases
  • Abnormal – inconclusive
  • Quantify level of VA
    Useful in cases of functional overlay
  • Patient can influence results gained
    Cooperation
    Fixation
    Eyelids
    Muscle activity (crying, tensing)
38
Q

What other tests can we use to investigate functional visual loss?

A
  • OCT
  • Imaging
  • Blood tests
  • Genetic testing
39
Q

What would you expect if this WASN’T functional visual loss?

10 year old male
C/o: blurred vision in one eye for 3 days
VA R 0.00 L 0.50

A

VA: Consistently reduced VA on different tests. Fixation & recovery.

CT: ? Slower / less accurate fix / recovery with LE

Stereotests: Reduced Stereoacuity

Vertical Prism: 1 clear, 1 blurred image

EDT: Reflects VA (pathology)

Pupils: RAPD

Low Visual Aid:
Neutralising / high cyl lenses
Vertical prism – move image
½ test distance
Encouragement / time

Mobility/Navigation Issues: Present

40
Q

What would you expect if this WASN’T functional visual loss?

45 year old female
C/o: VF defect, can only see tunnel vision
VA R 0.100 L 0.100

A

VF defect: Consistent & repeatable
Problems with mobility & navigation
Normal visual function in existing area of vision
Fundus abnormality

Can prove Functional Visual Loss by:
VF (repeat)
Observation (behaviour, mobility & navigation)
Electrodiagnostic testing
Fundus & media check
Unexpected peripheral objects / stimuli

41
Q

How do we treat functional visual loss?

A

Reassurance
- No abnormality or disease found
- Excellent prognosis

Advice that vision will improve
- Give patient a ‘way out’

Avoid reinforcing their claims
- Extensive investigations
- Additional attention
- Certificate of visual impairment (CVI)

Parents – not to punish child
- Cry for help

Tackle underlying cause
- Attention / bullying / exam stress / home situation

Counselling
- Stress / anxiety / depression

Psychiatric referral
- Specialist help

42
Q

What must we do at follow-up appointments for someone with functional visual loss?

A
  • Avoid reinforcing situation
  • Monitor change
  • Misdiagnosis
  • Central nervous system (CNS) neoplasms
    Psychiatric symptoms
    Visual loss
  • Side effect of medications
    Psychiatric medication

Strabismus 106 (35 decks)

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