Convergence Anomalies Flashcards
1
Q
What is convergence and what are the convergence anomalies?
A
- Vergence movement that allows visual axis to stay directed towards a near target
- Abnormality of convergence can result in:
o Convergence insufficiency
o Convergence paralysis
o Convergence spasm - Near point of convergence (NPC) is closest distance to which eyes can converge while maintaining BSV
2
Q
What are the differential diagnosis of convergence anomaly?
A
- If any sxs at near or convergence probs, think of these
- Not all of these are convergence problems – but can present with problems at near:
o Convergence insufficiency or paralysis
o Convergence spasm
o Accommodation insufficiency
o Accommodation spasm
o Exophoria of convergence weakness type-exophoria 10^ near>distance
Larger up close than in distance
3
Q
Describe convergence insufficiency (CI)?
A
- Definition: near point of convergence is less than 10cm
- Convergence can only be maintained at this distance with (real extensive) effort
- Can primary or secondary
- Highly treatable – most likely to be treated well, most treatable problem in orthoptics
- Primary:
o No other causes for convergence insufficiency are present including heterophoria (large exophoria at near) - Prevalence: 4.2-17.6% in children
4
Q
What is the aetiology of primary convergence insufficiency (CI)?
A
- Not really sure what causes it
- Pre-disposing factors:
o Large interpupillary distance
o Large periods of time only using distance fixation e.g. occupation such as bus driver, train driver - Precipitating factors:
o Fatigue from long periods of close work with/without poor lighting – physically harder to converge
o Illness
o Age – older the px the worse the convergence is – normal for convergence to get older (elderly)
o Medication/recreational drugs – may need to ask awkward questions to get these answers
o Pregnancy
5
Q
Describe secondary convergence insufficiency?
A
- To diagnose primary CI must discount all of following options before confirming it is primary
- Something else is causing the convergence to be poor – something preventing px to converge well
- Intermittent near exotropia
- Convergence weakness exophoria
o Exophoria bigger at near – eyes wanting to drift out up close so harder for px to converge properly - Neurological condition e.g. Parkinsons and horizontal gaze palsy
o Can get from stroke
o Harder to converge as eyes not moving horizontally - Whiplash after road traffic accident
o Can cause traumatic loss of fusion - Thyroid eye disease
o Muscles swell and get bigger – swollen eye muscles in orbit so eye can’t move as freely
o Can’t physically converge as medial recti are so swollen - Iatrogenic – medial rectus weakness after surgery
6
Q
What are the common symptoms of convergence insufficiency?
A
- Sxs usually vague but related to the near work
- Px often reports difficulty with reading or doing close work
- Intermittent diplopia during near work
- Blurred vision during near work
- Frontal headache – constantly trying to converge
- Eyestrain
- Difficulty concentrating
o Hard for people who do a lot of reading or do a lot of near work/computer work for work - Movement of print
o That’s them trying to converge and when they’re not
7
Q
What investigations would you carry out in convergence insufficiency?
A
- Case history
o Asking relevant & specific Q’s regarding near work – particularly if px is vague
Suggest things and see if that identifies with px
o Ask regarding previous tx – convergence insufficiency can be recurrent - Distance & near vision
o Near vision may be reduced if also associated with accommodation insufficiency - Cover test (&prism cover test) & angle of deviation
o Investigation for exophoria – particularly at near. Important for appropriate diagnosis & management
o Do at near and distance – measure the deviation at both distances - Assessment of convergence
o Can look at accommodation too - Accommodation
o Binocular accommodation may be reduced
o Uniocular accommodation likely to be normal although associated accommodation insufficiency has been reported in some children - Fusional amplitude
o Looking at motor fusion
Ability to keep eyes straight base in (esophoria) or base out (exophoria)
o Measured with prism bar in free space or synoptophore
o Base out range may be reduced
8
Q
How long does convergence insufficiency last?
A
CI doesn’t always go away long term – can manage them though
If they stop doing exercises & then start doing exams for e.g. CI can be recurrent
9
Q
How would you assess convergence?
A
- Accurate assessment of convergence can be achieved by using the RAF rule
o Use RAF rule instead of doing it in free space – need exact measurements - It allows for specific measurement of convergence (cm) & accommodation (D)
- It is equipment with near point of convergence measurements, dioptres of accommodation and appropriate levels of accommodations based on patient’s age
10
Q
What are the components of the RAF rule?
A
- Tells you what is reduced convergence on RAF rule
- Measurement of 20cm – convergence is defective
- Convergence -> use target of dot with line – easier for px to determine if it is double
- Accommodation -> use letters as need to know when it is blurry
11
Q
How do you use the RAF rule?
A
- Ensure px is wearing appropriate near correction – may be reading glasses or full correction if they are young
- Place RAF rule on px’s check under their lower eyelids
- RAF rule should be held in a very slightly depressed position
- Appropriate target should be selected for what is being measured – start at 50cm line with dot for convergence
- Clear instructions should be given to the px
- Px should be encouraged to maintain single vision when being assessed
o “tell me when it starts to become double – if it starts to become double try to keep it single and let me know when you cannot keep it double - Keep a good pace – not too slow – so px doesn’t lose interest
12
Q
How would you record the results of the RAF rule?
A
- All 3 measurements – not an average easier to show a fatigue if write all 3 – they may not be able to maintain convergence without persistent effort (note this too)
- If effort was exerted if v easy to do for px then no CI if hard and they really need to pull eyes in then could be CI even if about 10cm
- If convergence was broken, which eye diverged
- If the patient appreciated diplopia
E.g: Binoc to 8cm, 10cm, 10cm c effort then LE diverges c diplopia
13
Q
What is the treatment for convergence insufficiency?
A
- Correction of refractive error
o If myope – can have bigger exo if not corrected fully - Orthoptic exercises
- Convergence exercises:
o Smooth convergence: pen to nose exercises
o Jump convergence: dot card - Base in prisms: correct near exotropia
o Make eyes straight again & then treat with exercises
14
Q
Describe convergence paralysis?
A
- Ability to converge is completely lost
- May be primary or secondary
- Primary:
o No previous history
o Investigation rules out other secondary causes e.g. already had MRI scan - Secondary:
o Head trauma – could be road traffic accident
o Neurological cause e.g. Parinauds syndrome, encephalitis, multiple sclerosis
Affecting brain stem can cause convergence issues
15
Q
What aree the clinical features and management of convergence paralysis?
A
- Clinical Features:
o Diplopia for all distances nearer than infinity
o Exotropia at near
CI may not have XOT at near (may have XOP)
o Ocular motility is normal in primary convergence paralysis
o Accommodation may or may not be impacted - Management:
o Once secondary convergence palsy is ruled out/underlying cause is investigated
o Conservative management:
Base in prisms to correct exo deviation
Occlusion to prevent diplopia
If accommodation is impacted, hypermetropic prescription in combination with base in prisms
o Botox to lateral rectus may be temporary fix – weakens LR – textbook suggestion - Convergence paralysis not as common
o Significant convergence insufficiency is more common
