Convergence Anomalies

Question 1

What is convergence and what are the convergence anomalies?

Answer 1

• 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

Question 2

What are the differential diagnosis of convergence anomaly?

Answer 2

• 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

Question 3

Describe convergence insufficiency (CI)?

Answer 3

• 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

Question 4

What is the aetiology of primary convergence insufficiency (CI)?

Answer 4

• 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

Question 5

Describe secondary convergence insufficiency?

Answer 5

• 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

Question 6

What are the common symptoms of convergence insufficiency?

Answer 6

• 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

Question 7

What investigations would you carry out in convergence insufficiency?

Answer 7

• 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

Question 8

How long does convergence insufficiency last?

Answer 8

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

Question 9

How would you assess convergence?

Answer 9

• 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

Question 10

What are the components of the RAF rule?

Answer 10

• 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

Question 11

How do you use the RAF rule?

Answer 11

• 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

Question 12

How would you record the results of the RAF rule?

Answer 12

1. 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)
2. 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
3. If convergence was broken, which eye diverged
4. If the patient appreciated diplopia
   E.g: Binoc to 8cm, 10cm, 10cm c effort then LE diverges c diplopia

Question 13

What is the treatment for convergence insufficiency?

Answer 13

• 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

Question 14

Describe convergence paralysis?

Answer 14

• 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

Question 15

What aree the clinical features and management of convergence paralysis?

Answer 15

• 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

Question 16

Describe convergence spasm?

Answer 16

• Excessive convergence
• May also be associated with accommodative spasm
• Transient episodes of convergence
• Needs to be differentiated from other causes of esotropia e.g. 6th nerve palsy
  o New onset eso – make sure their abduction is okay
• Hard to manage so need to make sure it is this
  o Rule everything else out
• Convergence spasm will demonstrate:
  o Full ocular motility – full abduction (6th nerve palsy will not)
  o Pupils miosis when convergence
  o Dolls head – full eye movement – move pxs head one way and check eyes move the other way
• Pxs with convergence spasm may be suffering from significant stress in other aspects of their life (not always)
• Spasm may be exacerbated with testing – not seen when simply chatting to px about other things

Question 17

What is the management of convergence spasm?

Answer 17

• Management:
  o Reassurance & relaxation techniques
   Px needs to understand it is nothing to worry about
   Close eyes and relax
   May need to signpost them to other services if they mention other things going on in life
  o Cycloplegic drops & plus lenses may be useful in short term
   Cyclo stops them accommodating
• Sometimes related to underlying esophoria – treat the esophoria
• Diff diagnosis: 6th nerve palsy, underlying esophoria

Question 18

What is the near triad?
What is primary CI unlikey to have?
What will accomm insufficiency have?

Answer 18

Near triad  pupils constrict, converge and accommodate
Primary CI – unlikely to be manifest squint at near
Accomm insufficiency – exo at near but not clinically relevant as accomm problem not convergence

Question 19

What is not normally affected in convergence problems?

Answer 19

If vision affected at near – then that’s an accommodative problem
Vision not normally affected in convergence
Don’t mix up a near XOT with a convergence problem when convergence is normal