Week 5 - Convergence anomalies Flashcards
What is convergence? Abnormality in this cause?
Convergence is a vergence movement that allows the visual axis to stay directed towards a near target.
An abnormality of convergence can result in the following:
• Convergence Insufficiency
• Convergence Paralysis
• Convergence Spasm
Near point of convergence (NPC) is the closest distance to which the eyes can converge while maintaining binocular single vision.
Differential Diagnosis
• Convergence Insufficiency or Paralysis
• Convergence Spasm
• Accommodation Insufficiency
• Accommodation Spasm
• Exophoria of convergence weakness type- exophoria 10^ near>distance
Convergence insufficiency
• Definition: Near point of convergence is less than 10cm.
- Convergence can only by maintained at this distance with effort.
• Can primary or secondary. Highly treatable.
• Primary: No other causes for convergence insufficiency are present, including heterophoria.
- Prevalence: 4.2%-17.6% in children
Aetiology of primary convergence insufficiency
Pre-disposing Factors:
• Large interpupillary distance
• Large periods of time only using distance fixation e.g., occupation
Precipitating Factors:
•Fatigue from long periods of close work with/without poor lighting
•Illness
•Age
•Medication/recreational drugs
• Pregnancy
Secondary Convergence Insufficiency causes
• Intermittent near exotropia
• Convergence weakness exophoria
• Neurological condition e.g., Parkinsons and horizontal gaze palsy
•Whiplash after road traffic accident
• Thyroid eye disease
• latrogenic- medial rectus weakness after surgery
Common symptoms:
•Patient often reports difficulty with reading or doing close work.
• Intermittent diplopia during near work.
• Blurred vision during near work.
• Frontal headache.
• Eyestrain.
• Difficulty concentrating.
• Movement of print.
Investigation
• Case History
• Distance and Near Vision
• Cover Test and Angle of Deviation
• Assessment of Convergence
• Accommodation
• Fusional Amplitude
Expand on:
Case History
Distance and Near Vision
Cover Test and Angle of Deviation
• Case History
- Ask about near work.
- Ask previous treatment- convergence insufficiency recurrent
• Distance and Near Vision
- Near vision may be reduced if associated accommodation insufficiency
• Cover Test and Angle of Deviation
- Investigation for exophoria- particularly at near. Important for appropriate diagnosis and management.
• Assessment of Convergence
• Accommodation
• Fusional Amplitude
• Accommodation
- Binocular accommodation may be reduced. Uniocular accommodation likely to be normal although associated accommodation insufficiency has been reported in some children.
• Fusional Amplitude
- Measured with prism bar in free space or synoptophore. Base out range may be reduced.
Assessment of convergence:
• Accurate assessment of convergence can be achieved by using the RAF rule.
• It allows for specific measurement of convergence and accommodation.
• It is equipment with near point of convergence measurements, diopters of accommodation and appropriate levels of accommodations based on patient’s age.
How to use the RAF:
• Ensure px wearing near correction
• Place RAF rule on px cheek, under lower lids
• RAF rule should be held slightly depressed
• Appropriate target should be selected for what being measured, start at 50cm
• Clear instructions should be given
• Px should be encouraged to maintain single vision
Recording results of RAF rule:
- All three measurements- not an average!
- If effort was exerted.
- If convergence was broken, which eye diverged.
- If the patient appreciated diplopia.
Example:
Binoc to 8cm, 10cm, 10cm c effort then LE diverges c diplopia
Treatment for a convergence insufficiency
Correction of Refractive Error
Orthoptic Exercises
Convergence Exercises:
• Smooth and Jump convergence
- Smooth convergence: Pen to nose exercises
- Jump convergence: Dot card
Base in Prisms:
Correct near exotropia
Convergence Paralysis types
The ability to converge is completely lost.
• May be primary or secondary.
• Primary:
- No previous history.
- Investigation rules out other secondary causes.
• Secondary:
- Head Trauma
- Neurological cause e.g, Parinauds syndrome, encephalitis, multiple sclerosis.
Clinical Features of Convergence
Paralysis
• Diplopia for all distances nearer than infinity.
- Exotropia at near.
• Ocular motility is normal in primary convergence paralysis.
• Accommodation may or not be impacted.
Management of Convergence Paralysis
Once secondary convergence palsy is ruled out/underlying cause is investigated…
Conservative management:
• Base in prisms to correct exo deviation.
• Occlusion to prevent diplopia.
• If accommodation is impacted, hypermetropic prescription in combination with base in prism
Botox to lateral rectus may be temporary fix.
Convergence Spasm definition and management
Excessive convergence.
May also be associated with accommodation spasm.
Transient episodes of convergence.
Needs to be differentiated from other causes of esotropia e.g., sixth nerve palsy.
Convergence Spasm will demonstrate:
• Full ocular motility- full abduction.
• Pupil miosis when convergence.
• Dolls head- full eye movement.
- Patients with convergence spasm may be suffering from significant stress in other aspects of their life.
- Spasm may be exacerbated with testing- not seen when simply chatting to patient about other things.
Management:
- Reassurance and relaxation techniques.
- Cycloplegic drops and plus lenses may be useful in short term.
Primary Convergence Insufficiency: Symptoms, signs
• Symptoms
- Blurred vision for near- binoc.
Headache and asthenopia
• Signs
- May have small exophoria at near
Convergence weakness type exophoria:
Symptoms, signs
• Symptoms
Blurred vision for near- binoc.
Headache and asthenopia
• Signs
Exophoria at both distances. Near> distance by 10^BI
Convergence Paralysis: Symptoms, signs
• Symptoms
- Diplopia
• Signs
- Near exotropia
Accommodation insufficiency: Symptoms, signs
• Symptoms
Blurred vision at near- binoc and unioc. Headache
• Signs
May have an exophoria for near
