
The commonest form of childhood strabismus

Esotropia causes an uncrossed diplopia: right image comes from right eye and vice versa


## Accommodative esotropia

- Accommodation and convergence are linked neurologically

- AC:A varies between people eg. young hypermetropes will naturally accommodate to see clearly

- Primary factors

  - Uncorrected hyperopia
  - Accommodative convergence
  - Insufficient divergence


- Usually presents between 1 and 5 years of age, average of 2.5 years old
- **No diplopia**: the deviating eye is suppressed
- Patients may alternate fixation
- Less than half develop amblyopia

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Common features of accommodative esotropias

- Intermittent first, then constant

- Family history

- May be triggered by fatigue, injury, illness

- Amblyopia likely

- Diplopia unlikely

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- There may or may not be a refractive component (or overlap/mixed)

  - Refractive

    - A physiological response in high hypermetropia due to the excessive amount of accommodation needed to focus on targets (even distant ones) which is linked to a proportional amount of convergence

    - Spectacles correct/improve alignment when there is a refractive component

    - Normal AC:A ratio

    - Normal BSV

    - Equal deviation at near and distance

    - Eso only arises intermittently at first with fatigue/illness

    - If only partially accommodative, surgery can be considered if there is potential for BSV

      - Partially accommodative cases are more associated with amblyopia and bilateral superior oblique weakness

    - The measured hyperopia usually increases until children are 5-7 years old, beyond which point the Rx can be decreased to stimulate fusional divergence

  - Non-refractive (ie. convergence excess): 20%

    - High AC:A ie. disproportionate convergence for every unit of accommodation

        - An esotropia of ≥10PD for near compared to distance confirms a clinically high AC:A

    - Managed with orthoptic exercises, **bifocals** (relieves accommodation and thus convergence), miotics (eg. phospholine iodide) temporarily if non-compliant with glasses, surgery (eg. bimedial recession, if potential for BSV or for cosmesis)


## Non-accommodative

- Infantile esotropia

  - Most common non-accommodative subtype

  - Family history may be present

  - Presents &lt;6 months, patient neurologically normal

    - Full extraocular muscle movements



- **Large angle** ie. > 30PD (similar for near and distance)

- Alternating fixation (therefore low risk of amblyopia)

- Low BSV potential

- Normal refractive correction for age (ie +1 to +2)

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Features associated with infantile esotropia

  - **Dissociated vertical deviation** (80%): upwards drift of occluded eye. Superior rectus recession or inferior oblique anterior transposition can be considered to correct.

  - **Latent nystagmus**: horizontal conjugate jerk nystagmus on covering one eye (or manifest latent ie. nystagmus with both eyes open but amplitude increases when one eye covered)

  - **Inferior oblique overaction**: hyperdeviation in adduction, producing a** V pattern** (60-70%)

  - **Asymmetry**of optokinetic nystagmus

  - **Cross fixation** in side gaze: ie uses left eye in right gaze and vice versa. May mimic bilateral six nerve palsies but abduction can be demonstrated by doll’s head manoeuvre, rotating the child or temporary patching

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### Treatment

  - Treatment of amblyopia

  - Correction of hypermetropia

  - Surgery: timing of surgery can be challenging. Typically done between 6 and 12 months of age

    - Before 6 months: spontaneous recovery can occur (hence no surgery before then)
    - Early surgery may achieve better long-term alignment and chance for BSV/stereopsis
    - But carries increased GA risks and less accurate preoperative measurements eg. prism cover test
    - Options: bimedial recession, unilateral MR recession, LR resection, IO recession if IOOA
    - Target 10PD of residual eso


## Microtropia

- Small angle (&lt;10PD)

- Strong binocular cooperation compared to other forms of strabismus

- Typically asymptomatic

- Deviation may not be detectable on cover test in microtropia with identity (ie. ARC)

  - In microtropia without identity, the fixation point of the deviated eye does not align with the fovea of the fellow eye so there is a small movement on cover test

- Associated with anisometropia especially **hypermetropia** +/- astigmatism

- Abnormal retinal correspondence is present but normal fusional amplitudes

- Central suppression scotoma in the deviating eye

- Reduced but present stereopsis

- The 4PD test will produce movement when placed over the normal eye but no movement over the suppressed eye.

- Managed with refractive correction and treatment of amblyopia



Strabismus

Esotropia

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