A Child With Intermittent Exotropia and a Worried Parent
A 5-year-old boy is brought by his mother because she notices his right eye 'drifts out' when he is tired or daydreaming, especially in bright sunlight when he screws up one eye. It has been present for about a year and seems more frequent. He is otherwise well, has no glasses, and attends mainstream school. On examination, visual acuity is 6/9 in each eye with a matching picture test. Cover test shows a well-controlled intermittent exotropia of about 20 prism dioptres at distance, 10 at near, with good stereoacuity on the Titmus test. Anterior and posterior segments are normal. Refraction under cycloplegia is +0.50 DS in each eye.
1. How do you classify this and what is your initial management?
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Classification: Intermittent exotropia, distance > near (divergence excess pattern), well controlled with good stereoacuity, in a child with normal acuity and a normal fundus. The photophobia/squinting in bright light is a classic sign of intermittent exotropia - the child closes one eye to avoid diplopia when the deviation becomes manifest.
Initial management:
- Observation and parental education is appropriate for a well-controlled intermittent exotropia with good stereoacuity and no functional deficit. Many remain stable for years.
- Correct refractive error - even low hyperopia can help control; prescribe the cycloplegic refraction if it improves control, and treat any significant astigmatism or anisometropia.
- Address any amblyopia risk - acuity is equal here, so no patching.
- Lifestyle advice - encourage outdoor play and near work; avoid excessive fatigue.
- Review in 3–6 months with repeat cover test, control score, and stereoacuity.
Do not rush to surgery: the natural history is variable, and operating on a well-controlled deviation with good stereoacuity risks overcorrection and intractable diplopia.
2. What objective signs would push you toward surgery, and what are the risks of operating too early or too late?
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Signs that push toward surgery:
- Deteriorating control - increasing frequency of manifest deviation, needing to close one eye, or a rising Newcastle control score.
- Loss of stereoacuity or a new suppression scotoma on testing.
- Increasing angle on serial measurements (e.g. >25–30 PD at distance) or a deteriorating distance/near pattern.
- Progressive refractive change or an emerging vertical deviation.
- Psychosocial impact - child teased, or parent reports functional difficulty.
Risks of operating too early:
- Overcorrection leading to consecutive esotropia, diplopia, and loss of binocular function - particularly dangerous in a child with good stereoacuity.
- Loss of the ability to use the deviation as a 'safety valve'.
- Anaesthetic and surgical risks in a young child.
Risks of operating too late:
- Irreversible loss of binocular potential and progression to a constant exotropia with suppression.
- Amblyopia if a microtropia develops.
- Psychosocial and educational impact.
Decision: operate when there is documented deterioration in control, stereoacuity, or angle, not on the basis of a single visit. Document serial measurements and involve the parents in the decision.
3. The mother asks about non-surgical options and whether glasses or exercises will 'fix' it. What do you advise?
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Non-surgical options:
- Refractive correction - if hyperopia is present, full or near-full correction can improve control by stimulating accommodation and convergence. In this child the refraction is low, so benefit is limited but worth a trial.
- Over-minus lenses - a small additional minus (e.g. -1.00 to -2.00 DS) can stimulate accommodation and improve control in some children, but causes blurred distance vision and is poorly tolerated long-term; use cautiously and only with clear benefit.
- Part-time occlusion or penalisation - treats associated suppression/amblyopia; not a cure for the deviation.
- Orthoptic exercises (convergence exercises) - useful mainly for convergence insufficiency-type exotropia with a near deviation; less effective for distance excess.
- Prism adaptation - rarely used in children; can help assess fusional potential pre-operatively.
Advice to give:
- Glasses may help control but will not 'cure' the deviation; exercises have a limited role in this pattern.
- The mainstay for a deteriorating intermittent exotropia is surgery, timed when control or stereoacuity worsens.
- Emphasise regular review, and that the aim is to preserve binocular vision, not just cosmetic alignment.