Intermittent Exotropia in a Seven-Year-Old: Observe, Overminus, or Refer?
A seven-year-old girl is brought by her mother because the right eye turns out when she is tired or in bright sunlight. The mother has noticed it more often over the past year, and sometimes the child closes one eye outdoors. Best-corrected visual acuity is 6/6 in each eye. Cycloplegic refraction is +1.25/-0.50 × 180 in each eye. Cover test shows an intermittent exotropia of 18 prism dioptres at distance and 12 prism dioptres at near, with a control score of 3 on the Newcastle Control Score (0 = best, 7 = worst). Near point of convergence is 10 cm; stereoacuity is 60 seconds of arc at near. There is no vertical deviation, no dissociated vertical deviation, and fundoscopy is normal. The mother has read about surgery and asks whether her daughter needs an operation now, or whether exercises or glasses would be enough.
1. Interpret the control score and the clinical findings. What do they tell you about severity and risk of progression?
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The Newcastle Control Score of 3 is in the moderate range: it indicates that the exotropia is intermittent but occurs often enough to be noticed at home and in the clinic. The distance deviation (18 PD) is larger than the near deviation (12 PD), which is typical of divergence excess or a simulated divergence excess pattern. Preserved 60-second stereoacuity and 6/6 acuity are reassuring, but they do not rule out progression. The history of closure in bright sunlight suggests suppression or photophobia from the exodeviation. At this level, many clinicians would not operate immediately; the decision depends on control, stereoacuity, angle stability, and parental goals. A deterioration in control score, a constant deviation, or a fall in stereoacuity would push toward referral.
2. Compare three management options - observation, refractive correction or overminus, and surgery - and state your first-line plan with a review interval.
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First-line: prescribe the full cycloplegic correction and review in 3 months. Correcting +1.25 D of hyperopia may improve control in some children by reducing accommodative convergence demand, although the evidence is modest. If control remains moderate or worsens, a trial of overminus lenses (-1.00 to -2.00 D) can be considered, but it carries a risk of inducing myopia and should be used with caution and close monitoring. Part-time occlusion or vision therapy may help suppression but does not reliably cure the deviation. Surgery is generally reserved for children with poor or deteriorating control, constant exotropia, or significant functional or cosmetic concern; refer to a paediatric ophthalmologist if the control score reaches 4 or more, the angle increases, or stereoacuity declines. Observation alone is reasonable only with clear monitoring.
3. What specific advice would you give the mother about monitoring and when to return sooner?
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Ask the mother to keep a simple diary of how often the eye turns, whether it happens at distance or near, and whether the child closes one eye or complains of double vision. Photographs can help. Return sooner if the deviation becomes constant, if the child reports diplopia, if school performance or reading changes, or if there is a sudden increase in frequency. Routine review should include cover test, control score, stereoacuity, and refraction. Explain that many children remain stable, but some progress, so monitoring matters more than choosing surgery immediately.