A 9-year-old with intermittent exotropia and a school report of poor concentration

This is intermittent exotropia, distance type, with a well-compensated near deviation and mildly reduced convergence.

Interpretation:

• Distance exophoria of 8Δ breaking to 14Δ XT after 30 seconds - the deviation is controlled most of the time but decompensates under dissociation. A break after prolonged dissociation is normal; the relevant question is control in free space, not the dissociated angle alone.
• Near exophoria of 6Δ - essentially normal; convergence is adequate for near work.
• NPC 12 cm break / 15 cm recovery - mildly receded; normal is often quoted as under 10 cm, so this is borderline rather than clearly abnormal.
• Stereoacuity 60 seconds of arc - good, indicating no significant suppression or amblyopia.
• Cycloplegic refraction essentially emmetropic with low astigmatism - no significant refractive error to correct.

Does it need treatment? Intermittent exotropia is common and many children remain stable. Treatment is indicated when there is deteriorating control, increasing frequency or size of the manifest phase, or functional symptoms.

Evidence-based reasoning:

• The landmark randomised trial of surgery versus observation in childhood intermittent exotropia found no significant difference in control at three years, so surgery is not automatically indicated for a moderate, well-controlled deviation.
• Over-minus lenses are used by some clinicians but cause accommodative strain and are not supported as a first-line treatment for a well-controlled case.
• Part-time occlusion or over-minus may be trialled where control is deteriorating.
• Vision therapy/orthoptics for convergence insufficiency has better evidence where near findings dominate; here the near deviation is minimal.

Conclusion: this child does not need surgery now. He needs monitoring of control and a clear plan for when to escalate.

Does it explain the classroom problems? Probably not on its own. The deviation is well controlled, stereoacuity is good, and acuity is normal. Poor concentration when copying from the board has many causes, and the most important ones to exclude here are:

1. Refractive error - cycloplegic refraction shows low hyperopia with against-the-rule astigmatism under 1.00 D. This is unlikely to be the cause, but if he is symptomatic you could trial the correction; do not over-prescribe.
2. Accommodative or convergence dysfunction - NPC is borderline at 12 cm; measure accommodative amplitude and facility to complete the picture.
3. Visual processing or educational factors - poor board-copying can reflect distance acuity, seating position, or a learning difficulty rather than a binocular problem.
4. General health - sleep, hearing, attention.

Responding to the mother:

• Glasses: the refractive error is small; glasses are not clearly indicated for the exotropia and are unlikely to fix the classroom issue. If a trial is given, explain it is a trial and set a review date.
• Surgery: not indicated now. Explain that the randomised evidence shows observation and surgery produce similar control at three years, and that surgery carries risks including overcorrection. Explain the signs that would prompt referral - the eye drifting more often, especially at near or when tired, or the child closing one eye in sunlight.
• School: suggest seating near the board and a review of whether the difficulty is visual at all; consider a report to the school.

Plan: review in 3–6 months with control assessment (e.g. a standardised control score), repeat stereoacuity, and repeat NPC. Refer to orthoptics if control deteriorates or near symptoms emerge.