A 4-year-old child is referred for apparent outward deviation of both eyes. Corneal light reflexes are concentric and cover-uncover testing reveals no movement of either eye. The interpupillary distance is wide. What is the explanation?

• A Bilateral sixth nerve palsy
• B Intermittent exotropia missed on testing
• C Congenital motor nystagmus with null point
• D Positive angle kappa simulating exotropia ✓

Explanation

D wide interpupillary distance combined with a positive angle kappa makes the eyes look divergent although they are straight, a pseudoexotropia. In positive angle kappa the visual axis falls nasal to the pupillary axis, so the corneal reflex sits nasal to the pupil centre and the eye appears turned out. Centred, symmetrical reflexes with no movement on cover-uncover testing exclude a true squint, and bilateral sixth nerve palsy would show genuine abduction limitation with a convergent posture.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

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