A 4-year-old presents with intermittent exotropia that is larger at distance than at near, with a difference of >15 prism dioptres. This pattern is known as what, and what does it suggest about motor fusion?
- A Divergence excess exotropia; poor negative fusional vergence at distance ✓
- B Convergence insufficiency exotropia; defective negative fusional vergence
- C Basic exotropia; equal distance and near deviation
- D Sensory exotropia; due to monocular visual deprivation
Correct answer: A. Divergence excess exotropia; poor negative fusional vergence at distance
Explanation
Divergence excess type intermittent exotropia is characterised by a distance deviation at least 15 prism dioptres greater than the near deviation. This reflects poor negative fusional vergence (fusional convergence) at distance, allowing the eyes to diverge without the convergence stimulus that operates at near. Management includes minus lens therapy (to stimulate accommodative convergence), orthoptic exercises, and surgical recession of lateral rectus when the deviation is large and persistent.
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.