Expansion
Touch with five, blink with seven
Mnemonic
“V in, VII out”:
- Afferent - ophthalmic division of the trigeminal (V1)
- Efferent - facial nerve (VII), to orbicularis oculi, giving a bilateral blink
Interpreting the result follows directly:
- Neither eye blinks when one is touched, but both blink when the other is touched: an afferent (trigeminal) lesion on the first side
- Only the opposite eye blinks: an efferent (facial) lesion on the tested side
An early absent corneal reflex is a classic sign of a cerebellopontine angle lesion such as a vestibular schwannoma, because V, VII and VIII are crowded together there.
Touch the cornea, not the sclera, and approach from the side so the blink is not merely a visual threat response.
Expansion
- Afferent - CN V1, ophthalmic division of the trigeminal nerve
- Efferent - CN VII, facial nerve, orbicularis oculi