Wednesday, April 20, 2011
Trick of the Trade: Corneal reflex test
The corneal reflex test (blink test) examines the reflex pathway involving cranial nerves V and VII. Classically the provider lightly touches a wisp of cotton on the patient's cornea. This foreign body sensation should cause the patient to reflexively blink.
This maneuver always makes me a little worried about causing a corneal abrasion, especially if you are examining a very somnolent patient. You are wondering -- Is there no blinking because you're not touching the cornea hard enough? You apply harder pressure but still no blink. You repeat the test and now the patient finally blinks. That's 3 times you've just scraped against the cornea.
What's an alternative approach?
Apply drops of sterile saline on the eye.
When a patient presents with a low GCS, you want to perform rapid neurologic exam. I've been seeing our neurologists do a quick simple test for corneal reflexes. Grab a pre-filled sterile saline syringe, typically used to flush IV's, and squirt a few drops on the eye. Look for the patient to blink.
This seems much safer and definitive of a test of the corneal reflex.