Health Questions and Answers

Question: What information can be obtained from the eye examination of the comatose patient?

Answer:

The eyes should be examined for position, reactivity, and reflexes. When the eyelids are opened, note the position of the eyes. If the eyes flutter upward, exposing only the sclera, suspect psychogenic coma. If the eyes exhibit bilateral roving movements that cross the midline, you know that the brainstem is intact. Pupil reactivity is the best test to differentiate metabolic coma from coma caused by a structural lesion because it is relatively resistant to metabolic insult and usually is preserved in a metabolic coma. Pupil reactivity may be subtle, necessitating use of a bright light in a dark room. Testing of the eye reflexes is the best method for determining the status of the brainstem
Two methods can be used:
(1) oculocephalic (doll’s eyes)
(2) oculovestibular (cold calorics)
Oculocephalic testing requires rapid twisting of the neck, which is a bad idea in the unconscious patient because occult cervical trauma may be present. Oculovestibular testing is easy to do and can be done without manipulating the neck. The ear canal is irrigated with 50 mL of ice water. A normal awake patient has two competing eye movements: rapid nystagmus away from the irrigated ear and slow tonic deviation toward the cold stimulus. Remember the mnemonic COWS (Cold Opposite, Warm Same), which refers to the direction of the fast component.A patient with psychogenic coma has normal reflexes and exhibits rapid nystagmus. A comatose patient with an intact brainstem lacks the nystagmus phase, and the eyes deviate slowly toward the irrigated ear. If the eyes do anything else (usually not a good sign), refer to Goetz to determine the location of the lesion (Goetz CG: Neurology. Philadelphia, W.B. Saunders, 1999).

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