The corneal reflex depends on the function of cranial nerves V and VII. To evaluate the corneal reflex, the examiner uses a cotton-tipped applicator, the tip of which has been pulled into a thin strand about 1.3 cm in length. The examiner stabilizes the patient's head by placing a hand on the patient's eyebrow and head. The patient is asked to look to the left side as the cotton tip is brought in from the right side to touch the right cornea gently. This is demonstrated in Figure 21-11. A prompt bilateral reflex closure of the eyelids is the normal response. The examination is repeated on the other side by reversing the directions.
The responses on the two sides are compared. The sensory limb of the corneal reflex is the ophthalmic division of the trigeminal nerve;the motor limb is conducted through the facial nerve.
In performing the corneal reflex test, touch the cornea and not the eyelashes or conjunctiva, which will elicit an inaccurate result.
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