Corneal sensation is tested by

To test the corneal sensations, the patient is asked to look ahead; the examiner touches the corneal surface with a fine twisted cotton (which is brought from the side to avoid menace reflex) and observes the blinking response. Normally, there is a brisk reflex closure of lids. Always compare the effect with that on the opposite side. The exact qualitative measurement of corneal sensations is made with the help of an aesthesiometer. Reference: A K KHURANA COMPREHENSIVE OPHTHALMOLOGY, Edition 4, page-547