Hypertonic saline test for ophthalmic nerve impairment.

In order to compare the accuracy of methods for testing ocular surface sensitivity (e.g. function of the first branch of the trigeminal nerve) three different methods were compared in patients with unilateral acoustic neurinomas. The three methods 1) hypertonic (3%) saline in the conjunctival sac (apparently not previously described in the literature) 2) esthesiometer (Cochet & Bonnet) touching of the cornea, and 3) touching the cornea with a cotton wool wisp, was found to reveal reduced ocular surface sensitivity on the neurinoma side in 50% (hypertonic saline), 23% (esthesiometer) and 14% (cotton wool wisp) of cases, respectively. With McNemar's test for comparing test methods the 3% saline test proved significantly more sensitive than the cotton wool wisp test (p < 0.05), but not significantly more sensitive than the esthesiometer test (p > 0.10). The advantage of the 3% saline test, apart from its high sensitivity, is that it does not require sterilization of any equipment as is the case for the esthesiometer nor, in contrast to the methods using corneal or conjunctival touch, does it require perfect visual control by means of a magnifying glass in order to be performed accurately, and it is not affected by visual stimuli. It should therefore be the preferred test of assymetry in ophthalmic nerve function.