Reflex and steady state tears in patients with latent stromal herpetic keratitis

To compare tear production in patients with stromal herpetic keratitis with that in healthy control subjects.

After instillation of 2 microL fluorescein into both eyes, the tear-fluorescein concentration was measured by fluorophotometry. During the first 10 minutes, steady state tear turnover (TTO-1) was determined. After a nasal alcohol stimulus to induce reflex tears, a second steady state tear turnover (TTO-2) was obtained during 15 minutes. The index of reflex lacrimation (IRL) was calculated as the percentage decrease in tear fluorescein concentration directly after the stimulus. TTO-1, TTO-2, and IRL were determined in the patients' affected eyes (n = 12), in the patients' healthy contralateral eyes, if possible (n = 9), and in one eye of healthy control subjects (n = 24).

The TTO-1 in the affected and healthy eyes of patients was approximately two times lower than the TTO-1 in eyes of healthy control subjects (P = 0.012 and P = 0.024, respectively) and almost equal to the TTO-2 in eyes of healthy control subjects (P = 0.32 and P = 0.40). There were no significant differences in the values of TTO-1, IRL, and TTO-2 between affected and healthy eyes of patients (P > 0.5). IRL and TTO-2 did not differ significantly among the three groups (P > 0.5).

Both eyes of the patients were dry. The dryness could be due to a defective reflex lacrimation under physiological conditions that can still be induced by nonphysiological nasal excitation. The cause of this may be demyelination of both trigeminal root entry zones as a result of a unilateral eye infection by the herpes virus. Another possibility is that dryness predisposes to herpetic infection or recurrent inflammation.