Tear studies in ocular rosacea.

To determine whether tear pH in ocular rosacea was alkaline or acidic compared to normal, I studied tear pH measured by pH electrode or paper in 12 patients with rosacea without ocular manifestations, 23 patients with mild ocular manifestations, and nine patients with severe ocular manifestations. There was no diagnostically useful difference in tear pH between any of these groups and normal controls. Possible pitfalls include the effect of anesthetic eyedrops on tear pH, the effect of basal tear secretion, and discrepancies between electrode and paper measurements. Measurements by pH paper cannot be adjusted by an error constant to yield an equivalent electrode value. Treatment of active ocular rosacea with tetracycline for one month had no effect on tear pH in six patients.