Diagnostic Eye Drops and Pain Sensitivity: A Marker for Dry Eye Syndrome?

The aim of this prospective study was to evaluate whether the duration and intensity of pain induced by commonly used diagnostic eye drops correlate with the presence and severity of dry eye syndrome.

This study included 33 patients (66 eyes) undergoing routine evaluations at tertiary ophthalmology clinics from 2016 to 2017. Each eye received one drop of either oxybuprocaine or tropicamide. Pain intensity and duration were assessed using a visual analog scale and a stopwatch. Dry eye syndrome was diagnosed and graded according to international guidelines, incorporating clinical signs and standardized tests. Statistical analyses included Kruskal-Wallis tests for discrete variables and Pearson correlations for continuous variables, with significance set at P <0.05.

Patients with dry eye syndrome experienced significantly longer pain duration compared with those with healthy eyes ( P = 0.035). Pain intensity was notably higher in patients with severe dry eye ( P = 0.048). Duration of pain correlated with corneal fluorescein staining ( P = 0.027). In eyes treated with oxybuprocaine, shorter tear break-up time and lower Schirmer test results were significantly associated with pain response ( P = 0.021 and P = 0.037, respectively). In eyes treated with tropicamide, pain intensity was significantly associated with functional limitations ( P = 0.042).

This study highlights that pain sensitivity to commonly used diagnostic eye drops is a potential marker for the presence and severity of dry eye syndrome. Clinicians should consider evaluating pain responses during routine examinations as a simple, supplementary tool for identifying patients who may benefit from further diagnostic investigations and tailored management.