Ocular discomfort is a persistent problem that many dry eye patients face. Now, a new study in The Ocular Surface reports the capsaicin stimulus test may be a helpful tool for clinicians to better understand pain sensitivity in their patients with short tear film break-up time (TBUT) dry eye.
A team of researchers enrolled 22 eyes of 22 patients with short TBUT dry eye and 11 healthy eyes as a control group. The dry eye patients were divided into two groups based on responses to standard dry eye treatments: 10 non-responders (intractable dry eye) and 12 responders (responsive dry eye). The investigators measured mechanical touch and mechanical pain using a Cochet-Bonnet esthesiometer in addition to capsaicin-induced pain and duration with the capsaicin stimulus test. The study also considered psychological distress among the patients.
The researchers found mechanical touch sensitivity was similar between all three groups. However, mechanical pain sensitivity was higher in the responsive dry eye group compared with patients in the intractable dry eye and control groups.
Additionally, capsaicin-induced sensitivity was lower in the intractable dry eye group compared with the other two, and capsaicin-induced pain duration was shorter in the intractable dry eye group vs. those who responded to treatment.
Of note: patients who didn’t respond to treatment reported more psychological distress than the controls.
Patients with intractable short TBUT dry eye were less sensitive to the effects of capsaicin than patients with responsive short TBUT dry eye and the healthy eye group, the researchers noted. Altered neural activation may contribute to the development of dry eye symptoms in the short TBUT dry eye subjects, and the capsaicin stimulus test may be used to better understand pain sensitivity in these patients, they added.
Kaido M, Inoue S, Kawashima M, et al. Capsaicin-induced pain sensitivity in short tear break-up time dry eye. The Ocular Surface. July 24, 2020. [Epub ahead of print].