Abstract
Purpose :
To examine the effect of a TRPM8-agonist containing eyedrop (Rohto® Hydra) on tear meniscus area and height (TMA, TMH) as measured by an Optical Coherence Tomography (OCT) imaging system, compared to artificial tears (Systane® Ultra).
Methods :
6 normal subjects participated with no history of ocular surface disease, no prior diagnosis of dry eye, no current symptoms of ocular discomfort, and no history of artificial tear use. Each subject underwent OCT imaging of the tear meniscus of both eyes pre-treatment using a Heidelberg Spectralis® OCT with OCT2 module. Rohto® Hydra, which contains menthol, a potent TRPM8 agonist, was compared to Systane® Ultra due to similarities in secondary ingredient profile and viscosity. Study dose was 1 GTT OU. Post-treatment assessments occurred after 15 minutes to assure that the drops themselves were not falsely increasing TMA and TMH, and to avoid any influence of transient drop comfort/discomfort. ImageJ was used to measure TMA and TMH from acquired images.
Results :
Pre-treatment TMA/TMH were not significantly different within each patient from one day to the next (p = 0.83). 15 minutes after instillation of Rohto® Hydra drops, mean TMA/TMH values increased significantly from 202.3/21.4 to 286.3/25.1 (TMA: p < 0.01, TMH: p < 0.01). 15 minutes after instillation of Systane® Ultra drops, mean TMA/TMH increased non-significantly from 209.4/22.6 to 240.0/24.7 (TMA: p = 0.17, TMH: p = 0.15). These findings suggest that Rohto® Hydra drops were able to induce lacrimation, possibly via TRPM8 activity. Although the role of TRPM8 in lacrimation has been thoroughly established in mice and rodent models, its role in human lacrimation is not yet well defined.
Conclusions :
A TRPM8-agonist containing eyedrop was shown to possibly induce lacrimation. OCT imaging successfully detected these increases in tearing. TRPM8 is a potential target in drug development of dry eye products.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.