In Vitro and In Vivo Visualization of Perfluorohexyloctane, an Eye Drop for Dry Eye Disease, Using Infrared Emissivity

Abstract

Purpose: To visualize the behavior of perfluorohexyloctane (PFHO), an eye drop to treat dry eye disease (DED), on the surface of saline in vitro and on the human ocular surface using infrared emissivity. Methods: Emissivity videos were used to measure the spreading and disappearance rates of PFHO on saline (with and without mucin for spreading rate) and layered over a 125 nm film of meibum on the surface of saline using a TearView camera. Ocular surface emissivity was videoed in a volunteer without DED before and after instillation of 1 drop of PFHO. Videos were exported and converted to still photographs, and grayscale levels measured. Results: PFHO formed a layer over saline that spread at a mean (SD) rate of 0.89 (0.5) cm2/s and disappeared at 0.0760 (0.0055) μL/min, consistent with reported rates of evaporation for PFHO. Mucin in the subphase did not alter spreading rate (P > 0.2). In vitro, a single drop of PFHO spread over the top of a 125-nm thick film of meibum remaining for 3.3 hours. In the volunteer, an increase in emissivity was detected on the ocular surface for ≥5 hours. Conclusions: PFHO quickly spread to form a layer over the surface of saline or meibum in vitro and was detected on the ocular surface in vivo for ≥5 hours after topical administration. This supports findings that PFHO forms a long-lasting barrier to evaporation at the air–liquid interface of the tear film and thus reduces signs and symptoms of DED.