In Vitro Inhibition of Evaporation with Perfluorohexyloctane, an Eye Drop for Dry Eye Disease

OBJECTIVE: Perfluorohexyloctane (PFHO) MIEBO(TM), formerly (NOV03) is a single component, water-free eye drop approved by the Food and Drug Administration in the United States for the treatment of dry eye disease. We evaluated the in vitro inhibitory effect of PFHO on the evaporation rate (R(evap)) of saline. METHODS: Evaporation rates were measured gravimetrically at 25°C or 35°C. The evaporation rate (R(evap)) of phosphate-buffered saline (PBS) was measured following the application of 11-200 µL PFHO or 100 µL artificial tears (Soothe XP [Bausch + Lomb, Bridgewater, New Jersey], Systane Balance [Alcon, Fort Worth, Texas], and Systane Ultra [Alcon]). The effect of PFHO on the R(evap) of PBS was further evaluated following the addition of 50 mg/mL mucin to PBS and compared with that of meibum lipid collected from a 68 year-old White volunteer. RESULTS: At 25°C the mean (SEM) R(evap) of PBS alone or PFHO alone was 4.06 (0.06) and 0.137 (0.004) µm/min, respectively. Layering 100 µL PFHO over PBS inhibited the R(evap) of PBS by 81% (P < 0.0001), whereas artificial tears had no effect. The presence of mucin attenuated the inhibition of the R(evap) of PBS by PFHO by 17% (P < 0.0001). At 35°C, the R(evap) of PBS was inhibited by 88% when layering 100 µL PFHO over PBS and 28% when applying a single 11 µL drop of PFHO (P value < 0.0001 for both). Meibum lipid inhibited the R(evap) of PBS by 8% at this temperature, whereas the combination of a drop of PFHO plus meibum inhibited the R(evap) of PBS by 34%. CONCLUSIONS: PFHO significantly inhibited the R(evap) of saline in this in vitro model. The data support the idea that PHFO may form an antievaporative layer on the tear film surface and may be a functional substitute for the native tear-film lipid layer in patients with dry eye disease.