Evaluating the lubricating effect of semifluorinated alkanes on the ocular surface

Abstract

Purpose : Dry eye disease (DED) is one of the most prevalent ocular surface disorders causing significant pain and discomfort to patients. Recently, the semifluorinated alkane (SFA), perfluorohexyloctane (NovaTears®; EvoTears®) has been introduced as a preservative-free tear substitute for the treatment of DED symptoms. This study evaluated the mechanisms by which perfluorohexyloctane exerts its lubricating effect on the ocular surface in comparison to the shorter alkane chain SFA, perfluorobutylpentane.

Methods : Interactions of both SFAs with the ocular surface were evaluated ex vivo using high speed photography on excised porcine corneas. The influence of SFAs on tear fluid dynamics was evaluated in vivo after twice daily instillation into healthy rabbit eyes for seven days and was compared to the instillation of saline. Lipid layer grade (LLG), tear evaporation rate (TER) and tear volume were observed daily during the course of treatment, while tear osmolarity was observed before commencing the study and on the final day of treatment. Safety and tolerability were also assessed by clinical scoring and sodium fluorescein staining.

Results : Ex vivo studies showed that both SFAs rapidly spread on the ocular surface with the volume-adjusted spread area being significantly larger than that of a saline drop. The contact angle of SFAs on the cornea was almost 0°. A significant improvement in LLG was observed immediately after instillation of a single dose of both SFAs (p < 0.05) in vivo. Improvement in LLG appeared to be more sustained upon instillation of perfluorohexyloctane with a statistically significant improvement being evident from day 5 onwards (p < 0.05). No significant changes in TER, tear volume or tear osmolarity were observed after application of either SFA over the course of seven days. Both the SFAs were also well tolerated on the ocular surface.

Conclusions : Both SFAs showed excellent corneal wetting properties and tended to rapidly spread on the ocular surface. Perfluorohexyloctane was found to progressively improve the LLG after topical application supporting its lubricating effect on the ocular surface to provide symptomatic relief to DED patients.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.