Abstract
This paper discusses the spreading of gel-based ophthalmic formulation on the cornea surface assumed to be flat. We show that gel-based formulations exhibit rheological behaviors that the Herschel–Bulkley model can describe. The continuity and momentum equations are solved numerically using the monofluid formulation and the volume-of-fluid (VOF) method. We investigated the influence of the rheological properties, namely the consistency, the yield stress, and the flow behavior index, on the spreading of a gel-based artificial tear over the cornea surface. We propose optimal values of these properties for efficient gel-based artificial tears.
Highlights
The tear film spreads across the cornea surface to keep it wet and lubricate and protect eyes from infections, dirt, and dust
The latter is the deepest layer of the tear film; it allows the aqueous layer to adhere to the cornea
Tear film instability and tear evaporation can lead to tear film breakup (TBU) and result in a transient spike in saltiness that can cause inflammation of the cornea surface [2,3]
Summary
The tear film spreads across the cornea surface to keep it wet and lubricate and protect eyes from infections, dirt, and dust. The tear film includes lipid, aqueous, and mucus layers [1]. The aqueous layer, which constitutes most of the tear volume, flows over the precorneal mucus layer. The latter is the deepest layer of the tear film; it allows the aqueous layer to adhere to the cornea. Tear film instability and tear evaporation can lead to tear film breakup (TBU) and result in a transient spike in saltiness that can cause inflammation of the cornea surface [2,3]. TBU occurs when a tear film thins to the point that the lipid layer touches the cornea surface. TBU can be caused by tear evaporation, Marangoni-driven tangential flow, and dewetting due to a defective corneal surface [4]. Because of prolonged exposure to the screens of electronic devices, DED affects persons of diverse ages, including children [8,9]
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