Dry eye disease (DED) is a
chronic condition of the ocular surface characterized by a loss of the tear film homeostasis and accompanied by symptoms such as eye discomfort and visual disturbances. DED is classified as aqueous deficient
dry eye (ADDE),
evaporative dry eye (EDE), and mixed
dry eye etiologies. The mainstay treatment in the management of DED is
artificial tear drops or
lubricant eye drops that replenish the aqueous and/or
lipid layer of the tear film. These are available as both
lipid-based and non-
lipid-based formulations, with/without preservatives.
Lipid-based
lubricant eye drops can stabilize the tear film
lipid layer, reduce tear evaporation, and improve signs of EDE. In this review, we present the formulation components, mechanism of action, and summary of preclinical and clinical evidence on a
lipid-based formulation -
propylene glycol-
hydroxypropyl guar (PG-HPG) nanoemulsion
lubricant eye drops (SystaneTM Complete). These
eye drops consist of the demulcent (
lubricant), PG (0.6%). HPG forms a soft, thin, cross-linked in situ gel matrix with
borate ions, when exposed to the tear film, which prolongs
lubricant retention and provides ocular surface protection. Dimyristoyl
phosphatidyl glycerol, an anionic
phospholipid, helps in replenishing the
lipid layer of the tear film. Moreover, the nanoemulsion formulation serves as a depot for delivery of dimyristoyl
phosphatidyl glycerol to enhance ocular surface coverage. Preclinical and clinical evidence demonstrate that PG-HPG nanoemulsion
lubricant eye drops are safe and effective in providing temporary relief of symptoms of DED, regardless of its subtypes. Specifically, it provides sustained reduction in
dry eye symptoms, improves tear film stability/
lipid layer grade, and improves ocular surface characteristics.