Cationic Emulsion as Artificial Tears: An In vivo Evaluation in Dry Eye Rabbit Models.
Environmental factors like pollution, exposure to Video display terminals, ageing, drugs etc lead to ocular fatigue finally terminating into dry eye (keratoconjunctivitis sicca). Constant tear evaporation leading to exacerbated drying of ocular surface is an archetype. Hence the potential of a cationic submicronic emulsion as artificial tears was investigated. Submicronic emulsion system was formulated by dispersing a medium chain triglyceride in the aqueous phase with the aid of stirring, high speed homogenisation and employing a synergistic combinations of three emulsifiers; Solutol HS 15, Cremaphor EL and HPMC. Oleylamine (a cationic lipid) was used to impart positive surface charge to the oil globules. The emulsion was evaluated for pH, specific gravity, viscosity, osmolarity, globule size, zeta potential and surface tension.To evaluate the system potential as artificial tears, rabbit models resembling evaporative dry eye condition were developed using 0.2% Benzalkonium chloride. Efficacy of the emulsion system was evaluated by observing for chemosis, conjunctival hyperemia and mucosal discharge by digital photography. Tear production was measured using Schirmer tear test I.The developed cationic emulsion system revealed submicronic globule size (133nm), positive zeta potential (+63mV), desirable osmolarity(266 mOsms) and low surface tension (38milliN/m). Treatment involving emulsion instillation twice a day for 5 days was found to be therapeutically effective in alleviating the induced dry eye symptoms. Furthermorethe system increased the tear production from lower values (7-9mm) in dry eyes to basal values (15-16mm) in healthy eyes.