Purpose: The authors aimed to produce a new tear substitute capable of providing both lubrication and nutrition, based on a novel nutrient-containing therapeutic ocular surface medium (TOSM).
Methods: Viscous substances, including hypromellose (HPMC), carbopol, and sodium hyaluronate (SH) were added to the TOSM at various concentrations. Three commercial preservative-free artificial tear substitutes, Hypromellose (Pharmacy of Moorfields Eye Hospital, London, UK), Thilo-Tears (a carbomer; Alcon Pharma GmbH, Freiburg, Germany), and Vislube (a hyaluronate; Chemedica AG, Munich, Germany) were used as control preparations. Their viscosity and surface tension were measured. Human corneal (HCE-T) and conjunctival (IOBA-NHC) cell lines were used to investigate cell proliferation and viability in response to the formulations by means of a luminescence-based ATP assay and a calcein AM/EthD-1 assay.
Results: HPMC, carbopol, and SH increased the viscosity of TOSM significantly. The surface tension of TOSM was reduced by HPMC, but not by carbopol or SH. TOSM-HPMC supported cell proliferation and viability better than TOSM-carbopol and TOSM-SH. TOSM-HPMC and TOSM-carbopol supported cell proliferation significantly better than the corresponding commercial artificial tears. However, TOSM-Vislube supported cell growth significantly better than TOSM-SH.
Conclusions: TOSM-HPMC showed superior lubricant and nutrient properties with moderate viscosity and little cytotoxicity. It thus could be an ideal nutrient and lubricant tear substitute for dry eyes and should be evaluated in a clinical study.