Abstract
Purpose :
In ideal contact lens (CL) fitting the lens could surf on cornea while riding on thin film of tears and the lens may repeatedly detach and reattach. Seamless reattachment depends on the interfacial profile of mediating film. We hypothesize that lubricants with asymmetric profile of interfacial interactions with both CL and cornea are the least favorites to serve CL wearers.
Methods :
Studied surfaces were corneas of freshly excised rabbit eyeglobes, at induced dry conditions with or without mucin removal, and hydrogel CL (pHEMA/MAA) with 38 or 57% water content. Investigated formulations were anionic (AEM) and cationic (CEM) nanoemulsions (castor oil, emulsifier, surfactant, glycerol and anionic or cationic entity), povidone 5% (PVP), hydroxypropyl methylcellulose 0.3% (HPMC), a combination of polyvinyl alcohol 1.4% and povidone 0.6% (PVA-PVP), sodium hyaluronate 0.1% (SH) and Saline. Contact angles of each formulation on each surface were measured by FTA 125 (First Ten Angstroms Inc). Contact angles were considered asymmetric when comparisons reached statistical significance (Kruskal-Wallis, p<.05).
Results :
CL_38% vs. dry cornea: Asymmetric contact angles were determined for PVP (p .0209), HPMC (p .0433), PVA-PVP (p .0433) and Saline (p .0209). CL_38% vs. dry cornea with mucin removal: Asymmetric contact angles were determined for AEM (p .0209), CEM (p .0209), SH (p .0209) and PVP (p .0209). CL_57% vs. dry cornea: Asymmetric contact angles were determined for 5 formulations, sparing HPMC (p .0833) and PVP (p .7728). CL_57% vs. dry cornea with mucin removal: Asymmetric contact angles were determined for all studied formulations.
Conclusions :
Under our assumptions, both charged emulsions and polyanionic hyaluronate were favorites to serve between 37%-water CL and dry cornea with preserved mucin, implying a role of electrostatic interactions with the anionic mucin. All of them lost ground when mucin was removed, and Saline along with low polymer % formulations, HPMC(0.3%) and PVA(1.4%)-PVP(0.6%), became favorites. HPMC and PVP(5%) were the only favorites in the case of 57%-water CL on dry cornea and preserved mucin, implying a role of the reported non-Newtonian behavior of higher concentration of PVP and showcase the merits of HPMC as the only formulation that excelled in more than one scenario. None of the formulations could fit the extreme case of 57%-water CL on dry cornea with removed mucin.
This is a 2020 ARVO Annual Meeting abstract.