In-vivo and in-vitro ESI-TOF Lipidomic Analysis of Hydrogel Contact Lenses

Abstract

Purpose:: It has been previously reported that lipid deposition on silicone hydrogel lenses exceeds conventional lenses. The impact of this lipid deposition may have significance in understanding alterations in tear stability and lens surface wettability. The purpose of this study was to evaluate lipids doped for an extended one-week period on traditional hydrogel and silicone hydrogel contact lenses (etafilcon A, lotrafilcon B, and senofilcon A) using mass spectrometry and to compare these results to in-vivo data with the same lens types.

Methods:: In phase I, an equal molar (5mmol each) fatty acid amide doping solution (oleamide, steramide, myristamide, palmitamide, and euracamide) was made using HPLC grade chloroform/ saline. The chloroform was subsequently evaporated off under nitrogen gas. Out-of-package contact lenses were soaked for one week while on a rotator. In phase II, eight normal, successful extended wear contact lens patients wore the three lens types for one week each. Lipids were extracted from the lenses and analyzed by Micromass LCT mass spectrometry equipped with an orthogonal electrospray source (Z-spray) operated in positive ion made. The doping solution was analyzed alone for comparison in phase I.

Results:: Analysis of the artificial doping solution and lenses showed the following [M+Na] values: myristamide at m/z of 250.1, palmitamide at m/z of 278.1, oleamide at m/z of 304.1, stearamide at m/z of 306.1, and euracamide at m/z of 360.1. Oleamide was the most abundant fatty acid amide present on all contact lenses (average relative peak intensity vs. doping solution 98.5%).The rank order of lipid deposition (greatest to least) was as follows: oleamide >> erucamide > myristamide > palmitamide > steramide. Total lipid assessment demonstrated the least amount of lipid deposited on etafilcon A (139843 average intensity peak count) < lotrafilcon B (2183863 average intensity peak count) < senofilcon A (241865 average intensity peak count). In-vivo data demonstrated primarily oleamide deposition, which is consistent with the distribution of fatty acid amides in the tear film.

Conclusions:: This data indicates that silicone hydrogel lenses are likely to deposit more fatty acid amides, primarily oleamide, than traditional hydrogel lenses in-vivo and in-vitro. The impact of this deposition on tear stability and lens wettability need further exploration.

Keywords: contact lens • lipids • cornea: tears/tear film/dry eye