Deposition of cholesterol on contact lenses varies significantly between lens materials, reports a study in the January 2016 Optometry and Vision Science.1 Though silicone hydrogel (SH) materials are known to increase oxygen transport to the ocular surface, certain chemical components within these materials may also negatively impact wettability (and potentially patient comfort) if exposed to very high levels of lipids.2-4 To date, however, no study has investigated the degree to which daily disposable lenses uptake lipids—in particular, cholesterol.
Researchers at the University of Waterloo in Canada incubated three SH materials and four conventional hydrogel (CH) materials in an artificial tear solution containing radioactive C-labeled cholesterol. Each was submerged for two, six, 12 and 16 hours to simulate typical daily disposable lens wear times.
Results indicated both contact lens type and length of incubation were factors in the amount of cholesterol deposition. No significant difference in the amount deposited on the SH materials was observed; a difference did exist among the CH materials. Overall, however, SH materials deposited more cholesterol than CH materials.
These results suggest a number of things, the authors say. First, daily disposable patients who exhibit relatively heavy levels of lipids in their tears due to factors such as meibomian gland dysfunction may benefit from certain CH lens types, such as nelfilcon A and etafilcon A materials. Additionally, wearers who require higher oxygen transport but exhibit oily tears should be aware of potential wetting issues when wearing SH daily disposable lenses. However, the researchers point out that further study is needed to determine if the lipid profiles in question are in fact detrimental to lens wear, given their very low levels.
Other caveats: this study only considered one lipid type, cholesterol (many others are found in the tear film); the deposition of certain lipids could be beneficial to lens wear (as previously reported by the same group); and the amount of lipid deposited may not be as important as whether the lipids under investigation are oxidized or remain in their natural state.5
1. Walther H, Subbarman L, Jones LW. In vitro cholesterol deposition on daily disposable contact lens materials. Optom Vis Sci. 2016 Jan;93(1):36-41.
2. Jones L, Subbarman LN, Rogers R, Dumbleton K. Surface treatment, wetting and modulus of silicone hydrogels. Optician. 2006;232:28-34.
3. Maldonado-Codina C, Morgan PB. In vitro water wettability of silicone hydrogel contact lenses determined using the sessile drop and captive bubble techniques. J Biomed Mater Res A. 2007;83:496-502.
4. Read ML, Morgan PB, Kelly JM. Maldonado-Codina C. Dynamic contact angle analysis of silicone hydrogel contact lenses. J Biomater Appl. 2011:26:85-99.
5. Lorentz H, Rogers R Jones L. The impact of lipid on contact angle wettability. Optom Vis Sci. 2007; 84;10: 946-53.