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H.I. Lorentz, R. Rogers, L.W. Jones; In vitro Deposition of Lipid Onto Contact Lens Materials Can Lower Contact Angle Wettability of Surface–Modified Silicone Hydrogel Contact Lens Materials . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2389.
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© ARVO (1962-2015); The Authors (2016-present)
To analyze the effect of in vitro lipid deposition on conventional hydrogel (CH) and silicone hydrogel (SH) lens wettability, assessed by contact angle (CA) measurement.
Five SH (balafilcon [BA]; lotrafilcon A [LOA]; lotrafilcon B [LOB]; galyfilcon [GA]; senofilcon [SE]) and 4 CH materials (etafilcon [ET]; omafilcon [OM]; alphafilcon [AL]; polymacon [PO]) were doped with two different lipid doping solutions (LDS) containing cholesterol, oleic acid, and oleic acid methyl ester. The concentration of the lipids in the LDS was approximately 2.5x and 30x that seen typically in the eye. Lenses were soaked in the two LDS types for 2 or 5 days and compared with lenses soaked in Phosphate Buffered Saline (PBS) only. After soaking, advancing CAs were measured on a customized computerized device using a sessile drop method.
Compared with PBS, CAs for BA, GA and SE were unaffected by soaking in the LDS, with typical CA values of >95° (p>0.05). The surface–treated SH materials (LOA; LOB) both exhibited markedly reduced CAs after lipid exposure, with the 30x LDS reducing the CA to <5° (p<0.01). The CH materials all exhibited lower CAs after soaking, with values typically decreasing to 35°, which was significantly lower than that seen with PBS (p<0.01).
Exposure to lipid may actually improve the wettability of certain SH and CH materials, particularly those SH materials that are surface–treated. This may help to explain why certain SH materials improve in comfort during the first few hours or days of wear. Further work is required to determine how long is required before the lipid contamination becomes deleterious rather than advantageous.
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