The impact of intermittent air exposure on lipid deposition.
OBJECTIVE
To analyze the impact of intermittent air exposure on the in vitro deposition of two radioactive lipids on various contact lens (CL) materials, using a custom-designed model blink cell.


METHODS
Six different CL materials (balafilcon A, lotrafilcon B, comfilcon A, senofilcon A, etafilcon A, and omafilcon A) were mounted on the model blink cell pistons, which cycled the lenses in and out of a complex artificial tear solution (ATS) that contained a trace amount of C-cholesterol or C-phosphatidylcholine. For the short-term experiment, air-exposed lenses were continuously cycled in and out of the ATS for 10 h. Longer term incubations for 6 days were tested with lotrafilcon B and balafilcon A materials incubated in C-cholesterol ATS. The air-exposed CLs were cycled for 14 h then submerged for 10 h each day. For both experiments, the control lenses were submerged for the entire test period. After incubation, lenses were processed, and deposited masses were quantified.


RESULTS
Exposure to air resulted in increased amounts of cholesterol deposited by 1.6 to 4.3 fold on omafilcon A, balafilcon A, comfilcon A, and senofilcon A (p ≤ 0.03) compared with submerged lenses. No differences in deposition were observed for etafilcon A and lotrafilcon B (p > 0.05). The longer term incubation of lotrafilcon B and balafilcon A showed statistically significant increases in cholesterol deposition for both air-exposed lens materials (p < 0.02) with the increase in deposition 1.8× and 2.8×, respectively. For phosphatidylcholine, all air-exposed lenses had increased masses of deposition. These deposits were statistically greater by 1.1 to 1.6 times for omafilcon A, comfilcon A, lotrafilcon B, and senofilcon A (p < 0.04), but not statistically different for etafilcon A or balafilcon A (p > 0.05).


CONCLUSIONS
This study found that lipid deposition profiles are CL material dependent and that intermittent air exposure can influence the mass of lipid deposited.
Centre for Contact Lens Research, School of Optometry and Vision Science, University of Waterloo, Waterloo, Ontario, Canada.
Holly
H
Lorentz
Miriam
M
Heynen
Warda
W
Khan
Diana
D
Trieu
Lyndon
L
Jones
D003263:Contact Lenses, Hydrophilic; D005136:Eye Proteins / Q000032:analysis*; D006801:Humans; D008055:Lipids / Q000032:analysis*; D013500:Surface Tension
D005136:Eye Proteins; D008055:Lipids