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Hendrik Walther, Lakshman N Subbaraman, Lyndon William Jones; . Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):6105.
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To develop a novel, in vitro model to determine pre-lens non-invasive tear breakup time (NIBUT) and to compare the NIBUT values of different daily disposable (DD) contact lenses (CLs) using this model.
Three silicone hydrogel (SH) (delefilcon A, somofilcon A, narafilcon B) and two conventional hydrogel (CH) (etafilcon A, nesofilcon A) DD lens materials were incubated in an artificial tear solution (ATS) containing a variety of proteins and lipids. A model blink cell (MBC) was utilized, in which the CLs were submerged in the ATS for 3 seconds (s) and exposed to air for 10 s, to mimic intermittent air exposure. CLs were taken out of the blister pack and the initial (T0) NIBUT was measured. Thereafter, breakup times (n=4) of the CLs were determined after 2, 6, 12, and 16 hours (h) of incubation. A corneal topographer (CA-100, Topcon Canada) was used to illuminate the lens surfaces and changes of the placido ring image on the lens surfaces were captured with a digital video camera (Canon-XA10).
Overall, NIBUTs ranged from 26.19 ± 5.79 s to 1.23 ± 0.13 s. When comparison was made between lens types (all time points pooled), nesofilcon A showed the longest NIBUT (p<0.001). At T0, CH CLs revealed significantly longer NIBUT (p≤0.001) than SH CLs. After 2 h, nesofilcon A showed the longest NIBUT, however, this was only statistically significant over delefilcon A (p≤0.001). After 6 h, nesofilcon A was significantly longer than all other CLs (p≤0.001). Etafilcon A showed a significantly superior NIBUT of 6.13 ± 0.36 s (p≤0.001) over all other CLs after 12 h. With a NIBUT of 3.6 ± 0.26 s, delefilcon A had the longest breakup time (p≤0.001) after 16 h of incubation, when compared to other CLs. Statistically significant (p≤0.05) changes of NIBUT within the lens materials varied between the examined time points. NIBUT decreased significantly (p≤0.002) between T0 and 2 h for all CLs, except for somofilcon A (p=0.728). NIBUT between T0 and 16 h was significantly lower for all CLs (p≤0.001).
A novel in vitro model has been developed which could be used to determine pre-lens NIBUT values. By using a MBC for lens incubation and by incorporating intermittent air exposure, it is possible to mimic CL wear, in vitro. NIBUT reduced gradually over time and varying levels of deposition on different CLs seem to impact the measured pre-lens NIBUT of various lens materials.
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