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Hendrik Walther, Lakshman Subbaraman, Lyndon W. Jones; In Vitro Dehydration of Daily Disposable and Silicone Hydrogel Contact Lens Materials. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6121.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the in vitro bulk dehydration of various daily disposable (DD) and silicone hydrogel (SiHy) contact lens materials.
Four conventional hydrogel (CH) DD (hilafilcon B, nelfilcon A, omafilcon A, etafilcon A), four SiHy DD (delefilcon A, narafilcon A, narafilcon B, filcon II 3) and seven SH frequent replacement (FR) (balafilcon A, lotrafilcon A, lotrafilcon B, comfilcon A, enfilcon A, senofilcon A, galyfilcon A) contact lenses (n=3) were removed from their blister packs and dehydration analysis was performed gravimetrically (Sartorius MA 100H). Wet weights were measured immediately after removing the lenses from the blister pack and dry weights were determined after lenses were dried for 2 min, using a 600W microwave. In addition, lens materials were continuously assessed for water loss over a 20 min time period at 22°C and 34°C.
There was a significant reduction in the water content (WC) over time for all the tested lens materials (p<0.01). Overall, SiHy lenses exhibited slower rates of dehydration than CH lenses. Among the DD lenses, delefilcon A (the DD lens with the lowest WC) displayed the lowest dehydration (31.9±1.7% at 22°C and 29.4±0.8% at 34°C). The higher WC materials showed the highest amount and fastest rate of dehydration (p<0.01). Among the SiHy FR materials, lotrafilcon A showed the least amount (23.3±2.9% at 22°C) and slowest rate of dehydration, although it was not statistically significant (p>0.05) compared with lotrafilcon B and senofilcon A. Comfilcon A (FR SiHy with highest WC) exhibited the highest amount (41.3±0.9% at 22°C) and fastest rate of dehydration (p>0.05). There was a good correlation between measured and manufacturer quoted values for WC (R2=0.99).
Bulk dehydration rates of contact lenses are closely related to the initial WC of the material. Lens materials with a higher WC dehydrate more and faster than low WC materials. Increasing the ambient temperature leads to a reduction in the rate of dehydration for some lens materials. Further work is required to relate these in vitro dehydration rates to dehydration rates in eye.
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