Qualitative and quantitative characterization of the in vitro dehydration process of hydrogel contact lenses

Abstract

DR curves under the conditions of the present study can be described as a three-phase process. Phase I consists of a relatively uniform DR with a duration that ranges from 10 to almost 60 min and is strongly correlated with the EWC of the polymer as it is the CD during this phase. Overall, HEMA-based hydrogels dehydrate to a greater extent and faster than silicone-hydrogel materials. There are differences in water retention between lenses of similar water content and thickness that should be further investigated.

Influence of environmental factors in thein vitrodehydration of hydrogel and silicone hydrogel contact lenses

“…Its scale was capable of measuring up to 0.0001 g. After taking the lens from the blister, the excess water was gently removed by blotting with a Resma filter paper (Filtros Anoia, Barcelona, Spain). The CLs were then placed on a convex plastic in order to simulate the lens on the ocular surface with only the anterior surface directly exposed to air . The maximum time between taking away the CL from the blister and its weighing was 15 seconds in order to minimize dehydration before obtaining the first reading.…”

“…The parameters derived from the dehydration exhibited by the CLs were expressed as dehydration rate (DR) and valid dehydration (VD) …”

Alginate nanohydrogels prepared by emulsification-diffusion method

“…For these reasons, polymeric hydrogels have been used as scaffolds in tissue engineering, [13][14][15] sustained-release drug carriers, [16][17][18] biosensors, 19,20 and contact lenses. 21,22 Alginate is probably one of the most frequently studied hydrogel-forming polymers. Alginate is a representative biocompatible natural polymer which is a linear copolymer of (1,4)-linked β-D-mannuronate and its C-5 epimer α-Lguluronate residues.…”

Mapping micromechanical properties of soft polymer contact lenses

“…Topography images clearly show residual structural lines for all lens materials except Comfilcon A. These lines are usually attributed to mold defects, which are transferred to the lens surface during cast molding [47]. Despite the fact that all four lens types were manufactured by cast molding, Comfilcon A material does not show a characteristic web-like structure of linear defects.…”