Contact lenses silicone-hydrogel

Various fluoroalkyl SAM molecules were incorporated in silicone hydrogel contact lens formulations to evaluate their effect on silicone hydrogel lens surface compatibility with tear fluid [47-49). The clinical measures of compatibility were wettability and deposition as described in the experimental section. Typical clinical results in Table 6 showed that the presence of SAMs at the lens surface had a positive effect on lens performance. Both the wettability by tear fluid and deposition from tear fluid were improved by the presence of the SAMs in the hydrogel lenses. However, the desired performance levels of 3.9 wettability and <0.1 deposition were not achieved. 

Dracopoulos, A. In vitro assessment of medical device toxicity Interactions of benzalkonium chloride with silicone-containing and p-HEMAcontaining hydrogel contact lens materials. Eye Contact Lens... 

N. Efron, and P.B. Morgan, Trends in use of silicone hydrogel contact lenses for daily wear. Contact Lens Anterior Eye, 31, 242-243,2008. 

Kiinzler, J. Ozark, R. Low Modulus Fluorosiloxane-Based Hydrogels for Contact Lens Application. In Silicones and Silicone-Modified Materials Glarson, S. J., Fitzgerald, J. J., Owen, M. J., Smith, S. D., Eds. AGS Symposium Series 729 American Chemical Society Washington, DC, 2000 pp 296-307. 

While the silicone polymer phase provides a high enough oxygen permeability, it also dominates the surface characteristics, i.e., the surface of silicone hydrogel is too hydrophobic to be used as a contact lens. The silicone phase also readily absorbs... 

Ophthalmologic Intraocular lens Contact lens Corneal bandage Poly(methyl methacrylate) Silicone-acrylate, hydrogel Collagen, hydrogel... 

Silicone Hydrogels. A new class of hydrogels based on silicone has been developed (14). These materials were developed in an attempt to combine the high oxygen permeability of polydimethylsiloxane and the excellent water absorption characteristics of conventional non-silicone hydrogels. This new class of hydrogels was developed primarily for contact lens application. These silicone hydrogels are also prepared by free-radical poljnnerization techniques. 

As one can see from Eq. 6, the permeability of a soft contact lens is directly proportional to its water content (Figure 5.53). Whereas the moisture content of early PHEMA lenses was only ca. 35%, more recent silicone-based hydrogels contain up to 70% water. Though hydrophilic lenses are able to absorb water and permit extended wear without comeal irritation, an increase in water content also corresponds to lower mechanical strength that may result in tearing/scratching. 

So-called soft contact lenses are actually made from a polymer hydrogel with a composition of up to about 50% water (the older hard lenses were a solid piece of plastic). If you are a contact lens wearer, you will know what happens when you leave a soft lens to dry out it shrinks and becomes hard like plastic. Dried up lenses will regain their former shape if soaked in water as the polymer network swells and refills with water. Some of the most current contact lens technologies, such as overnight or continuous wear lenses, are based on silicone hydrogels (polymers with a silicon backbone). 

Silicone Hydrogels Materials for Contact Lens Applications... 

Keywords Biocompatibility, contact lens, silicone hydrogel, hydrophilic polymers... 

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