Disadvantages of Hydrogel Contact Lenses

 Hydrogel contact lenses consist of interconnected polymers.
Hydrogel contact lenses, also known as soft contact lenses, consist of superabsorbent, interconnected polymers. As of 2010, there are two main types of these lenses on the market: traditional or HEMA lenses, which contain the compound 2-hydroxyethyl methacrylate, and silicone hydrogel lenses, which use silicone instead. Both types of hydrogel lenses have advantages over their hard counterparts, known as RGP (rigid gas permeable) contact lenses. However, they also have several disadvantages.

According to Jorge E. Roldan, when he was in the Department of Biological Sciences at Louisiana Tech University in 2003, hydrogel contacts have low mechanical strength, meaning that they cannot easily withstand the application of outside forces. So when you try to pick up a hydrogel lens with your fingers, it will often temporarily lose its shape, and in a worst-case scenario, it can tear. This makes them considerably more difficult to handle in comparison to their hard counterparts. Handling problems cause the insertion and removal process of hydrogel contact lenses to take longer and can also cause you to accidentally drop a lens.
While silicone hydrogel lenses tend to allow for sufficient air permeability, the traditional hydrogel varieties do not. According to a 2004 article by Robert B. Steffen and Kevin P. McCabe in Contact Lens Spectrum, a common problem with traditional hydrogel lenses is that they do not let in enough air. This can cause your contacts and eyes to feel dry after long periods (throughout a day), and in worst-case scenarios, can cause corneal edema. According to Innvista, corneal edema is your body’s response to excessive dryness of the eye and is associated with the soaking of the cornea with fluids. These fluids can cause blurred vision, halos around lights, and eye pain.
Silicone hydrogel contact lenses, despite their high levels of air permeability, perform poorly when it comes to contamination, and are more likely to cause infection than their traditional counterparts. According to Robert B. Steffen and Kevin P. McCabe's 2004 article in Contact Lens Spectrum, possible problems that can result from contamination of silicone hydrogel lenses include the formation of superior epithelial arcuate lesions (SEALs), which are splits in your eye’s epithelial, and contact lens–related papillary conjunctivitis (CLPC), a condition wherein the thin tissue known as conjunctiva swells in the white parts, or sclera, of your eye, according to E. Lawrence Bickford's article at The EyeCare Connection.
According to a document revised in 1999 (School of Optometry, University of Missouri–St. Louis), hydrogel contact lenses require sterilization chemicals that are more complex and thus more expensive than those required for hard contact lenses. Silicone hydrogel contacts in particular require a specialized—and expensive—surface treatment or coating in order for them to maintain their moistness.

2 comments:

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