Disposable lenses

Clinical experience has shown that certain types of lens materials are more prone to deposit problems. In general, lenses with negatively charged moieties at the surface accumulate greater amounts of lysozyme, the principal tear film protein (10). The introduction and use of disposable lenses make these deposits and their clinical problems less significant. 

In addition, assessment of the patient s contact lens cleaning regimen is also important. Cleaning regimen, once a critical component to lens care, has been eliminated with daily disposable lens replacement and has evolved with frequent lens replacement. Daily cleaning is essential, and when applicable, disinfection with a hydrogen peroxide system may still be an important consideration.The use of enzymatic cleaning has diminished because disposable lenses have replaced the need for it, but it may be a consideration in select cases. 

Leahy, C. D., Mandell, R. B., and Lin, S. T., Do disposable lenses solve the problems of extended wear Contact Lens Spectrum, April (1989). 

In particular, the lathe cut method (1) makes it possible to manufacture a lens with special curvature, this allows a high value-added lens specifically tailored to the user to be made. On the other hand, the direct method is suitable for mass production and is particularly suited for daily disposable lenses. Unfortunately, the current polymerization technique still has residual monomer and less molding precision than desired. 

The popularity of the disposable lens concept is expected to continue, and the future should bring about lenses having enhanced clinical performance combined with the convenience of disposabdity. 

Contact lenses come in a wide variety there are soft lenses and hard lenses there are some you can wear night and day for a month or more, and disposable ones that you need wear only for a day there are lenses that let your eyes breathe there are bifocal lenses and there are even lenses to correct astigmatism, a condition of the lens of the eye which makes everything seem blurred. All are products of years of research by chemical companies like Novartis, Ciba Vision, and Wesley Jessen. There are even coloured lenses that can make blue eyes bluer, and sport lenses that enable tennis players to keep their eye on the ball by enhancing the colour of a yellow tennis ball relative to its surroundings. 

Smewski ME, Kracher GP, Gottsch JD, Stark WJ. Use of the disposable contact lens as a bandage contact lens. Arch Ophthalmol 1991 109 318. 

All ages and both genders may be affected. Although study results vary widely, 3% to 15% of rigid lenses wearers and 5% to 10% of soft contact lens wearers are reported to develop GPC. Eighty-five percent of GPC occnrs in hydrogel lens wearers.The incidence of GPC is lower in those wearing disposable versus conventional contact lenses and is lower with more frequent versus less frequent lens replacement. 

The management of GPC depends on the severity of symptoms. Management includes frequent lens replacement or disposable contact lenses, appropriate contact lens cleaning, and vigilant monitoring of contact lens wearing time. Medical management includes use of mast cell stabilizers, topical NSAIDs, and steroids. 

Soft lenses are made of hydrophilic hydrogel polymers that contain 36-74% water. Other plastics and copolymers are added to alter the physical characteristics of the lens. The diameter is 10.5-15.5 mm and the thickness at the center 0.03-20 mm. Soft lenses can correct most optical defects, including myopia, hyperopia, and astigmatism. Bifocal lenses are also available. They can be colored with either transparent hnes or opaque patterns to change apparent eye color or to mask malformations of the cornea or iris. They are available for daily, weekly, and twice-weekly disposable nse, 1-3 months frequent replacement, and annual replacement. 

Peterson, R.C. Wolffsohn, J.S. Nick, J. Winterton, L. Lally, J. Clinical performance of daily disposable soft contact lenses using sustained release technology. Cont. Lens. Anterior Eye 2006, 29 (3), 127-134. 

The importance of clean cuvettes is self-evident. Routinely, all non-disposable cuvettes should be emptied immediately after use, rinsed repeatedly in the solvent (e.g. water), then with clean ethanol or acetone and dried with low pressure air or nitrogen from a cylinder. It is prudent to install a filter (such as those with pore sizes of 0.45 pm used in filter sterilization) in the gas line. Cuvette washers (e.g. Aldrich) wash, rinse, and dry cuvettes. Cotton wool buds can also be usefiil for dislodging interior, stubborn marks and for drying. The outside optical surfoces should be polished with clean lens tissue. Note that plastic squeety bottles generally used for solvents contain plasticizers such as butyl phthalate, which can interfere with critical UV spectra. 

Skin <1 month Fixation, adjusting eyesight Adhesive bandage, disposable contact lens Acrylic adhesive, etc. polyvinyl alcohol, poly (2-hydroxyethyl methacrylate), etc. 

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