Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site ski.UUCP Path: utzoo!linus!philabs!cmcl2!seismo!lll-crg!qantel!ptsfa!ski!dr From: dr@ski.UUCP (David Robins) Newsgroups: net.med Subject: Re: Contact lenses Message-ID: <220@ski.UUCP> Date: Wed, 8-Jan-86 17:29:11 EST Article-I.D.: ski.220 Posted: Wed Jan 8 17:29:11 1986 Date-Received: Fri, 10-Jan-86 05:42:25 EST References: <640@wjvax.wjvax.UUCP> Organization: Smith-Kettlewell Institute, S.F., CA. Lines: 84 > A friend of mine, who has a pair of soft, daily wear, toric lenses tells > me that he uses distilled water to rinse his lenses after cleaning them > instead of saline solution in order to save money. I asked my fitter > about this was told that using distilled water, even for rinsing, would > damage the lenses by bloating them with water and increasing their size. > This strikes me as odd since saline is primarily water and since the > enzymatic solution which the lenses must be routinely soaked in is in part > composed of distilled water. > > What gives here? *Is* pure distilled water harmful to soft lenses, or does > my fitter have stock in a company that produces saline solution? Pure distilled water will swell the thickness of soft contact lenses, especially if they are soaked rather than rinsed. This can make the lenses uncomfortable by temporarily changing the curvature. Also, the lenses may adhere to the eye, resulting in a corneal abrasion. Repeated cycling of the lens in this manner can permanently disrupt the plastic structural bonds, ruining them. However, some contact lens specialists are recommending rinsing, after the application of lens cleaner, under running tap water; they say this removes the viscous cleaner more easily than bottled solutions, without causing permanent damage. This is followed by heat sterilization in saline, or cold sterilization in hydrogen peroxide solutions. Note that the lenses are not soaked in water. Enzyme tablets are usually dissolved in saline, not water. The most important factor here is that any RINSING solution *AFTER* the lens is sterilized, should be sterile also. Distiller water, out of the bottle, is *NOT* sterile. Many corneal ulcers have been attributed to the use of home-made saline used to rinse lenses after sterilization. It is fine to use the home-made saline to rinse lenses after cleaning, but before sterilization. No rinsing should be needed after sterilization, but if the case arises, the now-sterile saline in the lens case can be used, or a commercial sterile (preferably non-preserved) saline can be used. Saline tablets are very cheap- rinse with home-made saline, rather than just distilled water. > I have also run into a number of people who wear their daily wear lenses > as if they were extended wear lenses, siting that the only difference between > the two types of lenses is thickness (and not a very significant difference). > I wouldn't mind leaving my lenses in over night once in a while, but all > those warnings that I read about my eyes falling out if I don't clean them > every day keep me from trying. The chief difference is the oxygen permeability of different contact lenses. Extended-wear lenses are more permable, due to high-permability polymer, high water content, or extreme thinness. The Bausch & Lomb O-series lenses were introduced originally as a daily-wear lens, being 1/4 thickness of the original thicker lenses. (the U-series lens is about 2x as thick as the O-series.) They found that the O-series had enough oxygen permeability for extended wear use. This in not true of all soft lenses. Many have insufficient permeability for extended-wear, and could lead to painful, temporary problems such as corneal edema or corneal abrasions with lens adherence. The reason is that with the lids closed at night, less oxygen is available for transmission through the lens. In additions, the lacrimal system produces less tears at night, and less oxygen is carried under by tears. Also, since much less lens movement occurs at night, there is more tendency for adherence to occur. A more subtle problem, if the lenses are not painful, is neovascularization of the corneal. In response to chronic oxygen deprivation, new tiny capillaries grow in from the limbus (edge of the cornea). Some of this occurs in many contact lens wearers; significant (over 1-2 mm.) growth is an indication for discontinuing the lenses. -- ==================================================================== David Robins, M.D. Smith-Kettlewell Institute of Visual Sciences 2232 Webster St; San Francisco CA 94115 415/561-1705 {ihnp4,qantel,dual}!ptsfa!ski!dr The opinions expressed herein do not reflect the opinion of the Institute!