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!dual!ptsfa!ski!dr From: dr@ski.UUCP (David Robins) Newsgroups: net.med Subject: Re: Contact lenses and astigmatism... Message-ID: <193@ski.UUCP> Date: Thu, 8-Aug-85 19:51:15 EDT Article-I.D.: ski.193 Posted: Thu Aug 8 19:51:15 1985 Date-Received: Mon, 12-Aug-85 05:31:15 EDT References: <3420@fritz.UUCP> <549@leadsv.UUCP> Organization: Smith-Kettlewell Institute, S.F., CA. Lines: 42 > In article <3420@fritz.UUCP>, pwb@fritz.UUCP (Phil Bonesteele) writes: > > Hello. I hope to glean some information from informed persons on the > > topic of contact lenses. > > The optometrist's opinion was that for my weak prescription, soft lenses > > wouldn't improve my vision all that much. But that gas permeable > > hard lenses would correct my mild astigmatism and still leave me with > > clear vision. ------------------- > I too have an astigmatism. A few years ago I got a pair of gas permeable hard > contact lenses and from what my optometrist told me, they have reshaped my > cornea. In normal wear they make the cornea conform to the lens and this > apparently permanently reshaped the lens. I don't know if an astigmatism > can be "cured" by this method, though. All rigid contact lenses "mould" the cornea through normal wear. If two surfaces meet, and one is softer (ie, the cornea), it "gives" and conforms to the spherical back surface of the contact lens. Howver, since gas-permable lenses are somewhat flexible, due to the plastics used, theis lens can warp; if it doesn't, the moulding occurs. Also, the degree of moulding is influenced by the lack of oxygen beneath the lens; thus, gas-permable lenses *may* cause less of this effect. In additon, the degree of moulding is influnced by one's own genetic makeup....some people have a tendency to warp, perhaps permanently. Some cases of acquired keratoconus, which is seen in non-contact lens wearers also, may occur at higher incidence with rigid contact lenes, especially if fitted too tightly. In the the second letter, above, there is an error. The contact len reshapes the cornea, not the lens (of the eye). Hopefully the reshaping is not permanent, which indicates something bad is happening. The usual moulding springs back in a few hours to a few weeks. (It is this prolonged effect that is aimed for by orthokeratologists; contact lens fitters who are TRYING to flatten or mould the cornea for a temporary better acuity.) -- ==================================================================== 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