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Medical Forum / General / Vision / April 2004Contact lenses with cylinders
Hello to all. Don't know if I correctly typed, is there contact lenses with minus dioptry and cylinders, or this cylinders can only be setup on glasses. Btw can someone explain me what is this cylinder and what deffetc is that? Thank you. Soft contacts are called "toric" when they correct astigmatism. Ordinary soft lenses are "spherical" because they have the same power along every diameter. Real eyeballs aren't exactly spherical. Sometimes the refracting surfaces are shaped more like a football or the outer edge of a doughnut (torus-toric). The toric shape on the cornea can be matched with a toric shape in glasses or contacts, to make a toric lens clearer than a spherical one. But the lens has to be held at a certain orientation. If you fold your glasses up and look through one lens at different orientations, people with astigmatism see blurry if their glasses are turned vertical. Contacts, too. Toric contacts are only clear in one orientation and finding a brand and shape to stay in place can be tricky. Actually, toric lenses are clear in two orientations. Can you see why? -MT > Hello to all. > [quoted text clipped - 4 lines] > > Thank you. > Actually, toric lenses are clear in two orientations. Can you see why? Yes, unfortunately. :-( I have a buckle on my right eye (a strip of rubber sewn on the eyeball to fix a retinal detachment). Thus my astigmatism cannot be completely corrected with simple cylinder. I'm told that there is nothing else available. My vision isn't so great with that eye anyway, so I'm not so concerned.  SignatureDan Abel Sonoma State University AIS dabel@sonic.net I didn't explain that "cylinder" is a term for the _difference_ between the steepest and flattest curves on a toric surface. -MT > Hello to all. > [quoted text clipped - 4 lines] > > Thank you. >I didn't explain that "cylinder" is a term for the _difference_ between the >steepest and flattest curves on a toric surface. Thank you, I understand now, so If I turn my glasses verically I will not see that good as in horisontal way. And then yes, lenses can rotate by axis so there is no help. Thank you. > And then yes, lenses can rotate by axis so there is no help. Toric contacts do sometimes rotate on the axis so that they don't work. However, they are weighted on the bottom so they generally stay in position. I have worn torics for years. You put them in and then blink a few times. Before you blink your vision is blurry. After blinking a few times things come into focus better. SignatureDan Abel Sonoma State University AIS dabel@sonic.net > > And then yes, lenses can rotate by axis so there is no help. > > Toric contacts do sometimes rotate on the axis so that they don't work. > However, they are weighted on the bottom so they generally stay in > position. Dan, there are dynamic stabilized toric contactlenses to, contactlenses which are wedge shape tapered (thinner) in a straight line at the top and bottom. Due to the pressure of the eyelids they are forced keep stable in a more or less horizontal position. I.e the Acuvue toric soft lenses. Furthermore there are contactlenses with a toric shaped backcurve which are falling in place on the opposite toric shape of the cornea ( simple explained ) Jan (normally Dutch spoken) I have worn torics for years. You put them in and then blink a > few times. Before you blink your vision is blurry. After blinking a few > times things come into focus better. |
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