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Medical Forum / General / Vision / January 2005Why are prisms badly tolerated by patients?
Hi all, Several times I read that prisms are not tolerated well by strabismus patients. I wore them too and did not feel comfortable. But I can't exactly pinpoint the reasons. Does anyone know why prisms are not tolerated?? Peter > Hi all, > [quoted text clipped - 4 lines] > > Peter I haven't found that to be the case. Sometimes, people with strabismus have a form called non-commitant strabismus, where there is a paralysis or paresis of one nerve or muscle. This causes the deviation to be variable depending on the position of gaze. In other words, the eyes may deviate quite a bit when looking down and to the right, but not up and to the left, etc. The value of the prism in the eyeglasses, on the other hand, is constant. Prescribing prism is something of an art, or at least a practiced skill. DrG DrG, Thank you for the reply. As I come to think about it, yes, the cause of my discomfort is this variability. Are there progressive prisms on the market - e.g. 5 prisms gradually growing to 10 prisms all in one lens? Could that be the solution? What about the distortion of images associated with prisms? Best regqrds, Peter > > Hi all, > > [quoted text clipped - 17 lines] > > DrG >What about the distortion of images associated with prisms? Trans chromatic aberration may be high enough, depending on the degree of prism and the strength of the Rx, to induce color fringing and blur. This can be minimized by using higher abbe value lens materials like standard plastic and crown glass. Hope this helps Robert Martellaro ~~~~~~~~~~~~~~~~~~ Optician/Owner Roberts Optical robopt@execpc.com ~~~~~~~~~~~~~~~~~~ "Science is a way of trying not to fool yourself." - Richard Feynman |
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