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Medical Forum / General / Vision / April 2005Lens Material - Again
sphere/cyl/axis -5.25 -.50 50 -5.25 -.75 105 Went with Pentax 1.67 (vanity!), but now struggling to focus with indoor lighting and mid distance objects (3-25 ft.) found in an office setting. Outdoor distance vision and reading seem decent, but the “sweet spot” peripherally seems even slimmer than my older polycarb lenses. Lens and perscription have been double checked. Can chromatic aberration be coming into play? Better suggestions on lens material (brands) for a remake? Thanks, Stan > sphere/cyl/axis > -5.25 -.50 50 [quoted text clipped - 10 lines] > > Thanks, Stan Can you see better if you move your frame around on your face? This would be an indication of a poor fitting (fitting height/PD not measured properly or lens not placed properly in the frame). Also, try one eye at a time. Also, do you have Proceed or Proceed II Short model of lens? Is you Rx stronger than before? (this exaggerates distortion problems, especially if the add power is stronger). You didn't say what your old lens design was (manufacturer and model). For example, Varilux Panamic or Rodenstock Multigressiv2, etc. Polycarb has an abbe value of 30, and Seiko 1.67 has an abbe value of 32 (slightly better). Mark thanks, The lenses seem centered (confirmed by optician). My right eye is giving me more trouble having gone from a -5.0 to -5.25, the left eye is adjusting better to an axis change of 124 to 105. Previous lenses were Featherweights – not exactly stellar optics, Stan >sphere/cyl/axis >-5.25 -.50 50 [quoted text clipped - 10 lines] > >Thanks, Stan Stan, Problems with office lighting could be due to the absence of an anti-reflection coating. Incorrect lens positioning will reduce acuity at all distances, on-axis or off-axis, for reasons unrelated to transverse chromatic aberration. So changing the lens material will not necessarily improve the vision. Since the Rx and lens powers have already been checked, it's now time to measure the vertical and horizontal monocular PDs (distance between pupils), vertex distance (eye to lens), panto (lens tilt), and BC (front lens curve). My guess is that the vertical OCs are too low with the lenses resting too far from the eyes. Hope this helps, Robert Martellaro ~~~~~~~~~~~~~~~~~~ Optician/Owner Roberts Optical robopt@execpc.com ~~~~~~~~~~~~~~~~~~ "An expert is a person who has made all the mistakes that can be made in a very narrow field." - Niels Bohr Thanks Robert, The lenses are AR coated and they adjusted panto tilt to match my previous frame. I've been in them almost two weeks and my right eye always feels over "amped" by noon. I will have the vertical OCs checked. Secondly, the new frames and lenses are a different shape from the last few frames (Rectangular, less deep, wider lenses) so perhaps I haven't adjusted for the extra head movement required. My wife loves the style, but I'm thinking of backing off to a more familiar feel. If I do change, what type of lense would you recommend (fashion giving way to optics) in order to reign in some of the variables? Stan This site is down. I'm trying to reply, but Google is timing out.. >Thanks Robert, > [quoted text clipped - 11 lines] > >Stan Stan, A less complex lens design will help, but that's like saying it's safer to drive drunk on a six lane road instead of a two lane road because there is more room to weave and avoid the ditch. If your present 1.67 lens is aspheric, try a "finished" non-aspheric 1.67 from Essilor. However, I would strongly recommend a second opinion on the fit. Hope this helps Robert Martellaro ~~~~~~~~~~~~~~~~~~ Optician/Owner Roberts Optical robopt@execpc.com ~~~~~~~~~~~~~~~~~~ "An expert is a person who has made all the mistakes that can be made in a very narrow field." - Niels Bohr Robert thanks for the advice. I had the lens position double checked today by another optician I trust (turned out ok). They suggested going back to a non-aspheric design as well, preferrably somthing with a higher abbe value. Stan |
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