Does anyone know where to get periscope eyeglasses, and also where to get more information about fitting them?
Does anyone know where to get periscope eyeglasses, and also where to get more information about fitting them?
Last edited by smallworld; 10-25-2016 at 08:23 AM.
What is reality but a concept unique to each of us? Can anything be classed as real when our perceptions differ greatly on so many things? Just because we see something a particular way does not make it so.
if you mean "periscopic" you might want to check out "Bed Specs."
Yes, like that, but with a prescription lens. I've only seen a pair once in my life for a patient with extreme kyphosis.
What is reality but a concept unique to each of us? Can anything be classed as real when our perceptions differ greatly on so many things? Just because we see something a particular way does not make it so.
About 15∆ of yoked base up prism will bring objects lower towards the straight-ahead gaze.Originally Posted by smallworld
Hope this helps,
Robert Martellaro
Science is a way of trying not to fool yourself. - Richard P. Feynman
Experience is the hardest teacher. She gives the test before the lesson.
The amount of prism and the material used will dictate how much deviation you'll be inducing. As Robert pointed out, yoked base up would move object down, base down, just the opposite. To figure out how much displacement you will be inducing you can use the deviating approximation formula;
DA = a X (n-1)
Where;
DA = deviated angle
a = apical angle
(n-1) = refractive index of prism material
15 diopters of prism in crown glass gives us;
15 x (1.523 - 1 ) =7.84 degree of angle change as opposed to using 1.67 high index;
15 x (1.67 - 1 ) = 10.05 degree of angle change
This approximation formula starts losing some accuracy above 15 D of prism, but it's close enough for horseshoes when figuring out angle change.
Fresnel's should be on the table if you need more deviation than can be ground into your primary lenses. Keep in mind though that there will be a loss of acuity due to LCA's with high prism amounts and/or low abbe materials like poly.
I meant to also add that Fresnel's are made of poly (vinyl chloride) with an index of 1.54. The highest amount of prism available today is a 40D which would have a 21.6 degree of angle change (approx.)
If the patients back is so severely humped that their primary gaze is directly at the floor, I don't think the prism would help at all. Also my patient is still driving, so I'm not sure what options we have. I'm guessing it's not common anymore for a patient with this medical condition to wait until almost 80 to see their first medical and eye doctor in their life.
What is reality but a concept unique to each of us? Can anything be classed as real when our perceptions differ greatly on so many things? Just because we see something a particular way does not make it so.
I agree. No conventional/Fresnel is gonna help while on her feet. In a sitting position she's probably ok with driving/ watching tv, ect.
Try Epic Labs...
http://epiclabsinc.com
They may be able to mount a prism/mirror, similar to what is used for 'Bed Specs'.
Hope this helps,
Robert Martellaro
Science is a way of trying not to fool yourself. - Richard P. Feynman
Experience is the hardest teacher. She gives the test before the lesson.
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