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Medical Forum / General / Vision / December 2005100, 120 and other super high plus diopter lenses? WOW!
http://www.msiprecision.com/catalog/images/OI-100M.jpg http://www.msiprecision.com/catalog/images/OI-120M.jpg http://lpoproducts.com/Products/images/LPO189.jpg I never knew it was possible to make such high plus diopter lenses! I researched into this when my ophthamologist used a +90 diopter lense to look in my eyes. That thing was nearly spherical not unlike a marble! If one were to look into a lens with a dioptric value higher than the axial length of your eye, would light focus *outside* your eyeball? I know an emmetropic eyeball is +60 diopters and placing a plus lens makes light focus in front of the retina but as long as the lens is less than +60 light would come to a focus still inside your eye. How do the optics of a lens higher than +60 work if light now comes to a focus *outside* your eye? Would there be a difference between a +66, +78, +90, +100 or even +120? Would light of a super high plus come in focus at a point still inside the lens? Or right after it finishes traveling thru the lens? Would you be able to see clearly from 1cm away from your eyeball itself or 1cm away from the surface of the plus lens when its held to your eye? How high can plus lenses get really? > If one were to look into a lens with a dioptric value higher than the > axial length of your eye, would light focus *outside* your eyeball? Yes. The real, inverted image forms between the lens and the observer. This very common technique is called indirect ophthalmoscopy. Would there be a difference between a +66, +78, > +90, +100 or even +120? Yes. Image size and field of view. +20 D. lenses are only used with an opthalmoscope, 78 and 90 are only used with a slit lamp. Thanks! So if one were to look thru say a +120d lense, would he be seeing everything upside down? Also whats the difference between dioptric value and magnification times? Take a magnifying glass lens thats marked as 10x for example or a microscope eyepiece marked as 10x, 15x, 20x or so? What dioptric value would such lenses have? > Thanks! So if one were to look thru say a +120d lense, would he be > seeing everything upside down? Yes, and it doesn't need to be that strong. You get the same effect if you hold any plus lens farther away from your eyes than it's focal length. > Also whats the difference between dioptric value and magnification > times? Take a magnifying glass lens thats marked as 10x for example or > a microscope eyepiece marked as 10x, 15x, 20x or so? What dioptric > value would such lenses have? approximately 4 D. per x mag. applies to single lens systems, with microscopes or other multiple lens systems you have to multiply the components. (gross simplification/approximation) You get the same effect if > you hold any plus lens farther away from your eyes than it's focal length. (providing the object viewed is also beyond the lenses' focal length) On 12/30/05 7:41 AM, in article 1135957294.960703.261070@g47g2000cwa.googlegroups.com, "acemanvx@yahoo.com" > http://www.msiprecision.com/catalog/images/OI-100M.jpg > http://www.msiprecision.com/catalog/images/OI-120M.jpg > http://lpoproducts.com/Products/images/LPO189.jpg What is the purpose of such lenses? Certainly, a 100D or even a 200D lens is not all that difficult to get if the numerical aperture (or f/no.) is not a problem. It is done for microscope lenses all the time. Bill -- Ferme le Bush > What is the purpose of such lenses? Certainly, a 100D or even a 200D lens is > not all that difficult to get if the numerical aperture (or f/no.) is not a > problem. It is done for microscope lenses all the time. In eye exams, +90 D lenses are used (although 78 is more common) in conjunction with a slit lamp biomicroscope to get a nice, although inverted, binocular view of the retina. Useful especially for fine 3-D viewing of the macula. I can't think of any use for 100 D or more single lenses. w.stacy, o.d. |
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