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Medical Forum / General / Vision / June 20078 base lenses non corrective
I have a pair of sunglasses that have a star reflection that comes from sunlight being reflected form car windows, oncoming headlights,or other reflected sunlight. The manufacturer says that my eyes may be "8 base sensitive" I have several other quality sunglasses that do not exhibit this problem. Anyone ever experience this ? Foz On Jun 8, 7:43 pm, f...@bellsouth.net wrote: > I have a pair of sunglasses that have a star reflection that comes > from sunlight being reflected form car windows, oncoming headlights,or [quoted text clipped - 3 lines] > problem. Anyone ever experience this ? > Foz do you have other wrap-around sunglasses? are you "8 base sensitive" in these as well? On 6/9/07 7:32 AM, in article 1181399547.358426.252740@p47g2000hsd.googlegroups.com, "michael toulch" <michaeltoulch@hotmail.com> wrote: > On Jun 8, 7:43 pm, f...@bellsouth.net wrote: >> I have a pair of sunglasses that have a star reflection that comes [quoted text clipped - 7 lines] > do you have other wrap-around sunglasses? > are you "8 base sensitive" in these as well? What are "8 base lenses"? Is it a trade name? Bill -- Support the troops. Impeach Bush. Oh, I forgot about Cheney. >On 6/9/07 7:32 AM, in article >1181399547.358426.252740@p47g2000hsd.googlegroups.com, "michael toulch" [quoted text clipped - 16 lines] >Bill >-- Support the troops. Impeach Bush. Oh, I forgot about Cheney. It's the base curve or front curve of the lens measured in diopters. Higher numbers mean increased curvature. Interestingly, if there is no Rx, the back or ocular curve is very close to, but not equal to the front curve. Here's why... http://www.optiboard.com/forums/attachment.php?attachmentid=1837 In regards to reflections, I would check if the lenses have an anti-reflection coating. I would also look at the quality of the optics i.e., waves, warpage, unwanted prism and power etc. Robert Martellaro ~~~~~~~~~~~~~~~~~~ Optician/Owner Roberts Optical Wauwatosa Wi. ~~~~~~~~~~~~~~~~~~ "Science is a way of trying not to fool yourself." - Richard Feynman On 6/11/07 9:56 AM, in article kguq63d552pme3bskf617b176qv86d3lmf@4ax.com, >> What are "8 base lenses"? Is it a trade name? >> [quoted text clipped - 5 lines] > or > ocular curve is very close to, but not equal to the front curve. Here's why... Why not just call it a 125 mm or a 1/8 m sphere? Will that remove too much jargon from the practice of optometry? Bill  SignatureIraq: About three Virginia Techs a month > Why not just call it a 125 mm or a 1/8 m sphere? Will that remove too much > jargon from the practice of optometry? From the start, opticians used diopters because millimeters aren't additive. Lenses always have two surfaces and one must always a "base curve" in calculations or tooling. So you can't make lenses without a term that expresses '8 diopter base curve'. "8 base" certainly is jargon, but if the term didn't exist you'd need something else. What's twisty about the term "base curve" is that those who tool in minus cyl consider the front surface to be "base" and with the old tools made in plus cyl form the *back* surface was "base." -MT On 6/12/07 4:23 PM, in article Epidne-YQ55Ht_LbnZ2dnUVZ_hmtnZ2d@giganews.com, "Mike Tyner" <mtyner@mindspring.com> wrote: >> Why not just call it a 125 mm or a 1/8 m sphere? Will that remove too much >> jargon from the practice of optometry? [quoted text clipped - 15 lines] > > -MT How about a 8 diopter sphere? Bill SignatureIraq: About three Virginia Techs a month > How about a 8 diopter sphere? Dunno. He has a drawer of "8 base" lenses, a drawer of "6 base" and some "4 base" and perhaps a drawer of "2s". The more curved, the more distorted. "8-base-sensitive" is awfully jargonish but it's common usage if you're in the business. -MT >> Why not just call it a 125 mm or a 1/8 m sphere? Will that remove too much >> jargon from the practice of optometry? > >From the start, opticians used diopters because millimeters aren't additive. 1/f1 + 1/f2 = 1/f3 is a lot more awkward than D1 + D2 = D3. >Lenses always have two surfaces and one must always a "base curve" in >calculations or tooling. [quoted text clipped - 4 lines] >"8 base" certainly is jargon, but if the term didn't exist you'd need >something else. Radius of curvature in millimeters. >What's twisty about the term "base curve" is that those who tool in minus >cyl consider the front surface to be "base" and with the old tools made in >plus cyl form the *back* surface was "base." > >-MT With direct to surface freeform technology we can pretty much make the lens anyway we want, limited only by the software/point files. Robert Martellaro ~~~~~~~~~~~~~~~~~~ Optician/Owner Roberts Optical Wauwatosa Wi. ~~~~~~~~~~~~~~~~~~ "Science is a way of trying not to fool yourself." - Richard Feynman On 6/14/07 2:03 PM, in article 7u4373hek2u87q4jgp0l4huanah1jl40nt@4ax.com, >>> Why not just call it a 125 mm or a 1/8 m sphere? Will that remove too much >>> jargon from the practice of optometry? [quoted text clipped - 31 lines] > "Science is a way of trying not to fool yourself." > - Richard Feynman There are mathematical terms, called curvatures, that are the reciprocals of radii. The term curvature is usually used for curves in a plane but can also be used for surfaces. There is nothing preventing curvatures from being measured in diopters. Curvature and radius of curvature are discussed in almost any beginning calculus text. If you want to get fancier, look at a book discussing differential geometry. They discuss the osculating paraboloid that gives a best fit to a surface. There will be two radii of curvature and two curvatures (measurable in diopters) at the point of contact. If the two curvatures are different then there will, at a minimum, some (optometric) cylinder in the surface. This differential geometry approach will be applicable to aspheric surfaces as well. Bill SignatureIraq: About three Virginia Techs a month |
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