Talk:Corrective lens

message: How about some historical information?  —Preceding unsigned comment added by 96.234.251.124 (talk) 15:08, 1 September 2010 (UTC)
replies: text: Historical information can be found on the glasses page and the contact lens page.Garvin  Talk 16:49, 2 August 2013 (UTC)
thread_title: History?

message: Some of the explanations need better wording and more accurate descriptions. Maybe someone more knowledgable can help in this regard.MichaelGoldshteyn 14:48, 8 September 2006 (UTC)
replies: text: I've tried with recent edits.  Are there specific areas that need attention now?Garvin (talk) 10:19, 13 January 2008 (UTC)
thread_title: Comments

message: The axis defines where the two powers (sphere and cylinder) are located. The sphere is almost always 90º from the cylinder. (This is regular astigmatism, which is by far more common than irregular astigmatism where separations are other than 90º).
This is garbage! A sphere has no axis (besides the optical axis which points normal to the lens surface or into the paper plane of the diagram referred to here). Irregular astigmatism is somewhat a misnomer by ophthalmologist, as in a wavefront sense, "regular" astigmatism is simply the lowest order even aberration (does not change sign on the opposite side of the pupil) that can be corrected by a "cylinder", anything that does not fit in that scheme and causes "blurring" is called "irregular" astigmatism by ophthalmologists, while more correctly, different (higher) orders of coma (odd symmetry), astigmatism (even symmetry) and even higher oder spherical aberrations can appear, but the irregularity here is not related to any orientational angle.
However, it is known that in a typical population, certain orientations of regular astigmatism are more common than other ones. Maybe this kind of irregularity was meant here, but it´s not the usual meaning of that term.  —Preceding unsigned comment added by 84.174.203.127 (talk) 22:26, 27 March 2008 (UTC)
replies: text: This comment raises some good points.  An effort should be made to describe things both in terms of physical optics and vision correction.  It is better to bridge these fields of study than to isolate them. Garvin  Talk 16:53, 2 August 2013 (UTC)
thread_title:  Sphere "axis", irregular astigmatism 

message: This qualification is necessary since best-form spherics are always[verification needed] better than aspherics for an ophthalmic lens application.
This cannot really be true in the strict mathematical sense, because mathematically, the spherical "best form" is only 
one special case of the a general "free form" surface. So, a "best form" is a restricted "free form" surface, hence, you 
reduce the number of available degrees of freedom to solve the problem at hand. With less number of free parameters, the result
cannot be better than a more general solution. However, for reasonable metriks, it is true, that a flatter "free form" is 
likely not as good as the more curved spherical "best form"! 195.127.179.227 (talk) 15:34, 30 January 2008 (UTC)
thread_title:  Best form vs. free form 

message: Reminder to editors: per Wikipedia:Manual of Style (trademarks), the trademark symbols ™ and ® should not generally be used in Wikipedia articles. Trademarked names are rendered using standard English text formatting and capitalization, without special marks or symbols. More info in the linked Guideline. --Srleffler (talk) 19:12, 15 June 2008 (UTC)
thread_title:  Trademarks 

message: Google results show that MR-10 is made by Mitsui Toatsu in Japan. Seiko seems to be using the MR-10 material. Shouldn't that be listed in the chart as opposed to leaving it blanc?24.83.148.131 (talk) 09:23, 21 June 2008 (UTC)
thread_title: Manufacturer of MR-10

message: This diagram from the section "Abbe number" was combined with the caption "The effect of changing the spherical form of the lens on chromatic aberration". The diagram is not of a lens with a differing "spherical form", it is a diagram of another lens type, an Achromatic lens, not talked about in the article. Fountains of Bryn Mawr (talk) 16:28, 13 October 2009 (UTC)
thread_title: Wrong diagram

message: Does anyone make achromatic eyeglasses to correct chromatic aberration at high lens diopters (+/- 10)? I am aware that these would look odd and be rather thick, but would also result in extremely good color acuity. DMahalko (talk) 02:09, 9 May 2010 (UTC)
thread_title:  Achromatic eyeglasses? 

message: There is something interesting that comes to mind, when discussing shattering of eyewear. Cathode ray tubes typically include a tensioned steel band around the front of the screen, which helps to strengthen the glass and support it during an impact event.
Could a tensioning band strengthen eyewear against blunt impact? Could lenses be made much thinner yet with a structural band around the outer edge?
For this to work the band would have to be so tight that it compresses the lens slightly, and probably would have to be separate from the eyeglass lens mounting.
DMahalko (talk) 07:01, 9 May 2010 (UTC)
thread_title:  TV / CRT implosion band? 

message: I see "−1.00 +0.25 x 180" in the text. Is that correct or is that a "times" symbol like this: "−1.00 +0.25 × 180"? —Ben FrantzDale (talk) 12:20, 2 September 2010 (UTC)
replies: text: Both are correct.  When handwritten, it is the same mark as the letter "x".  Digitally, most people type the letter "x" because it is easier.  The "times symbol" × is not inaccurate, though there is no multiplication that should be implied by its use.Garvin  Talk 17:00, 2 August 2013 (UTC)
thread_title:  Typography: x versus × 

message: The description & definition of the terms spherical, cylindrical, and axis, including having terms like 'meridian' etc., mixed in, is totally USELESS. Maybe if the reader is an optometrist and already understands the terms, it may make sense...but I am a physicist, I've studied and used optics (microscopes, telescopes, particle accelerators!), but the 'explanations' presented here make no sense, the terms are defined circularly. How about some drawings which clearly show the relationships of these quantities that any high school student (who has had geometry) can understand clearly?
As another reviewer said, a sphere has no axis (until you define it, or rotate it..). The terms are defined as someone working in the field would define them for incoming students, but there is no connection to fundamental mathematical definitions.  — Preceding unsigned comment added by 62.167.120.140 (talk) 13:49, 23 March 2013 (UTC)
replies: text: I'll take a look.  True, the terminology used is that of the optical industry.  I'll try to improve things a bit.  (See my answer above)Garvin  Talk 17:02, 2 August 2013 (UTC)
thread_title:  explanation of spherical, cylindrical, and axis TOTALLY UNCLEAR. 

message: I removed the following section:
===Aspheric===
Aspheric lenses are typically designed to give a thinner lens, and also distort the viewer's eyes less as seen by other people, producing better aesthetic appearance. Older texts may refer to lenticular lens polynomial designs, and advantages of curvatures that do not produce Scotoma, or a blind spot.
It was poorly written and not pertinent to the article; at least not in the location I removed it from.  An update to discuss the latest lens technologies and how they differ from the traditional types described could include some of this information about aspheric lenses.  If someone can improve the section, the information could be re-inserted into the article. Garvin  Talk 16:08, 2 August 2013 (UTC)
thread_title:  Aspheric section removed 

message: The term Corrective Lens applies to any form of corrective lens. (See the introductory paragraph of this article.)  The second half of the article discusses topics that apply only to spectacle correction (glasses).  I plan to incorporate that information into the glasses article and eliminate the redundancy here, as a link to the glasses article should suffice. Send a message to my talk page if you disagree.  Garvin  Talk 16:46, 2 August 2013 (UTC)
replies: text: 4 years later, this information still seems out of place, but the glasses article does not seem more suited to contain it.  Probably best to just leave all the technical stuff here and leave the glasses article as information about the societal importance of eyewear. Garvin  Talk 16:40, 27 October 2017 (UTC)
thread_title:  Proposal: Move information to [[Glasses]] 

message: I added the paragraph "Trivex was originally developed for the military, as visual armor. PPG Industries took the technology andadapted it for the optical industry. Trivex is a urethane based pre-polymer. PPG named the material Trivex because of its three main performance properties. The three main properties are superior optics, ultra light weight, and extreme strength." from the paper at triple w dot uccs.edu/~rtirado/trivex_lens.pdf . I did not change the glasses article. Just here, because I was not sure if copying a paragraph directly is allowed by Wiki.173.180.7.3 (talk) 12:17, 10 December 2013 (UTC)
replies: text: , something that would be useful is reliable sources that we can cite. For example, in this edit you mention that Trivex is or was used for fighter jet canopies. It would be great if there's a source for that, particularly if it reports the date it was created. Today I updated the Trivex section and had to guess at the 1994 date. The source I used says "Four years after CR 39's 50th anniversary"[http://www.eyecarebusiness.com/articleviewer.aspx?articleID=50369 and as CR-39 is reported as being developed in 1940 I guessed Trivex came out in or around 1994. That source also says it was "transparent armor".  FWIW, that source also has that PPG developed CR-39.  Is that true? Google for "transparent armor" term nothing that looked like a useful source. I did not try to chase down the connection between PPG and CR-39. --Marc Kupper|talk 21:44, 21 January 2017 (UTC)
thread_title: More Trivex Info

message: Should self correction have its own page? -- it is a subtopic to this page- but does not fit well with the others --- there is quite a lot of literature on the topic and I know at least one company selling them commercially.--Currystove3 (talk) 03:20, 11 February 2015 (UTC)
thread_title:  self correction own page 

message: An enormous amount of material is duplicated from this article on Glasses.  The content has diverged, and I am trying to merge carefully, but I just did the section "Ophthalmic material property tables" and accepted the content of the other article en masse because it looked more updated and it is difficult to check everything completely.  Editors of this article may wish to check this section for accuracy and check the edit history to see if any changes should be restored.  Thanks! -- Beland (talk) 19:16, 23 August 2016 (UTC)
thread_title:  Merging from Glasses 

message: This article could make it clearer how there are concave lenses and convex lenses and how one type of lens corrects short-sightedness and one type corrects long-sightedness (I can never remember which is which!) Vorbee (talk) 08:46, 23 October 2017 (UTC)
replies: text: Those topics are better discussed in Lens (optics), but perhaps links to that article would be appropriate. The reason I say that is that nearly all forms of corrective lenses are ophthalmic: a convex front surface and a concave back surface.Garvin  Talk 16:11, 27 October 2017 (UTC)
thread_title: Convex lenses and concave lenses

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