Talk:Progressive lens

Discussion

The article includes a discussion, which I've taken the liberty of moving here. I shall rewrite the discussion in the article into a paragraph intended to present an overview.

Industry practitioners perfer not to use the term "distortion" when describing the useless area of a progressive lens. Instead they will often opt for the following terms: surface astigmatism, aberration, blended areas, sand, soft focus, image swim, blurring, less clear, and my personal favorite, peripheral transition areas. Make no mistake however, if you have a strong prescription, you will be moving your head back and forth like you're watching a tennis match, to read a 8.5x11 piece of paper.

NOTE: The above paragraph was written by a person known to be against progressive lenses and in favor of lined bifocals. Many people with "strong prescriptions" are able to read an 8.5x11 paper without needing to move their head "like they are watching a tennis match". It is important to purchase high quality lenses, and even more important to have your glasses made and fitted by a competent optician who is highly experienced in fitting progressive lenses. It is also beneficial to avoid the narrowest eyeglass frames (i.e. the frames with very small vertical dimension) and choose a frame that is somewhat larger instead.

Bidmead (talk) 14:17, 28 June 2008 (UTC)

In my opinion as a scientific layman, there is truth to both of the above. There is no such thing as a perfect progressive lens (PAL)--selection involves multiple tradeoffs. When it comes to how effective you and your optometrist are at navigating those tradeoffs, your mileage may vary. The information-packed Sheedy, Hardy, Hayes paper (freely available by selecting FULL-TEXT PDF at http://www.optometryjaoa.com/article/S1529-1839(05)00292-7/abstract ) compares 23 PAL types from the patient's viewpoint. Some PAL types--there are hundreds--will give nearly anyone "tennis-match" near vision but in turn have other benefits, including lower "distortion" (for which there are many synonyms, as PALs are highly complex, computer-generated, aspheric lens curves.) I have large frames, started with bifocals, and have had two different PAL types (both chosen before I read the Sheedy paper). The second was a worse fit than the first; it does indeed have "tennis match" vision. I expect to change it more knowledgeably next time. —Preceding unsigned comment added by 67.58.135.77 (talk) 23:10, 5 July 2009 (UTC)

Link above to paper by Sheedy, Hardy & Hayes is dead. I am guessing it might have been this article:

"Progressive addition lenses — measurements and ratings."

Other (more recent) articles may also be of interest, such as "Optical performance of progressive addition lenses (PALs) with astigmatic prescription." by de Lestrange-Anginieur & Kee in Scientific Reports.

—DIV (1.129.105.55 (talk) 10:09, 11 February 2021 (UTC))

Tone

This article should be rewritten in an encyclopedic tone. For example, "your mileage may vary" is not encyclopedic in tone. Anomalocaris (talk) 08:15, 16 July 2009

This Article

I made a small edit, however I am planning to rewrite this article in the near future. It appears to have been written by someone with an obviously keen interest in, but limited knowledge of optics, who has not been getting on with varifocal lenses. Snaisybelle (talk) 22:16, 10 March 2010 (UTC)

The diagram needs to be properly incorporated into the article. It is not referred to in the text and has detail which is not explained either. 24.67.13.62 (talk) 00:09, 25 December 2011 (UTC)

New tags

Just put a lot of tags on this article. The biggest issues I see are: the article doesn't seem to be written as an encyclopedia article, rather as an essay about how to use bifocals. The quality of the material varies, sources are not marked for most of the claims, the bottom section reads as an instructional manual -- in short, this article needs major revision work done, and could especially benefit from an expert in the optometry. L.cash.m (talk) 01:11, 23 January 2013 (UTC)

Graphic

I do not understand the graphic now included (https://upload.wikimedia.org/wikipedia/commons/9/95/ClearVisionArea.jpg). It looks like it ought to be helpful, but not unless somebody can explain it a little! (What do the big circles mean? what do the little dots mean? what do the vertical lines mean.... can anybody edit the article to explain?David Couch (talk) 18:07, 7 June 2014 (UTC) OK, I added a little (what the big circles mean -- which I found at the graphic's URL but also added an tag. But I see it is from a possibly biased site: www.induceddyslexia.comDavid Couch (talk) 18:42, 7 June 2014 (UTC)

Associated solids like a "Half circle of revolution"

What are the surface solids of single vision lenses? Wikipedia quickly answers it: spheres.

And what are the surface solids of (fully) progressive lenses? Appaaarently that are that snail house alike solids you get when you let a half circle rotate around its closing diameter with a linearly changing diameter. Such HCR ("Half Circle of Revolution") surface lenses seem to play an important role here! (Are Varilux 2 lenses actually HCR lenses???)

● The hence mathematically exactly described idea of a "HCR lens" would make it fascinating to demonstrate, but is there one single YouTube video which optically demonstrates a real HCR lens?

● Such a HCR lens would be indeed like many flat and infinitely thin spherical lens pieces with linearly increasing refraction power put together. If they would be only almost infinitely thin the result would be small stairs (similar like in Fresnel lenses) only in that side regions where progressive lenses allegedly have their distortion areas. So this distortion seems to result from a smooth edgeless surface exactly there where HCR lenses actually should have pieces of spherical lenses (arranged in small stairs). Were such Almost-progressive lenses ever considered and directly compared with HCR lenses? MathLine (talk) 01:31, 12 June 2015 (UTC)

Lens design

It seems we have no information on how a progressive lens actually meets the need of the wearer. I guess the appropriate section for that would be "Lens design", if we had that section. Currently, there's some information about that under History, but that is mostly marketing gobbledygook, such as "appropriate reading power was given to the wearer". Is there someone who knows enough about this to create such a section? — Sebastian 19:58, 16 December 2015 (UTC)

Images

Photograph of view through a progressive lens

Is the existing photograph what it claims to be? See discussion. —DIV (1.129.105.55 (talk) 09:49, 11 February 2021 (UTC))

Schematic diagrams

The article would benefit from schematic diagrams depicting:

• typical regions of the lens intended to correct near, intermediate and distance vision (for example could be similar to one used by Adelaide City Optometrists, but with extra annotation of the top, middle & bottom);
• shape of the lens in cross-section.

—DIV (1.129.105.55 (talk) 09:49, 11 February 2021 (UTC))

Cost

Could anyone find some quantitative data regarding cost difference compared to

• SVD plus reading glasses;
• bifocals.

Rather than blandly stating "Progressive lenses are more expensive [...].", it'd be nice to know that they're, say, typically 50 to 75% more expensive. The "typically" should probably be based on actual sales. I am guessing it might vary a bit around the world. —DIV (1.129.105.55 (talk) 11:35, 11 February 2021 (UTC))

Optics

It would be nice to have more information about the optical theories in the article. E.g. are the lenses conceptually based on "hyper conic sections".

What are the limitations in applying the technology to people with astigmatisms?

What are typical dimensions for the nominal regions of distance vision, intermediate vision, near vision, and blurriness/fuzziness (towards the lower corners)? Need to recognise variation, but could say, for instance, top third for distance, then channel of 10 to 20 mm wide progressing through intermediate to near, and blurry either side of the channel. But need reference(s).

All of this would be useful in the article. —DIV (1.129.104.76 (talk) 11:25, 12 February 2021 (UTC))

Blurry region

Another issue it would be good to clarify: is it really technically impossible to avoid the blurry regions, or is it a practical constraint of not wanting to make the lens too thick/thin, or needing to fit within spectacle frames that are relatively 'flat', or for cosmetic reasons only blended to avoid making it obvious that the lenses are not simply single vision lenses (per [1])? —DIV (1.129.104.76 (talk) 11:45, 12 February 2021 (UTC))