Interesting Optical Facts?

[Loki]

I just wondered if anyone had any random but interesting (and potentially not even useful beyond entertainment) optical facts, be it lenses, frames. or equipment?

I love a bit of random trivia

[drk]

https://www.2020mag.com/article/does...atients-vision

[drk]

[drk]

"The outlier"

[drk]

Just Observable Error For Lateral Color

“ we know that 5 Diopters of prism introduces enough lateral color to cause about the same amount of blur as does 0.12 diopters of power error…

There is also evidence that when this error is in the neighborhood of ¼ prism diopter it may be bothersome to some patients.


(editor: picky, picky!)

[drk]

Plus Vs. Minus Powered Lenses
plus lenses yield more lateral chromatic aberration than minus lenses of identical power.

This is because of the front surface curvature and thickness of the lens, which combine to produce more prism (when examined at the 30-degree viewing angle). More prism means more lateral color! The example below illustrates how light rays behave at such an angle.



(editor: I "knew" that, but I didn't KNOW that.)

[drk]

... we see for a poly lens with Abbe of 30, powers of +4 and above have lateral color errors of more than twice that of our 0.12 threshold...At those levels, some observers would find it bothersome. For those powers at 4 Diopters and above, if lateral color is a concern and yet impact considerations are important, materials like Trivex, with an Abbe of 45, is also an option.

Certainly for powers below 2 Diopters, lateral color will not be noticeable to the wearer.

dick.whitney@zeiss.com

[wmcdonald]

For those who did not know Mr. Davis, he was truly one of the founders of Opticianry in this country. His family founded Davis and Sons, In Mass (1843-1873_ Remarks at Harvard: John Davis, originally from a family of opticians in Leeds, settles in Derby in 1843. Initially his business produces optical equipment, microscopes, telescopes as well as thermometers and barometers. He then specializes in mining equipment. Upon his death in 1873, the business continues under his son Henry. Products after this time are signed Davis - Derby.Manufacturers of optical, surveying and mathematical instruments and later mining instruments. Opticians were often selling other things. Jewelry, etc. There was no Optometrist in those days, Opticians ran around the country in a wagon, selling items, which included reading glasses. That's where we come from!

There were John's to follow, and one signed my Master's Certificate back in 1975 as one o the founders of the ABO, no NCLE then, just the ACO. That exam did cover both spectacles and contact lenses, which made sense, Opticians did 2 things! We found as time marched on some couldn't pass the exam, and we did the brilliant thing of separating the two. The beginning of the dumbing down of Opticianry!

You can see this John Davis's work in the Optical Heritage Museum, where our colleague, Dick Whitney does a marvelous job of displaying all things Optical. There is tremendous history here that has always made me proud! Look into it.

Thanks for mentioning Mr. Davis! I met him only a few times, but he was a leader for us!

[drk]

The synthesis:

Poly, while a good low-power lens material, is not as good for higher powers due to chromatic aberration, especially for higher plus powers, where trivex will do better, visually.

And where should we "cut off" "higher power? How about -6.00 and +4.00?

[iD]

The synthesis:

Poly, while a good low-power lens material, is not as good for higher powers due to chromatic aberration, especially for higher plus powers, where trivex will do better, visually.

And where should we "cut off" "higher power? How about -6.00 and +4.00?

I'd say +/- 5.00

[drk]

Another take-home point is that we don't have to worry about the prism amounts that are used for the typical phoric conditions (2^ BI, etc.). But for the mega-prism situations (shudder) like 6^BO with 4^ BD OD, then we're going to get blur.

So material matters with prism. Maybe NEVER do polycarb with prism and use trivex or CR39 and make the lenses small.

[Uilleann]

How does asph poly [+ or -] factor into your equation Doc?

[drk]

[Uncle Fester]

The edges of a paper, prepackaged, single vision, uncut lens is known as the gusset.

[kittyeyes]

Interesting Fact? I'm just not sure.
I know I'm in the minority here as an optician with a license to fit contact lenses, but I'm wondering if anyone else is concerned about the report of PFAS in contacts. The study (www.mamavation.com) reports that Acuvue, Coopervision and Alcon all said the study was B.S.
I called and spoke to one of the investigators at Carnegie-Mellon (Terrance Collins) and I don't prescribe some of the silicone hydrogel contacts that I used to.
If you search www.mamavation.com, you'll have to load the search bar with "contact lenses"-the study was given to the 3 companies in 5/23 and was printed in Vision Monday in 11/23.

[Lensman11]

Many decades ago when glass ruled you had to put the lens in cutter before you edged it. The cutter used the pattern and cut the lens 2 mm larger than the finished size. After the lens came out of the cutter you had to remove the excess glass with a cribbing plier sometimes you would get lucky and the excess came out in one piece this was called a ringer every beach person save them on a nail near where he worked to have bragging rights to show how good he was at cribbing the lenses.

[Michael22]

Ray-Bans are called Ray-Bans because they ban the rays from the sun from entering your eyes

[AngeHamm]

Many decades ago when glass ruled you had to put the lens in cutter before you edged it. The cutter used the pattern and cut the lens 2 mm larger than the finished size. After the lens came out of the cutter you had to remove the excess glass with a cribbing plier sometimes you would get lucky and the excess came out in one piece this was called a ringer every beach person save them on a nail near where he worked to have bragging rights to show how good he was at cribbing the lenses.

I worked with glass circa 1990 and never once saw this. We just edged glass on an old Weco edger. Took forever. Interesting and weird.

[Judy Canty]

I've scribed and cribbed glass lenses a couple of times, then beveled them on a ceramic wheel. Learned from the very old school OD I worked for. Circa 1973.

[Uncle Fester]

Check this out all you youngsters:

https://www.optiboard.com/forums/showthread.php/11314

[Robert Martellaro]

By means of prismatic spectacles, the visual field can be reversed or distorted (e.g., switching top and bottom, or left and right). Visuomotor skills recovered to near-baseline levels after long term adaptation to inverting or reversing goggles of several days or even weeks.

http://www.allgemeine-psychologie.in...ide%20down.pdf

[KrystleClear]

Cr39 stands for Columbia Resin (the company that developed it) and the 39 comes from it being the 39th attempt. Maybe everyone knows that, but I learned it while studying for the ABO and thought it was kinda funny.

[Michael22]

Cr39 stands for Columbia Resin (the company that developed it) and the 39 comes from it being the 39th attempt. Maybe everyone knows that, but I learned it while studying for the ABO and thought it was kinda funny.

Oh wow I've never heard of that, very interesting

[Prentice Pro 9000]

According to my friend getting a doctorate in Math(no I don't know the specific math). You cannot have an equation like Martin's lens tilt that compensates for BOTH the tilt and wrap at the same time. It would involve "torsion" or some such.

[Lensman11]

Cr39 was originally made to line the fuel tanks on ww2 bombers at the end of the war they started looking for other outlets for the material.