Methods for Estimating Lens Thickness by Darryl Meister

[Steve Machol]

One in a series of excellent articles by Darryl Meister of SOLA Optical. Requires Adobe Acrobat Reader Version 4.05 or higher.

[sea]

this methed is so important to me.i want to know whether it has some other ideas to reduce the thickness of lenses.

[Darryl Meister]

The article mainly concentrates on calculating thickness. The most common techniques for minimizing thickness in low- to moderate-powered lenses include:

* Using high-index lens materials
* Using lens materials that allow for thinner centers
* Minimizing the decentration of the optical centers
* Using frames with a smaller effective diameter
* Choosing frames with a smaller eyesize and larger bridge
* "Rolling" (rounding off) the edge of the lens in minus powers
* Avoiding exotic frame shapes
* Minimizing the amount of the lens protruding from the front of the frame with bevel placement

Moreover, in minus powers, you can minimize the apparent thickness of the lens by:

* Polishing the edge to a glossy finish
* Using a plastic frame with thicker rims
* Using an antireflection coating
* Painting the edge to match the rim of the frame

When the prescription includes a cylinder component, you can also choose a frame shape that will minimize the thickness difference produced by the cylinder power for the prescribed axis. For instance, a strong minus cylinder at axis 180 will have excess edge thickness through the vertical meridian. An oval-like frame with a large "difference" (wider eyesize than depth) will minimize the edge thickness produced by this prescription.

Best regards,
Darryl

[Tom Hubin]

Hello,

I am new to this list so may not be strictly proper.

In the 1970's I was an Army optician in Denver and a civilian optician in Maryland with a Virginia license. I also taught opticianry with Ken Wagner and Jim Matthews at Essex Community College in Baltimore. These days I am an optical engineer but still poke my nose into old interests.

I was referred to this list when I asked at sci.med.vision for info and manuals for the Essilor MBX edger. I still need that info but probably need to find the right place to ask.

I just happened onto this thread regarding the weight of lenses. I too did some math in the 1970's to figure out how much a pair of glasses might way. At first this was just to help teach but later I cleaned it up and published the article referenced below.

"Weight of Lenses", T. Hubin, THE DISPENSING OPTICIAN, Jul 1978

I have a copy here someplace but no idea where at the moment. If there is a method for posting files I will try to find it, scan it, and post it as a JPG file or something like that.

BTW, my math was similar to that posted in the thread for sections of spheres but I doubt that I actually put that much math detail into the published article.

Tom Hubin
thubin@earthlink.net

[Darryl Meister]

Hi Tom,

Welcome to the 'Board.

You can submit your article in this forum (the OptiBoard File Directory) by starting a new thread with a description of the file. You can then attach the file to the thread. Once the thread and file are approved, they will show up in this forum. You might want to visit the other thread (http://www.optiboard.com/forums/showthread.php?t=12797) to add a link back to your newly posted article, as well.

Best regards,
Darryl

[Tom Hubin]

Hello Darryl,

I'm lost. I thought I had responded to that thread. Now I can only find it with the link that you provided. I have no idea how to include my response in that thread.

Tom Hubin
thubin@earthlink.net

[Darryl Meister]

This is actually the OptiBoard File Directory. You probably thought this was the thread you were looking for because of the title, which refers to an article I wrote for Optical World magazine many years ago and is now available for download in this thread.

This is the forum in which you would post any files to download (including a copy of your article). The thread on lens weight appears in the Ophthalmic Optics discussion forum. You can get there by clicking on the Ophthalmic Optics link in the main OptiBoard page, which lists all of the discussion forums.

Best regards,
Darryl

[Steve Machol]

Welcome to OptiBoard Tom. It looks like you're doing pretty good to me. :)

Here's the innstructions on submitting a new file to this directory:

http://www.optiboard.com/forums/showthread.php?t=12630

Of course a lot of this will depend on the format if the file. Do you only have a hard copy of it right now?

[Tom Hubin]

Hello Steve,

> Welcome to OptiBoard Tom.
> It looks like you're doing pretty good to me. :)

Thanx. This is a little more awkward than the public user lists and the Yahoo groups in which I often participate.

> Here's the innstructions on submitting a new file to this directory:

> http://www.optiboard.com/forums/showthread.php?t=12630

> Of course a lot of this will depend on the format if the file.
> Do you only have a hard copy of it right now?

I found the magazine and noted an error and correction in the margins. I can scan to create JPG files but I don't think I can make any type of text based file. I will end up with 6 separate files, 1 for each page of the article. I can zip them into 1 file. Any other suggestions for how to do this?

Tom Hubin
thubin@earthlink.net

[Steve Machol]

This is really off-topic so I may delete our posts in this thread later, but I'm not sure how useful or readable scanned JPGs will be. If you want to try this, send me a Private Message when you are ready and I'll send you my email address to send the pics to.