SHAW Lens?

[Oscar]

System For Ophthalmic Dispensing

Go to page 514 (preview with missing pages).

Math corrections!

Remole Prism, Magnification, and Lens Form Analysis

For VI at near, Prentice is good for low powers. For higher powers, it overstates differential induced prism for minus, and understates for plus.

Shaw also uses dissimilar corridor lengths to minimize VI at near.

Best regards,

Robert Martellaro

wowow... i have a hard copy of this but this would make it so much easier without having to lug it everywhere. does this have unlimited uses? i see a purchase option at the top.

[Robert Martellaro]

wowow... i have a hard copy of this but this would make it so much easier without having to lug it everywhere. does this have unlimited uses? i see a purchase option at the top.

The eBook is about the same price, I think. However, I keep my art on the walls, and my books in a bookcase because...

https://archive.nytimes.com/www.nyti.../18amazon.html

Without too much blather, the Shaw Lens is not about acuity.
Yes, it's digital, but it's not about position of wear or field of view.

It's about two things:
1. Iseikonic design for severe anisometropes (and presumably rare others like retinal stretching, etc.) who have resultant aniseikonia (unequal image size)
2. Prism imbalance off axis from unequal lens powers.

How they achieve #1 is not unheard of...manipulate the shape factor via base curve and center thickness compensations. (See Dick post. Post, Dick, post.)

How they achieve #2 is unheard of. pretty much.

Paraphrasing Brooks and Borish from their book mentioned previously...hypothetically, if both lenses have equal dynamic spectacle magnification (by manipulating BCs and CTs), we will also eliminate VI. Moreover, the absence of prismatic effect will apply to the entire binocular field.

I suspect it gets tricker with large degrees of cylinder; maybe correcting the horizontal with BC/CT choices and solving the vertical meridian with unequal corridor lengths or segment styles.

It was claimed to me that Prentice's Rule on prism induction off-axis is "rough" and they have a more elegant/sophisticated way to do it.

Remole's equations are more accurate, especially with plus powers (see my earlier post).

Best regards,

Robert Martellaro

[drk]

Ok, I think I get it.

If we have minimized magnification differences by manipulating thickness (among other things), then we've AUTOMATICALLY minimized prismatic imbalance!

Makes heap sense!