Originally Posted by
optical24/7
Magnification is caused/induced by power, material, index, thickness, vertex along with lens size and decentration ( the last two both relate to thickness). Asphericity potentially could or could not influence magnification by thickness*. ( Atoric, not this Rx.)
To control or reduce magnification as much as possible, you need to address all of the above. The two variables that will mean the most are thickness and vertex on any Rx. Controlling thickness starts with lens size and PD ( As small and round/oval as possible and FPD as close as possible to patient's PD). Material (index) will make a difference because higher index's uses (require) flatter curves reducing the thickness (and vertex). (Be aware that not all hi-indexes have great abbe values. With high powers like the above, you need to start thinking of LCA's and their affect on their vision). Using a frame that sits as close as possible to their eye reduces the vertex distance.
* As far a aspheric/atoric helping. Depends. If you're talking using corrective curve deviation that we traditionally think of with aspheric/atorics, no. A +/-.50 cyl would have an extremely small amount of "curve deviation" for the cyl. The smaller the lens, the less curve deviation or asphericity is required. This is a 49 eye size so little deviation is induced. I don't think just asphericity ( or atoricity) in this small of eye size would reduce thickness much.
Now then, if you were to do a radical aspheric design like IceTech ( I don't work for them) makes then you could reduce the thickness even more. ( by radical asphericity I mean a radical curve deviation to remove lens material, not a corrective curve deviation. Think SuperModular lenses (ok, I'm old and remember those..)
I'm sure someone will add or correct me on the above.
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