minification/magnification

[mirage2k2]

What exactly is it about a lense that decreases minification/magnification?

Is it aspheric design?
Is it lense form?
Is it high index?

I have 2 pairs, one aspheric 1.74 and one best-form CR39 - not only do my eyes look smaller in the aspheric 1.74 but so does the rest of the world!

For my +6 rx I find working on my pc harder with the apsheric 1.74 because the text is smaller!

I think aspheric design is the major influence on minification/magnification due to the changing power in the periphery ... but is it also because of the flatter lense form ... and does high index have anything at all to do with it

[chip anderson]

Vertex distance from the eye can have a lot to do with it also. The closer it is the less magnification or minification for that matter. Of course a lot of this has to be predetermined by your nose, eyelash and brow length. But if frames are available and your physiology allows things to be closer, the effect is minified.

Other factors: Lens thickness, smaller lenses (in plus anyway) are thinner give less magnifying effect.

Asphericty does also have some effect, especially in plus precriptions.

There is no way to completely eliminate these effects in a given precription.

Chip

[mirage2k2]

Thanks chip.

I might be wrong but I think for a plus rx magnification is good for the eyes ... because bigger print, etc. is easier on the eyes ... as I said wearing my aspheric 1.74 at work, on the PC, my eyes have to work harder because the text on the screen is smaller.

I know that it's a good idea to have minimal BVD ... I can see this in a mirror ... if my specs are riding on the end of my nose my eyes look huge . Whenever someone is about to take a photo of me I always ensure that my specs are pushed right up against my face :D

[HarryChiling]

When considering magnification or minification you need to concern yourself with 2 things the shape factor and the power factor. The shape factor takes into consideration thickness, front curve, and index. A change in any of these would result in a change in the mag or min of the glasses. Also the power factor wich has the power and the vertex distance (vertex distance in this case should be considered from the pupil and not the corneal apex) a change in any of these would result in a change in the min or magnification. I think in your case the biggest factor would probably be due to the front curve of the lenses.