How is the surface astigmatism determined in varifocals? I am aware that surface astigmatism varies depending on rx and lens design. However if I chose a frame with a small 'A' measurement would this allow surface astigmatism to be cut off. Is this the case?
Or do small 'A' measurement frame restrict the field of view as the surface astigmatism is more in the px field of view.
Thanks in advance guys
ps I'm fairly new to optics
Sure, it gets removed, but I don't think that's a viable option.
If you have a round frame, you can have the minimum A and B dimensions, but that's not very attractive, right now.
It is very simple and no need to measure ................
Originally Posted by Star12345
It is very simple and no need to measure ................
The higher the addition the higher the distortion on the surface and the smaller the clear reading area.
They are OK for people in their early years of aging, but when you really get there, they are more of a problem.
Welcome to OB.
The current state of the art for minimal surface astigmatism with a progressive addition lens is about 75% of the add power. Looking at the illustrations below we can see that the surface astigmatism can be managed and distributed, but not eliminated, or cut off.
http://64.50.176.246/cecourse.php?ur...essive_lenses/
Science is a way of trying not to fool yourself. - Richard P. Feynman
Experience is the hardest teacher. She gives the test before the lesson.
Round is in! We stock a lot of round/ish designs not only to follow trends, but also because a rounded frame will offer less distortion as well as a thinner lens on higher Rx. Remember to keep the curvature of the frame in mind as well- ex. putting a myope in a wrap frame will cause more distortion than a flat frame in single vision or multifocal.
Have I told you today how much I hate poly?
Round frame are definitely in and I'm really liking them. I was just interested in how well varis go with round frames. Thanks for all your answers and help.
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