Magnification That May Surprise You

David Lewerenz, OD, FAAO talks about low vision optics.

Cara Moore: Hi everyone. Thanks for watching Optometry TV. I’m Cara Moore joined now by Dr. David Lewerenz. Thanks for being here.

Dr. David Lewerenz: My pleasure.

Cara Moore: We are talking about low vision optics for rehabilitation. Let’s start with what practitioners may not know.

Dr. David Lewerenz: Well, there are several features of the optics of magnifiers that might surprise some people, even those who have been through an optics course in optometry school. For example, if you’re using just the standard handheld magnifier, like you can get a lot of different places like the traditional Sherlock Holmes kind of magnifier. There are instances where you can actually get more magnification out of that if you look through the top part of your glasses, the distance part, then if you look through the bifocal, which is totally counterintuitive, and most people wouldn’t expect. Another surprising feature is that in lots of different kinds of magnifiers, you can have two different people using the exact same magnifier. You can get different levels of magnification based on how it’s used. So there are a lot of features like that that determine the performance of a magnifier that a lot of people just don’t realize. And that’s some of the things I’m going to concentrate on in my course.

Cara Moore: What about telescopes? We may think of them really as just viewing from afar, but what about near?

Dr. David Lewerenz: Telescopes are thought of as mostly a distance vision device, but they can be focused at near and there are some surprising things about that as well. You can put a lens on the end of the telescope to focus it at a shorter distance and then there are variable focus telescopes that you can just twist it to focus it near. And some people might not realize that the variable focused ones, if they’re focused at near, actually magnify a little more than the fixed focused one with the lens on the end. So that’s another kind of surprising aspect of telescope magnification.

Cara Moore: And practitioners seeing these things in day to day practice they may find that a bit surprising.

Dr. David Lewerenz: They may find that surprising. Yes.

Cara Moore: All right. Well Doctor, we appreciate you being here.

Dr. David Lewerenz: Thank you very much for having me.

Cara Moore: And thank you all for watching Optometry TV.

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