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February 17, 1888: Birthday of Otto Stern more: Today in Physics  





A Progressive(s) Year.


Ok, if I actually finish this I'll be two months in a row that I've gotten to writing something here. Maybe I'll even make this a belated New Years resolution, to post something every month this year and update my other web pages more regularly.

If you go to an optometrist in English Canada the odds are they graduated from the School of Optometry at the University of Waterloo. Part of my TA duties when I was at Waterloo was teaching one section of an optics lab required by pre-optometry students. I've wondered if one day I'll find myself being examined by one of my former students. My latest prescription has me wondering if my latest optometrist is a former student who didn't like the mark I gave him!

Ok, I'm not really wondering about that, but I'm getting 50+ and have hit that stage where a single focal length doesn't work for eye glasses. In the good old days I was just myopic (near sighted). That means my eyes focused too strongly and hence I have needed defocussing lenses in front of my eyes to get the focus onto the retina. However, the eye has to adjust the focal length for various distances. The problem many of us hit, especially as we get older, is that we also become "far-sighted". That is we cannot focus on nearby objects. Hence we also need additional focussing in front of our eyes. That is, we need glasses that somehow let us choose whether to focus or defocus. I've been having increasingly more and more trouble reading for the last few years and had actually been looking forward to getting "progressives". Ok, so admitting you need progressives is like sudden onset oldness. Suddenly you can no longer hide from being in decline. Progressives sound like the ideal solution - look out the top of the lens to see distances, look out the bottom to see things that are near (such as reading a book). Unlike the "bifocals" of old, these progressively change the focal length so one can theoretically find an optimal viewing angle for objects at any distance, and if you're hung up on not looking old, there is no line announcing it to the world.

So I got my progressives a year ago, and as you've probably gather I'm underwhelmed. I was told they would take some getting used to, but a year of having nothing ever in really good focus isn't quite what I had in mind. Ok, I exagerrate. With enough head tilting I can eventually get most things in focus. However, that means something like point my face at the floor and looking upwards through the top of the lens to look across the room (for example to watch tv) and holding a book against my chest, looking straight ahead, then pointing my eyes down my nose to read smallish print. Other stuff just takes a lot of experimentation. Mostly I can't be bothered and just live with the fact the world is somewhat fuzzy these days. I've concluded that mastering progressives is more about triumph of the human spirit against adversity than it is about good optic technology. Next time my prescription changes I'll have to think hard about my options, maybe some new options will be coming around by then.

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