Old age creeping up
Nov. 21st, 2006 11:31 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
ellarienI just noticed something as I was reading, being a bit more conscious of my vision just now because of the new glasses.
My corrected 'near point' is now at about 20cm. I seem to remember from high-school optics that that's about where it is for people with normal vision, but mine has been closer in than that, even with glasses, for as long as I can remember. (The glasses do push it out an inch or two, so that I've long had the habit of whipping them off if I want to look really closely at something; on the other hand, I need the 'distance' glasses to focus on things at computer-screen or book-on-lap distance, which are way past the uncorrected far point and have been for more than twenty years.) Presumably, I could now get the effect from a magnifying glass that the textbook examples (which always assumed a 20cm focal length for the human eye) give; I always felt vaguely cheated about that one, because you don't get nearly as much magnification starting with a shorter focal length.
My corrected 'near point' is now at about 20cm. I seem to remember from high-school optics that that's about where it is for people with normal vision, but mine has been closer in than that, even with glasses, for as long as I can remember. (The glasses do push it out an inch or two, so that I've long had the habit of whipping them off if I want to look really closely at something; on the other hand, I need the 'distance' glasses to focus on things at computer-screen or book-on-lap distance, which are way past the uncorrected far point and have been for more than twenty years.) Presumably, I could now get the effect from a magnifying glass that the textbook examples (which always assumed a 20cm focal length for the human eye) give; I always felt vaguely cheated about that one, because you don't get nearly as much magnification starting with a shorter focal length.
