By Ctein
Unsurprisingly, human vision pops up regularly as a topic in these pages. Most especially, its failings. We take it for granted when it works perfectly. Unfortunately, sooner or later, it stops working perfectly.
Many of us develop the need for glasses at an early age. I became nearsighted when I was six or seven. By my teenage years, I was very nearsighted. This could come in handy. Without my glasses, I could focus down to about six inches, meaning I could do delicate and meticulous close-up work without the aid of magnifiers. Great for spotting prints.
My bio-cameras have unusually good specifications. My visual acuity is 20/12 in my left eye and 20/15 in my right, meaning I can resolve details about one third finer than average. I also have unusually good color discrimination; a 1 CC color change is obvious to me.
As I've aged, I've gradually become less nearsighted; my close-focusing distance is now out to nine inches. It's normal to become more hyperopic over time. Unfortunately, I'm normal in another way: I developed presbyopia. With age the eye's lens becomes less flexible and cannot focus over as wide a range as when we were young. I have almost no focusing ability left. Basically, my "cameras" still have great resolution and great color fidelity, but they're equipped with fixed-focus lenses.
Presbyopia happens to everybody; how soon and how severely vary with the individual, but we all lose focus accommodation. Folks with previously perfect eyesight find themselves needing reading glasses as they get older. The muscles in their eyes cannot distort the stiffer lens enough to bring the focus down to a comfortable reading distance, especially with slight progressive hyperopia.
Presbyopia is responsible for a lot of the arguments over camera ergonomics. If you've still got good focus accommodation, a non-adjustable eyepiece on a camera isn't a big deal. If you've got serious presbyopia, the lack of an adjustment can be a deal killer for you. Similarly, folks who are going hyperopic and presbyopic with age can find camera-back LCD screens a real pain to use. (They work great for me; after 40+ years of looking over the top of my glasses for doing close-up work, it's instinctive for me to peer at an LCD that way.)
I really, really hate presbyopia. How much? I've actually investigated getting flexible corneal lens implants, even though I'm not even close to needing nonelective cataract surgery. Unfortunately, they're not really ready for prime time, according to my expert counsel.
Bifocals only give me two zones of sharp focus, with everything in between fuzzy, and even after 20 years I'm still not used to the dividing line. Progressive lenses? Then I'd never have the entire field of view sharp, just some portion of it. That would drive me nuts even faster than uniform blurriness.
Around the house, I only wear my reading glasses unless I'm watching TV. Most everything I do is within a couple of feet of my face. I live with the rest of the room looking slightly blurry. I travel with three pairs of glasses; the bifocals, the reading glasses, and an intermediate pair that's good for things about 10 feet away (if I'm going to an art exhibit, that's what I'll usually wear).
Vision-wise, I am not a happy camper.
A few months back, Paula caught an item on NPR about adjustable-focus eyeglasses called Superfocus. The lens frames contain a liquid-filled adjustable lens with a tensioning slider in the bridge. Moving the slider back and forth causes the lens to flex, changing its optical power over a range of 2.75 diopters. Your pair of prescription lenses magnetically snap into the frames. Those lenses would give you correct infinity vision in a normal pair of glasses. In the Superfocus glasses they combine with the liquid lens to give you a continuous range of focus from infinity down to near reading distance.
Last week I got a new eye exam and plunked down a honking big wad of cash. I'm out nearly a grand for the exam, the glasses, and a one-year loss/damage insurance policy. (I've never lost or damaged a pair of glasses in my life, but this is new technology—I'm willing to buy a little insurance for the first year just in case I do something stupid.) If these work, they may not be as breathtakingly expensive as they seem. One pair of glasses replaces the two (bifocals and reading) that I'd be buying usually.
The big question is how long the frames really last. I'm not sure anyone knows, seeing as the technology isn't that old. The company only warrants materials and workmanship for a year. I'm hoping that's a pro forma thing and not a predictor of future performance. If the frames hold up well, I'm only spending $100 or so every time I need new glasses instead of $300. If I get five years out of the frames, it's only about twice as expensive as regular glasses. Ten and I break even.
I can think of reasons why I might not like these. But what the hey, it's an experiment. And one that's a lot less expensive and risky and, well, nuts than voluntarily getting my eyes cut into. Fortunately, there's a 30-day money-back guarantee. If I hate them, I can return them and buy my usual regular glasses.
Delivery is supposed to be in 3–4 weeks. I'm keeping my fingers crossed. I should have a report for you early next month.
Ctein
Columnist Ctein meets you eye-to-eye every Wednesday morning at TOP.
Original contents copyright 2013 by Michael C. Johnston and/or the bylined author. All Rights Reserved. Links in this post may be to our affiliates; sales through affiliate links may benefit this site.
A book of interest today:
(To see all the comments, click on the "Comments" link below.)
Featured Comments from:
Bear.: "When I first came to Oz as a kid, I was introduced to Norman Hunter's 'Professor Branestawm' books (which seem to be completely out of fashion). I now—unintentionally—look rather like the good professor. To quote from the highly reliable source (SA), Wikipedia: 'He has five pairs of spectacles—one for reading, one for writing, one for out of doors, one for looking at you over the top of and a fifth pair for looking for the others on the frequent occasions when they get lost.' And other pairs of spectacles are often mentioned.
"My ophthalmologist says it's bunkum that my presbyopia issues are caused by reading as a kid—rather, my eye's natural focus distance was affected by my childhood reading, and also my present extensive reading and computer use, but not the ability to focus."
R. Edelman: "The statement that 'it is normal to become more hyperopic over time' needs some clarification. With the loss of accommodative ability that eventually progresses into presbyopia, hyperopes who are under-corrected require more hyperopic correction, and myopes who are over-corrected require less correction. With continued aging of the natural crystalline lens inside of the eye, many people develop nuclear sclerosis of the lens. In these cases, the lens becomes more dense and therefore more effective at bending light. In other words, the index of refraction of the lens increases. This causes a shift towards less hyperopia or more myopia. In some people, this process actually improves their uncorrected vision, a phenomenon that was described in the past as 'second sight.' All of these changes are caused solely by the aging of the lens of the eye, as most adult eyes that are untouched by surgery remain fairly stable in their dimensions, such as axial length and corneal refractive power."
