Cognitive Daily

Casual Fridays: Corrected vision

Our son Jim doesn’t like wearing his glasses, so we got him contacts. Then we found out that he wasn’t wearing his contacts, so about a month ago we made him start wearing his glasses again. Today at our parent-teacher-student conference, his English teacher remarked that today was the first time she had ever seen him wearing glasses. Apparently, he takes the glasses off as soon as he gets to the bus stop.

Since neither Greta nor I spend even a waking moment without our glasses, we were curious how much of the time other people wore glasses. Hence today’s study. You will first be directed to a page with a vision chart. We ask you to remove your glasses or contacts, stand 10 feet away from the computer monitor, and tell us the smallest line you can read. You’ll then click on a link to a short survey asking about your eyeglass/contact habits.

Clearly the vision test will only give a rough approximation of visual acuity, but we think it should be good enough for our purposes. Don’t worry, you won’t be responsible for making sure Jim wears his glasses!

Before you start, make sure you’re ready to remove your glasses or contacts (or remove them in advance), and that you have 10 feet (about 3 meters) clear space in front of your computer.

Click here to participate.

As usual, you’ll have until 11:59 p.m. Eastern Standard Time on Wednesday, March 22, to submit your response (or until we have 250 responses, whichever comes first).


  1. #1 Karl
    March 17, 2006

    But you are not distinguishing between eyes. With my right eye I have about 20-30 vision so I can read the 30 line with both eyes open. But with my left eye only I can’t even read the top line.

  2. #2 Lab Cat
    March 17, 2006

    I have agree with Karl. I can see ok with my right eye, but very little with my left.

    When I was a teenager, I stopped wearing my glasses. I couldn’t stand the teasing, especially as I didn’t seem to need them. It turned out I didn’t need them, between my two eyes I had a perfect eye: One for long distance and one for close up.

    I started wearing them for driving and then finally writing up my PhD killed off my distance vision. I can remember the shock of seeing that extra world beyond what was normally my far distance. I probably should wear them more often. I do have prescription sunglasses, so when I am outdoors on a sunny day I am, in fact, wearing my glasses.

  3. #3 ColinB
    March 17, 2006

    Yeah, I still remember the shock of a world with edges when I got glasses at 9.

    Amazing how you can think you’re getting along just fine when all of a sudden a small change can alter your entire perception.

    I also new a guy who got glasses at around 19, and since he was almost blind in one he suddenly was presented with depth perception! He said that he spent a half hour or so looking at cds in a music store, turning them this way and that to see the edges approach and recede.

    And the car ride home that evening REALLY freaked him out. :v)

  4. #4 Scott Reynen
    March 17, 2006

    So should we not participate if we don’t wear glasses or contacts? You seem to be assuming we do when you tell us to take them off first.

  5. #5 Claw
    March 17, 2006

    There is an inherent flaw with showing an eye chart on a computer monitor. Different people may have different resolutions set on their monitors. For instance, I have rather good vision, so I set 1600×1200 on my 19″ monitor, which makes the chart look small. On the other hand, some another person who have worse vision might set 800×600 on the same exact monitor (one of my coworkers does this), which would make the chart look huge.

    Because users may adjust the display resolution to suit their own eyesight ability, you may end up getting the same results from people independent of their eyesight ability, since the same chart will look larger for someone with worse eyesight.

  6. #6 Claw
    March 17, 2006

    As an addendum to my previous comment, there is something that could be done to fix this flaw. Before showing the eyechart, you can display a line of fixed pixel length and ask the person to measure it with a ruler and indicate its length in the survey. You can then use this measurement to accurately scale and compensate for the eye chart size variation across different monitors and resolutions.

  7. #7 Dave Munger
    March 17, 2006

    We’re happy for people who don’t wear glasses or contacts to participate — we’ll take your results into account when we analyze the results.

    And yes, this is not a perfect vision test; we just thought it would be better than trying to rely on participants’ imperfect recollection of their visual acuity.

  8. #8 Zeno
    March 18, 2006

    My right eye is better than my left eye, too.

    By the way, the tricky part of the exam was finding a way to get 10 feet away from the computer screen. There’s not a lot of open space in this computer room!

  9. #9 Karl
    March 18, 2006

    Since you haven’t told us what you are looking for with this test, I don’t know whether the following will be pertinent or helpful or irrelevant, but here it is: I am at the age when one starts to get cataracts. My ophthalmologist says that when he removes the cloudy lens he can replace it with a prescription lens which will include adjustment for astigmatism so that I will no longer need glasses for distance vision. (Due to a different, standard problem, though, I will still need reading glasses). The thought is somewhat scarey. Since I have worn glasses for 50 some years, I cannot imagine what it will be like not to have to. weird!?

  10. #10 Dave Munger
    March 18, 2006

    Re: the various comments on how this isn’t a very accurate eye exam. Point taken — computer monitors vary.

    However, there is some method to our madness. We don’t test each eye individually, because what we’re interested in is real-world vision: how you do without corrective lenses. While an optometrist needs to know your vision in each eye separately, we want to know if there’s a relationship between someone’s vision using both eyes together (as they do in the real world) and how much they wear their corrective lenses.

  11. #11 Nathan Myers
    March 19, 2006

    I didn’t need to take the test to know that I wouldn’t be able to read the top line, with either eye. I can’t wear glasses because they would be so thick, and produce so much distortion, that they would give me headaches. Fortunately, hard contact lenses are very good nowadays, and hardly give me a moment’s trouble.

    Before I got my first glasses, the world was a softer place. I had already learned to recognize people by their gait and stance, a skill I retain 35 years later; I can still recognize a friend a half-mile away. Curiously, each country has a characteristic gait, making Americans overseas (e.g.) easy to spot by their oblivious icebreaker-like progress through crowded thoroughfares. Old Swedes walk like Swedes, but young Swedes (<40) walk like Americans -- Californians, in fact -- evidently a product of television exposure.

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