vision acuity simulator

This comes via Bright Eyes News (where I get almost all my vision-related news): an online vision acuity simulator – you can enter a prescription and see a simulation of what a vision chart would look like to someone with that prescription who isn’t wearing glasses.  [Updated 3/1/2009:   As Annie notes in the comments, the simulator will only show prescriptions between -5 and +5, any worse and you’ll get a note that it’s beyond simulation range.] As anyone who’s read this blog for a while knows, I’m fascinated by learning more about what Zoe sees.  But nearly as interesting as the simulation were the following disclaimers:

  • The magnitude of the optical aberration (how blurry the image gets) depends on the width of the eye’s pupil, which changes all the time.
  • The brain and vision-related neurons make a lot correction work in creating an illusion of a sharp image with clear edges.
  • A positive spherical diopter [farsightedness] in prescription can be cancelled by the eye’s own lens, but with a constant load on the ciliary muscle.

Basically, this means that what the simulation shows for Zoe is not necessarily what she perceives when she isn’t wearing her glasses.  For one, her brain is correcting some of the image, but more importantly, because of her accomodative esotropia, she can cross her eyes to compensate for some of the blurriness, it just means that if she does that, she’ll see double, and eventually her brain will turn off the input from one eye leading to amblyopia.  (Many thanks to Dr. Bonilla-Warford of Bright Eyes news for helping me make sense of this).

simulation of what Zoe might see without her glasses, using +4 and +4.25 as the prescription.  From

Simulation of what Zoe might see without her glasses, using +4 and +4.25 as the prescription. From

6 responses to “vision acuity simulator

  1. Wow Ann this was amazing! Aubrie is a +5.75 in both eyes & this website couldn’t simulate b/c it was beyond the scope. I was able to look at a +5 in both eyes & it’s amazing. I just can’t really fathom this b/c I have perfect vision. Granted it may not be exactly how she sees, but still wow! Thanks for posting this. I’m going to share it with my husband. I think he’ll be shocked as well. No wonder when she wakes up at 2AM she’s terrified in her bed. A dark house & vision like this would be overwhelming at 3. Thanks again for sharing!


  2. Someone recently suggested that I try this vision simulator to get an idea of how my daughter sees. The website is Everything is in German but it is easy to figure out, You can enter a prescription and it shows what several different images look like. The first number they are looking for(Alter) is age.

    I thought it was pretty cool. Since I have 20/20 vision it really gave me insight to how poor her vision is. I can not wait until My German friends translate everything it says.

    I now know my teenage daughter if full of it when she tells me her vision is fine without contacts or glasses. We have been battling her since the age of 3 to wear them. Her 1st eye Dr. told me how much she would love her glasses, because her vision is terrible. I have been waiting for her to love glasses and contacts for 11 years now. She would rather not see than wear correction.


  3. I find that each of these simulations significantly exaggerates the subjective lack of clarity of vision, personally. My prescription is -1.0 / -2.25 x 170 and I find that simulating a prescription around -0.25 / -0.75 is much closer to what my vision seems like to me for the real-life scenes.

    Taking the site as an example, entering 21-30, -1.00 & -2.25 (my prescription) the Snellen chart is probably a reasonable guide of what I am able to accurately read, however it doesn’t appear anything like as blurry to me. However, in the image of the freeway, although I would struggle somewhat to read the sign, in the simulated image it is almost impossible to see the cars at all!. That is certainly not the case for me in reality… the edges of objects are blurry, but I have no difficulty seeing that objects are there.

    I post this in particular due to comments like “I now know my teenage daughter is full of it”, where people seem to be judging their children based on computer simulations of questionable accuracy. I lived without glasses or with poor prescriptions for many years, and often it is hard to notice as the deterioration for me at least has been gradual. I certainly wouldn’t risk driving without correction to my sight as this is risking peoples’ safety, and I appreciate the improved clarity of vision I get now from wearing glasses regularly, but it is a personal choice.


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