On Diopters and Eye Surgery

Greetings dear readers. As some of you might have noticed, it’s been a while since I have written up anything that was not a book review. That was due partly to WordPress’s handy auto-post feature which allowed me to create a month-long buffer for Chick Lit Wednesday reviews and also because I was really busy.

What follows probably won’t be interesting to anyone who doesn’t care about vision problems, but otherwise it will be very informative.

My mom just had eye surgery to remove her cataracts and to get her lenses replaced (I could tell you about how the surgery actually works but I won’t because it’s kind of horrifying–or maybe I’m just squeamish. You can read more about it here and there are probably horrible videos of it somewhere but I’m not looking.)

Anyway, during all of the prep and the post-op follow ups we both learned a lot about vision prescriptions and I thought I’d share my knowledge with you all because I’m an information professional now and that’s kind of what we do.

So my mom had myopia and astigmatism which basically means she was profoundly nearsighted and had really terrible vision. Recently, because of her cataracts, her vision was really bad even with the glasses.

When you’re nearsighted it means that your eye is longer than normal from front to back (incidentally, if you are farsighted your eye is shorter from front to back which is a lot more difficult to work with in eye surgeries because there is less room to work in the eyeball). My mom had one bad eye and one extremely bad eye. The really bad was a full centimeter longer than an average eye.

Over the course of her examinations I also learned what her diopters were in each eye.

Now, when I was growing up my friends used to ask each other what power their glasses were (all of my friends wore glasses, true story) and I never took part because I never knew what they were talking about. It turns out they were discussing diopters which are the units of measurements used to determine what shape a lens (for glasses or contacts) should be to bring your vision closer to 20/20 (perfect) vision.

For farsighted people diopters are positive (+1, +2, etc) and for nearsighted people they are negative (-1, -2, etc) because concave and convex lenses are used respectively to correct vision. (Doesn’t make sense? Check out this site–scroll down to the “How a Lens Works” section.) In terms of diopters, zero is perfect vision.

Anyway, that’s well and good but it doesn’t really mean anything in terms of what a person’s vision actually is. I did a quick search online and found this conversion chart (scroll down to “How to Convert Diopters to 20/20 Vision”). I don’t know about anything else the site had to say but the chart looked good.

So, if you have your glasses prescription handy or your contact lens box nearby you can figure out your vision. My mom’s vision was horrendous: -7 in her “good” eye and -15 in the other–those aren’t even listed on the chart I found (don’t worry though her vision is almost 20/20 now).

My vision is around 20/400. When I first saw this, the same as when I was first told I had astigmatism, it was a real jolt and I was kind of horrified. At the same time, it was validating because my family (who all have really bad vision like my mom) finally believed me when I told them I had terrible vision. It also confirmed my suspicion that when my friends and I would talk about bad vision none of them really understood what truly bad vision was. (I always have friends who say they have bad vision but later tell me that they just choose to not wear their glasses because they’re annoying. I couldn’t navigate safely on the street without my glasses.) A bittersweet victory if there ever was one.

Since this has been my life for the last couple of months, it was all really interesting to me. If you’ve made it this far, maybe it was interesting to you too. If you want to give me a thrill, chime in with your own vision. I will give a PRIZE of some sort (not yet sure what) to the first person who can prove (with photographic evidence) that they have worse vision than me.