Chit Chat

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.

7 thoughts on “On Diopters and Eye Surgery”

  1. i don’t, but my mother is blind in one eye and loves to tell how she found out about it in school when they did the lame eye test, and she covered her right eye and saw nothing. my father in law had worse than yours and was excused from duty in the military, because they worried that he was more of a risk to his unit if he lost his glasses.

    i hope your mom’s surgery went well and that she is recovering at home. hospitals are not the best place to recover, unless you are really really sick.

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    1. My mom’s bad vision wasn’t diagnosed until school either–until then her mom just thought she was really affectionate when she held her face really close so she could see it!

      Your father-in-law’s story reminds me of one of my favorite celebrity stories: Peter Falk was in the Merchant Marines. He has a glass eye so during the eye test, of course, he told the doctor about it. The doctor told him to do the best he could! (I have an uncle who, for the hearing test, they tapped him on the shoulder because he was deaf in one ear.)

      And Mom’s recovering well, thanks :)

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  2. I have terrible vision. I don’t know what my 20/ something vision is, but my diopters are 5.25 in my right eye and 7.00 in my left. I found out about it when my mom did a homemade eye exam- she took me outside to read license plates. Getting your first pair of glasses is a miracle. I could finally read the street signs, and did so out loud all the way home. I went outside that night, and saw my very first star. And talk about navigating safely- I could finally read the STOP signs!

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  3. I found your site when I did a search on ‘eye vision charts’. I hope your mom is all healed up.

    Well, I beat you with the bad eyes. I’m -7.5 and -8 in my left and right eyes.

    Thanks for the link to the Diopter Measure vs 20/20 measure conversion. I didn’t know how that worked. Apparently anything beyond, and including, -6.00 is severe myopia. :-/

    I wonder if eye exercises really work to improve vision. I’m skeptical, as doctors seem to say nothing short of surgery/glasses/contacts can improve vision.

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  4. i just wish someone would correlate the more severe myopias with the common 20-something measurement … my children have -7 to -8 diopters and i have -10 and -11, yet when we hold our hands in front of our eyes to show how far we can see clearly, it’s very nearly the same distance. nobody else seems to get how myopia forces you to rely on other senses than vision except other “severely affected” people.

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  5. I think i have everyone beat.. after a retinal detachment in my left eye ( severe myopia, non injury) . i am now -15 diopters in my left eye (most likely worse cause i flunked the vision test for renewing my drivers licence) oh, and my GOOD EYE (THE RIGHT) is -13! MATCH THAT! i CAN’T HAVE LASER BECAUSE MY CORNIAS ARE SO THIN. I’D HAVE A CORNIA REPLACEMENT IN ORDER TO HAVE THE SURGERY.AS FAR AS “HAND BEFORE YOUR FACE” MY MIRROR HAS MASCARA BECAUSE I HAVE TO BE THAT CLOSE TO THE MIRROR…I LITERALLY APPLY MY MAKE-UP FROM MEMORY! I DO PUT MY GLASSES ON TO MAKE SURE I DON;T LOOK LIKE CLOWN! YOURS THE BLIND JEANNIE FISH.

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  6. 32 years ago I was a guinea pig for radial keratotomy because my vision was so bad. -17.25 in my right eye and -20.5 in my left eye. The doc did 8 cuts in my right eye and 32 in the left eye. Left improved to -.75, the right to -4.25. Now I have epiretinal membranes in both eyes; while they remove them they’ll replace my lenses since I’m just starting to get cararacts. I don’t want to spend the extra $1800 to get lenses that will correct my severe astigmatism, but I’ve worn glasses for 49 years, so that’s no big deal.

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