My eyes are better...sort of.
February 22, 2005 11:35 AM   Subscribe

During a recent trip to the optometrist, I was told my nearsighted eyes had improved, and was given a new prescription, only to find the new specs left me blurry.

Turns out the new prescription was only a little too weak. My eyes really are better according to objective measurements, but subjectively, my brain hasn't yet caught up. At least that's how my doc explained it. I'm back with my old prescription for a while, and wondering what the heck my brain is up to. I don't even know where to begin googling. Can someone name and explain this phenomenon?
posted by frykitty to Health & Fitness (16 answers total) 1 user marked this as a favorite

It sounds to me like your optometrist is full of crap. If your prescription is a little to weak things in the distance will be a little blurry. On the other hand, if your prescription is a little too strong, you'll see fine. Maybe what your optometrist meant is that you haven’t gotten used to a blurry image. Your glasses should be set exactly right not a little less or a little more.

undercorrected glasses bad for your eyes, although it was believed for a long time to be better for them. Maybe your optometrist hasn't caught up.
posted by delmoi at 11:49 AM on February 22, 2005

Er, actualy if your perscription is too strong, you'll have trouble seeing objects that are very close to your face, that's all. And things will be more distorted.
posted by delmoi at 11:53 AM on February 22, 2005

I've definitely seen this effect, in the exact same circumstances. From what I can tell, I don't think it's your brain, I think it's the muscles in your eye--specifically, the ones that control the focus of the lens in your eye.

Basically, they get in or out of shape just like any other muscles, and compensating for the weaker prescription means that they actually have to work harder to hold things in focus. Until they get used to that extra work, they're going to simultaneously get blurry easily, and feel strained more easily, but if you ease into the new lenses, you should be fine in a little while. (Worked fine for me.)
posted by LairBob at 11:55 AM on February 22, 2005

Perhaps I'd better explain a little more. I went in for my initial exam, was told my eyes had improved, and was given new glasses that were pretty blurry at a distance.

I went back to a different optometrist and explained what happened. She examined my eyes, and found that yes, they'd improved, but that they hadn't improved as much as the first doc thought--the prescription really was too weak--however, there was still improvement.

There are two types of measurements done in the office--one that is objective, and actually measures the shape of your eyes, and one that is subjective, and measures how you see. Those measurements are different.

Until my brain adjusts, I'm going to have a slightly stronger prescription than my objective measurement shows I need. I may be able to go to a weaker prescription in the future.

When I mentioned this to the optitian taking my frame order, he had also heard of this. Unfortunately, I neglected to ask either of them what the technical term is.
posted by frykitty at 11:58 AM on February 22, 2005

Ah-ha! Lairbob: that makes a lot of sense. Why she didn't say "muscle" instead of "brain" is beyond me.
posted by frykitty at 12:00 PM on February 22, 2005

frykitty, I had a similar thing with my contacts prescription. My eyes had actually improved to the point where my contacts were giving me better than 20/20 vision, which I had grown accustomed to. Then they tried to switch my prescription down so that I was back to 20/20, and I balked. I'm really rather attached to the more-than-perfect eyesight. My glasses (new prescription) still give me a headache, so I tend to stick to the contacts (old prescription).

So some of that may be playing into your situation, too.
posted by occhiblu at 12:12 PM on February 22, 2005

whoa. the way the eye works, when it is completely relaxed, you are focussed as far away as possible (the lens is "pulled flat" by surrounding ligaments). in a "perfect " eye, that should mean infinity. for short-sighted people it is not, and so you need glasses to correct.

so, first thing, it's not a lack of muscles that stops you from seeing things far away. muscles are exactly what you don't want.

second, "better than 20/20" makes no sense. if you have lenses that are too strong then when your eye is relaxed nothing will be in focus. you need to contract muscles slightly even to look at distant objects. that is bad for two reasons. first, your eye is not relaxed even when looking at distant objects and second, you're "using up" the adjustment, which leaves you with less ability to focus on things nearby. so stronger lenses than required make your overall vision worse.

ok, that (afaik) is fact, this next bit is speculation. since you have been accustomed to over-strong lenses, your brain may be having a hard time telling the muscles to "let go" and relax sufficiently to see very distant objects. that seems to be the explanation you have been given. it sounds a bit odd to me, though (there's something called "temporary myopia" that's similar, but it lasts for just a few minutes).
posted by andrew cooke at 12:31 PM on February 22, 2005

I have that happen when there's too much of a change between my old 'script and the new one. We (the optometrist, the optician, and I) have learned to "sneak up" on the new 'script. The optometrist will do a full exam, determine where the 'script should be, and write me two 'scripts, one to be filled that day, and one to be filled after a couple of weeks. The second 'script is the correct one, but if we went straight to it, it wouldn't work.

It's a combination of the muscles in the eyeball and the brain getting in a rut. (In my case, there's also slowly progressing keratoconus.)

Think of it as video filters. Your brain knows what stuff is supposed to look like, and will make the image look right, even as the input is changing. Then when you change the input, it's still applying the filters. It can take a while to get the filters changed.
posted by jlkr at 12:34 PM on February 22, 2005

The explanation I'd been given may be erroneous, but while on this "too strong" prescription for the past seven years, my eyesight first improved and now has remained constant; before that, I was getting stronger prescriptions each year. The optometrist who wanted to down-grade my prescription was an asshole, however, who did claim that giving me a weaker prescription than necessary should exercise my eyes, so he may just have been both (1) wrong and (2) a bad explainer!

Maybe the moral is just that what constitutes "correct vision" varies greatly between optometrists.
posted by occhiblu at 12:38 PM on February 22, 2005

Maybe you should start going to an opthalmologist. Opthalmologists have more education (typipcally, an M.D. degree + 3 years of specialty training) and know about a much broader range of treatment and eye health issues. Optometrists may have a doctor of optometry degree, but it is not the same kind of training an MD will have. I have serious vision issues and have been around the block with contacts and glasses since I was 13; I've found I get consistently better, more careful treatment from opthalmologists, though the optometrists are cheaper. Just a suggestion.
posted by Miko at 1:45 PM on February 22, 2005

Alos, with regard to changing prescriptions: as nearsighted people age, particularly in their thirties, vision will improved due to the gradual hardening of the retina that happens to everyone. For those with good natural vision, this is a downgrade in vision. For the nearsighted, it may improve vision. Sometimes optometrists who are used to treating a lot of very light prescriptions (you know, the reading-glass' types, people who can drive without their glasses) will presume a stronger prescription is always needed as the patient's age increases. But for those of us with severe nearsightedness, the retina hardening will actually allow us to wear a lighter prescription.
posted by Miko at 1:49 PM on February 22, 2005

Yes, opthamologists have more training and can treat a much broader range of conditions than an optometrist can.

But that doesn't make them any better at reading your eyes and giving you an accurate prescription.

Similarly, physicians have more training and can do more stuff than nurses or PA's can, but that doesn't make them any better at giving an injection or suturing a minor wound.

I'd think that for a routine prescription, you want to go to someone who reads jillions of eyes every year and spends all his/her time reading eyes. It's not that they're simply cheaper; I suspect that they're just as good if not better at getting prescriptions for normal-boring eyes.
posted by ROU_Xenophobe at 2:04 PM on February 22, 2005

... one that is subjective, and measures how you see...

Better here, or better here? A or B? 1 or 2?

My opthamologist (I second the recommendation) told me that I was 'very perceptive' and I was very flattered. I apparently can make a fine distinction between very subtle levels of correction. I think I'm just very used to the process since I've been doing it for so long.

Miko: I don't think my myopia ever got better, it just stabilized for a while when I was in my thirties and then got very slightly worse last go-round. Now I'm on bifocals.
posted by fixedgear at 2:10 PM on February 22, 2005

But that doesn't make them any better at reading your eyes and giving you an accurate prescription.

No, I think it does make them better at it. Treating eyes well is not the same as cleaning a minor wound (though, given a choice, I'd rather have a physician do that, too). Eyes are sensitive and fragile and vision is something I just don't want to compromise on.

The opthalmologists I've seen have spent a lot more time reading my prescription, and were more sensitive about my desire for the best correction. They really fine-tune it in a way I've never seen an optometrist do. They also have all evidenced greater understanding of the trade-offs of any high prescription -- sharpness for distortion, strength for comfort, etc. They've also all spent more time on patient education.

There are some good optometrists out there, certainly, but even the best I've seen wasn't as good as any of the 3 opthalmologists I've gone to since I started looking for a better level of eye care. In addition to prescriptions, they look out for your overall eye health as well as your vision, and in fact can sometimes see early signs of pathology in the eye that will later manifest themselves in your body. They dilate at every annual exam, and tell you about whether your retina is still securely attached or showing early signs of detachment. It's also nice to go to one person for your prescription, the occasional bout of pinkeye or burst blood vessel, and a general eye health checkup.
posted by Miko at 2:49 PM on February 22, 2005

The absolute worst 'script I ever got was from an opthalmologist. It was completely and totally wrong. Just because they've got the advanced training, etc, doesn't mean that they're going to be better at doing eye exams.

I've been to a number of opthalmologists, and all (except my current one) have been very quick to tell me how much better it is that I'm seeing them rather than an optometrist, and then they'd rush through the optical exam and give me a 'script that had to be tweaked at least once before it's wearable. My optometrist, on the other hand, allows 90 minutes for an annual exam, and doesn't rush; and once we figured out the "sneaking up", I haven't needed to have a 'script tweaked in six pairs of glasses.

I see my opthalmologist every couple of years to check on the progress of the keratoconus. When I need to go to contacts for that, he'll prescribe those, but will send me to my optometrist for followups. My optometrist is very good, and checks eye health as well as vision.
posted by jlkr at 3:52 PM on February 22, 2005

Miko, my experience is the opposite of yours. I find I get much more attention and care from optometrists than from ophthamologists, who seem to think that just taking a prescription is beneath them, or want to get on to something more interesting or lucrative, and they're more likely to treat me as just a pair of obedient eyes to do with as they will instead of explaining anything.

They dilate at every annual exam

Optometrists don't in New Hampshire?
posted by ROU_Xenophobe at 4:03 PM on February 22, 2005

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