ELI5: Why can I see better wearing eye glasses, than contact lenses?

dannyunderpants · 2014-12-30T22:05:43+00:00

You may be more astigmatic than you realize. Spherical vision defects — defects which are symmetric around the axis of the eye — can be corrected about as well with either glasses or contact lenses. The reason should be obvious: A contact lens has no orientation relative to the axis of the eye, so it works best when the correction also has no orientation about the axis. People who have simple myopia or simple hyperopia (near-sightedness or far-sightedness) get spherical lenses, either worn as eyeglasses or contacts.
Astigmatism, on the other hand, can't be corrected (fully, anyway) with a spherical lens. An astigmatism can only be corrected with a lens that focuses the light one way in the direction that's parallel to the floor and another way in the direction that's perpendicular to the floor. These kinds of lenses are called toric lenses (because they're a section of the outer surface of a torus, or doughnut-shape), and it should be obvious that they have to have a fixed orientation relative to your head. Since spherical contact lenses only have one axis of curvature, you can never get the same fidelity of correction out of a spherical contact lens that you can get out of a toric eyeglass lens.
There are toric contact lenses, but as a rule they tend to be pretty expensive (because they don't have the same economies of scale of spherical lenses) and they don't yield corrective results that are as good as myopic or hyperopic people get from spherical lenses. In order to work, a toric lens has to be centered on your cornea and correctly oriented relative to your eyeball, so there's a lot of blinking involved.
So long story short, even a "minimal" astigmatism is probably enough to make a dramatic difference between the correction you get from your spherical (or even toric, if you wear them) contacts and your toric eyeglasses.

blink_and_youre_dead · 2014-12-30T22:34:01+00:00

FWIW I see better with contacts than glasses. No astigmatism, acuevue 2. I just thought that was the norm.

urbster1 · 2014-12-30T23:26:11+00:00

For acuity, sure, glasses will always be better. I tend to think of it more like the larger amount of lens material means it can be more precisely sculpted for more accurate refraction. A contact lens is an order of magnitude smaller so the optics aren't the same and are likely to be fuzzier. However, contacts are going to be better for your peripheral vision. Granted, if you're like most people who sit in front of screens most of the time, you may not use it much. But if you were to use a wider range of your vision and came to rely on it, you'd probably start to prefer contacts, I'd guess.

mouthpipettor · 2014-12-30T22:00:29+00:00

I hope someone answers you because I have the exact same experience. It's likely a soft plastic contact can only remedy astigmatism so much. I wonder if rigid contacts would offer better clarity for us?

mrkrabz1991 · 2014-12-31T06:34:14+00:00

I the opposite. My vision is MUCH clearer and better with contacts over glasses.

Mousi · 2014-12-31T09:20:36+00:00

For me, it's mostly my night vision that's terrible with contacts. I always get a glow around bright objects that obscures the things around them. This makes it very hard to read text that's illuminated at night, like signs and billboards.
This is also a problem with glasses, but less so.

seamonkee · 2014-12-31T19:19:48+00:00

You'll need to get fitted better for your contacts.
I have fairly bad astigmatisms in both eyes and what makes the biggest difference for contacts is getting fitted properly for them. They shouldn't move around like crazy and yes, blinking should help when they may get misaligned on your eyes, but properly fitting contacts are a rare and beautiful treat. Not sliding around as much is the biggest difference, but also with the correct curvature to your eye makes your vision much, much better (anecdotally, in my experience).
I've been wearing contacts for 25 years. Started when I was 12 years old in gas permeable hard lenses (awful things). Eventually as the tech became better I switched to torics as well and still wear torics, but what's been the difference is a perfect fitting and I've only had 2 out of a dozen optometrists do that for me. Good luck. You'll really have to find an eye doc that really cares and an office that will reorder contacts until you find the best fit. Oddly enough, my best fitting pair of contacts came from an elderly doc in a walmart, even after going to independent eye doctors. So, expensive may not be better.

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