# How come degraded eyesight still holds with a mirror? [closed]

When you use a mirror to look at something, you can position it at an angle arbitrary to your face and still look at an object far away. My question is, for degraded eyesight, how come the picture is still degraded in the mirror? Is it because of an imperfect mirror? Is it theoretically possible to have a mirror that when looked at an angle with perfect scattering to give you better vision than without the mirror, just looking regularly with degraded vision? I am just wondering, it seems like a photonic process, but i don't know enough about the eyes to turn them into any sort of functional system

• No, if your eyes are defective, the quality of an image cannot be upgraded with a mirror. – The Last Word Sep 30 '14 at 5:56
• You need to clarify the question - it would help to be a little more concise and say why you think it should help to use a mirror – rg255 Sep 30 '14 at 6:12
• I asked this same question to my high school physics teacher when we were going over optics. I'm nearsighted, and wondered why I could see clearly from 6 inches away, but if I looked at a mirror from 6 inches away things were still blurred. The answer has to do with the angles of light entering the eye instead of distance. – user137 Sep 30 '14 at 14:11

It's been too long since physics to have a good answer, but I know that if you look at an object in a flat mirror, the light coming off the mirror would be identical to light coming a real object in the same position. The angles of the light rays are the same. Therefore, no matter how close the mirror is to your face, your eyes treat the image as if it's coming from 10 feet away, or however far the object in the mirror is away from the mirror. Bent mirrors will change this, that's why you get the "OBJECTS IN MIRROR ARE CLOSER THAN THEY APPEAR" warning.

I made a diagram to to try and explain it better.

The eye is looking at a mirror, the light from the arrow on the left of the mirror reflects off the mirror and toward the eye. The eye sees an image that appears as if it were behind the mirror, on the right.

• The working of a mirror is not what the OP is asking about. The question is whether a defective eye can see a clear image reflected off a mirror (i think). – The Last Word Sep 30 '14 at 5:52
• If the mirror is shaped to correct the image, then yes, just like how lenses can adjust the light so that it enters the defective eye in such a way the eye focuses it into a good image, a mirror could be made to do the same thing. However, getting the focal length right will be very hard and you'd have to put your eye in the exact same position relative to the mirror every time you use it. Flat mirrors will not fix the image and defective eyes will still see the images poorly. – user137 Sep 30 '14 at 14:08

Degraded eyesight can mean two basic processes:

1) Degradation of the imaging optics in your eye that focus light onto the retina such that light is not focused correctly, or 2) Damage to the retina itself so that light is focused, but signals to your brain are not generated in response to light.

What these two processes have in common is that they are problems with your eyes ability to process and interpret light. Placing a mirror close to your eye (but outside of it) does not directly compensate for either of these problems because, other than transforming the coordinate system, it doesn't actually do anything to the light or to your eye.

Possibly what you are thinking of by "degraded" eye sight is simply being near or far sighted, which is the specific case where your vision still works normally, but your eye does not under some conditions (nearby for farsighted, etc) due to a loss of accommodation (the physical flexing the lens of your eye that adjusts its focusing). In this case, a curved mirror can be chosen that operates just like eye glasses.