I'm very near-sighted and I heard that eyesight can be improved by wearing your glasses as little as possible because it will force your eyes to work harder and very slowly improve your eyesight. Does anyone know if this is true?

I have heard that too. My eyesight changes with many things... mostly what I eat.
Like when I eat good healthy meals and don't drink soda it is a bit better. I wear my glasses on and off and the less I wear them the better my eyes seem to be.
I heard of a pair of glasses that have pin holes that you can wear to read and it helps focus better to improve your eyesight.

Also fresh fruits and vegetables, anti oxidents such as ginkgo and beta carotene are good
But if you have high blood pressure or some other health problems I think you have to be careful with ginkgo.
Also omega fatty acid, vitamin C, eyebright and bilberry are good.

Here is a good site
Eyesight help for poor eyesight, review of herbs, vitamins, supplements (http://www.yohimbebark.net/eyesight.html)

I think it's a load of rubbish personally your eyes need help for a reason, either because they are too long (short sighted) or too short (long sighted) or the muscles too weak (long) or strong (short) however as we have no control over these muscles you can not exercise them. People think their vision is better when they don't wear their glasses for a while, this is because your eyes over compensate and strain and get used to the reduced vision. The pinhole lenses don't actually inprove your vision as such they focus ALL the light on the macula (used for seeing fine detail) and as a result the light is more dense making it easier to distinguish light levels. Please don't just stop wearing yoiur glasses esp if you drive. Consult your optician.

Please don't listen to this stuff I really don't believe it! First off short sightedness is caused by either parts of the eye being too long or the muscles being too strong and long sighted people either have parts of their eyes too short or the muscles too weak. Either way you cannot change the prescription of your eye by yourself. We have no control over the muscles in our eyes so we can't exercised them to help. Also this pinhole lens that's mentioned focuses light onto the macula (the part of the retina that gives us fine detail vision) as the light doesn't get a chance to disperse the retina is able to distinguish between the shades of light easier, however you then loose your peripheral so whts the point?? Please be careful if you take any advice esp if you drive. The optician has given you glasses for a reason please just use them. If you don't like wearing glasses try contact lenses or check about laser surgery.

Sorry my last quote didn't come up when I went back so put it again sorry :(

Eye sight can begin to deteriorate due to poor nutrition and free radicals. It can be improved by improving health if the problem is due to these reasons.
My chiropractor has improved eye sight simply through correcting the spine and changing peoples eating habits and supplements.

For what it is worth, I have benefited rather amazingly from vitamin C. I began using vitamin C in 1978 but not in large doses. I remember moving it up to one gram [1, 000mg] four times a day, divided doses, several years ago and later increasing it to 2 grams, four times a day, during the winter months. In 2002 when I went for my drivers license renewal and took the vision test, the tester surprised me by passing me without glasses. In 2002 and 2006, when I went for my drivers license renewal, I passed the vision test easily without glasses. I now drive day or night and have no problem. [Of course, I take other vitamins and minerals daily].