Why do glasses let us see better and how do they work?

Answer 1

Myopia (nearsightedness) is a condition in which the light rays from a distant object are focused anterior to (in front of) the retina therefore resulting in a blurred image at the retina. Eyeglasses for myopia cause the light to diverge (or spread out) upon passing through the lens. By diverging the light before it encounters the eye the focus of light is moved more posteriorly so as to focus directly on the retina.

Hyperopia (far sightedness) is a condition in which the light from a distant object focuses posterior to (or behind) the retina therefore resulting in a blurred image at the retina. Eyeglasses for hyperopia cause the light to converge (focus more strongly) upon passing through the lens. By converging the light before it encounters the eye the focus of light is moved more anteriorly so as to focus directly on the retina.

Presbyopia is a condition of the eye in which, due to aging, the person has lost the ability to CHANGE the focus of the eye when reading or doing any near point visual task. A prescription for presbyopia replaces the amount of focusing the patient has lost so they are able to read clearer at near.

Astigmatism is a condition of the eye in which, due to a distortion in the shape of the cornea, the patient has two separate prescriptions. By placing two separate appropriate prescriptions in the eyegasses (this works the same as in myopia or hyperopia depending upon which type of prescription is present) the light is brought to a focus directly on the retina.

There are other aspects of prescriptive correction such as prism, slab off, tints, refractive index, etc. that perform specific tasks when employed but your question was probably more addressed to the above discussion. Hope this helped.

Answer 2

The eyeball has a curved lens; this focuses light so that we can see things clearly. When a person is young and the eye is healthy, the lens changes its shape as we look at something close, then changes again when we look off in the distance. If the eye is damaged or diseased, it looses its elasticity and cannot focus clearly at different distances. Men are typically near-sighted, meaning they can see clearly close-up, but not at a distance. Women are typically far-sighted, meaning they can see clearly in the distance, but not up close.
What glasses do is to mimic the lens in the eye; so far, glasses cannot refocus, but can focus only at far distance, middle distance or up close. This works for awhile, but as a person's eyesight continues to deteriorate, a person needs bi-focals, then tri-focals.
I wear two different pairs, one for typing, reading, close-up work, another pair for watching a movie or driving. I can still read without glasses. My problem with bifocals is that when I drive, I look up (I would look through the reading part of bifocals); when I read, I look down (or through the distance part of bifocals). Even worse, when I go down stairs, I see through the close-up part; the steps are fuzzy at best. So, I do not wear bifocals. (This is a common complaint of many older persons.)
But, the simple answer is: glasses help us see better by focusing the light into our eye. But, there is a trade off: glasses also make things look smaller than what they are, which is why it takes time to adapt to wearing glasses in the first place and to adapt to a big change in glasses.

Answer 3

I agree with Dr. Yagman