Myopia, hyperopia and astigmatism are all types of glasses problems.
These are the reasons why most people need to wear glasses.
Myopia is an eye condition where the focusing power of the eye is too strong, and for that reason, we need to wear negative power lenses to reduce the focusing power of the eye and bring the image of the world to focus on our retina.
Hyperopia, is also called long-sighted, is the opposite. This is where the focusing power of the eye is not enough and so we need to use a plus power lens in front of the eye to bring the image of the world into focus on our retina.
Very often people will have a combination of either myopia and astigmatism or hyperopia
The last issue is astigmatism. Astigmatism is where the eye, rather than being completely round shaped, is actually slightly oval shaped and elongated and that can either be elongated horizontally or vertically. This requires a special type of glasses lens to correct it, called a Toric lens. Very often people will have a combination of either myopia and astigmatism or hyperopia and astigmatism and therefore glasses will be composed of either a plus lens, to correct the hyperopia or long-sightedness, combined with a toric lens to correct the astigmatism, or in cases of myopia, a negative power lens to correct the myopia and a toric lens to correct the astigmatism.