Astigmatism is an imperfection in the curvature of your eye’s cornea or lens.

It may be helpful to think of the normal eye as being shaped like a basketball. With astigmatism, it's shaped more like an American football (egg- or oval-shaped). When the steepest curve runs vertically, with the football lying on its side, it's called:

• with-the-rule astigmatism

When the steepest curve runs horizontally, with the football sitting on its end, it's called:

• against-the-rule astigmatism

https://www.aao.org/eye-health/diseases/what-is-astigmatism

Hyperopia (farsightedness), is a refractive error, which means that the eye does not bend or refract light properly to a single focus to see images clearly. In hyperopia, distant objects look somewhat clear, but close objects appear more blurred.

https://www.aao.org/eye-health/diseases/hyperopia-farsightedness

Myopia is a refractive error. Refractive errors happen when your eye does not focus light properly on the retina. That focusing is called refraction (bending).

For you to see clearly, light rays must travel through your cornea and lens. The cornea and lens refract the light so it lands on the retina. The retina turns light into signals that travel to your brain and become images. With refractive errors, the shape of your cornea or lens prevents light from bending properly. When light is not focused on the retina as it should be, your vision is blurry.

Myopia is a common condition that affects an estimated 25% of Americans. It is an eye focusing disorder, not an eye disease.

https://www.aao.org/eye-health/diseases/myopia-nearsightedness

Presbyopia is when your eyes gradually lose the ability to see things clearly up close. It is a normal part of aging. In fact, the term “presbyopia” comes from a Greek word which means “old eye.” You may start to notice presbyopia shortly after age 40. You will probably find that you hold reading materials farther away in order to see them clearly.

https://www.aao.org/eye-health/diseases/what-is-presbyopia