Refraction problems include:
- Myopia - short-sightedness, which is decreased distance vision caused by the eye ball being longer than normal or the cornea (front surface of the eye) being steeper than normal or a combination of these factors.
- Hyperopia - far-sightedness, which is decreased near vision caused by the eye ball being shorter than normal or the cornea being flatter than normal or a combination of these factors.
- Astigmatism – when light rays focus on two different points, due to the cornea or lens not being smooth enough caused by some areas being steeper/flatter than normal (this is sometimes explained as the eye having a “rugby ball shape”)
- Presbyopia – the decreased ability of the eye’s crystalline lens to focus clearly on near objects, due to a loss of elasticity, typically occurring from the age of forty years.