The more common ocular problems are called refracting problems, that are related to the way the light hits or refracts in the retina.
- Myopia: the light rays are focused in front of the retina, either because it focuses in excess, or because the eye is much too long. The result is a blurred vision at long distance.
- Hyperopia: the images focus behind the retina, either because the cornea possesses a limited focus power, or because the eye is not sufficiently long. The result is a blurred vision at short distance.
- Astigmatism: it happens when the cornea does not present the same curvature in all its areas that is the reason why the light focuses in several points of the retina causing a distorted and blurred vision.
