The eye is actually like a camera. The front part of the eye focuses images onto the area at the back of the eye called the retina. If the image cannot be properly focused on the retina due to an increased or decreased axial length of the eye, or differences in the corneal structure, this indicates the presence of a refractive error.
There are four types of refractive errors:
Myopia: This occurs when the anterior-posterior length of the eye is longer than normal, causing light rays entering the eye in parallel to focus in front of the retina. Myopia is a structural feature and is often inherited genetically.
Hyperopia (Farsightedness): This occurs when the anterior-posterior length of the eye is shorter than normal, causing light rays to focus behind the retina. Structural and hereditary factors are the most common causes of hyperopia.
Astigmatism: This results from the cornea at the front of the eye being elliptical rather than perfectly round, like a baseball. Patients with astigmatism experience problems with both near and distance vision. Astigmatism can occur together with myopia or hyperopia.
Presbyopia: This develops as the lens of the eye loses flexibility with age, making it difficult to focus. Presbyopia is a natural part of aging.
