What are Refractive Visual Abnormalities or Errors of Vision

By refractive visual abnormalities we mean those problems in which the eyes are unable to focus the image of the object they are looking at on the macula of the retina. In these cases, the image is focused either further forward (myopia) or further back (hyperopia) than the retina, or the rays from the object are not all focused on the same level but at different levels with each other in relation to the retina (astigmatism).

Refractive problems include presbyopia, which is not due to anatomical defects of the eye but to the progressive hardening of the crystalline lens, which loses the ability to change its curvature and consequently the ability to adapt and focus at short distances.