Keratoconus isn't a refractive error itself. It is a disease related to the cornea, in which the cornea is progressive thinning and its shape is irregular. In this case, it will result in myopia and astigmatism which are both the refractive errors. keratoconus is usually caused by allergies, asthma, and excema (atopic disease). People who often rubbing their eyes can also have the chance of getting keratoconus.
Keratoconus is a progressive eye disease in which the normally round cornea thins and begins to bulge into a cone-like shape. This cone shape deflects light as it enters the eye on its way to the light-sensitive retina, causing distorted vision. There are several factors that cause Keratoconus: an imbalance of enzymes within the cornea, overexposure to ultraviolet rays from the sun, excessive eye rubbing, a history of poorly fitted contact lenses and chronic eye irritation.Keratoconus can result in nearsightedness and/or astigmatism, those are all refractice errors. Eyeglasses cannot help to patient with keratoconus, but contact lenses can. Learn more at http://www.allaboutvision.com/conditions/keratoconus.htm