Keratoconus is a degenerative disorder which affects the cornea. The shape of the cornea becomes more conical due to structural changes in the internal tissue, more specifically in the corneal collagen.
The main anatomical signs of keratoconus are a thinning of the cornea in the central or adjacent areas almost always accompanied by the same zone becoming raised causing high levels of irregular astigmatism, which leads to distorted vision.
Irregular astigmatism cannot be corrected using traditional methods such as glasses or soft contact lenses and good quality vision can only be achieved with hard contact lenses which may cause discomfort.
At an advanced stage, keratoconus brings about very poor quality vision and the progressive thinning of the cornea may in some cases lead to the cornea actually tearing making a corneal transplant necessary in order to avoid the loss of the eyeball.