Keratoconus is a bulging distortion of the cornea, leading to loss of visual acuity.

Keratoconus

Keratoconus is a slowly progressive thinning and bulging of the cornea, usually bilateral, beginning between ages 10 and 25. Its cause is unknown.

Risk factors include the following:

• Family history of keratoconus
• An atopic disorder
• Vigorous eye rubbing
• Lax eyelids
• Certain connective tissue disorders (eg, Ehlers-Danlos syndrome, Marfan syndrome, osteogenesis imperfecta)
• Down syndrome
• Congenital disorders with poor vision (eg, Leber congenital optic neuropathy, retinopathy of prematurity, aniridia)
• Obstructive sleep apnea

The distorted cone shape of the cornea causes major changes in the refractive characteristics of the cornea (irregular astigmatism) that cannot be fully corrected with glasses. Progressing keratoconus necessitates frequent change of eyeglasses. Contact lenses may provide better vision correction and should be tried when eyeglasses are not satisfactory. Corneal transplant surgery may be necessary if visual acuity with contact lenses is inadequate, contact lenses are not tolerated, or a visually significant corneal scar (caused by tearing of stromal fibers) is present.

Newer treatments seem promising. Implantation of corneal ring segments appears to have the potential to improve visual results by increasing tolerance of contact lenses and thus saving selected patients from transplantation. Corneal cross-linking, an ultraviolet light treatment that stiffens the cornea thereby preventing progressive bulging and thinning, has had positive results in European studies and may become more common.

Last full review/revision October 2012 by Melvin I. Roat, MD, FACS