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By Melvin I. Roat, MD, FACS, Clinical Associate Professor of Ophthalmology; Cornea Service, Sidney Kimmel Medical College at Thomas Jefferson University; Wills Eye Hospital

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

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:

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 collagen cross-linking, an ultraviolet light treatment that stiffens the cornea thereby preventing progressive bulging and thinning, is used throughout Europe and has recently been approved for use in the US.

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