Corneal dystrophy (human)

Corneal dystrophy is a group of rare hereditary disorders characterised by bilateral abnormal deposition of substances in the transparent front part of the eye called the cornea.

A corneal dystrophy can be caused by an accumulation of extraneous material in the cornea, including lipids and cholesterol crystals.

Corneal dystrophy may not significantly affect vision in the early stages. However, it does require proper evaluation and treatment for restoration of optimal vision. Corneal dystrophies usually manifest themselves during the first or second decade but sometimes later. It appears as grayish white lines, circles, or clouding of the cornea. Corneal dystrophy can also have a crystalline appearance.

There are over 20 corneal dystrophies that affect all parts of the cornea. These diseases share many traits:

Corneal dystrophies affect vision in widely differing ways. Some cause severe visual impairment, while a few cause no vision problems and are diagnosed during a specialized eye examination by an ophthalmologist. Other dystrophies may cause repeated episodes of pain without leading to permanent loss of vision.

Diagnosis can be established on clinical grounds and this may be enhanced with studies on surgically excised corneal tissue and in some cases with molecular genetic analyses. As clinical manifestations widely vary with the different entities, corneal dystrophies should be suspected when corneal transparency is lost or corneal opacities occur spontaneously, particularly in both corneas, and especially in the presence of a positive family history or in the offspring of consanguineous parents.

Superficial corneal dystrophies - Meesmann dystrophy is characterized by distinct tiny bubble-like, punctate opacities that form in the central corneal epithelium and to a lesser extent in the peripheral cornea of both eyes during infancy that persists throughout life. Symmetrical reticular opacities form in the superficial central cornea of both eyes at about 4–5 years of age in Reis-Bücklers corneal dystrophy. Patient remains asymptomatic until epithelial erosions precipitate acute episodes of ocular hyperemia, pain, and photophobia. Visual acuity eventually becomes reduced during the second and third decades of life following a progressive superficial haze and an irregular corneal surface. In Thiel–Behnke dystrophy, sub-epithelial corneal opacities form a honeycomb-shaped pattern in the superficial cornea. Multiple prominent gelatinous mulberry-shaped nodules form beneath the corneal epithelium during the first decade of life in Gelatinous drop-like corneal dystrophy which cause photophobia, tearing, corneal foreign body sensation and severe progressive loss of vision. Lisch epithelial corneal dystrophy is characterized by feather shaped opacities and microcysts in the corneal epithelium that are arranged in a band-shaped and sometimes whorled pattern. Painless blurred vision sometimes begins after sixty years of life.

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