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A 63-year-old female presented for evaluation of blurred vision and complained of mild eye irritation for the past 20 to 30 years. On exam, her best corrected visual acuity was 20/25 in both eyes. The slit lamp exam is demonstrated above with similar findings reportedly seen on exam of her sister and daughter.

1.	The slit lamp images demonstrate involvement of which layer(s) of the cornea?
	a -- epithelium There are tiny intraepithelial cysts seen most prominently in the interpalpebral zone, symmetrically in each cornea.
2.	The diagnosis is:
	e -- Meesmann's corneal dystrophy This is Meesmann’s corneal dystrophy, also known as juvenile hereditary epithelial dystrophy. This rare dystrophy is characterized by numerous, tiny microcysts in the corneal epithelium of both eyes that increase in number throughout life. Cysts can sometimes be identified in childhood, although clinical symptoms frequently do not become evident until adulthood, when the cysts rupture and cause symptoms such as foreign body sensation, contact lens intolerance, tearing, photophobia, and mildly diminished visual acuity.  Some patients remain asymptomatic throughout life, while severe cases may result in corneal scarring and permanent visual impairment.   Treatment of mild symptoms includes ocular lubricants, cycloplegia, and therapeutic contact lenses.  For severe cases, treatment with epithelial debridement, phototherapeutic keratectomy, and lamellar keratoplasty has been advocated.
3.	A pathologic specimen would show:
	d -- a fibrogranular material, "peculiar substance" in the epithelial cells on electronic microscopy The fibrogranular material seen on electron microscopy is described as a “peculiar substance.” Histology demonstrates a thickened and irregular epithelium with cells showing perinuclear vacuolization and intracytoplasmic inclusions.  Presumably, the characteristic microcysts are composed of dying cells that fail to form their intermediate filament cytoskeleton and therefore, are easily damaged by minor trauma.
4.	Inheritance is:
	a -- autosomal dominant Mutations in the keratin genes KRT3 and KRT12 have been identified as a disease-causing defect with autosomal dominant inheritance. These genes encode the K3 and K12 keratin proteins which form a heterodimer and are expressed in the corneal epithelium.  The K3/K12 keratin pair has a structural role in maintaining corneal epithelium integrity. Contributing Authors:  Jay J. Meyer, M.D. and Kenneth L. Cohen, M.D.