A form of hereditary corneal dystrophy in which there
is an accumulation of amyloid deposits, or abnormal protein fibers, throughout the
middle and anterior stroma of the cornea. These deposits in the stroma appear on
an eye examination as clear, comma-shaped overlapping dots and branching filaments,
creating a lattice effect. Over time, the lattice lines grow opaque and involve
more of the stroma. They also gradually converge, giving the cornea a cloudiness
that may also reduce vision. These abnormal protein fibers can accumulate under
the cornea's outer layer -- the epithelium -- causing it to erode. This condition
is known as recurrent epithelial erosion. These erosions alter the cornea's normal
curvature, resulting in temporary vision problems. These erosions also expose the
nerves that line the cornea, causing severe pain. Even the involuntary act of blinking
can be painful.
To ease this pain, eye drops and ointments may help by reducing the friction
on the eroded cornea. In some cases, an eye patch may be used to immobilize the
eyelids. With effective care, these erosions usually heal within three days, although
occasional sensations of pain may occur for the next 6-to-8 weeks.
Although lattice dystrophy can occur at any time in life, the condition usually
arises in children between the ages of 2 and 7. By about age 40, some patients have
scarring under the corneal epithelium, resulting in a haze on the cornea that can
greatly obscure vision. In this case, a corneal transplant may be needed. Although
people with lattice dystrophy have an excellent chance for a successful transplant,
the disease may also arise in the donor cornea in as little as three years. Early
lattice and recurrent lattice arising in the donor cornea responds well to treatment
with the excimer laser.
Lattice dystrophy is caused by mutation in the gene encoding keratoepithelin.
Three other forms of autosomal dominant corneal dystrophy are also caused by mutations
in this gene, which maps to chromosome 5q31.
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