KERATOCONUS
Keratoconus
is the most frequently encountered deformation of the cornea.
It is a conical, usually bilateral central deformation of the cornea
with opacification and thinning of the cornea.
Occurrence is familial, although women are more likely to be affected
than men.
Keratoconus is probably a genetic disorder. It can occur in families
with varying paths of hereditary transmission. Occasionally keratoconus
is associated with trisomy 21 syndrome (Down syndrome) as well as
with atopic dermatitis and other connective-tissue disorders such
as Marfan's syndrome.
The clinical course of the disorder is episodic; the increasing protrusion
of the cornea
usually produces bilateral irregular myopic astigmatism. Rarely keratoconus
can cause tears of Descement's membrane due to the continuous stretching.
The entire cornea can then bulge out at this site. This is referred
to as acute keratoconus. Symptoms of acute keratoconus include sudden
loss of visual acuity accompanied by intense pain, photophobia, and
increased tearing.
The diagnosis is usually made with a keratoscope, ophthalmometer
(reflex images will be irregular) or corneal topography. The examiner
can also detect keratoconus without diagnostic aids by standing behind
the patient and pulling the patient's upper eyelids downward. The
conical protrusion of the surface of the cornea will then be readily
apparent due to the deformation of the margin of the eyelid (Munson'sign).
Degeneration
of visual acuity can usually be corrected initially with eyeglasses.
Hard contact lenses will be required as the disorder progresses. However,
after a certain point, the patient repeatedly will lose the contact
lenses. Then the only possible treatment used to be penetrating keratoplasty
(transplantation of a corneal graft from a donor into the patient's
cornea). In recent years there is a new solution, which is called
intacs (intracorneal ring). Now only in advanced keratoconus penetrating
keratoplasty (corneal transplant) is performed.
The prognosis for penetrating keratoplasty in treating keratoconus
is good because the cornea is has no blood vessels in keratoconus.
