Keratoconus
We see through the cornea, which is the clear,
central part of the front surface of the eye. Normally, the cornea has a
spherical shape, but sometimes, however, the structure of the cornea is just
not strong enough to hold this round shape and the cornea bulges outward like a
cone. This condition is called keratoconus.
What Causes Keratoconus?
Tiny fibers of protein in the eye called collagen
help hold the cornea in place and keep it from bulging. When these fibers
become weak, they cannot hold the shape and the cornea becomes progressively
more cone shaped.
Keratoconus may run in families, and appears more
often in people with certain medical problems, including certain allergic
conditions. It's possible the condition could be related to chronic eye
rubbing. Quite often, though, there is
no eye injury or disease that explains why the eye starts to change.
Keratoconus usually starts in the teenage years. It
can, though, begin in childhood or in people up to about age 30. It's possible
it can occur in people 40 and older, but that is less common.
The changes in the shape of the cornea can happen
quickly or may occur over several years. The changes can result in blurred
vision, glare and halos at night, and the streaking of lights.
The changes can stop at any time, or they can continue for decades. In
most people who have keratoconus, both eyes are eventually affected, although
not always to the same extent. It usually develops in one eye first and then
later in the other eye. With more advanced form of the condition, glasses do
not offer satisfactory vision correction, and specialist contact lenses are
generally fitted to achieve best acuity. In advanced stages, a corneal
transplant may be required.
A recent surgical alternative
to corneal transplant is the insertion of intrastromal corneal ring segments. A
small incision is made in the periphery of the cornea and either one or two thin arcs of polymethyl
methacrylate are slid between the layers of the stroma on one or both
sides of the pupil before the incision
is closed. The segments push out against the curvature of the cornea,
flattening the peak of the cone and returning it to a more natural shape. The
procedure, carried out on an outpatient basis under local anaesthesia, offers
the benefit of being reversible and even potentially exchangeable as it
involves no removal of eye tissue.
#keratoconus #kerarings #intacs
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