Keratoconus is a progressive condition affecting the structure of the cornea, the clear front surface of
the eye. The collagen structure of the cornea is defective resulting in the cornea becoming progressively
thinner, causing it to bulge and form an irregular conical shape rather than a normal round dome shape.
Onset and diagnosis is usually made during puberty and later teenage years. Both eyes are generally
affected at the same time but progression can often be asymmetrical, with one eye worse than the
other. The degenerative process of keratoconus continues for 10-20 years following onset before
The exact cause of keratoconus is unknown but there are strong genetic links and it is believed that
factors such as rubbing eyes and hot environments exacerbate the condition.
Corneal Cross-Linking (CXL)
Corneal cross-linking is a minimally invasive outpatient procedure designed to treat progressive
keratoconus (and, sometimes, other conditions that cause a similar weakening of the cornea).
The corneal cross-linking procedure strengthens and stabilise the cornea by creating new links between
collagen fibers within the cornea. The two-step procedure applies specialty formulated riboflavin
(vitamin B) eye drops to the surface of the eye immediately followed by a controlled exposure of the eye
to ultraviolet light.
Corneal cross-linking can be combined with other procedures for keratoconus treatment. For example, it
can be performed along with implantation of tiny arc-shaped corneal inserts called INTACS to reshape
and stabilise the cornea in more advanced cases of keratoconus.
Intracorneal Rings (INTACS)
INTACS corneal inserts or implants are a minimally invasive surgical option used primarily for the
treatment of keratoconus. INTACS are two tiny, clear crescent-shaped pieces of a plastic polymer that
are inserted into the cornea to reshape the front surface of the eye.
Full Thickness Corneal Transplant
Your entire cornea may need to be replaced if both the front and inner corneal layers are damaged. This
is called penetrating keratoplasty (PK), or full thickness corneal transplant. Your diseased or damaged
cornea is removed. Then the clear donor cornea is sewn into place.
PK has a longer recovery period than other types of corneal transplants. Getting complete vision back
after PK may take up to one year or longer.
With a PK, there is a slightly higher risk than with other types of corneal transplants that the cornea will
be rejected. This is when the body’s immune system attacks the new cornea tissue.
Partial Thickness Corneal Transplant
Sometimes the front and middle layers of the cornea are damaged. In this case, only those layers are
removed. The endothelial layer, or the thin back layer, is kept in place. This transplant is called deep
anterior lamellar keratoplasty (DALK) or partial thickness corneal transplant. DALK is commonly used to
treat keratoconus or bulging of the cornea.
Healing time after DALK is shorter than after a full corneal transplant. There is also less risk of having the
new cornea rejected.
In some eye conditions, the innermost layer of the cornea called the “endothelium” is damaged. This
causes the cornea to swell, affecting your vision. Endothelial keratoplasty is a surgery to replace this
layer of the cornea with healthy donor tissue. It is known as a partial transplant since only this inner
layer of tissue is replaced.
There are a few types of endothelial keratoplasty. They are known as:
- DSEK (or DSAEK) — Descemet's Stripping (Automated) Endothelial Keratoplasty
DMEK — Descemet's Membrane Endothelial Keratoplasty
Each type removes damaged cells from an inner layer of the cornea called Descemet’s membrane. The
damaged corneal layer is removed through a small incision. Then the new tissue is put in place. Just a
few stitches are needed to close the incision. Much of the cornea is left untouched. This lowers the risk
of having the new cornea cells being rejected after surgery.
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