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Keratoconus Side Bar
By Dr. Stella Mugo, Opthamologist
[email protected]
Definition: It is the progressive thinning of the Cornea – the clear outer front portion of the eye, causing
it to become conical instead of its usual round shape. It leads to short- sightedness (Myopia), irregular
astigmatism and corneal scarring, which may cause mild to severe visual impairment. For some it
worsens with time, but may halt at any stage between mild and severe Keratoconus. The onset is
usually at puberty and the condition progresses up to the late thirties where it can stop.
Causes: Genetics, ocular allergy and eye rubbing. A recent study at the KNH eye clinic and found that
30.9% of patients with allergic conjunctivitis had Keratoconus.
Symptoms: Progressive loss of vision with ghost images, frequent changing of spectacle correction with
unsatisfactory results, and ocular allergies with frequent eye rubbing. Some patients present with acute
pain and whitening of the cornea due to hydrops – when the cornea becomes extremely thin and
stretched, the inner layer breaks allowing fluid in the eye to seem through he middle collagen layer. This
makes the cornea hazy, white and painful. It heals leaving a scar which leads to visual impairment.
Some patients present with acute hydrops.
Diagnosis: By clinical signs, keratometry (checking the corneal refractive power) and by corneal
topography. Of the 3 methods, corneal topography is most recommended as it detects the earliest signs
of keratoconus before patient’s vision is impaired.
Complications: The main complication of keratoconus is severe visual impairment or blindness due to
high myopia with astigmatism and corneal scaring secondary to hydrops.
Management: Depends on the disease progression and stage.
Early stages: Spectacle correction is an option for those patients who can achieve 6/12 or better
vision. However spectacles do not correct irregular astigmatism. Contact lenses are used by
more than 90% of keratoconus patients. Soft contact lenses may be used in early stages. In
later stages Rigid Gas Permeable Contact Lenses may be used. Scleral contact lenses have been
used in patients with irregular anterior corneal surface.
Intracorneal ring segments inserted via channels made mechanically or with help of
Femtosecond Laser can also be used. This does not eliminate progression of keratoconus but, it
delays the need for corneal transplant.
Corneal Collagen Crosslinking is a new treatment for early progressive keratoconus. It slows
down or even stops the progression of keratoconus. Crosslinking involves, use of UV light and a
photosensitizer to strengthen chemical bonds in the cornea.
It is contraindicated in patients with, corneal thickness less than 400 microns, keratometry of
more than 60 dioptres, those who have had prior herpetic infection or severe corneal scarring.
Corneal Transplant technically Penetrating Keratoplasly is the recommended method of
treatment those with severe keratoconus or corneal scarring.
Lamella keratoplasty has been the management for keratoconus in cases without significant
corneal scaring or corneal hydrops. It reduces the risk of graft rejection because the descements
membrane and endothelium are preserved.