Keratoconus is a progressive thinning of the cornea, the clear”window” at the front of the eye. This thinning of the cornea makes it more susceptible to the normal pressure inside the eye, causing the cornea to bulge outward, in a cone-like shape. Irregular astigmatism is caused by the bulging cornea, resulting in blurry or distorted vision.
The underlying cause of keratoconus is not fully understood. Studies have suggested a genetic link, however most patients with keratoconus do not have another family member with the condition. Genetic studies suggest a deficiency in the collagen structure of the cornea in patients with keratoconus, resulting in weaker support of the shape of the cornea. There is higher incidence of keratoconus in patients with atopic disease, such as eczema, asthma or chronic allergy. Because the cornea of patients with keratoconus is thinner and structurally weaker than a normal cornea, it is more susceptible to minor trauma. Patients with keratoconus should never rub their eyes, as there is a link between frequent eye rubbing and progression of the disorder.
Patients with keratoconus may experience blurry or distorted vision that is not improved with spectacles. An untrained observer will not usually notice anything abnormal about the appearance of an eye with keratoconus, however your eye doctor can detect changes in the shape of the eye with a keratometer or corneal topographer, and can often observe changes in the appearance of the cornea with a slit lamp microscope.
Patients with mild cases of keratoconus may be able to achieve adequate vision through spectacles or specialty soft contact lenses. Many patients with keratoconus are fit with rigid gas permeable contact lenses. The rigidity of the lens allows the tears to pool under the contact lens, creating a more optically smooth surface by masking the irregular astigmatism. Some patients will need to wear glasses over the contact lenses in order to achieve optimal vision correction. In advanced cases of keratoconus, patients may be unable to be successfully fit with rigid contact lenses. These patients may be fit with a scleral lens, a large diameter specialty lens, or a corneal transplant may be indicated. Currently, procedures designed to slow the progression of the disorder through collagen crosslinking are being evaluated in clinical trials.