Keratoconus (KC) is one of the most extensively investigated corneal degenerative diseases across the whole ophthalmology field; little remains known about the cause of the condition, although treatment options, of varying degrees of efficacy, do exist.

In short

The standard treatment for relatively early-stage KC is cross-linking, which has the potential to reduce corneal curvature by approximately 1.0–1.5 D. The procedure involves treating the cornea with riboflavin and then irradiating it with UV-A light waves to strengthen the collagen bonds in the cornea, which enhances stiffness and increases resistance to progressive keratoectasia.

Cross-linking treats the entire corneal surface, although the dystrophic, malacic and ectasic factors that characterize KC generally concern only one "sector" of the cornea, particularly in the initial stages of the disease.

Symmetrical treatment is pointless

Figure 1: Corneal map demonstrating symmetrical treatment effects, or the "Weighing Scale Effect".

It is pointless attempting to flatten an area that is already refractively flat, or whose curvature radii are normal. If a KC treatment that constricts the elastic proteins of collagen, such as cross-linking, is applied to the entire corneal surface, the flattening effect achieved will be uniform, which is less than desirable. This is because symmetrical treatment enhances the difference between the ectasic area and the normal curvature of the rest of the cornea, resulting in a partial regularization of the surface of the cornea in the ectasic area. We call this the "Weighing Scale Effect", where the flattening of the blue sector on the corneal map (Figure 1) (where the cornea is normal) induces a "balancing" effect, with subsequent reduction in the flattening in the yellow-red (ectasic) region.

I believe a good surgeon should respect the asymmetry of corneal deformation with which KC presents; hence, my treatment for KC focuses only on correcting the deformation and on restoring normal curvature radii, as far as possible. I have now been using selective asymmetrical treatment to reduce ectasia and to correct (at least partially) the related spheroastigmatic myopic ametropia for 23 years.

New surgical options

Asymmetrical Radial Keratotomy (ARK)

I first conceived Asymmetrical Radial Keratotomy (ARK) surgery (and then Mini-ARK surgery, for less grave cases) to regularize, remould, compact and improve the asymmetrical unevenness of the cornea's anterior surface. To date, these are the only surgical options available that offer these benefits.

In ARK, which is used to correct and implode the KC, a diamond-tipped scalpel is used to create 1.5–2 mm long microincisions, which are generally only performed on the extroverted corneal region, outside the field of the pupil, with approximately 30° incremental increases from 90° to 270°. In 98% of cases, correctly performed ARK is effective in KC, both to stop the disease and for refractive functional recovery.

The surgery is performed under local anaesthesia as an outpatient procedure, and requires no bandaging. The procedure takes between one and three minutes per eye and ensures good results instantly. Postoperatively, special eyewashes are prescribed (for a treatment period of approximately seven days) and, in a few cases, patients are required to use sunglasses for a few days.