UV Light for Keratoconus

UV Light is used to treat patients with a condition known as Keratoconus.

What is Keratoconus?

Keratoconus is a corneal condition where the cornea becomes irregular in shape (ectasia). As analogy a perfect corneal surface is spherical (round) like a soccer ball. Astigmatism is a condition where the cornea is more curved in one meridian than the other and can be thought of being shaped like a rugby ball. Keratoconus is an extreme form of astigmatism (irregular astigmatism) where the astigmatism is no longer symmetrical. An analogy could be that it is shaped like the surface of an “egg” (Figure 1). This creates a blurred image on the retina and the degree of blur is proportional to the degree of irregular astigmatism. While patients can have a genetic predisposition to the disease it is often sporadic in nature. Eye rubbing, especially in atopic individuals, is a definite risk factor for the disease and also risk factor for progression of disease.

Left, normal ‘spherical’ shaped cornea.  Right, ectatic ‘egg shaped’ cornea

How do we treat patients with keratoconus?

The treatment revolves around two goals.

• Providing some form of optical correction to improve the quality of vision for the patient
• Preventing patients’ disease from worsening.

Reducing disease progression

Keratoconus is a progressive disease usually up to the patient’s mid thirties. If they suffer from atopic disease and rub their eyes they may be at risk of progressing despite their age. Atopic symptoms should be treated appropriately.

Patients who are very young at presentation or who have been documented with signs of disease progression should be treated with collagen cross linking therapy. This involves applying a dye to the cornea (riboflavin) and applying an ultraviolet laser to the cornea (Figure 4). This creates a reaction within the cornea leading to collagen fibres “cross linking” thereby stiffening the cornea and resisting further ectasia. Approximately a third of patients will show some improvement in their disease. If however patients continue to progress the treatment can be repeated.

Keratoconus affects approximately 0.5% of the population. The disease severity determines how early the disease presents itself and how it is treated. Glasses or RGPs are the preferred first treatment option. Surgery can be used for cases of glasses or RGP intolerance. If the disease is mild to moderate intrastromal ring segments may be indicated. If the disease is severe then Keratoplasty is required to restore vision. Younger patients with evidence of, or at risk of, disease progression are treated with collagen cross linking. 

Figure 1: Left, normal “sperical” shaped cornea, Right ectatic “egg shaped” cornea

Figire 2

Figure 3: Cornea with intrastromal rings implanted into the corneal stroma through channels created with a femtosecond laser. 

Figure 4: Laser lamp applying ultraviolet light to the riboflavin impregnated cornea (fluorescein labelled) .