Keratoconus more common than widely assumed

Keratoconus is a progressive corneal disease that can impair vision. Early diagnosis and treatment can be crucial for preventing severe and permanent loss of vision.

Estimates for the prevalence of the corneal disease keratoconus have varied. Historically the condition was considered relatively rare, with a reported prevalence of around 0.05 % (1, 2). However, several recent studies have found the prevalence to be higher. In a Norwegian study, we estimated it to be 0.19 % in the general population (and higher in younger age groups) (3), while a study from the Netherlands calculated a prevalence of 0.27 % (4). A longitudinal cohort study from Australia found the prevalence to be as high as 1.2 % among 20-year-olds (5). We suspect that keratoconus is significantly underdiagnosed in Norway.

Keratoconus is an ocular condition in which the cornea weakens and acquires a conical shape. This is often accompanied by thinning of this part of the cornea, and imperfections in the corneal curvature (astigmatism), which can become increasingly irregular and difficult to correct with glasses. The patient will then experience blurred vision. Keratoconus usually occurs in both eyes, but due to significant asymmetry, many patients only notice impaired vision when their stronger eye is affected. By then the condition may already have caused severe and permanent loss of vision in the other eye. The condition usually begins in the late teens or early twenties, and in the Norwegian study, 73 % of patients were male (3).

Progression can now be halted using corneal collagen cross-linking (CXL)

There is at present no cure for keratoconus. Symptomatic treatment in the form of glasses or contact lenses is therefore important. In most cases, progression stops as a result of the corneal ageing process, with an increase in stiffness of the corneal stroma usually occurring around the age of 30. However, a number of patients already have permanent visual impairment at this stage. In the past, keratoconus was treated with corneal transplantation, but this was appropriate only for advanced cases. Today, progression can be halted using corneal collagen cross-linking (CXL). The formation of new crosslinks is induced in the cornea with the aid of vitamin B2 (riboflavin) and UV light, resulting in stiffening of the cornea (6). Corneal collagen cross-linking was introduced in Norway a little over ten years ago and has led to a marked reduction in the number of corneal transplantations in this patient group (7).