Keratoconus – Common, yet uncommon

In this Acta Ophthalmologica Award and Gold Medal Honorary Lecture (the Lundsgaard Gold Medal Honorary Lecture) I will summarize and review the work on the elusive corneal disease keratoconus (KC) I have carried out together with collaborators and research students over more than 30 years. It has been a long journey, from basic biochemical work to clinical studies comparing and evaluating different regimens for corneal crosslinking. KC is a bilateral, albeit usually asymmetric, progressive ectatic corneal disorder, in which the cornea becomes thinner and regionally biomechanically weaker. Due to the intraocular pressure the weakest part of the cornea is extruded, forming a central or paracentral cone, which in turn generates irregular optical aberrations and deterioration of the quality of vision. KC has traditionally been considered a noninflammatory, rather rare corneal degeneration, but over the past decades such a description has become increasingly difficult to defend. KC shares many biochemical features with inflammatory diseases for example in the pattern of cytokine expression and is-at least according to some studies-associated with atopic dermatitis and eye rubbing. Furthermore, with the emerge of modern corneal imaging techniques, an increasing number of KC cases is discovered today, and today's consensus is that KC should be considered as a relatively common eye disease with a prevalence "approaching" 1:300. It typically begins during adolescence or early adulthood and progresses until the age of 30-35. Thus-in contrast to many of the major causes of visual impairment such as cataract, glaucoma and age-related macular degeneration-KC is uncommon, almost unique, in being predominantly a disease of young people. I have spent the past 30 odd years trying to understand this intriguing corneal degeneration and will try to explain why and how in this article.