The prevalence of keratoconus (KCN) has been estimated to be approximately 1:2000,1 designating it as a rare condition. (See “KCN: A Brief Overview,” below.) A recent study in Ophthalmology challenges this.
Overview
Specifically, “Prevalence of Keratoconus Based on Scheimpflug Imaging: The Raine Study” showed that the prevalence of KCN was 1 in 84, which is significantly higher than previously reported. What’s more, while there was no association in the study between prevalence and gender, race, body mass index, use of contact lenses or spectacles, history of allergic eye disease, or pregnancy, there was one with regular cigarette smoking. A total of 38.5% of KCN patients were smokers as compared with 14.6% of non-KCN patients (p=0.04).2
The study was comprised of 1259 patients, age 20, in Australia. KCN was defined as a Belin/Ambrosio enhanced display score of 2.6 or greater in either eye, as per the Pentacam (Oculus) for Scheimpflug imaging.
KCN: A Brief Overview
KCN is a progressive, non-inflammatory, ectatic condition of the cornea that commonly begins in adolescence and may progress to severe vision loss. The condition may be associated with both genetic and environmental factors, such as eye rubbing. Prior to the advent of corneal cross-linking (CXL), there was little to be done to slow KCN progression. Specifically, it was not uncommon for teenagers who had KCN to present to the eye care practitioner with significant astigmatism and receive supportive interventions, such as frequently updated glasses and contact lenses until they required a corneal transplant.
Value
The true value of the Raine Study to corneal specialists is increased awareness. That is, as eye care practitioners are now more aware of the increased prevalence of KCN and have access to advanced diagnostic technologies, they can look for KCN much earlier.
These patients can then undergo CXL before significant vision loss has occurred, dramatically changing their quality of life. Translation: KCN patients who may not have progressed to a corneal transplant, but would have possibly progressed to full-time contact lens dependence, may now be stabilized earlier and, therefore, may be able to maintain excellent vision in glasses. CP
References
1. Romero-Jiménez M, Santodomingo-Rubido J, Wolffsohn JS. Keratoconus: A review. Cont Lens Anterior Eye. 2010; 33:157–166.
2. Chan E, Chong EW, Lingham G, Orth M, Stevenson LJ, Sanfilippo PG, Hewitt AW, Mackey DA, Yazar S. Prevalence of Keratoconus Based on Scheimpflug Imaging: The Raine Study. Ophthalmology 2021;128:515-521.
