BLOG: Is keratoconus prevalence on the rise?
In the past, keratoconus was thought to be a rare corneal disease. In a study conducted by Chan and colleagues in Olmstead County, Minn., in 1982, about one out of every 1,835 people were affected by the disease.
Recently, new data have surfaced suggesting that keratoconus (KCN) may not be as rare as we once thought.
For example, the Raine Study found that the prevalence of the disease was around 1.2%, or one out of every 84 people, in a cohort of 1,259 patients from Western Australia (Chan et al). Globally, Hashemi and colleagues performed a meta-analysis on worldwide keratoconus rates with a concluded value of about one in 750. Such a large increase in the prevalence between studies conducted many years apart and in different populations leads us to question why this could be occurring.
For starters, the eye care profession has been putting a lot of effort into educating the public on the importance of eye exams in general, especially at early ages. For example, the InfantSee program, through the AOA Foundation, has helped to incorporate eye exams into the yearly wellness checks of children, with the hopes of detecting eye disease that could hinder future success. Keratoconus is not necessarily diagnosed at ages 6 or 12 months, the age for the InfantSee program, but growing public awareness of the importance of eye exams has translated into more annual pediatric eye exams.
Corneal diagnostic technology has also come a long way since 1982. At that time, the diagnosis of KCN was based on retinoscopy and irregular keratometry mires, which left room for error in interpretation and the potential for missing early, subtle disease. With the advent of corneal topography and tomography systems, diagnosis can happen much earlier. Corneal tomography systems like the Pentacam (Oculus) allows for imaging of not only the anterior surface of the cornea, but of the posterior aspect as well. This is crucial because steepening seen on the posterior float can indicate early keratoconus, and this steepening can precede visual symptoms or clinical signs at the slit lamp.
The Raine study investigated the correlation between a multivariable regression analysis based on the Belin/Ambrosio Enhanced Ectasia Display on the Pentacam, denoted as BAD-D, and the presence of keratoconus. This study concluded that with a BAD-D value of more than 2.17 (representing a deviation from the normative database), there is an 86% sensitivity and a 96% specificity for diagnosing KCN in those who already have known disease, and there is an 80% sensitivity for a BAD-D value of 2.6 or more. A BAD-D score of 2.6 or more demonstrated a 0.1% false positive rate for diagnosing KCN. These data can prove helpful in diagnosing keratoconus objectively instead of relying on clinical appearance alone and can help eliminate doctor-to-doctor discrepancies in interpretation of the BAD-D, improving the accuracy of KCN detection.
Awareness of the systemic associations and risk factors related to the development of KCN, including Down’s syndrome, asthma, atopic diseases leading to chronic eye rubbing, connective tissue disease and long-term gas-permeable contact lens wear, has aided diagnosis as well.
The ability to detect KCN early is more important than ever because now instead of monitoring the disease until the patient loses vision or needs a penetrating keratoplasty, we have a safer treatment. Corneal cross-linking involves the use of riboflavin that is photoactivated by ultraviolet-A radiation to increase the amount of cross-links that occur within the cornea, increasing strength and halting progression (Cifariello et al).
With patients becoming more educated on the importance of eye health and diagnostic technology continuing to improve, we now can halt the progression of keratoconus, changing the course of our patients’ lives.
- Chan E, et al. Ophthalmology. 2020;doi:10.1016/j.ophtha.2020.08.020.
- Cifariello F, et al. J Ophthalmol. 2018;doi:10.1155/2018/4947983.
- Hashemi H, et al. Cornea. 2020;doi:10.1097/ICO.0000000000002150.
For more information:
Mitch Ibach, OD, FAAO, is a residency-trained optometrist at Vance Thompson Vision in Sioux Falls, S.D., who specializes in anterior segment surgical care including cataracts, corneal diseases, glaucoma and refractive surgeries. He can be reached at firstname.lastname@example.org.
Kristen Walton, OD, graduated with honors from her class from Indiana University School of Optometry. She is currently doing her residency at Vance Thompson Vision in Sioux Falls, S.D., managing ocular disease, refractive and pre- and postoperative ocular surgery care. She is also a member of the South Dakota Optometric Society.