BLOG: Diagnosis of early keratoconus – a conundrum, a proposal
Modern medicine champions preventive care, and we should apply this concept to our patients with keratoconus.
With the availability of corneal collagen cross-linking as an effective treatment to stop progression, it is essential for practitioners to diagnose the disease as early as possible. If we can catch keratoconus early and treat it with corneal collagen crosslinking, we can prevent advanced disease and the need for corneal transplantation and, if applied at the first signs, we could prevent any meaningful visual impact.
It’s simple in concept, but its implementation presents a quandary. In the earliest stages of keratoconus there are scant symptoms and signs of disease. Virtually all eye exams would fail to diagnose it. In 2017, a mean age of diagnosis was reported by Godefrooij and colleagues as 28.3 years old, far from the disease’s earliest manifestations, suggesting that keratoconus is developing sooner than we diagnose it. How do we solve this conundrum? How can we diagnose keratoconus earlier?
Diagnosing keratoconus earlier
Certainly, this problem can be solved by using advanced diagnostic equipment. In 2020, corneal topographers are very affordable and should be a part of every clinic. This technology has been around since the late 1980s but has dramatically improved and decreased in cost over the years. It’s the classic gold standard for diagnosis of keratoconus. Its more capable successor, corneal tomography, provides an all-encompassing review of corneal metrics to find subtle changes to differentiate a normal cornea from early keratoconus.
Both devices are extremely capable, but they typically are not used as part of the pre-examination workup of patients in a busy, non-cornea/refractive setting. The question then becomes, how can we incorporate these devices most effectively to screen for keratoconus?
The answer may be in the form of a combination device that incorporates multiple relevant instruments like a corneal topographer, wavefront aberrometer and corneal tomographer, among others. Such devices may be an ideal pre-examination tool, used on everyone for the necessities, such as autorefraction and sim Ks, but also providing in-depth objective cornea and visual quality data. However, incorporation of a device like this might not be reasonable for a practice with perfectly functional single utility pieces of equipment. In a perfect world all doctors would have the newest, most sophisticated devices and the time and freedom to examine all patients with said devices. The reality is not that.
Screening for keratoconus
However, the recommendation that every practitioner has at the very least the bare minimum equipment — a corneal topographer — is not outrageous, it’s downright sensible. So, for those with one (and those who will get one) the question then becomes: How can we most effectively use it to screen for keratoconus?
The answer lies in who and when we screen. Like the age-related cancer screening recommendations set forth by the American Cancer Society, we should screen those around the common age of onset of keratoconus: the pediatric population.
Although there is little peer-reviewed literature on pediatric incidence and prevalence of keratoconus, two recent studies stand out. Netto-Torres and colleagues reported a prevalence of 1:21 in a Saudi Arabian population 6 to 21 years old, and El-Khoury and colleagues reported an incidence of 0.53% over a 5-year period for patients age 14 years and younger compared with 3.78% for patients older than 14 years. There is a consensus that keratoconus develops in the early teenage years.
It would be prudent to obtain a baseline topography prior to clinical manifestation of the disease, allowing for future comparison. Based on the literature, a reasonable age to start screening would be 10 years, prior to 14 years where thereafter the incidence of keratoconus increases. Annual screening topography should be performed with annual examination for those without findings or risk factors and more frequently depending on risk factors.
We know the commonly quoted prevalence of keratoconus is approximately 1:2,000, derived from Rabinowitz’s 1998 review. Most recently, a meta-analysis was published in Cornea in early 2020. Hashemi and colleagues found the prevalence of keratoconus as approximately 1:725 worldwide. Also published in Cornea in November 2019, Papali’i-Curtin and colleagues’ study evaluated the prevalence of keratoconus in a New Zealand adolescent population. In this population, they found 1:191 individuals, and. of note, the Maori population had an increase in prevalence reported at 1:456.
All of this is to say that keratoconus is much more common than we previously thought, and we have an effective treatment to stop progression of the disease. Thus, it is incumbent upon the practitioner to diagnose the disease as early as possible. The use of advanced devices, targeted screening and liberal criteria for workup may find keratoconus at its earliest state.
That, then, begs the question: Is there a universally agreed-upon definition for early keratoconus? There isn’t, but that’s a topic for another time.
El-Khoury S, et al. J Refract Surg. 2016;doi:10.3928/1081597X-20160513-01.
Godefrooij DA, et al. Am J Ophthalmol. 2017;doi:10.1016/j.ajo.2016.12.015.
Hashemi H, et al. Cornea. 2020;doi:10.1097/ICO.0000000000002150.
Papali'i-Curtin AT, et al. Cornea. 2019;doi:10.1097/ICO.0000000000002054.
Rabinowitz YS. Surv Ophthalmol. 1998;doi:10.1016/s0039-6257(97)00119-7.
Torres Netto EA, et al. Br J Ophthalmol. 2018;doi:10.1136/bjophthalmol-2017-311391.
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John D. Gelles, OD, FIAO, FCLSA, FSLS, is the director of the specialty contact lens division at the Cornea and Laser Eye Institute-Hersh Vision Group and the CLEI Center for Keratoconus, a subspecialty clinic dedicated to research and treatment of keratoconus, in Teaneck, N.J. His clinical work is dedicated exclusively to specialty contact lenses and surgical comanagement for keratoconus, corneal disorders, ocular surface disease and postsurgical corneal conditions. He is a subinvestigator for multiple keratoconus-specific clinical trials.