Tomographically Determined Keratoconus Found in One in 334 Kids

This high number was seen in an underserved minority pediatric population.

Patients with subclinical disease and KC suspects may display posterior corneal changes and/or pachymetric abnormalities using the Pentacam’s Belin/Ambrósio report; however, anterior corneal surface changes may not be present. Photo: Kami Parsa, MD/Wikimedia Commons. Click image to enlarge.

The prevalence of keratoconus (KC) has been undergoing a re-evaluation of late, as newer research shows the condition to be more common than previously believed. Looking to provide greater clarity, researchers recently conducted a prospective study in a Chicago-based pediatric population. To determine the prevalence of keratoconus, they used Scheimpflug corneal tomography on kids aged three to 18.

The scans determined corneal thickness in various ways using metrics specific to the Oculus Pentacam.  One such measurement is called back elevation at the thinnest point (BETP). To differentiate non-KC cases from keratoconus suspects or patients, criteria were as follows:

• no keratoconus – final D <2.00 in both eyes
• KC suspect – final D ³2.00 and <3.00 in combination with BETP ³18mm for myopia and ³28mm for hyperopia/mixed astigmatism in at least one eye
• definite KC – final D of ³3.00 with BETP ³18mm for myopia or ³28mm for hyperopia/mixed astigmatism in at least one eye

Of 2,007 children, six were classified as KC, with a prevalence of one in 334, three were classified as KC suspects, with a prevalence of one in 699, and total prevalence of KC suspects and KC yielding a ratio of one in 223. Overall, this study indicates a higher prevalence of KC than what has been previously reported of the pediatric population. Based on this observation, the study authors relay that “the frequency of abnormal corneal findings in this population warrants consideration to expand universal screening for KC with tomography that can detect KC before vision loss as part of a comprehensive ocular examination.”

Adding to this concern, many studies on the prevalence of KC only report on adult populations. As such, current tomography indices used for early diagnosis and monitoring of the condition use normative data from the Pentacam tomographer, but the data is not well-established for the pediatric population.

This is a concern, as “identification of both KC and KC suspects is important, so these patients can be diagnosed early, monitored closely and early intervention can be initiated to prevent disease progression,” the authors argue. This can be combatted with increasing the awareness about KC prevalence by eyecare practitioners and more generally, the overall healthcare community.

Being able to diagnose children earlier, hopefully before significant vision loss, would add the potential benefits of earlier treatment, resulting in prevention of advanced disease states, preserved vision and an overall ability to maintain long-term quality of life.

Looking toward future efforts, the authors propose that “screening for KC and KC suspects should be part of a routine pediatric eye examination, particularly for those patients showing risk factors such as high astigmatism, reduced best-corrected visual acuity, family history of KC or aberrant corneal presentation.”

Harthan JS, Gelles JD, Block SS, et al. Prevalence of keratoconus based on Scheimpflug corneal tomography metrics in a pediatric population from a Chicago-based school age vision clinic. Eye Contact Lens. February 2024. [Epub ahead of print].