New data reveals startingly high prevalence of keratoconus in pediatric patients

Image Credit: AdobeStock/LIGHTFIELDSTUDIOS

Keratoconus (KC) is a progressive, bilateral, asymmetric corneal ectasia that results in central or paracentral corneal thinning and steepening.^1,2 The loss of corneal biomechanical strength along with progressive thinning and steepening leads to irregular corneal astigmatism and decreased vision.¹ Several ocular, systemic, and genetic conditions as well as environmental factors have been associated with an increased risk of developing KC. These include but are not limited to eye rubbing, allergy, atopy, and asthma.^1,3

The literature has reported that KC usually develops during the second to third decades of life based on the manifestation of clinical signs and symptoms.¹ KC typically progresses until the fourth decade but may present earlier or later in life.¹ Men and women are equally affected and certain ethnicities have a higher prevalence of the disease.⁴ When KC presents at a younger age, the disease tends to be more progressive and severe.⁵ These young patients are more likely to need a corneal transplant compared with patients diagnosed later in life.⁶

Prior to the introduction and utilization of corneal tomography, KC was often diagnosed based on observed clinical signs of varying severity and presentation including the following: reduced best corrected visual acuity, scissor reflex on retinoscopy, increased irregular astigmatism, greater corneal curvature, Charleux sign (oil droplet reflex), Fleischer ring, Vogt striae, subepithelial scarring, prominent corneal nerves, Munson sign, Rizzuti sign, and corneal hydrops.^1,7 With the continued advancements and innovations of corneal tomography, KC can be diagnosed earlier when global pachymetric and anterior and posterior elevation analyses of the cornea are utilized.

The most accepted US prevalence of keratoconus (1:2000) in the adult population is from the Olmsted County, Minnesota, 1986 study and is now considered an underestimate of the true prevalence of the disease.⁸ Patients from the Olmsted County study were diagnosed with KC based on irregular retinoscopy reflexes and keratometry mires.⁸ Utilizing advanced technologies including corneal imaging, the reported prevalence of KC in the adult population ranges between 1:50 and 1:750.⁹ What remains unknown is an established prevalence of keratoconus in the pediatric population, due to many factors.

The Illinois College of Optometry and International Keratoconus Academy of Eye Care Professionals (IKA) designed and developed a large-scale study that screened for the presence of KC based on objective metrics derived from Scheimpflug corneal tomography to establish the prevalence of KC in a pediatric population. The results of this study have recently been published¹⁰ and are summarized in this article.

In a prospective, observational, single-center study by Harthan et al,¹⁰ subjects aged 3 to 18 years who presented for comprehensive eye examinations between 2017 and 2019 were recruited from the Princeton Vision Clinic, a community-based program, run by the Illinois College of Optometry and serving the pediatric population within the Chicago public school system. Subjects included in this study were predominantly low income and primarily members of 2 minority racial/ethnicity populations (Black and Hispanic). In addition to vision and ocular health assessment, Scheimpflug imaging from the Pentacam corneal tomographer (OCULUS Optikgeräte GmbH) was obtained on each eye.¹⁰

Scheimpflug tomography scans (Belin/Ambrosio Enhanced Ectasia; BAD3) were performed on each eye of every subject and generated BAD Final D (Final D) and Back Elevation at the Thinnest Point (BETP) measurements.¹⁰ The prevalence of KC has been reported using only the BAD3 Final D. However, the BAD3 was not designed to diagnose KC; the index flags when a cornea is abnormal.¹¹ To improve specificity of KC detection using the BAD3 Final D, BETP was added.¹⁰

The criteria used to differentiate non-KC from KC suspects/KC was: Non-KC, Final D < 2.00 in both eyes; KC Suspect, Final D ≥2.00 and < 3.00 in combination with BETP ≥ 18 µm for myopia, ≥ 28 µm for hyperopia/mixed astigmatism in at least 1 eye; and KC, Final D of ≥ 3.00 with BETP ≥18 µm for myopia or ≥ 28 µm for hyperopia/mixed astigmatism in at least 1 eye.¹⁰

There has been some concern as to whether pediatric patients can successfully be imaged with corneal tomography. This study demonstrated that tomography could effectively be acquired in a pediatric population. 2206 subjects were recorded, removing duplicate and poor-quality scans—leaving 2007 subjects.¹⁰

What did the results of this study demonstrate regarding the prevalence in this pediatric population? Six of 2007 subjects were classified as KC, resulting in a prevalence of 1:334. Three of 2007 subjects were classified as KC suspects, resulting in a prevalence of 1:669. There were 9 of 2007 subjects classified as KC or KC suspect, resulting in a prevalence of 1:223.¹⁰

The results of this study¹⁰ are significant for practitioners as it has previously been reported that KC can significantly impact social and educational development and quality of life in children.¹² However, early diagnosis of the disease and intervention with corneal collagen cross-linking approved by the FDA in 2016 (KXL Avedro, now iLink; Glaukos), may not only halt the progression of KC,¹³ but may also maintain best-corrected vision in the pediatric population when combined with spectacles or contact lenses.^14,15

The recently published study demonstrates that the prevalence of KC in this US-based pediatric population is higher than previously reported, highlighting the importance of early screening for the disease.¹⁰ Clinicians may miss diagnosing pediatric patients with keratoconus, specifically early keratoconus, and keratoconus suspects, especially if no clinical signs are present. Corneal tomography is not considered in the standard of care in pediatric comprehensive eye examinations. Identifying KC earlier and implementing KXL when appropriate will prevent a decline in visual outcomes and subsequently improve long-term quality of life for this population. Screening for KC and KC suspects with corneal tomography (to identify posterior corneal changes and/or pachymetric abnormalities) should be part of the routine pediatric eye examination, not only for those who demonstrate high risk factors but also to identify those who may present with subclinical disease.¹⁰

References:

1. Santodomingo-Rubido J, Carracedo G, Suzaki A, Villa-Collar C, Vincent SJ, Wolffsohn JS. Keratoconus: an updated review. Cont Lens Anterior Eye. 2022;45(3):101559. doi:10.1016/j.clae.2021.101559

2. Romero-Jiménez M, Santodomingo-Rubido J, González-Méijome JM. The thinnest, steepest, and maximum elevation corneal locations in noncontact and contact lens wearers in keratoconus. Cornea. 2013;32(3):332-337. doi:10.1097/ICO.0b013e318259c98a

3. Gomes JA, Tan D, Rapuano CJ, et al; Group of Panelists for the Global Delphi Panel of Keratoconus and Ectatic Diseases. Global consensus on keratoconus and ectatic diseases. Cornea. 2015;34(4):359-369. doi:10.1097/ICO.0000000000000408

4. Abu-Amero KK, Al-Muammar AM, Kondkar AA. Genetics of keratoconus: where do we stand? J Ophthalmol. 2014;2014:641708. doi:10.1155/2014/641708

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6. Gordon MO, Steger-May K, Szczotka-Flynn L, et al; Clek Study Group. Baseline factors predictive of incident penetrating keratoplasty in keratoconus. Am J Ophthalmol. 2006;142(6):923-930. doi:10.1016/j.ajo.2006.07.026

7. Edrington TB, Zadnik K, Barr JT. Keratoconus. Optom Clin. 1995;4(3):65-73.

8. Kennedy RH, Bourne WM, Dyer JA. A 48-year clinical and epidemiologic study of keratoconus. Am J Ophthalmol. 1986;101(3):267-273. doi:10.1016/0002-9394(86)90817-2

9. Hashemi H, Khabazkhoob M, Yazdani N, et al. The prevalence of keratoconus in a young population in Mashhad, Iran. Ophthalmic Physiol Opt. 2014;34(5):519-527. doi:10.1111/opo.12147

10. 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. 2024;50(3):121-125. doi:10.1097/ICL.0000000000001072

11. Belin MW. Keratoconus and ectatic disease: evolving criteria for diagnosis. Klin Monbl Augenheilkd. 2020;237(6):740-744. doi:10.1055/a-1077-8105

12. Belin MW, Kundu G, Shetty N, Gupta K, Mullick R, Thakur P. ABCD: a new classification for keratoconus. Indian J Ophthalmol. 2020;68(12):2831-2834. doi:10.4103/ijo.IJO_2078_20

13. Wollensak G, Spoerl E, Seiler T. Riboflavin/ultraviolet-a–induced collagen crosslinking for the treatment of keratoconus. Am J Ophthalmol. 2003;135(5):620-627. doi:10.1016/s0002-9394(02)02220-1

14. Downie LE, Lindsay RG. Contact lens management of keratoconus. Clin Exp Optom. 2015;98(4):299-311. doi:10.1111/cxo.12300

15. Mazzotta C, Traversi C, Baiocchi S, et al. Corneal collagen cross-linking with riboflavin and ultraviolet A light for pediatric keratoconus: ten-year results. Cornea. 2018;37(5):560-566. doi:10.1097/ICO.0000000000001505