Pediatric Keratoconus: What Ophthalmology Residents Should Know

While many are aware of keratoconus and its implications in adult patients, the disease is present in the pediatric population. Awareness of its presentation, course, and treatment options is imperative in this age group to best preserve vision in these often rapidly developing eyes. Keratoconus is an ocular disorder of the cornea.

Due to progressive thinning and corneal shape changes as the collagen is reorganized.^1–3 Instead, it resembles a cone as the cornea thins and bulges outward.^2,4,5 The conical corneal shape may lead to vision distortion and photophobia as the light cannot properly focus on the retina1.

Although the exact etiology is unknown, genetic and environmental factors are involved. Certain risk factors that increase an individual's likelihood of developing keratoconus during their lifetime.

Keratoconus risk factors:

Positive family history of keratoconus
Vigorous rubbing of the eyes, chronic eye inflammation (e.g., hay fever, asthma)^1,2
Certain systemic conditions like Down Syndrome and Ehlers-Danlos syndrome^2,5

Keratoconus is usually first diagnosed in the late teens, and early 20’s, and typically progresses for approximately 10-20 years.^2,6

Signs and symptoms

Despite affecting both eyes, keratoconus progression and severity may differ between the eyes, resulting in asymmetry.^1,4 Early symptoms include blurry vision, glare, halos, photophobia, and sudden worsening of vision; symptoms are slowly progressive.^1,2

Diagnosis

Keratoconus diagnosis is made through a thorough history and physical exam by an ophthalmologist.⁵ Key diagnostic tests include corneal topography and tomography for mapping, slit-lamp examination, and pachymetry.^1,2 Corneal topography is the most accurate method of keratoconus diagnosis, and it allows for precise disease progression tracking.¹

Corneal topography and tomography involve characterization of the corneal surface and mapping of the curvature in a three-dimensional image.¹ Slit-lamp examination ensures detection of abnormalities that may be present in the outer and middle corneal layers, while pachymetry allows for corneal thickness measurement.¹

Treatment

Keratoconus management involves slowing disease progression and improving visual acuity. During the early stages of keratoconus, patients are encouraged to wear glasses or soft contact lenses to correct any mild changes in vision and astigmatism. However, as an individual’s vision deteriorates, patients are often offered rigid gas-permeable or scleral contact lenses.

In addition, corneal tissue can be stabilized in cases of progressive disease via corneal cross-linking surgery.² Corneal cross-linking (CXL) is an in-office procedure that was FDA approved in April 2016 (Hopkins), and it allows for new corneal collagen bondage, thus strengthening and preserving corneal shape.^1,2

Advanced keratoconus cases may require procedures such as a corneal ring or, eventually, a corneal transplant. Due to the uncomfortable nature of a simple contact lens, corneal rings are implanted in an office procedure within approximately 15 minutes to flatten the corneal surface1 and thus improve visual acuity. Eventually, progressive corneal scarring calls for a corneal transplant in many patients,^1,5 but transplants pose a risk for donor/host rejection and post-surgical infections, not to mention the myriad of medications needed to be administered post-surgery to help avoid any signs of rejection.

Pediatric keratoconus

Although extensive research has been reported for keratoconus in teens and adults, the youngest documented child to acquire keratoconus is 4 years old.^3,7

Sabti et al. report a case of a girl with Down syndrome who was later diagnosed with bilateral keratoconus and secondary amblyopia.⁷ Due to disease progression, CXL was performed. Upon initial presentation, the best-corrected visual acuity (binocular) was 20/100; with CXL, vision improved to 20/807. This provides further evidence for the ability of CXL to arrest keratoconus progression.⁷

Pediatric keratoconus is more aggressive due to the dynamic environment of a more naïve and maturing cornea. The corneal collagen remodeling rate is higher, along with a greater likelihood of development of corneal opacities and the need for keratoplasty. Despite changes in the pediatric population, the current treatment plan for both adults and children is similar.³

Adult patients with corneal cross-linking have better results and more sustainable effects over more extended follow-up periods with better outcomes in adults ages 18–39.^3,6 Pediatric patients post-CXL have increased corneal astigmatism 6 and 12 months post-treatment.³ Thus, it is imperative to continue close follow-up care in the pediatric population to prevent worsening.

Of note, it is imperative to understand the original FDA approval for the corneal crosslinking treatment in the pediatric population. As noted in the accepted proposal, corneal crosslinking is only FDA approved for “patients 14 years of age and above for treatment of progressive keratoconus. The safety and effectiveness of corneal collagen cross-linking have not been established in pediatric patients below 14 years."⁸

Thus, at this time, unless CXL is being used off-label and when pharmaceutical treatment is no longer viable for these individuals, patients are usually offered corneal transplant surgery.⁶

CXL in the pediatric population reduces the chance that a child will need a corneal transplant in the future.⁹ Per Erin Stahl, MD, a pediatric ophthalmologist and chief of ophthalmology at Children’s Mercy Hospital in Kansas City, Missouri, it is important to initiate CXL early because it takes years for crosslinking to naturally occur in children’s’ corneas.¹⁰

Dr. Stahl routinely performs CXL in patients as young as 10-13 years old, although its use is off-label10. Some studies have shown CXL to be safe and effective in children 13-18 years and can help delay the need for a corneal transplant, thus preventing the complications that come along with such a procedure (i.e., long term steroid use, corneal transplant rejection, and repeat surgeries.)¹⁰

Conclusion

Keratoconus is an ocular disorder of the cornea that leads to collagen weakening and re-organization. The conical shape adopted by the cornea leads to vision distortion. Although most patients are diagnosed in their early 20’s, there have been cases reported in children as young as the age of 4.

Keratoconus in the pediatric population is much more aggressive and may lead to ophthalmological surgical procedures early and thus more often than that seen in adults. However, corneal cross-linking has been a promising treatment option in children as young as ten years, even though it is currently an off-label option.

References

Keratoconus | Johns Hopkins Medicine. Accessed March 4, 2022. https://www.hopkinsmedicine.org/health/conditions-and-diseases/keratoconus
Keratoconus | AOA. Accessed March 4, 2022. https://www.aoa.org/healthy-eyes/eye-and-vision-conditions/keratoconus?sso=y
Mukhtar S, Ambati BK. Pediatric keratoconus: a review of the literature. Int Ophthalmol. 2018;38(5):2257-2266. doi:10.1007/s10792-017-0699-8
Keratoconus - NORD (National Organization for Rare Disorders). Accessed March 4, 2022. https://rarediseases.org/rare-diseases/keratoconus/
Keratoconus - Symptoms and causes - Mayo Clinic. Accessed March 4, 2022. https://www.mayoclinic.org/diseases-conditions/keratoconus/symptoms-causes/syc-20351352
Keratoconus - American Association for Pediatric Ophthalmology and Strabismus. Accessed March 4, 2022. https://aapos.org/glossary/keratoconus
Sabti S, Tappeiner C, Frueh BE. Corneal Cross-Linking in a 4-Year-Old Child With Keratoconus and Down Syndrome. 2015;34(9):1157-1160.
Brayboy F, Swann R, Smith J, Willard D. NDA 203324, PHOTREXA VISCOUS and PHOTREXA, and KXL System Original 1: Treatment of Progressive Keratoconus Original 2: Treatment of Corneal Ectasia Following Refractive Surgery Material Reviewed for This NDA Names of Discipline Reviewers Pediatric Review .; 2015.
Corneal Cross Linking | Boston Children’s Hospital. Accessed March 4, 2022. https://www.childrenshospital.org/conditions-and-treatments/treatments/corneal-cross-linking
Stahl E. Pediatric CXL. CRSTEurope. Published October 2020. Accessed March 4, 2022. https://crstodayeurope.com/articles/2020-oct/pediatric-cxl/