Originally published in the November 2023 NKCF Update.
Recent articles make a strong case for evaluating adolescents with Trisomy 21 for keratoconus.
In one review of the ophthalmologic challenges faced by children with Down syndrome (DS), the authors noted these children have a much higher rate of ocular disease than their neurotypical peers. In infancy, their vision is comparable to other children, but after age 2, reduced contrast sensitivity and vision acuity are observed.
Up to 80% of children with DS have significant refractive error (chiefly hyperopia or farsightedness in those of Caucasian descent, and myopia or nearsightedness in Asian children). Strabismus (crossed eyes) is observed in about half of children with DS. Congenital cataracts are 10 times more prevalent in children with DS, and keratoconus is up to 30x more likely to impact an individual with DS.
Some experts have proposed the link between keratoconus and DS is a collagen-related abnormality; others suggest that DS is associated with greater frequency of eye rubbing. Still others speculate that a ‘keratoconus gene’ is found on chromosome 21.
The prevalence of children with DS who also have keratoconus has been reported ranging from 0% to 71% in the medical literature. Researchers at Boston University School of Medicine concluded that selection bias and the small size of some studies, as well as technology used, account for the huge variation. They found that papers that did not report a DS/KC connection included studies with infants and very young children as study subjects; keratoconus is rarely evident that early in life. All studies that reported rates >10% utilized corneal topography to diagnose disease.
A 2021 study from Norway using National Registry data estimated prevalence of keratoconus as 5.5% among persons with Down syndrome. This is 30x higher than in the general population.
While the rate of keratoconus among the general public is not certain, and depends on several factors including geography, ethnic origin, and diagnostic tools used to detect the disease, what is understood is that those with DS have a hgiher rate of disease and would certainly benefit from treatments like crosslinking. Doctors should educate parents and guardians about the importance of annual eye exams and if there are suspicious findings to closely monitor children with DS for signs of keratoconus.
References: Ophthalmologic and neuro-ophthalmologic findings in children with Down syndrome, Jain A, Boyd NK, Paulsen KC, et al, Am J Med Genet Semin Med Genet, doi: 10.1002/ajmg.c.32068. Online ahead of print, Oct 4, 2023.
Systemic Associations with Keratoconus, Unni R, Lee HJ, Life, 13:1363, https://doi.org/10.3390/life13061363, 2023.