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Heather A Anderson, Jason D Marsack, David A Berntsen, Jessica Horne Mathew, Katrina E Parker, Ralph J Herring, Norman E Leach; Corneal Topography Map Comparison of Subjects with and without Down Syndrome. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2458.
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© ARVO (1962-2015); The Authors (2016-present)
Individuals with Down syndrome (DS) are believed to have a greater prevalence of keratoconus. The purpose of this study was to compare clinician assessments of corneal topography normality for subjects with and without DS.
Corneal topography was obtained for 140 subjects with DS and 138 age-matched controls (mean age = 25±9.6 yrs, range = 7-59). Coded printouts were generated for a randomly selected eye of each subject showing axial, tangential, and elevation maps, K values, shape factor, and the placido ring image, and then shuffled into one set to mask evaluators to subject group. Three optometrists with advanced cornea and contact lens training independently classified each printout as abnormal, normal, or poor scan quality. Scans judged as poor quality were excluded from further analysis (n = 20).
The distribution of map classification differed significantly for DS subjects versus controls (Chi-Square, p<0.001) with more DS maps unanimously classified as abnormal by the clinicians (23.6% vs 0.7%). Conversely, more control maps than DS maps were unanimously classified as normal (81.2% vs. 23.6%). The remaining maps received mixed classifications. Further analysis was performed for the unanimously classified maps using one-way ANOVA and post-hoc Tukey (p<0.05). Flat corneal power differed significantly between control maps classified as normal (42.64±1.32D), DS maps classified as normal (43.48±1.32D), and DS maps classified as abnormal (46.55±1.68D) (F (2, 175) = 99.81, p<0.001). Corneal toricity also differed between control normal (0.95 ± 0.62DC), DS normal (1.50±1.01DC), and DS abnormal maps (2.16±1.93DC) (F (2, 175) = 17.59, p<0.001). Shape factor was significantly elevated for both DS normal (0.54±0.14) and DS abnormal (0.46±0.26) classified maps versus control maps classified as normal (0.38±0.11) (F (2, 175) = 15.34, p<0.001), but did not differ from each other.
A higher percentage of the features quantified with corneal topography fall outside of clinical norms for individuals with DS versus controls. Significant differences included steeper and more toric corneas with elevated shape factor, even in the subjects with DS classified as normal. Although these findings can be associated with keratoconus, further study is warranted to determine if the observed findings are stable structural differences, or manifestations of progressive pathology.
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