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Jason D Marsack, Pete S Kollbaum, Heather A Anderson; Comparing Topographic Metrics of Disease Detection in Individuals with and without Down Syndrome.. Invest. Ophthalmol. Vis. Sci. 2016;57(12):6245.
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© ARVO (1962-2015); The Authors (2016-present)
A high incidence of refractive error and an association with keratoconus (KC) have been reported for the Down syndrome (DS) population. Mathematical metrics that utilize corneal topographic data have been developed to distill complex corneal surface data into a single number in order to detect the presence of KC. Two such metrics are 1) maximum corneal power and 2) KISA%, a combination of 4 independent topographic metrics: central corneal steepening (central K), inferior-superior dioptric asymmetry (I-S), degree of regular corneal astigmatism (AST) and skewed radial axis index (SRAX). The purpose of this study was to compare topographic disease detection metrics in both eyes of individuals with and without DS.
Zeiss Atlas corneal topography was attempted on 140 subjects with DS (age range: 8 to 55, mean: 25±9 yrs) and 138 control subjects with self-reported unremarkable ocular history (age range: 7 to 59, mean: 25±10 yrs). Subjects where at least 1 measure of topography was not recorded in both eyes (DS: 23 and control: 0) were excluded from further analysis. Maximum corneal power was determined from the topographic data. Indices central K, I-S, AST, SRAX were calculated and combined to calculate KISA%.
Maximum corneal power in the right eyes (mean±std: 48.87D±4.47D) and left eyes (48.56D±4.20D) of subjects with DS were not statistically different. Likewise, in control eyes, maximum corneal power in the right eyes (44.66D±1.75D) and left eyes (44.59D±1.69D) were not statistically different. In subjects with DS, the KISA% values in the right eyes (1Q: 9.60, M (median):23.33, 3Q: 50.13) and left eyes (1Q: 6.81, M: 12.38, 3Q: 33.56) were significantly different (p = 0.0251). In control eyes, KISA% values in the right eyes (1Q: 3.33, M:11.04, 3Q: 16.00) and left eyes (1Q: 3.74, M: 10.25, 3Q: 12.32) were not significantly different. For the DS sample, 22 subjects (19%) exhibited KISA% values indicative of KC unilaterally, with 7 subjects (6%) exhibiting these characteristics bilaterally. None of the control eyes exhibited KISA% values indicative of KC.
Between-eye differences in KISA% values were observed in the DS sample, and not seen in the control sample, suggesting more variability in disease severity in the DS group. Further analyses are needed to better characterize the inter-ocular variability for subjects with DS.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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