Optical coherence tomography (OCT) measurements in black and white children with large cup-to-disc ratios

Abstract

Children with large optic nerve head cups often pose diagnostic difficulty due to concern over possible glaucoma. This study’s purpose was to evaluate optical coherence tomography (OCT) measurement of the peripapillary retinal nerve fiber layer (RNFL) and macular thickness in healthy eyes of black and white children, comparing values for eyes with large cup-to-disc ratios against those with small cup-to-disc ratios (normal controls). Using Stratus OCT (OCT 3) (Carl Zeiss Meditec, Dublin, CA) a fast macular thickness and fast RNFL 3.4 protocol were performed on normal eyes of normal children. Included were children (aged 5–17 years) with normal ophthalmic examinations, drawn from data generated during an ongoing study of OCT in children. Excluded were eyes with corrected vision below 20/20, spherical equivalent >5 diopters, intraocular pressure >21 mm Hg, abnormal optic nerve rim, prematurity, family history of glaucoma. Clinical examination identified children with large cup-disc-ratios (0.5–0.8), and each was matched for age and race to a “normal control” with a small cup-to-disc ratio (<0.5). OCT-3 analyses were compared between eyes with optic nerve heads showing large cup-to-disc ratios (≥0.5) vs. those showing small cup-to-disc ratios (<0.5) for different sections of the macula and the peripapillary RNFL thickness. Analyses included OCT values and optic cup grading for 162 eyes of 162 children. White children with large cup-to-disc ratios had thinner mean RNFL thickness and macular volume compared to those with small cup-to-disc ratios (average RNFL = 100 ± 9 vs. 110 ± 8 μm, respectively, p = 0.0001, macular volume = 6.84 ± 0.41 vs. 7.03 ± 0.33 mm 3, respectively, p = 0.0186). On the other hand, black children with large cup-to-disc ratios had an equivalent mean RNFL thickness and macular volume compared to those with small cup-to-disc ratios average RNFL = 107 ± 10 vs. 107 ± 8 for both groups, macular volume = 6.81 ± 0.34 vs. 6.85 ± 0.28 respectively. Positive equivalence testing assumed a clinically significant difference of 10 μm for RNFL, and 0.2 mm 3 for macular volume. We report that white children with large cup-to-disc ratios have evidence of reduced/thinner RNFL and macular volume versus white children with smaller cup-to-disc ratios, as assessed by OCT. By contrast, this distinction was not found for black children in the present study.