Choroidal thickness and vascularity index in Chinese children with high hypermetropia using optical coherence tomography (OCT)

Objectives: The current study was to evaluate the choroidal thickness and vascularity index in Chinese children with high hypermetropia through enhanced depth imaging optical coherence tomography (EDI-OCT). Methods: : Cross-sectional study. A total of 21 children with high hypermetropia and 29 children with normal refractive status were retrospectively enrolled in the study. The measurement of the macular choroidal thickness（CT）, 7 points: the sub-foveal area point, the temporal and nasal points at a radius of 0.5-mm, 1.5-mm, and 3-mm were measured. After binarization of the OCT images, the total choroidal area (TCA), stromal area (SA) as well as the luminal area (LA) were identified and measured. The Choroidal vascularity index (CVI)was defined as the ratio of LA to TCA. The independent t-test for normal distributions and Kruskal-Wallis tests for non-normal distributions were used to compare other parameters between groups. The Tamhane's T2 test was performed to adjust for multiple comparisons between groups within each analysis. Results: : The SFCT in the high hypermetropic group was significantly thicker than that in normal controls (371.32 ± 63.09 μm vs. 325.03 ± 56.67 μm, P = 0.002). At 0.5mm, 1.5 mm, and 3.0mm in diameter, the nasal choroidal sectors of the high hypermetropia eyes were significantly thicker than that of the control (P < 0.05). For the choroidal vascular parameters, S.A. values were 1101604.39± 209973.14 μm 2 in the high hypermetropia eyes and 1072580.21 ± 229841.25μm2 in the control eyes; L.A. values were 2018339.60 ± 324292.51μm2, and 1786624.19 ± 238875.62μm2 in the two groups, respectively; TCA were 3112626.91 ± 521392.85μm2 and 2859204.39 ± 442897.88μm2 in the two groups. L.A. and TCA of the high hypermetropia eyes were significantly larger than that of the normal controls (P = 0.037, P = 0.002). The CVI differed significantly in the two groups (P = 0.001). Conclusion: The thicker choroidal thickness, rather than topographic features, is a biomarker of high hyperopia, but CVI is another more robust indicator.