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Material and Method: Four hundred eighty eyes from 240 subjects without glaucoma, retinal, or choroidal diseases underwent scanning of the retina and choroid using EDI-OCT. SFCT, FRPE, and CNRT measurements were based on the 1:1 micron images and were performed by two independent observers. The reliability of measurements between the observers was evaluated by intraclass correlation coefficient (ICC). The correlations of SFCT with FRPE, CNRT, age, and refractive error were analyzed.
Results: The mean age of the subjects was 36.22 years (range 20-81 years). The means (95% reference intervals) of SFCT, CNRT, and FRPE were 294.02 μm (137.14-450.90 μm), 174.22 μm (141.82-206.62 μm), and 41.94 μm (34.65-49.23 μm), respectively. SFCT and CNRT had excellent reliability between the two observers [ICC = 0.947 (95% CI, 0.918-0.963) and 0.929 (95% CI, 0.906-0.945), respectively], while FRPE showed good reliability [ICC = 0.729 (95% CI, 0.637-0.793)]. SFCT had a low positive correlation with FRPE (r = 0.179, p<0.0001) but not with CNRT (p = 0.317). SFCT showed a positive correlation with refraction (r = 0.338, p<0.0001) and a negative correlation with age (r = -0.166, p<0.0001). Regression analysis suggested that the SFCT decreased by 12.23 μm per one decade of life and by 11.42 μm per one diopter of myopia.
Conclusion: Normal values of SFCT in Thai population were obtained. SFCT significantly decreased with older age and higher myopia. SFCT was associated with FRPE, reflecting the same vascular supply of the choroid and retinal pigment epithelium. When measured with our technique based on the 1:1 micron images, the reliability of SFCT measurement was very high despite highly morphologic inter-individual variations.
Keywords: Choroidal thickness, EDI-OCT, Thai