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Tosho Rii, Yuji Itoh, Makoto Inoue, Akito Hirakata; Distinction of Cone Outer Segment Tips and Foveal Disruption Artifacts in Spectral-Domain Optical Coherence Tomography Images of Normal Eyes. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2880.
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To investigate the incidence and possible causes of obscured or disrupted cone outer segment tips (COST) line at fovea in spectral-domain optical coherence tomography (SD-OCT) images of normal eyes.
Seventy eyes of 35 individuals without eye diseases were included in this study. OCT images were taken using Cirrus HD-OCT (Carl Zeiss Meditec) with 5 line raster (5LR) and high-definition 5 line raster (HD5LR) modes. Images with signal strength (S/S) weaker than 6/10 were excluded. Distinction of COST lines was graded to A (distinct), B (discernible), or C (obscured). The integrity of COST line, external limiting membrane (ELM), and the photoreceptor inner segment and outer segment (IS/OS) junction at the fovea were recorded. Demographic data, refractive error of the eyes, signal strengths of the OCT images were acquired for analysis.
The distinction grades of COST line were grade A: 45%, grade B: 34%, grade C: 21% in 5LR mode; grade A: 81%, grade B: 11%, grade C: 8% in HD5LR mode. COST distinction grade was correlated to the COST distinction status of the fellow eye (r = 0.62). COST distinction grade and COST disruption were not significantly correlated to age, sex, refractive error of the eyes, or the S/S of the OCT images. The incidence of COST line disruption at fovea was 12.4% in 5LR mode; 10.3% in HD5LR mode. COST line disruption was always associated with ELM and IS/OS disruption. Hyper-reflectivity at the foveal pit surface was noted in 44% of the eyes with disrupted COST line in 5LR mode and in 87% of the eyes with disrupted COST line in HD5LR mode.
COST line distinction varies and disrupted COST lines are noted in approximate 10% of SD-OCT images of normal eyes. COST line disruption in eyes with normal visual function was associated with ELM and IS-OS disruption. The artifact is presumably due to the surface hyper-reflectivity at the foveal pit.
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