Foveal cone outer segment tips line and disruption artifacts in spectral-domain optical coherence tomographic images of normal eyes

Purpose: To determine the incidence of a continuous cone outer segment tips (COST) line at the fovea in spectral-domain optical coherence tomographic (SD-OCT) images of normal eyes.

Design: Prospective, interventional case series.

Methods: Forty-six right eyes of 46 normal individuals with visual acuities (VA) ≥20/20 were studied. SD-OCT images were obtained with a Cirrus HD-OCT instrument with both the standard 5-line raster and the high-definition (HD) 5-line raster scan modes. Images with signal strengths weaker than 5 (on a scale from 0 to 10) were excluded. The appearances of the COST line, photoreceptor inner segment/outer segment (IS/OS) junction, and external limiting membrane (ELM) line were determined in a masked way.

Results: The incidence of eyes with an intact foveal COST line was about 95%, and the incidence was not significantly associated with the age, sex, refractive error, signal strength, horizontal or vertical scans, and the use of either the standard or HD scans. Fragmented COST lines appeared to be attributable to blocking artifacts caused by a hyperreflectivity at the foveal surface because the COST fragmentation had corresponding fragmentation of the ELM and IS/OS junction lines. The correlation between a fragmented COST line and the hyperreflectivity on the retinal surface was significant for the vertical HD scans (P = .011) but not for the vertical standard, horizontal standard, or horizontal HD scans.

Conclusions: Commercial SD-OCT instruments can detect the COST line. Fragmentations of the COST lines in normal eyes are most likely artifacts caused by a parabolic reflection of a surface hyperreflectivity of the foveal pit.