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Sara Touhami, Elise Philippakis, Ramin Tadayoni, Alain Gaudric; Topographic Variations of Choroidal Thickness in Healthy Eyes on Swept Source Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2019;60(9):1843. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the topography of choroidal thickness in the posterior pole and beyond, and the location of the thickest choroidal area in healthy eyes.
Cross-sectional study on 64 eyes of 33 healthy subjects of mean age 37 years (22.5 to 50) and mean refractive error 0.7 D (-4.2 to +1.9). Image acquisition was by a swept source OCT working at 100kHz/sec. Choroidal thickness (CT) maps from 12 radial B-scans and 9x9mm OCT-Angiography CT maps were analyzed as well as choroidal vascularity measured on individual 12 mm B-scans.
Mean CT was above 300µm at all locations of the ETDRS map except for the nasal outer macula. The subfoveal CT (SCT) was representative of the overall choroidal macular thickness. The thickest choroidal point was 395 µm (223-548), retro foveal in only 1.8% of cases and located superior or temporal to the macula in 72.2% of cases, mostly beyond a 3mm radius from the fovea (75.9%). The TCP was infero macular in 27.8% of cases. In 31% of cases, subfoveal CT was> 400µm. The choroidal thickness pattern was symmetrical along a horizontal axis in 58.6% of cases. Among asymmetrical cases, 54.2% had a greater CT in the inferior quadrants.The CT pattern corresponded to the symmetrical or asymmetrical distribution of choroidal veins. In asymmetrical distributions, the watershed zone between superior and inferior choroidal venous drainage was oblique and outside the macula. The mean vascularity index was similar at the thickest (75.6%) and thinnest (74%) area (75.6% vs. 74%, p=0.787) in asymmetrical patterns, showing that choroidal thickness is mainly determined by the lumen of choroidal vessels.
Wide-field SS-OCT/OCT-A shows that different choroidal patterns exist in a healthy population under the age of 50. More than a third of the population has a thick choroid. The thickest point of the choroid is not retrofoveal. The asymmetrical thickness of the choroid between the upper and lower part of the fundus is due to the asymmetry of large vessel density. These findings should be taken into consideration when evaluating choroidal thickness in diseases.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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