Spatial Distribution of Posterior Pole Choroidal Thickness by Spectral Domain Optical Coherence Tomography

Abstract

PURPOSE: To study the spatial distribution of posterior pole choroidal thickness (CT) in healthy eyes using spectral domain optical coherence tomography (SD-OCT). METHODS: Fifty-nine eyes from 30 subjects with no retinal or choroidal disease were examined with high-definition (HD) OCT using macular volume cube scanning protocols. A randomly chosen subset also had multifield analysis performed (volume scans centered on and surrounding the optic nerve head [ONH]). CT was manually quantified using a validated reading center tool. For macular scans, mean CT was calculated for each Early Treatment Diabetic Retinopathy Study subfield. Compound posterior pole CT maps were also created through the alignment of OCT projection images. Regression analyses were used to evaluate the correlation between CT and axial length (AL), refractive error, age, sex, and ethnicity. RESULTS: Subfoveal CT was 297.8 ± 82.2 μm, which did not differ significantly from that of the inner macular subfields. CT was greatest in the superior outer subfield and thinnest in the nasal outer subfield. The most predictive models for macular CT included AL and/or age. Outside the macula, CT was thinnest inferonasal to the ONH. CONCLUSIONS: CT demonstrates large variations between individuals, but also at different locations within the posterior pole; substantial choroidal thinning inferonasal to the ONH was demonstrated. CT appears to correlate more with distance from the optic nerve than from the fovea and, thus, in future studies, the ONH may serve as a better reference point than the foveal center for expressing or depicting regional CT variations.