Analysis of Widefield Choroidal Thickness Maps of Healthy Eyes using Swept Source Optical Coherence Tomography

Abstract

We aimed to obtain widefield (WF) swept source optical coherence tomography (SS-OCT) data and examine the features of choroidal thickness maps of healthy eyes. The posterior pole choroidal thickness was examined for 127 eyes using enhanced-depth imaging (EDI) of SS-OCT with a viewing angle of 20 (vertical) × 23 (horizontal) mm, and choroidal thickness maps were generated. For SS-OCT image analysis, we developed a grid with inner and outer rings, each divided into superotemporal, inferotemporal, superonasal, and inferonasal quadrants, respectively, making up a total of nine subfields including the central 3-mm ring. The posterior pole choroidal thicknesses were significantly lesser at the periphery than in the central area, in the inferior field than in the superior field, and in the nasal field than in the temporal field (p < 0.001 for all). We also evaluated the effects of age and axial length (AL) on the WF choroidal thickness. Choroidal thicknesses in all subfields were negatively associated with advanced age (p < 0.05). Choroidal thicknesses in the central subfield and the inferonasal inner and outer subfields were negatively associated with AL (p = 0.042, 0.034, and 0.022, respectively). These findings provide insights into the two-dimensional characteristics of the choroidal thickness and their associations with age and AL.

Choroidal and Retinal Thicknesses in Healthy Eyes Measured with Ultra-Wide Field Optical Coherence Tomography

“…Variations in the choroidal and retinal thicknesses with age were analyzed in a few studies. Similar results to ours were reported by Hirano et al for UWF-OCT [11]. In a study of the ETDRS grid area, Pongsachareonnont et al also found a significant loss of retinal and choroidal thickness with age; only the nerve fiber layer thickness was age-independent.…”

“…The retina has an approximately double convex shape with a thicker part located around the optic nerve. A similar picture of the retinal and choroidal architectures analyzed by the UWF testing was drawn by Hirano et [11]. In other studies such a difference between the architectures of these anatomical entities was also brought up , however in standard field OCT examination.…”

“…To our knowledge, this is the widest field of view available at present in OCT devices and as such, enables to draw more extensive picture of the architecture of the globe. Just a few other studies with the use of UWF-OCT, without the need for creating a mosaic of images, were performed so far [11,12]. In our study, the choroid has the shape of a convex-concave lens, with the peripheral thickness higher at the temporal side compared to the nasal side and the upper side compared to the inferior side.…”