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Purpose : The essence of pachychoroid would be dilatation of vessels of Haller’s layer; however, there is no established method to quantitate vascular dilatation. The purpose of this study was to evaluate the vessels of Haller’s layer of pachychoroid eyes in a novel objective manner.
Methods : A retrospective study of 135 eyes of pachychoroid spectrum diseases and 135 eyes of age-matched healthy subjects. The en face image was created from 7×7mm 3D OCT scans and the image of top 25% in Haller’s layer was extracted by machine-learning-based program（H Shiihara, et al. Jpn J Opthalmol 2018）. The vessel area, vessel length, and mean vessel diameter were calculated with our developed software. After the en face image divided in two vertical images, top and bottom half, the number of vessels running in symmetrical direction was calculated and the ratio of symmetrical vessel was determined. The average of its ratio was defined as “Symmetry index”. These parameters were compared between pachychoroid spectrum disease group and normal control group.
Results : The vessel area was significantly larger in the disease group (27.0 ± 4.4 vs 22.5 ± 3.7mm2, P<0.001). The vessel length was significantly shorter in the disease group (152.5 ± 18.3 vs 160.0 ± 25.7mm, P=0.009). The mean vessel diameter was significantly larger in the disease group (0.180 ± 0.037 vs 0.142 ± 0.021mm, P<0.001). Symmetry index was significantly lower in the disease group (53.0 ± 6.0 vs 58.4 ± 6.3%, P<0.001). In discriminant analysis, mean vessel diameter and Symmetry index were independent factors to separate disease group from normal group.
Conclusion : Our new method disclosed the eye with pachychoroid spectrum diseases had dilated choroidal vessels and asymmetrical structure of Haller’s layer.
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