Evaluation of Choroidal Vascularity Index in Keratoconus Patients: Does Choroidal Vascularity Change in Keratoconus?

Abstract

Purpose: To investigate the choroidal structure in keratoconic patients with different severity using the choroidal vascularity index (CVI) derived from image binarization on enhanced depth imaging optical coherence tomography scans (EDI-OCT).

Methods: Sixty-eight eyes from 34 keratoconus (KCN) patients and 72 eyes from 36 healthy subjects were recruited in this prospective, noninterventional, comparative cross-sectional study. EDI-OCT was employed to measure choroidal parameters, including choroidal thickness (CT), total choroidal area (TCA), luminal area, stromal area, and CVI.

Results: Subfoveal CT was 354.6 ± 66.8 μm in the control group and 371 ± 64.5 μm in the KCN group (P = 0.86). There was no significant difference between control and KCN groups in terms of TCA (0.66 ± 0.14 mm² vs. 0.7 ± 0.12 mm²; P = 0.70), luminal area (0.49 ± 0.10 mm² vs. 0.53 ± 0.08 mm²; P = 0.67), and stromal area (0.16 ± 0.05 mm² vs. 0.17 ± 0.05 mm²; P = 0.84). CVI was also comparable in the control group (75.4% ±3.4%) and the KCN group (75.6% ±4.5%; P = 0.43). There was also no significant correlation between other choroidal parameters and KCN severity indices.

Conclusion: It seems that CVI as well as other choroidal biomarkers were not significantly different between patients with KCN and healthy subjects.

Keywords: Choroidal thickness; Choroidal vascularity index; Enhanced depth imaging optical coherence tomography scans; Keratoconus.

Figure 1

Enhanced depth imaging optical coherence tomography scan of the foveal area. Representation of a choroidal thickness measurement from the outer edge of the hyperreflective line (red asterisk), corresponding to the retinal pigment epithelium and Bruch’s membrane, to the choroidal-scleral junction (yellow dotted line). Measurements were taken at the subfoveal choroid with ruler tool

Figure 2

Representation of binarization technique for choroidal vascular index measurement. The image was converted to 8-bit and Niblack auto local threshold tool was applied. The luminal area (white arrow) and the stromal area (red arrow) are shown in black and white colors, respectively, after the binarization process