Evaluation of changes in choroidal vascularity during acute anterior uveitis attack in patients with ankylosing spondylitis by using binarization of EDI-optical coherence tomography images

Background: To evaluate the effect of the first acute anterior uveitis (AAU) attack on the choroid by using an image binarization tool on images from enhanced depth imaging (EDI)-optical coherence tomography (OCT) scans in patients with ankylosing spondylitis (AS). Methods: In this study, three groups were formed: uveitic eyes (UE; n = 20) of patients with AS, the non-uveitic eyes (NUE; n = 20) of these patients, and the eyes of healthy controls (n = 20). EDI-OCT images were obtained during the first AAU attack and at three months after treatment in patients with AS. An image binarization tool (ImageJ software; Bethesda, MD USA) was used on EDI-OCT images to determine choroidal structures. Choroidal vascularity index (CVI) was defined as the ratio of luminal area to total subfoveal choroidal area. Results: Compared to the convalescent period, CVI was found to be significantly increased in UE (63.2 +/- 2.87 vs. 60.9 +/- 5.2 %, p = 0.045) and NUE (63.8 +/- 5.67 vs. 61.5 +/- 4.3 %, p = 0.039), while stromal area (SA) was found to be significantly reduced only in UE (0.487 +/- 0.19 vs. 0.569 +/- 0.18, p = 0.012) in the attack period. Conclusions: Changes in the CVI values of UE and NUE groups in the first AAU attack shows that there is underlying choroidal inflammation in patients with AS. It also seems that SA is the most affected choroidal structure in eyes suffering from an attack. The present study revealed that CVI measurements can be used for follow-up and the determination of treatment response in AS patients with AAU attack.