Conference “Biomedical Engineering“ 79 Swept-Source Optical Coherence Tomography: Choroidal Analysis in Healthy Eyes G. Gudauskienė * , I. Matulevičiūtė, D. Žaliūnienė Department of Ophthalmology, Lithuanian University of Health Sciences, Lithuania * E-mail: gailemazeikaite@gmail.com Introduction. The choroid plays an important role in ocular metabolism, volume regulation [1]. The choroid receives 65-85% of ocular blood flow and this supply plays a significant role in subfoveal region as in the foveal avascular zone there is no retinal vascular supply [2]. Choroidal thickness (CT) has been reported to change with daytime, axial length and age [3-6]. Choroidal blood flow is resistant to meaningful changes in young, healthy individuals. However, choroidal blood flow and CT may be affected when the eye is diseased [7]. Correct choroid structural evaluation is not possible using spectral-domain optical coherence tomography (OCT) because of its posterior location and the light dispersal caused by retinal pigment epithelium cells. OCT with longer wavelength light sources has been established [8, 9], which enables deeper penetration and more accurate choroidal assessment. Swept source OCT (SS- OCT) with a 1050-nm wavelength has been applied to examine the choroid in healthy [10] and diseased eyes [11, 12, 13], allowing precise visualization of the chorioscleral interface [14, 15]. The aim of this study was to evaluate CT in healthy individuals using SS- OCT. Methods. 40 eyes of 20 healthy Lithuanian individuals were included in the prospective clinical study. The research was performed at the Department of Ophthalmology, Hospital of Lithuanian University of Health Sciences, Kaunas Clinics. The research followed the tenets of the Declaration of Helsinki. Informed consent was obtained from all subjects before examination and Kaunas Regional Biomedical Research Ethics Committee approved the study. Exclusion criteria were: myopia, hyperopia more than 3 D, eye dystrophies, degenerative diseases, prior ocular surgery, inflammation, glaucoma, choroidal abnormalities, nevus, pregnancy, arterial hypertension, haemangiomas, diabetes mellitus. Ophthalmological examination was performed, axial length was measured using Aladdin optical biometer based on optical low-coherence interferometry (Topcon, Tokyo, Japan) and CT was assessed using 1050 nm DRI Triton SS-OCT (Topcon, Tokyo, Japan). The CT measurements were obtained manually using callipers perpendicularly from the outer part of the hyper-reflective line (retinal pigment epithelial layer) to the line corresponding to the choroidal-scleral junction. Sub-foveal (SF) CT and CT at temporal distances from the central fovea of 1500 µm (T1500), 3000 µm (T3000), and nasal distances of 1500 µm (N1500), 3000 µm (N3000), were measured, total five different locations. Measurements were performed at the same time 1-2