The Valsalva maneuver (VM) is a forceful exhalation against a closed airway [1]. It can also occur during activities that can be done in daily life such as lifting heavy loads, severe coughing, vomiting and constipation. During VM, the sympathetic system is activated, blood pressure and intrathoracic pressure (ITP) increase, venous blood returning to the heart decreases, and peripheral vascular resistance increases with reflex tachycardia and sympathetic activation [2], [3], [4]. Due to the decrease in venous return, the pressure increases in the jugular, orbital and vortex veins and congestion occurs in the choroid which is the largest vascular network in the eye [5].

There are many studies investigating the effect of VM on parameters such as choroidal thickness (CT), corneal morphology, anterior segment parameters, pupil diameter, and intraocular pressure (IOP) [3,4,6,7]. VM can also cause retinal and macular hemorrhages, known as valsalva retinopathy, depending on the increase in IOP [8].

The choroid is a vascular layer that consists of blood vessels, stroma, melanocytes, and connective tissue and has the highest blood flow rate of all tissues in the body [9]. It nourishes the outer retina, including the photoreceptors and when the normal structure of the choroid is disrupted, this may cause dysfunction in the photoreceptor and retinal pigment epithelium (RPE) layer [10]. There is no anastomosis between the choroidal arteries and each terminates as an end-artery [11]. The choroid has an important role in normal ocular health. It is the structure that is affected in many intraocular pathologies such as age-related macular degeneration, polypoidal choroidal vasculopathy, and central serous chorioretinopathy [12], [13], [14]. The effects of systemic, ocular diseases, environmental factors and hormonal conditions on CT have been investigated [15,16].

Choroidal vascularity index (CVI) is a recently defined parameter that is calculated using optical coherence tomography (OCT) images and image binarization programs and quantitatively evaluates choroidal vascularity and has been found to be more objective and sensitive than CT [17]. It has been suggested that CT is more affected by environmental and physiological factors than CVI [18]. In recent years, the number of studies investigating the effects of systemic and ocular diseases on CVI has increased.

In our current study, we aimed to investigate the changes in CVI, subfoveal choroidal thicknes (SFCT), central macular thickness (CMT), and IOP using EDI-OCT images during VM in healthy subjects.