Glaucoma, the main cause of blindness in world, is a progressive and multifactorial neuropathy characterized by the presence of the typical damage of the optic disc, an irreversible loss of the retinal ganglion cells and their axons, thinning of the retinal fiber layer (RNFL) and functional visual defect [1,2].

There are many known risk factors, including increased cup-disk ratio, cup disc asimmetry, elevated intra ocular pressure and family history [3], [4], [5], [6]. Glaucoma is classified in open-angle and closed-angle glaucoma; in the first type there is an increased resistance of the aqueous outflow trought the trabecular meshwork, access to which may be blocked in the second type by the conformation of the iris [4].

Preperimetric glaucoma (PPG) represents a stage characterized by the presence of early structural and vascular damage to the optic disc before the appearance of visual field defects [3,4].

Moreover, early detection of structural and vascular changes are especially important for PPG to retard disease progression and preserve maximum vision.

Elevated intraocular pressure (IOP) has been considered the major risk factor [5] but the loss of visual function may continue even with controlled IOP [6]. In addition to the mechanical theory, a vascular component in the pathogenesis of glaucomatous optic neuropathy has been discussed for many decades [7], [8], [9], [10], [11], [12].

Indeed the choroid, the vascular layer of the eye, provides metabolic support to the prelaminar portion of the the optic nerve head (ONH) and changes in the choroidal and choriocapillary structure and circulation may play an important role in the pathogenesis of glaucoma [13], [14], [15], [16], [17].

The choriocapillary is the Inner layer of the choroid containing small, thickened blood vessels, in contact with the outer layer of Bruch's membrane. Provides nutrients and oxygen to the pigment epithelium and to the outer retinal layers including the visual cells. Furthermore, the increase of choroidal thickness (CT) and the decrease density of capillaries of choriochapillaries could have been implicated in the etiology of glaucoma [18,19].

To date is possible, using the enhanced depth imaging optical coherence tomography (EDI-OCT), to measure accurately the sub-foveal choroidal thickness (SFCT); on the other hand the optical coherence tomography angiography (OCT-A) has allowed to evaluate the perfusion status of different retinal and choroidal layers, including the calculation of the choriocapillaries vessel density (CCVD) [20].

The aim of the present study was to examine and measure SFCT and CCVD using respectivly EDI-OCT and OCTA in preperimetric and advanced glaucomatous eyes, in order to shed light on the vascular pathogenesis of glaucoma disease.