## 1 Introduction  
Following diabetic retinopathy (DR), Retinal vein occlusion (RVO) is the most known cause of vision deterioration due to a retinal vascular disorder [1, 2]. There are two major types of RVO: branch retinal vein occlusion (BRVO) and central retinal vein occlusion (CRVO). Hemi-CRVO (HRVO) has been considered by some authors as a subgroup of CRVO [3, 4, 5]. Although CRVO is less common than BRVO, it is associated with a worse visual prognosis, particularly in its ischemic form [4, 6]. More than 16 million adults are affected by RVO, with the incidence of BRVO being 3- to 10-times higher than CRVO [5, 7, 8, 9]. These numbers will undoubtedly rise because of the gradual elongation of the population's lifespan. Therefore, an increased risk for both BRVO and CRVO will particularly concern older individuals compared to younger ones [1; 10]. The pathogenesis of RVO is still not completely understood. Undoubtedly, arterial disturbances are a leading pathogenetic mechanism for RVO. In CRVO, because of the same adventitial sheath within the lamina cribrosa for the central retinal vessels, arterial stiffness affects neighboring veins. In BRVO, the compression of the veins at arteriovenous (AV) crossings, progressive changes concerning the venous walls, and the increased tendency to form blood dots are possible causes of the disorder [11]. Because of the varying anatomic relationships among retinal vessels, the risk factors for BRVO and CRVO may be different [10]. Three factors predispose individuals to thrombosis--damage of the endothelium, disturbed blood flow, and hypercoagulability--collectively defined as the Virchow's triad, play a role in the pathogenesis of RVO [5; 11; 12]. Some authors have suggested that systemic diseases that elevate the risk of changes in the endothelium or disturbed blood flow, such as hypertension (HTN), dyslipidemia, diabetes mellitus (DM), and heart diseases, are strictly connected with retinal vascular occlusion [10]. Although HTN is consistently indicated as a significant risk factor for both BRVO and CRVO, its connection with the diabetic condition is still controversial, and different studies have reported varying results on this subject [13]. Some studies have indicated DM as a risk factor for CRVO, but not BRVO [6; 14]. An interesting conclusion was drawn in the meta-analysis by [PERSON], which states that, in general, DM was not a risk factor for RVO in studies published before 2010. However, DM was attributed as a risk factor for RVO in studies published after 2010 [6]. The author implied that more recent studies might have been used more accurate methods. Moreover, the increasing number of studies, has made it possible to confirm a correlation between DM and RVO. However, no specific new methods of the detection of risk factors for DM and RVO have been pointed out in these published studies. Because of such heterogeneity of opinions in the literature, we decided to seek a different way to assess this correlation. For this purpose, we measured the skin autofluorescence (SAF), which assesses the accumulation of advanced glycation end products (AGE) in patients who have undergone an episode of CRVO or BRVO. AGES comprise heterogeneous groups of molecules, which accumulate in plasma and tissues during the natural process of aging. Studies had shown that prolonged exposure to hyperglycemia and consequently AGEs formation are responsible for irreversible changes and leads to progression of diabetic complications [15; 16]. The AGEs formation affects short-lived molecules such as circulating plasma proteins and lipids, as well as long-lived macromolecules, such as proteins in ocular lens [17; 18]. AGEs are accounted for \"metabolic memory\", which is responsible for chronic irreversible vascular abnormalities in diabetic patients, even with relatively good control of glucose level [16; 19].