## 4 Discussion
The lack of difference in the mean SAF value may come as surprising, considering the 10-year difference in the mean age between the CRVO and BRVO groups, as age is one of the factors elevating the SAF value [57]. These results suggest that in the CRVO group, with CRVO generally affecting younger people, there is an accelerated accumulation of AGEs in the skin. The mean SAF values in the CRVO group with DM (n = 4) and without DM (n = 6) were 2.98 a.u. and 2.44 a.u., respectively. These values differed greatly from the mean SAF values in the BRVO group with DM (n = 5) and without DM (n = 4), which were 2.6 a.u. and 2.7 a.u., respectively. These results may suggest that patients with CRVO are at a much higher risk of developing DM than patients with BRVO. We should emphasize the significant age difference between these two types of RVO. The mean age in the CRVO group was lower. In a healthy population, a lower age should be related to lower mean SAF values. Our results may indicate that in CRVO patients, the process of AGE synthesis advances faster than in BRVO patients. A higher percentage of patients with an increased risk of DM in the CRVO group compared to the BRVO group, based on the SAF measurement, may also indicate the faster process of AGE synthesis. In the CRVO group 10 (91%), 11 patients evaluated with SAF had a risk of DM based on the AGEs values. In the BRVO group 4 (44%), 9 patients evaluated with SAF had a risk of DM. There was a significant difference between these two groups (\(p=0.024\)). It is worth noting that the mean SAF value in patients with an increased risk of DM did not differ between two groups. From a clinical point of view, these results could indicate that among patients with an increased risk of DM, there is a higher tendency of developing CRVO rather than BRVO, and that RVO may emerge in younger individuals. The mean SAF value in diabetic patients was higher in the CRVO group compared to the BRVO group (2.98 a.u. and 2.6 a.u., respectively). Unfortunately, the CRVO group with DM was too small (n = 4) to assess statistical significance. Therefore, the observed tendency should be verified in a larger group of patients. It should also be noted that in the CRVO group, the standard deviation in the SAF values was relatively high compared to the BRVO and control groups (Table 2). The considerable dispersion of these results may indicate that not every patient with CRVO is at the same risk level of DM development. From a clinical point of view, it seems justified to assess the SAF in patients with CRVO in order to identify those at risk of DM. Apart from the fact that the incidence of DM in our study was higher than in other studies, we found a significant correlation between RVO and DM in the SAF measurement, which confirms the findings from other recent studies. We are aware of several concerning limitations of our study. First, our sample size was relatively small in comparison to other publications. Second, the follow-up of RVO was diverse. In addition, apart from laboratory tests, we did not perform a detailed assessment of the cardiovascular condition of the studied group. However, our main goal was to indicate a different way to find an association between DM and RVO. More well-devised studies on the relationship between RVO and DM with a larger number of responders should be undertaken in the future. In conclusion, measuring the advanced glycation end products (AGE) in the skin autofluorescence (SAF) is useful method of evaluating the risk of DM development in patients with RVO. We confirmed the correlation between retinal vein occlusion and diabetes mellitus, which was significantly pronounced in the CRVO form. Methodology: K.K. and P.Z. ; Software: K.K. and P.Z. ; Validation: P.Z. ; formal analysis: K.K. and P.Z. ; Investigation: K.L.-D., K.Z., Z.S., M.P. and M.S.-B. ; Resources: Z.S., M.P. and M.S.-B. ; Data curation: P.Z. and B.L.S. ; Writing--original draft preparation: K.K. ; Writing--review and editing: K.K., P.Z. and B.L.S. ; Visualization: K.K. ; Supervision: G.M.