Table 1 shows basic characteristics of the examinees, and ophthalmic clinical and laboratory data of the parameters that were analyzed in the study. Out of total number of examinees, there were 48 women and 41 men, the average age was 62.65 years (in the range from 50 to 81 years).
In all patients in the non-proliferative and proliferative DR group, existence of diabetes mellitus type 2 was proven, as well as the presence and type of diabetic retinopathy, according to the International Clinical Diabetic Retinopathy Disease Severity Scale – ICDRDSS (Table 2).
The duration of diabetes mellitus in the NPDR group was 17.1 years (16±7.36 years), and in the PDR group it was 18.13 (16± 7.76 years). There was no statistically significant difference in the duration of diabetes mellitus between the observed groups (p=0.589).
The maximum duration of DM in the NPDR group was found in subgroups with an advanced form of illness18±2.83 years, followed by subgroups of moderate and mild form of NPDR. In the PDR group, the longest duration of DM was recorded in a subgroup of patients with a mild form of disease of 20.5±6.63, followed by subgroups of moderate and severe PDR.
A statistically significant difference in the duration of DM between six analyzed subgroups of patients in relation to the clinical stage of DR, was not determined, p=0.707.
The value of glycated hemoglobin (HgA1c) was measured in all patients involved in the study. The average concentration of glycated hemoglobin in the blood of all patients is 7.15%±1.68%. A significant difference in the average level of glycated hemoglobin between observed main patient groups was determined, p=0.001. The highest average HgA1c value was observed in the group of patients with proliferative diabetic retinopathy (8.14%).
In the group of subjects with NPDR concentration, HgA1c was 7.96%, and in the control group 5.43%. A statistically significant difference was found between the average value of HgA1c in the control group and NPDR, p=0.001, and between the control and PDR, p=0.001. While a statistically significant difference was not found between the average values of HgA1c in the blood of patients with NPDR and PDR, p=0.599.
By examination of the fundus of the eye by direct or indirect ophthalmoscopy and biomicroscopy, the control group of the subjects excluded the existence of pathological changes in the retina, except changes in arterial hypertension, which were found in 67% of persons. The study did not include patients who were previously treated with laser photocoagulation, or who had any other eye treatment.
A statistically significant difference in mean visual acuity (BCVA) values was found between observed groups for right and left eye, p = 0.001, and for BCVA on average for both eyes together p = 0.001. The values of the best corrected visual acuity BCVA were significantly lower in the PDR group (mean 0.44, median 0.45) compared to values in patients with NPDR (mean 0.78, median 0.90) and patients from the control group (mean 0.97, median 1.0).
The mean intraocular pressure (IOP) value, measured by applanation tonometer, in this study in the control group of the subjects was 14.62 mmHg, in the group of NPDR 14.84 mmHg, and in group PDR 13.92 mmHg.
A statistically significant difference was not found in the average IOP values between the observed groups for the right p=0.347 and left eye p=0.467, and for the IOP average for both eyes together p=0.383.
The mean concentration of erythropoietin (Epo) in our analyzed blood sample was 8.48 mIU/ml. The highest average Epo serum concentration was found in the PDR group of patients, 9.95mIU/ml, then 7.0 mIU/ml in the NPDR group. The lowest Epo concentration was found in the control group of patients, 6.9mIU/ml (Graph 1). The Kruskal-Wallis test did not show a statistically significant difference in the Epo concentration between the observed groups, p=0.123. The Mann-Whitney test did not show a statistically significant difference between the patients of the main observed groups - between the control group and the NPDR (p=0.805), the control group and the PDR (p=0.087), as well as among the subjects in NPDR and PDR (p=0.071).
The mean Epo concentration in the NPDR group was 7.0mIU/ml, the highest concentration was recorded in the moderate NPDR group, while the lowest was found in the subgroup of patients with advanced NPDR. The Kruskal-Wallis analysis did not show significant differences in the erythropoietin level in the observed patient subgroups, p=0.781.
Further, with the Mann-Whitney test, a statistically significant difference was not found in the mean value of erythropoietin by comparison with the observed NPDR: mild and moderate p=0.519, mild and advanced p=0.933, moderate and advanced p=0.686.
The average Epo concentration in the PDR patients group was 9.95 mUI/l. Using the Kruskal-Wallis test, a statistically significant difference in Epo values in PDR patients was found in relation to the stage of clinical picture, p=0.007. By using the Mann-Whitney test, statistically significantly higher concentrations of Epo in the blood of patients in subgroups were moderate and advanced in PDR, relative to the mild, p=0.001. Whereas, there is no statistically significant difference in the serum Epo concentration between the two most severe forms of PDR, p=1,000.
Statistically significantly higher concentrations of Epo in the blood were found in the subgroup of advanced PDR compared to: control group (p=0.004), but also each subgroup of NPDR, compared to mild NPDR (p=0.035), moderate NPDR (p=0.039), and advanced NPDR (p=0.022).