Results
One hundred patients with RVO were selected (mean age 59 years, 42% females, mean BMI 27.5 kg/m). Of these, 26 had CRVO and 74 had BRVO. None of them had bilateral RVO, and the most affected eye was the left one. The main characteristics of the study population are shown in Table 1.
Local Factors
Among the local factors for RVO was ocular hypertension, for which only 15 were under treatment, and whose ocular pressure at the moment of the RVO were 20.8 ± 4.3 mmHg for the right eye and 21.6 ± 6.0 for the left eye. For those subjects without ocular hypertension, the mean ocular pressures were 15.9 ± 3.9 and 15.8 ± 3.0 for the right and left eye, respectively. These differences are highly significant when compared with the levels observed in those treated for ocular hypertension. The prevalence of elevated ocular pressure (ocular pressure ≥ 21 mmHg) was 7.6% among those without diagnosis of ocular hypertension and 33.3% among those 15 under treatment for ocular hypertension (p-value 0.003). In the two subjects with the highest ocular pressure values (42 and 40 mmHg), the affected eye was the unilateral one, whereas in those subjects with only mild elevations of the OP this concordance did not always occur. The funduscopy revealed cross signs in 17 patients.
Venous Factors
Only the prevalence of hyperhomocysteinaemia and aPLAs was similar to that observed in our cohort of young patients with DVT and/or PE or to the estimated prevalence observed in DVT or PE studies in the literature. It was significantly higher than that reported in the general population. For genetic thrombophilia, which includes factor V Leiden, G201210A mutation of prothrombin gene, protein C, S or antithrombin III deficiencies, the prevalence observed in the RVO group was similar to the one observed in the general population and was significantly lower than that observed in our cohort of DVT or for the estimated one in DVT/PE in the literature. For the D-dimer levels, only a small number of patients (17%) had abnormal levels (D-dimer ≥ 250 mg/dl). Because of the large differences in age between the RVO and the DVT groups, we have also included the comparison with the subgroup of RVO patients equal or younger than 50 years old. The results of the comparison of venous factors are shown in Table 2.
Arterial Factors
For matching, there were no differences in age, sex and BMI among the RVO and the comparison populations, except for age in the case of Pizarra. Individuals from this population were significantly younger than were the individuals with RVO (55.9 vs. 59.2, p < 0.05). Among the main arterial risk factors for atherosclerosis, the prevalence of hypertension was initially similar for all the populations; however, after a reclassification of hypertension status based on BP levels over 140/90 mmHg, this prevalence was markedly higher for the RVO group than for the other groups. Additionally, BP levels were significantly higher in the RVO group than in the others groups. The change in the prevalence of hypertension after reclassification was highly significant (from 47.4 to 80.8) indicating a large proportion of new diagnosed hypertension.
In the case of type 2 diabetes, the prevalence was significantly higher in Pizarra than in the other groups, but there were no significant differences among the RVO, Hortega or Segovia. After reclassification, there was a trend towards a higher prevalence in the RVO group when compared with those of Hortega and Segovia, but these differences were not significant. The glucose levels were significantly higher in the RVO than in Hortega or Segovia, but were lower than those observed in the Pizarra group. These differences in glucose levels among RVO, Hortega and Segovia were especially prevalent in the non-diabetic patients, indicating a higher prevalence of intolerance fasting glucose.
Finally, for lipid metabolism, the prevalence of dyslipidaemia under treatment was significantly higher in the RVO as compared with that for the Hortega group and was similar to the one observed in the Segovia group. Both LDL and HDL cholesterol were significantly higher in the RVO than in Hortega, whereas the opposite trend was observed for triglycerides. The results for the comparison of arterial factors are shown in Table 3 and Figures 1 and 2.
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Figure 1.
Prevalence of the main arterial risk factors in the retinal vein occlusion group and the comparison groups. Horizontal lines inside the bars mean the prevalence of the risk factor previous to the reclassification (see main text)
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Figure 2.
Box plot for the systolic and diastolic blood pressure factors in the retinal vein occlusion (RVO) group and the comparison groups grouped by the presence or absence of antihypertensive treatment. *,**,*** are statistically significant differences (p < 0.05, 0.01 and 0.001, respectively) between the RVO group and the other groups
Carotid Evaluation
A carotid ultrasound evaluation was performed in 48 patients. It showed evidence of atherosclerosis in a large number of subjects [36 (75%)]. Fifteen subjects had fibrolipidic plaques, eight had fibrocalcic ones and 10 had both types of plaque. The most affected carotid was the left, in 33 patients, with the majority of the plaques located at the bifurcation. The mean size of these plaques on the left side was 1.93, 2.21 and 2.36 mm for distal common carotid artery, bifurcation and internal carotid artery, respectively. The right carotid system was affected in 27 subjects, with an average plaque size of 1.8, 2.3, 2.0 and 2.5 mm for distal common carotid artery, bifurcation, internal carotid artery and external carotid artery, respectively.
Nor were there significant differences in sex, SBP, DBP, glucose or lipid levels among those subjects with or without carotid atherosclerosis. In the patients with carotid atherosclerosis, the RVO was in the right eye in 20 subjects (55.5%) and in the left eye in 16 (44.4%).