European Journal of Cardiovascular Medicine

Retinal vein occlusion (RVO) is a significant cause of vision loss, particularly among the elderly population, ranking as the second most common vascular cause of visual impairment after diabetic retinopathy [1]. RVOs are classified into three main types based on the location of the occlusion: central retinal vein occlusion (CRVO), branch retinal vein occlusion (BRVO), and hemicentral retinal vein occlusion (HCRVO). Globally, the prevalence of RVO is estimated at 5.20 per 1,000 individuals, with BRVO being more common (4.42 per 1,000) than CRVO (0.80 per 1,000) [2]. In rural Central India, a population-based study by Jonas et al. reported an RVO prevalence of 0.8%, with BRVOs being approximately seven times more frequent than CRVOs [3]. Despite its clinical significance, the precise etiology of RVO remains incompletely understood. However, systemic arteriosclerotic vascular diseases, hypertension (HTN), dyslipidemia, diabetes, and hyperhomocysteinemia have been identified as key risk factors [4, 5]. Additionally, RVO has been strongly associated with cardiovascular diseases (CVD) and stroke, highlighting its systemic vascular implications [4]. Emerging evidence suggests that inflammatory processes and endothelial dysfunction, which are central to the pathogenesis of atherosclerosis, may also play a critical role in the development of RVO. Vitamin D, a fat-soluble vitamin essential for bone health, is synthesized in the skin upon exposure to ultraviolet B (UVB) radiation or obtained through dietary sources. Beyond its classical role in calcium homeostasis, vitamin D has been implicated in various non-skeletal health outcomes, including cardiovascular and cerebrovascular diseases. Large-scale population studies have linked vitamin D deficiency to an increased risk of ischemic stroke, coronary artery disease (CAD), venous thromboembolism, and cardiovascular mortality [6, 7]. Notably, vitamin D supplementation has been shown to improve vascular endothelial function, particularly in individuals with diabetes, suggesting a potential protective role against vascular pathologies [8]. These findings raise the possibility that vitamin D deficiency may also influence retinal vascular health, potentially contributing to the development of RVO. This hypothesis is further supported by studies demonstrating improved outcomes in patients with heart failure and ischemic heart disease following vitamin D supplementation [9]. Furthermore, vitamin D has been shown to exert anti-inflammatory and anti-thrombotic effects, which may help mitigate the endothelial dysfunction and vascular inflammation implicated in RVO.

In the context of Bihar, India, where healthcare access and nutritional status are often suboptimal, the prevalence of vitamin D deficiency is likely to be high due to limited sunlight exposure, dietary insufficiencies, and socioeconomic factors. Bihar's population, particularly in rural areas, faces a dual burden of communicable and non-communicable diseases, with cardiovascular diseases and diabetes emerging as major public health challenges. The state also has a high prevalence of hypertension and dyslipidemia, both of which are established risk factors for RVO. Given the shared pathophysiology of atherosclerosis in RVO and other vascular diseases, it is plausible that vitamin D deficiency may play a role in the etiology of RVO in this population. However, there is a paucity of research exploring the relationship between serum vitamin D levels and RVO in this region. Understanding this association could provide valuable insights into the prevention and management of RVO, particularly in resource-limited settings like Bihar.

This study aims to investigate serum vitamin D levels in patients diagnosed with RVO and compare them with age-matched control groups in Bihar, India. By examining the potential link between vitamin D deficiency and RVO, this research seeks to contribute to a better understanding of the disease's etiology and inform preventive and therapeutic strategies. Given the high burden of vascular diseases and nutritional deficiencies in Bihar, this study holds significant clinical and public health relevance, potentially paving the way for targeted interventions to reduce the incidence and impact of RVO in this vulnerable population. Additionally, the findings may underscore the importance of addressing vitamin D deficiency as part of a comprehensive approach to managing retinal vascular diseases and improving overall ocular health in similar populations globally.

This case-control hospital-based study was conducted at the Department of Ophthalmology, Government Medical College and Hospital, Bettiah, Bihar, India. Written informed consent was obtained from all participants prior to their inclusion in the study, ensuring ethical compliance and voluntary participation. A total of 100 participants were enrolled in the study, comprising 50 cases confirmed with RVO and 50 age-matched controls without RVO. Cases were selected based on a confirmed diagnosis of RVO, while controls were individuals without RVO but within the same age range as the cases. Participants were recruited consecutively as they presented to the ophthalmology department and met the study’s inclusion criteria.

Inclusion Criteria:

For Cases (RVO Group):

1. Patients diagnosed with retinal vein occlusion (RVO).
2. Diagnosis confirmed through comprehensive ophthalmologic evaluation, including:

• Fundoscopy
• Fundus photography
• Optical coherence tomography (OCT) if macular edema is suspected

1. Age ≥ 21 years.
2. Willingness to provide written informed consent and participate in the study.

For Controls (Non-RVO Group):

1. Age-matched individuals without any clinical or diagnostic evidence of RVO.
2. No history or presence of any other retinal vascular pathology.
3. Age ≥ 21 years
4. Willingness to provide written informed consent and participate in the study.

Exclusion Criteria:

Ophthalmic Exclusions:

1. History of ocular trauma, uveitis, or glaucoma.
2. Presence of other retinal diseases, including:

• Diabetic retinopathy
• Age-related macular degeneration (AMD)
• Hypertensive retinopathy
• Retinitis pigmentosa

1. Prior intraocular surgery (except uncomplicated cataract surgery) within the past 6 months.
2. Presence of significant media opacities preventing retinal evaluation.

Systemic Exclusions:

1. History of chronic kidney disease (CKD), as it may affect vitamin D metabolism.
2. Chronic liver disease, which could alter vitamin D synthesis and metabolism.
3. Patients with known malabsorption syndromes (e.g., celiac disease, Crohn’s disease) that could affect vitamin D absorption.
4. Individuals on vitamin D supplementation or calcium supplements that may influence serum vitamin D levels.
5. Patients receiving systemic corticosteroids, bisphosphonates, or other medications known to interfere with vitamin D metabolism.
6. History of parathyroid, thyroid, or other endocrine disorders affecting calcium and vitamin D homeostasis.
7. Pregnant or lactating women.
8. Patients with a history of malignancy or undergoing active chemotherapy or radiation therapy.
9. Individuals unable to comply with study procedures, including those with severe cognitive impairment or psychiatric illness.

Patient History and Medical Records:

A detailed medical history was obtained from all participants, including information on diabetes mellitus (DM), hypertension (HTN), dyslipidaemia, coronary artery disease (CAD), and cerebrovascular accidents (CVA). Medical records were used to corroborate the reported history of these conditions.

General Examination:

A thorough general examination was conducted, including measurements of pulse rate, peripheral pulses, blood pressure, and higher functional status.

Ophthalmic Examination:

• Visual Acuity: Best-corrected visual acuity (BCVA) was assessed using the Snellen chart.
• Slit Lamp Examination: Anterior and posterior segment evaluations were performed using a slit lamp biomicroscope.
• Intraocular Pressure (IOP): IOP was measured using an applanation tonometer.
• Fundoscopy: Fundus examination was conducted using slit lamp biomicroscopy with a 90 D lens.
• Fundus Photography: Retinal photographs were taken using retinal camera documentation.
• Optical Coherence Tomography (OCT): In cases where macular edema was suspected, OCT was performed to confirm the diagnosis.

Systemic Evaluation:

• Blood pressure measurements were recorded.
• Fasting and postprandial blood glucose levels were assessed.
• Lipid profiles, including total cholesterol, low-density lipoprotein (LDL), high-density lipoprotein (HDL), and triglycerides, were analyzed.
• Serum homocysteine levels were measured.
• Electrocardiograms (ECGs) were performed to evaluate cardiovascular health.

Laboratory Analysis of Serum Vitamin D Levels: All participants were required to fast for 12 hours prior to blood sample collection. Blood samples were drawn, and serum was separated and stored at -20°C until analysis. Serum vitamin D levels were quantified using tandem mass spectrometry, a highly sensitive and specific method for measuring total vitamin D concentration. Vitamin D levels were categorized as follows:

• Deficient: <20 ng/mL
• Insufficient: 20–30 ng/mL
• Sufficient: >30 ng/mL

Statistical Analysis: The collected data was organized into a table using Microsoft Excel 2019. Next, the data was transferred to GraphPad version 8.4.3 for further statistical analysis. Continuous variables were expressed as mean ± standard deviation (SD), while categorical variables were expressed as frequencies and percentages. Comparisons between cases and controls were performed using independent t-tests or Mann-Whitney U tests for continuous variables and chi-square tests for categorical variables. A P-value of less than 0.05 was considered statistically significant.

The study investigated serum vitamin D levels in retinal vein occlusion (RVO) patients and compared them with age-matched control groups. The mean age of the cases was 58.15 ± 9.67 years, while the mean age of the controls was 58.97 ± 10.65 years. Statistical analysis revealed no significant difference in age distribution between the two groups (p > 0.05), indicating that the cases and controls were well-matched in terms of age. The demographic characteristics of the participants are presented in Table 1. In the 21-30 years age group, 6% of cases and 5% of controls were represented. Similarly, in the 31-40 years age group, 7% of cases and 9% of controls were observed. The 41-50 years age group comprised 5% of cases and 6% of controls, while the 51-60 years age group included 12% of cases and 13% of controls. The 61-70 years age group accounted for 13% of cases and 14% of controls, and the >70 years age group represented 7% of cases and 3% of controls. The total distribution of cases and controls was balanced, with 50 participants (50%) in each group. Gender distribution was also comparable between the two groups. Among the cases, 31% were male and 19% were female, while among the controls, 33% were male and 17% were female. No significant differences were observed in gender distribution between cases and controls (p > 0.05).

Table 1: Showing the age distribution among patients of both groups.

We found that superotemporal branched retinal vein occlusion (ST BRVO) was the most common type, accounting for 48% (24 out of 50) of the cases. This was followed by central retinal vein occlusion (CRVO), which was observed in 34% (17 out of 50) of the cases. The least prevalent type was inferotemporal branched retinal vein occlusion (IT BRVO), representing 18% (9 out of 50) of the cases (Table 2 and Figure 1).

Table 2: Showing the prevalence of different types of retinal vein occlusions in cases.

Figure 1: Prevalence of different types of retinal vein occlusions in cases.

(ST BRVO: Superotemporal branched retinal vein occlusion; IT BRVO: Inferotemporal branched retinal vein occlusion; CRVO: Central retinal vein occlusion)

Among the fifty cases of retinal vein occlusion (RVO), eight patients (8%) exhibited deficient levels of vitamin D (serum levels <20 ng/mL). Additionally, 42 individuals (42%) had insufficient vitamin D levels, falling within the range of 20–30 ng/mL. Notably, none of the cases demonstrated normal vitamin D levels (>30 ng/mL), indicating that all RVO patients had suboptimal vitamin D status. In contrast, among the fifty age-matched controls, no individuals were found to have deficient vitamin D levels. However, 14 controls (14%) had insufficient levels, while 36 controls (36%) maintained normal vitamin D levels. The comparison between the two groups revealed a statistically significant difference in vitamin D status, with a p-value of < 0.05. These findings underscore a strong association between low vitamin D levels and retinal vein occlusion, suggesting that vitamin D deficiency and insufficiency may play a role in the pathogenesis of RVO (Table 3).

Table 3: Showing the comparison of the vitamin D levels among cases and controls

The serum vitamin D levels in retinal vein occlusion (RVO) patients were compared to those in age-matched control groups (Table 4). It focused on different subtypes of RVO. The mean vitamin D level among the total RVO cohort was 21.08 ± 5.08 ng/mL, and there was no statistically significant difference among the subtypes (p = 0.803). ST BRVO had a mean vitamin D level of 21.45 ± 5.37 ng/mL, while CRVO had the lowest mean level at 20.41 ± 5.91 ng/mL.

Table 4: Showing the comparison of the vitamin D levels in different types of RVOs

Table 5 compares the prevalence of hypertension between the case and control groups. Among the cases, 37 individuals (37%) had hypertension, while 23 individuals (23%) in the control group also had hypertension. Conversely, 13 individuals (13%) in the case group did not have hypertension, compared to 27 individuals (27%) in the control group. The prevalence of hypertension was significantly higher among the cases (37%) than among the controls (23%). The chi-square test result (X² = 8.167) indicates a statistically significant difference between the two groups (p = 0.004). As the p-value is less than 0.05, this suggests that there is a statistically significant association between hypertension and the case group, indicating that individuals in the case group are more likely to have hypertension compared to those in the control group.

Table 5: Showing the comparison of the prevalence of hypertension among cases and controls

Table 5 presents a comparison of the prevalence of dyslipidaemia between the case and control groups. Among the cases, 11 individuals (11%) were found to have dyslipidaemia, while only 3 individuals (3%) in the control group had this condition. Conversely, 39 individuals (39%) in the case group did not have dyslipidaemia, compared to 47 individuals (47%) in the control group.  Overall, the prevalence of dyslipidaemia was significantly higher among the cases (11%) than in the controls (3%). The chi-square test result (X² = 5.315) demonstrates a statistically significant difference between the two groups (p = 0.021). Since the p-value is less than 0.05, this indicates that there is a statistically significant association between dyslipidaemia and the case group, suggesting that individuals in the case group are more likely to have dyslipidaemia compared to those in the control group.

Table 6: Showing the comparison of the prevalence of dyslipidaemia among cases and controls

Retinal vein occlusion (RVO) is one of the most common causes of sudden, unilateral vision loss, particularly in older adults. Multiple risk factors contribute to its incidence, though the exact pathophysiology remains unclear. Age is the primary risk factor, while additional factors include blood hyperviscosity, thrombophilia, diabetes mellitus (DM), cardiovascular diseases (CVD), cerebrovascular accidents (CVA), arteriosclerosis, and metabolic syndrome. Moreover, congenital thrombophilic disorders (e.g., hyperhomocysteinemia, factor V Leiden mutation, and anticardiolipin antibodies), as well as end-organ damage due to DM and hypertension (HTN), significantly increase the likelihood of RVO. Ophthalmic risk factors such as glaucoma and ocular hypertension further elevate the risk, as highlighted in a meta-analysis by Kolar [10]. While these factors are well-established, limited research has explored the role of vitamin D in RVO pathogenesis. In our study, all RVO patients exhibited either deficient (<20 ng/ml) or insufficient (20–30 ng/ml) vitamin D levels, while 36% of the control group had normal vitamin D levels (>30 ng/ml) [11,12]. Specifically, 8% of cases had vitamin D deficiency, and 42% had insufficient levels, demonstrating a significant difference in vitamin D status between cases and controls. Our findings align with a case-control study by Oli and Joshi, where 95% of RVO patients in a South Indian population had vitamin D levels below 20 ng/ml compared to only 8% of controls [13]. Similarly, Epstein et al. observed significantly lower vitamin D levels in RVO cases, although they could not establish a distinct difference between cases and controls [14]. A case report by Talcott and Eliott further documented severe vitamin D deficiency in patients with retinal vascular occlusion [15]. Additionally, Karimi et al. demonstrated that patients receiving oral vitamin D supplements exhibited greater reductions in central macular thickness and improved best-corrected visual acuity following intravitreal bevacizumab therapy [16].

An unusual case of bilateral central RVO in a patient with isolated vitamin D deficiency—without any other systemic risk factors—was also identified in our study. This patient showed significant improvement following intravitreal bevacizumab injections and oral vitamin D supplementation, suggesting a potential therapeutic role for vitamin D in RVO management. Our study also assessed vitamin D levels across different types of RVO but found no significant variations among them. However, patients with hypertension and dyslipidemia had a higher prevalence of RVO, confirming a strong association with these conditions. In contrast, traditional risk factors such as diabetes, smoking, hyperhomocysteinemia, CVD, and CVA did not demonstrate a significant relationship in our study. These findings are supported by O’Mahoney’s meta-analysis, which indicates that HTN and high cholesterol are major risk factors for RVO, while DM is associated with a relatively lower risk [17]. Dodson et al. further observed that HTN and hyperlipidemia are the most common systemic contributors to RVO, even in diabetic patients, reinforcing our findings [18]. A statistically significant association (p < 0.05) was noted between hypertension, dyslipidemia, and RVO, suggesting that individuals with these conditions are at a heightened risk of developing RVO compared to those without these risk factors. Consequently, all patients with vitamin D deficiency in our study were initiated on oral vitamin D supplementation. While the optimal dosage remains under investigation, a maximum daily intake of 4000 IU is generally recommended [19]. The findings of this study highlight the potential role of vitamin D deficiency in RVO pathogenesis and its possible implications for disease progression. Vitamin D is known to exert vascular protective effects by modulating endothelial function. The vascular endothelium expresses vitamin D receptors (VDRs) and 1-alpha-hydroxylase, which convert vitamin D into its active form. Vitamin D enhances nitric oxide (NO) production, thereby promoting vascular relaxation and reducing oxidative stress, as described by Kim et al. [20]. In vitro studies have demonstrated that vitamin D-VDR interactions enhance NO synthesis, mitigating endothelial dysfunction and oxidative damage [21, 22]. Given these mechanistic insights, vitamin D supplementation could serve as a potential adjunct in RVO management. However, our study has certain limitations, including the lack of vitamin D level assessment at the time of RVO onset, the inability to determine whether vitamin D deficiency was a predisposing factor or a consequence of the disease, and the absence of consideration for seasonal variations in vitamin D levels. Future large-scale, randomized controlled trials are warranted to establish whether vitamin D supplementation could influence RVO outcomes.

Our study demonstrates that low vitamin D levels are prevalent in RVO patients compared to age-matched controls, suggesting that vitamin D deficiency is a significant risk factor for the development of RVO. Additionally, hypertension and dyslipidaemia were also found to be significant risk factors. It is recommended that routine investigation of vitamin D levels be conducted in individuals with RVO, alongside screening for other risk factors. Patients found to have vitamin D deficiency should undergo ophthalmological examinations, and vitamin D supplementation should be provided as a prophylactic measure in cases of deficiency.

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