Vitamin D Levels in Patients With Central Retinal Vein Occlusion- a Prospective Controlled Study
Condition: Vitamin d Deficiency; Central Retinal Vein Occlusion
MeSH terms: Retinal Vein Occlusion; Vitamin D Deficiency
Study type: Observational

Summary: 
      Retinal vein occlusion (RVO) is a common vascular disease of the eye. Studies have shown that
      the risk of venous thrombosis is higher in winter so even concerning RVO. Studies have shown
      a possible link between sun exposure and venous thrombosis. Vitamin D levels have been shown
      to have a similar seasonal variation, with a peak occurring in the summer. The primary source
      of vitamin D is from sunlight when ultraviolet B (UVB) radiation penetrates the skin and
      converts 7-dehydrocholesterol to 25-hydroxycholecalciferol vitamin D3 (25-OHVitD) via
      previtamin D. In Stockholm situated at latitude 59˚ 20΄ North, it is not possible to
      synthesize vitamin D at sufficient levels in winter and the exposure time required to reach a
      standard dose is impractical from at least October through March.

      The aim of the study is to evaluate vitamin D levels in central retinal vein occlusion (CRVO)
      patients and compare them with the vitamin D levels in randomly selected control patients
      matched for age and month of disease onset. This is to evaluate whether vitamin D deficiency
      may be a risk factor in the onset of CRVO.

      The hypothesis of the study is that patients with CRVO have lower levels of vitamin d than
      matched controls.
    

Detailed description: 
      The study will last one year and is expected to include 120 patients with RVO and 120 control
      patients. The first 10 RVO patients visiting St. Erik's Eye Hospital with disease duration of
      maximum 3 months will be included in the study each month. The control patients will be
      chosen randomly by the Central Bureau of Statistics and matched for age and gender according
      to disease distribution known from previous studies. The control group will receive a letter
      with information of the study, informed consent form and details about the blood sampling
      procedure. Every month 50 patients in the control group will be invited to participate in the
      study. Only the first 10 control subjects will be included in the study. Each month a blood
      sample will be taken from 10 patients with RVO and 10 subjects in the control group. All the
      subjects will only have one blood sample taken during the study. Blood will be analyzed to
      measure the vitamin D level. Vitamin D levels will be compared at the end of the study
      between groups and evaluated according to the time of year for sampling. All the blood
      sampling will be done by the laboratory at Karolinska University Hospital. Participation in
      the study is completely voluntary. The details of the study has been reviewed and approved by
      the Ethics Committee.
    

Observational model: Case-Control
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Consecutive patients with central retinal vein occlusion diagnosed at St Eriks Eye Hospital
      
Biospecimen description: 
      Blood sample of vitamin D
    
Keywords: Vitamin d deficiency; Central retinal vein occlusion