Conditions That Can Cause Blood Clots in the Eye
Blood clots in the eye primarily occur as retinal vein occlusions (RVOs) or retinal artery occlusions (RAOs), with distinct systemic and ocular risk factors for each type.
Systemic Conditions Causing Retinal Vein Occlusions
For Branch Retinal Vein Occlusion (BRVO)
The most common systemic risk factors include 1:
- Arterial hypertension (most important)
- Hyperlipidemia
- Diabetes mellitus
- Coronary artery disease
For Central Retinal Vein Occlusion (CRVO)
CRVO has a different risk profile 1:
- Carotid occlusive disease
- Sleep apnea
- Cardiovascular disease and diabetes (associated with higher mortality)
- Systemic lupus erythematosus (3.5 times higher incidence than controls)
Hematologic and Thrombophilic Conditions
In patients under age 50 with CRVO, 58% have nontraditional risk factors 1:
- Elevated homocysteine levels (hyperhomocysteinemia)
- Factor V Leiden (controversial contribution)
- Antiphospholipid syndrome - particularly important in younger patients with arterial or venous occlusions 2
- Disseminated intravascular coagulopathy - causes thrombotic occlusion of choriocapillaris 3
Ocular Conditions
Primary Ocular Risk Factors
- Glaucoma (for CRVO) 1
- Ocular hypertension
- Retinal phlebitis (associated with BRVO) 1
- Arteriovenous crossing changes at branch points (local vascular factors for BRVO) 1
Systemic Conditions Causing Retinal Artery Occlusions
For Central Retinal Artery Occlusion (CRAO)
CRAO is classified as an acute ischemic stroke 4. The primary causes include:
- Ipsilateral internal carotid artery stenosis (37-40% have ≥70% stenosis) 4
- Cardiac emboli from valves, aortic arch, or great vessels
- Atherosclerosis (most common between ages 50-70)
- Carotid artery disease (present in 45% of cases) 5
Inflammatory/Vasculitic Causes
- Giant cell arteritis (arteritic CRAO) - requires immediate recognition 4
- Systemic vasculitides - can present with ocular manifestations as initial finding 6
Special Populations
Sickle Cell Disease
Patients with HbSC genotype have increased risk of proliferative sickle cell retinopathy despite milder systemic disease 7. Microvascular occlusions can affect every part of the eye.
Critical Clinical Pearls
Age is the single most important risk factor for both RVO types 1. The typical age range is 6th to 7th decade, though RVOs are relatively uncommon under age 40.
Prior RVO significantly increases fellow eye risk: 1% per year for CRVO in the fellow eye, and 10% over 3 years for any RVO type after BRVO 1.
Patients with any RVO have increased risk of cardiovascular events and all-cause mortality, necessitating comprehensive cardiovascular evaluation 1.
Important Caveat
In younger patients (under 50) presenting with retinal vascular occlusions, aggressive workup for hypercoagulable states and antiphospholipid syndrome is essential, as these represent nontraditional but significant risk factors 1, 2.