What is Conjunctival Injection?
Conjunctival injection is the dilation and engorgement of the conjunctival blood vessels, causing the white part of the eye (sclera) to appear red or pink. This is a non-specific clinical sign that indicates inflammation, irritation, or increased blood flow to the conjunctiva.
Clinical Appearance and Mechanism
- Conjunctival injection manifests as visible redness of the bulbar (white part) conjunctiva due to dilated and engorged blood vessels. 1
- The redness can range from mild pink discoloration to intense red appearance depending on the degree of vascular engorgement. 1
- This finding is bilateral in most systemic and inflammatory conditions, though it can be unilateral in localized processes. 1
Common Causes in General Context
- Conjunctivitis (infectious, allergic, or immune-mediated) is the most frequent cause of conjunctival injection. 1
- Viral conjunctivitis (including herpes simplex virus and varicella zoster virus) commonly presents with conjunctival injection along with other ocular symptoms. 1
- Immune-mediated conditions such as graft-versus-host disease, Stevens-Johnson syndrome, and ocular mucous membrane pemphigoid all feature bilateral conjunctival injection as a prominent sign. 1
Specific Context: Polycythemia Vera
- In patients with polycythemia vera (PV), conjunctival injection may occur as part of microvascular disturbances, which include transient ocular disturbances affecting approximately 14% of patients. 2, 3
- The hyperviscosity of blood in PV predisposes patients to vascular engorgement and microcirculatory symptoms throughout the body, including the conjunctival vessels. 3, 4
- Conjunctival injection in PV patients represents increased blood viscosity and vascular congestion rather than primary inflammation. 3, 4
Clinical Significance in PV
- Ocular symptoms in PV, including conjunctival injection and transient visual changes, are part of the broader spectrum of microvascular disturbances that also include headache, light-headedness, and neurologic symptoms. 2, 3
- These microvascular symptoms typically improve with appropriate treatment, particularly phlebotomy to maintain hematocrit below 45% and low-dose aspirin therapy. 2, 3, 5
- The presence of conjunctival injection alongside other PV symptoms (pruritus in 33-48% of patients, erythromelalgia in 3-5.3%, splenomegaly in 36%) should prompt evaluation for this myeloproliferative disorder. 2, 3, 6
Important Caveats
- Conjunctival injection is a non-specific finding that requires correlation with other clinical features to determine the underlying cause. 1
- In PV patients, distinguishing between conjunctival injection from hyperviscosity versus concurrent infectious or inflammatory conjunctivitis is essential for appropriate management. 1, 3
- Severe or persistent conjunctival injection in PV patients with inadequate hematocrit control may indicate need for more aggressive phlebotomy or cytoreductive therapy. 2, 5