What Causes Red Blood Vessels on the Sclera?

Red blood vessels visible on the white of the eye (sclera) refer to dilated capillaries in the bulbar conjunctiva or superficial sclera, or subconjunctival hemorrhage, observable under natural light or focused lighting. Based on the location of capillary congestion, bulbar conjunctival hyperemia can be classified into conjunctival hyperemia, ciliary hyperemia, mixed hyperemia, and localized hyperemia. So, what causes red blood vessels on the sclera? The following explains this issue.

What Causes Red Blood Vessels on the Sclera?

1. Eye Fatigue

This commonly manifests as red blood vessels appearing upon waking. If no pain, foreign-body sensation, or tearing is present, excessive concern is unnecessary. Simply avoid staying up late and ensure adequate sleep—ideally 8–10 hours per day—to allow spontaneous resolution. In more severe cases, patients should consult a physician for guidance on using topical ophthalmic medications to alleviate symptoms. Additionally, proper ocular hygiene must be maintained.

2. Ocular Inflammation

Ocular hyperemia with visible red blood vessels may indicate conjunctivitis. Besides redness, conjunctivitis often presents with photophobia and dry eyes. It commonly results from poor ocular hygiene—for example, rubbing eyes with unwashed hands or wiping eyes with contaminated towels, tissues, or wet wipes. Patients with conjunctivitis-induced red blood vessels should avoid rubbing their eyes and may be treated with topical antibiotic eye drops.

3. Elevated Intraocular Pressure

Increased intraocular or orbital pressure can impair local circulation, leading to localized congestion. This is frequently observed in acute angle-closure glaucoma or orbital space-occupying lesions. Additionally, “excess internal heat” (a traditional Chinese medicine concept) may cause ocular hyperemia and subsequent red blood vessels; treatment with heat-clearing and fire-purging medications may resolve the redness. Furthermore, abnormal venous return can also produce red blood vessels on the sclera. If pronounced vascular tortuosity is present, conditions such as cavernous sinus thrombosis or cavernous sinus arteriovenous fistula must be ruled out—prompt medical evaluation is essential.

The above outlines potential causes of red blood vessels on the sclera. We hope this information is helpful to you.