Causes of red eye

09 October 2025

Red eye is a common sign that can be alarming, but it does not always indicate a serious condition. It occurs due to dilation or inflammation of the blood vessels on the surface of the eye, making it appear reddish. Identifying the cause is essential for proper management.

Most Frequent Causes of Red Eye

1. Conjunctivitis

Inflammation of the conjunctiva, the membrane that covers the white part of the eye and the inside of the eyelids, is one of the main causes of redness. It can be:

• Viral: usually accompanied by tearing, watery discharge, and mild discomfort.

• Bacterial: causes purulent (yellow or green) discharge and a gritty sensation.

• Allergic: leads to intense itching, tearing, and watery eyes.

2. Dry Eye

When the tear film is insufficient or of poor quality, the ocular surface becomes irritated, causing redness, burning, and a foreign body sensation.

3. Subconjunctival Hemorrhage

A bleed beneath the conjunctiva that appears as a bright red spot in the eye. It usually causes no pain or vision loss and often resolves on its own within days or weeks.

4. Trauma or Irritation

Injuries, foreign bodies, prolonged screen exposure, excessive contact lens use, or lack of sleep can all cause eye redness.

5. Blepharitis

Inflammation of the eyelids due to dysfunction of the sebaceous glands leads to redness, discharge, and a feeling of heaviness in the eyes.

6. Acute Glaucoma

Although less common, it is a serious cause. It presents with severe eye pain, blurred vision, halos around lights, headache, and sometimes nausea. It requires immediate attention.

7. Uveitis

Inflammation of the uvea (the middle layer of the eye) causes deep redness, pain, light sensitivity (photophobia), and blurred vision. This also requires urgent care.

When to See a Doctor?

Not all cases of red eye are serious, but it is important to seek ophthalmologic care if you experience:

• Severe eye pain

• Vision loss

• Light sensitivity

• Persistent or heavy discharge

• History of eye trauma