Overview
The white of the eye is covered by a transparent membrane carrying fine blood vessels. Normally you barely see them; when the surface is irritated or inflamed those vessels dilate and the eye looks red. The redness itself is not the problem — it is the sign.
Where the redness sits tells you a great deal. Diffuse redness spread across the whole white usually means conjunctivitis, dryness or irritation. A deep red ring hugging the edge of the iris, called ciliary flush, means inflammation inside the eye and belongs to a very different and more urgent list.
What are the common symptoms?
- Redness across the whole white of one or both eyes
- Gritty, burning or itchy discomfort
- Discharge, crusting or watering
- A dense red ring immediately around the iris
- Redness with pain, light sensitivity or reduced vision
What causes it, and who is at risk?
Common and benign: dry eye, tiredness, alcohol, smoke, allergy, contact lens overwear, and subconjunctival haemorrhage — the dramatic solid red patch that is almost always harmless.
Infective and inflammatory: viral, bacterial and allergic conjunctivitis, blepharitis, keratitis and corneal ulcers, uveitis, scleritis and episcleritis. The urgent one is acute angle-closure glaucoma, which brings a red, painful, hard eye with haloes and nausea.
How is it treated?
Irritative redness settles with lubricating drops, a break from lenses and screens, and removing the trigger. Whitening drops that constrict the vessels are best avoided — they rebound worse when stopped.
Bacterial conjunctivitis takes antibiotic drops, allergic redness antihistamine drops, dry eye lubrication and lid care, uveitis steroid and dilating drops under supervision, and angle-closure glaucoma emergency pressure-lowering treatment and laser. Because those treatments conflict with one another, guessing is expensive.
When to get seen quickly
Red eye with significant pain, light sensitivity, reduced vision, a hazy cornea, or in a contact lens wearer, needs same-day care. So does redness after an injury or chemical splash, or redness with haloes, nausea and a rock-hard eye.
This page is general information, not a diagnosis. Only an eye care professional who has examined you can tell you what is actually going on.