Subconjunctival haemorrhage: a burst blood vessel in the eye

The white of the eye is covered by a thin, transparent layer called the conjunctiva. Gloucestershire Hospitals NHS Foundation Trust explains that the conjunctiva has many blood vessels and sometimes one of them can bleed, causing a collection of blood under its surface. The blood has nowhere to go, so it shows as a flat, bright red patch, which is why the NHS red eye page lists a bright red area in the white of the eye as a burst blood vessel.

Moorfields describes the signs as a flat, bright red haemorrhage in the conjunctiva. The leaflet from Gloucestershire says this small bleed can look alarming, but the condition on its own is not serious.

A subconjunctival haemorrhage is not a bleed inside the eye. It sits on the surface, under the clear membrane, which is one reason vision is normally unaffected.

Many people feel nothing at all. Gloucestershire Hospitals says it is not unusual to realise you have one only when you see it in the mirror, and that it is rarely painful but may make the eye feel a bit gritty. Moorfields says some people describe a mild popping sensation in the eye before they notice the redness, and some have a mild foreign body sensation or an eye ache.

Moorfields notes that people are usually symptom free apart from the appearance of the eye.

Often there is no identifiable reason. Moorfields states that these haemorrhages usually have no cause, and that they are more common after coughing or vomiting excessively. They can also be caused by mild trauma.

Gloucestershire Hospitals lists rubbing your eye, coughing or vomiting, high blood pressure, injury to the eye, eye surgery, taking medicines that make you more likely to bruise, such as warfarin or aspirin, and blood disorders.

Moorfields advises clinicians to ask about the use of anti-inflammatory painkillers or blood thinners, and about any history of coughing, straining, trauma or vomiting, and to check the blood pressure. For the person with the red eye this means the questions at an appointment are usually about medicines, recent coughs or heavy straining and any knock to the eye.

Moorfields says that if there has been no trauma no treatment is required, and that the patient can be reassured that the haemorrhage will resolve over about a week or two. Gloucestershire Hospitals similarly says treatment is rarely required and the colour will gradually fade after a couple of weeks.

The NHS red eye page advises that, until a red eye has got better, you should try not to touch or rub the eye and avoid wearing contact lenses.

Gloucestershire Hospitals advises seeking medical advice if you have had a significant injury to the eye, the eye is painful, you cannot see the edge of the red area, your vision is affected, or you have experienced other unusual or unexplained bleeding or bruising. It also says that if you have raised blood pressure or take medication that affects blood clotting, you will need to see your GP for further monitoring.

Moorfields says that if the cause was trauma, referral to an ophthalmologist should be considered to ensure there is no underlying damage to the white of the eye or other injury, and that recurrent haemorrhages may need further investigation to exclude clotting disorders, although in most cases no serious underlying cause is found.

The NHS red eye page sets out a separate list of red flags for any red eye. It advises calling 999 or going to A&E if you have a red eye together with changes to your sight, such as wavy lines, flashing or loss of vision, if it hurts to look at light, if you have a severe headache and feel sick, if your eye is very dark red, if you have injured your eye or have something stuck in it, if the injury was caused by a dangerous liquid such as a chemical, or if one pupil is bigger than the other. It advises asking for an urgent appointment with a GP or optician, or getting help from NHS 111, if the eye is very painful and red or if you wear contact lenses and have a red eye.