What causes chronic red eyes and when to worry

SINGAPORE – Have you ever looked in a mirror and seen a startling red blotch in the whites of one or both eyes? What causes red eyes and when should you be worried?

Doctors tell The Straits Times that they most commonly treat red eyes caused by allergic or viral conjunctivitis. The resulting “pink eye” can last for weeks or months.

Dry eyes and wearing contact lenses for too long can also irritate the eyes, leading to redness.

Other causes of red eyes are eyelid infections or clogged oil glands at the eyelid margin.

Red eyes may also signal underlying infections or more serious health conditions. Here is what you need to know.

Why eyes turn red

Doctors say that eyes turn red when blood vessels in and around the surface of the eye become inflamed.

Blood flow to the conjunctiva, the thin layer covering the white of the eye, increases as part of the body’s immune response to viral or bacterial infection, or to allergens. As blood vessels dilate and become more prominent, the eye appears pink or red. This inflammation is known as conjunctivitis.

Blood vessels may also become inflamed in response to trauma, foreign bodies such as dust or dust mites, eyelid infection or irritation from wearing contact lenses for too long.

Sometimes, a blood vessel below the conjunctiva may burst. This subconjunctival haemorrhage leads to a red patch in the white of the eye.

Consultant ophthalmologist Low Jin Rong of Asian Healthcare Specialists explains that the blood vessels in the eye are fragile and can burst spontaneously on sneezing or coughing, or lifting heavy loads.

People with high blood pressure, or who are on blood thinners, may be more prone to such burst blood vessels.

Senior consultant ophthalmologist Jean Chai from Eagle Eye Centre says a subconjunctival haemorrhage usually resolves on its own in a couple of weeks.

Patients may feel fine, or have some mild discomfort, which can be resolved using artificial tears.

“It looks alarming, but is benign and does not affect vision,” she says.

Doctors say the number of patients they see with red eyes has remained constant over time, though they see spikes during waves of viral infection, or during haze season, when allergies kick in.

Tan Wei Jie of DTAP Clinics says: “The frequency of patients coming in for red eyes is still the same over the years. I usually see up to five cases a week and causes vary.”

When should you see a doctor?

Family physician Ding Si Yan says redness caused by allergies can resolve within a few days, as long as the patient responds to treatment.

Subconjunctival haemorrhages resolve within two to three weeks and conjunctivitis within a week, depending on the underlying cause, adds the deputy head and consultant at NHG Hougang Polyclinic.

Conjunctivitis may be caused by an allergic response or a viral infection. Patients are often given lubricant eye drops to relieve symptoms.

Bacterial infections are less common and are treated with antibiotic eye drops.

Chai says she has seen some cases of viral conjunctivitis lead to redness for up to a year.

Patients with viral conjunctivitis may also suffer from itchy eyes, blurred vision, eye discharge and swollen eyelids for two weeks. Patients are contagious, infecting close contacts such as family members.

People should err on the side of caution when it comes to red eyes, doctors say.

Consultant Yap Guan Hui from the Singapore National Eye Centre says that a number of severe and sight-threatening conditions present with red eyes. “Red eyes should not be a symptom that we treat lightly,” he adds.

More concerning causes of red eyes include corneal ulcers; some sexually transmitted diseases such as herpes, chlamydia and gonorrhoea; and acute angle-closure glaucoma. Glaucoma refers to a group of conditions that affects the optic nerve and can lead to blindness.

Senior consultant ophthalmologist Jay Siak of Eagle Eye Centre says people should seek medical help if their red eyes present alongside symptoms such as severe eye pain, blurred or reduced vision, sensitivity to light, headache or nausea.

They should also seek help if the redness does not improve over time, or worsens.

Tan says red eyes caused by sexually transmitted infections will persist until the infections resolve with treatment.

Red eyes may also signal poorly controlled high blood pressure, he adds. People with this condition may easily burst blood vessels in the eye on sneezing or coughing.

Dry eyes and dysfunctional glands

Low recalls a patient in her 50s who developed dry, red eyes for two reasons. The first was that she wore a surgical mask at work.

Wearing a mask directs a continuous stream of air towards the eyes. This leads to faster evaporation of the tears which normally keep the eye surface moist.

Increased mask-wearing at the start of the Covid-19 pandemic was cited as one of the reasons the Singapore National Eye Centre saw more patients with dry eye disease in 2020, compared with 2019.

Low’s patient also had issues with eyelid health that contributed to her dry, red eyes. The meibomian glands at the eyelid margin were clogged. These glands secrete an oil that forms a film over tears and reduces evaporation, keeping the surface of the eye moist.

He says meibomian gland dysfunction becomes more common as one ages. Sweat and dirt can also clog the gland, preventing it from releasing oil.

Treatment for this condition involves cleaning the eyelid, often with a warm compress to soften the oils in the gland, allowing them to be expressed.

In more severe cases, clinical treatment may be required. A specialised device in the clinic gently exfoliates the clogged area, cleaning off the bacterial crust and debris. Patients also get a medical-grade heated eye mask.

Eyelid hygiene is often overlooked, doctors add. Chai says eyelid inflammation, or blepharitis, along with meibomian gland dysfunction, can cause recurrent eye irritation and redness. These may lead to episodes of blurred vision and excess tearing.

Apart from eye lubricants and warm compresses, Chai says some patients may need steroids or antibiotic treatment.

They may even require punctal plugs to reduce the outflow of tears from the eyes. With more tears retained, the eye surface stays lubricated.

Steps to take to reduce red eyes

Low says more adults in Singapore are developing dry eye disease. “Dry eye disease is probably the fastest-growing contributor to chronic red eyes in adults today,” he adds.

This is because people spend a lot of time on their screens and in air-conditioned environments.

Wearing contact lenses also increases the likelihood of dry eyes, as does ageing.

Doctors say the solution is to limit screen exposure, and to remember to blink to keep the eyes lubricated.

Ding says: “When you look at screens for long periods of time, you might be so engrossed that you blink less. Your eyes dry out and can turn red.”

Using eye drops four times a day or more can help reduce dryness and alleviate redness caused by allergies. However, doctors say to look for eye lubricants that are free of preservatives.

Siak warns against wearing contact lenses when your eyes are irritated. Another bad habit he sees is people sleeping without taking out their lenses. This increases the risk of corneal infections, which can threaten vision.

He adds: “Red eyes are common, but persistent redness, recurring symptoms or vision changes should not be brushed off.

“Sometimes the visible redness is only one part of the picture. A proper eye check can help identify whether it is minor, recurring or linked to something more serious.”