A foreign body sensation in the eye

The cornea is the most sensitive part of our body, roughly 400 times more sensitive than the skin. So when something tiny such as an eyelash or a grain of sand gets into the eye it can cause considerable discomfort. A foreign body sensation can indeed indicate a foreign body, but various pathologies of the eye may cause this sensation as a symptom without any foreign body actually being present. This symptom is common and brings many patients to the ophthalmologist because of the discomfort that accompanies it. Visual fatigue arising from prolonged screen use may make it worse, because of reduced blinking and the impaired lubrication that prolonged staring at screens causes. Among the conditions in which a foreign body sensation in the eye can be experienced:

Dry eyes – when we blink, tears spread across the surface of the eye. Tears are produced in dedicated glands and drain through tiny openings called "puncta" through a system of ducts towards the nose. Tears fulfil several important roles, among them wetting the eye, lubrication, nourishing the eye and even an immune role in clearing and combating contaminants and foreign bodies. Tears are made up of several layers – a mucinous, an aqueous and a lipid layer. An imbalance in any of these components may cause dry eyes. People who suffer from dry eyes may suffer from insufficient tear production, from rapid drainage, or from poor tear quality. Symptoms of dry eyes include a sensation of irritation in the eyes, a sensation of roughness, itching or burning, a foreign body sensation, increased watering and even blurred vision.

Dry eyes are a common phenomenon from which a considerable proportion of the population suffers. There are several known risk factors for developing dry eyes, among them older age, drug treatment (for example antihistamines, antidepressants and blood-pressure-lowering medication), sex – it appears more often in females, patients suffering from thyroid problems and from diabetes, and environmental exposure – to smoke, a dry climate and wind, which increase evaporation of the tears. Another common condition that tends to cause dryness in the eyes is called blepharitis, a chronic inflammation of the eyelids.

Sjögren's syndrome – a specific condition that causes dryness in the eyes. It is an autoimmune syndrome that develops when the cells of the immune system attack and damage the lacrimal and salivary glands. The two most common manifestations of the disease are dryness in the eyes and in the mouth as a result of insufficient production.

A corneal abrasion – damage to the surface layer of the cornea, which is the transparent dome at the front of the eye. This condition is usually caused by trauma but can also be caused by other things, for example an inturned lash (trichiasis) or severe blepharitis. Further symptoms of a corneal abrasion include red and painful eyes, watering, blurred or hazy vision and increased sensitivity to light.

A corneal ulcer – ulcers of the cornea can develop as a result of a severe state of dry eyes or from a bacterial, viral, parasitic or fungal infection. Signs or symptoms of an ulcer can include redness, severe pain in the eye, a foreign body sensation, pus or discharge from the eye, blurred vision, increased sensitivity to light, eyelid swelling and a white spot on the cornea.

Fungal keratitis – a fungal infection of the cornea, which can develop as a result of contact lens use or injury to the eye. It too can cause, among other things, a foreign body sensation in the eye. Where an eye infection is suspected the ophthalmologist can take a sample from the lesion by gently scraping the cornea in order to determine the type of pathogen and treat accordingly.

A chalazion – a chalazion is a benign lesion of the eyelid that may remain after a stye at the same site has healed. The chalazion is made of scar tissue and it should not hurt, but a chalazion can cause a sensation of discomfort and a foreign body sensation in the eye.

A foreign body in the eye – a foreign body can adhere to the cornea or scratch it and cause significant symptoms of pain, discharge, sensitivity to light and blurred vision. Where a metallic body is involved it may adhere to the cornea, the eye becomes more and more irritated, red and painful, and rust is likely to appear around the particle. Sometimes the particle is visible on the eye, but it may be almost microscopic. The ophthalmologist has the equipment needed in order to remove these foreign bodies.

Sometimes a scar remains after they are removed, but in most cases it does not affect vision. After the foreign body has been removed, hygiene must be maintained, and if the treating doctor has instructed the use of an antibiotic this must be adhered to, since there is a risk of developing a local infection. Foreign bodies that enter the eye can become trapped under the eyelids, which will worsen the foreign body sensation in the eye and may cause scratches to the cornea that occur every time the eye blinks or when the eyes are rubbed. Rubbing the eyes should of course be avoided as far as possible, in general and especially when there is a foreign body in the eye.