Many people will encounter at least one of the symptoms of dry eye in their lifetime. For some, dry eye may be a mild, transient irritation, while for others it can be a significant, debilitating condition that interferes with daily tasks and can only be controlled with targeted dry eye treatment.
The condition of dry eyes has now been recognised as a real disease with real impact, sometimes called dry eye disease or dry eye syndrome. The global prevalence of dry eye disease varies, with some studies reporting up to 50% of the population suffers from some degree of the condition. As the symptoms of dry eye disease and its effects vary across such a wide range, dry eye is thought to be significantly under-diagnosed. Many people with only a mild case of dryness may opt to self-manage rather than seek the care of an eye care professional for dry eye treatment.
What is Dry Eye Disease?
Dry eye syndrome, or dry eye disease, is a little more complex than simply being eyes that feel dry. A healthy eye’s surface is covered by a stable layer of tears, known as the tear film. This tear film is composed of many different components, such as proteins, lipids, and antibodies, that work together to keep the surface of the eye well lubricated, protected, and nourished. The main bulk of the tear film is produced by three types of glands around the eye:
- The lacrimal gland is located above the upper eyelid, producing the watery, or aqueous, component of the tear film
- Goblet cells of the conjunctiva secrete a mucous layer which helps the tear film to adhere to the eye
- The meibomian glands line the upper and lower eyelids, secreting an oil which sits at the outer surface of the whole tear film, reducing evaporation of the aqueous component
There are a multitude of factors that can contribute to dry eye disease. Experts have divided the condition into two broad classifications – evaporative dry eye and aqueous deficiency dry eye. Evaporative dry eye occurs when the tear film is unstable and evaporates too quickly from the surface of the eye.
The majority of evaporative dry eye conditions are a result of a dysfunction of the meibomian glands mentioned earlier but can also be caused by blepharitis (accumulation of irritants around the eyelashes and subsequent inflammation of the eyelids), eye allergies, preservatives in eye drop medications, or contact lens wear. Most cases of dry eye disease are evaporative in nature. Aqueous deficiency dry eye comprises a much smaller percentage of dry eye disease but includes underlying causes such as autoimmune disease, systemic medications, laser eye surgery, or dysfunction of the lacrimal gland. Identifying the type of dry eye and the contributing factors is important for effective dry eye treatment.
What Are the Symptoms of Dry Eye?
The symptoms of dry eye are not always obvious, and some may be mistaken for other conditions, resulting in inappropriate treatments which are ineffective.
Symptoms of dry eye can include:
- The sensation of dryness: not everyone with dry eye will identify the eyes as actually feeling dry, though this is the most obvious symptom. The feeling of dryness can range in severity from person to person.
- Grittiness, stinging, or burning: these are also common sensations associated with dry eye. Some people may describe the feeling of having a foreign object, like an eyelash or speck of dust, stuck in the eye that can’t be washed out. The irritation felt by a dry eye is due to the underlying inflammation associated with dry eye disease, as well as the surface of the eye becoming exposed to the environment as the protective tear layer evaporates.
- Red eyes: while this is a common symptom of dry eye disease, the presence of a red or pink tinge to the whites of the eye or the rims of the eyelids can cause some people to seek inappropriate treatments, such as antihistamines or antibiotics, when there is no allergy or infection involved. Although the added moisture from these eye drops may help alleviate some of the redness, they are not an effective dry eye treatment.
- Blurry vision: because the tear film is the first refractive surface that light passes through in order to reach the back of the eye for vision, if this tear layer is uneven or unstable, it can cause vision to appear blurry. People with dry eye may find their vision is quite variable, especially between blinks.
- Glare sensitivity: light scattered by an uneven tear film may cause the eyes to feel more uncomfortable and sensitive to light sources, whether it be the sun outdoors or the light from a screen.
- Watery eyes: counterintuitively, watery eyes may in fact be a symptom of dryness. As the eye’s surface feels dehydrated, biological feedback mechanisms trigger a reflex to produce more tears, which can end up with the eye feeling watery instead.
Dry eye disease is a very common condition. In most cases it can be managed with simple remedies such as lubricant eye drops or home therapies such as warm compresses. In some cases, a comprehensive eye examination with an eyecare professional may be necessary to formulate a more intensive, targeted treatment plan.