What is Dry Eye Syndrome?
Dry eyes is a condition commonly known by several names including dry eye syndrome (DES), dry eye disease (DED), and ocular surface disease (OSD) among others. This condition is one of the main reasons people visit eye doctors. Dry eye is defined as a condition that affects the surface of the eye, disturbing the balance of the tear film, which covers the eye. This may lead to different eye symptoms such as inflammation, ocular surface injuries, and abnormalities in sensory nerves.
The tear film is a protective cover for the cornea in the eye that’s very thin (2 to 5.5 µm). This tear film is made up of three major parts often depicted as layers but it’s more complex than that.
1. Lipid layer: This is the outermost layer created by the meibomian glands in the eyelids, that helps to prevent tears from evaporating.
2. Aqueous layer: This is the thickest of the three layers and is in the middle. It’s created by the lacrimal glands and contains water, electrolytes, proteins, and other substances.
3. Mucin layer: This layer consists of glycoproteins, produced mainly by conjunctival goblet cells. These glycoproteins assist in the spread of the tear film over the cornea by adjusting surface tension.
The terms DES and DED verbally describe a common eye condition that’s caused by not having enough lubrication and moisture on the eye’s surface. This condition can lead to symptoms such as dryness, burning, irritation, redness, and blurred vision. Despite often being used as synonyms, the term dry eye disease (DED) refers to a wider understanding of the condition. This can make things confusing since different doctors and researchers use different terms.
DES typically informally refers to not producing enough tears or the tears being of poor quality, resulting in symptoms such as pain in the eyes. Both patients and doctors use this term to describe the condition.
On the other hand, DED more comprehensively explains the complexity of the condition. It acknowledges that there are different root causes of dry eye, including evaporative dry eye and aqueous deficit. DED encompasses a wider range of clinical presentations and causes.
DES and DED are differentiated by the fact that DES puts more focus on the symptoms and a decrease in the quality or quantity of tears, without much emphasis on the root causes. DED, however, acknowledges the multi-faceted nature of the condition and different types. There’s a report from 2017 by a Tear Film and Ocular Surface Society that gives a detailed categorization and explanation of dry eye disease considering factors such as inflammation, neurosensory irregularities and environmental causes.
Diagnosis and treatment are alike for DES and DED. Typically, a comprehensive eye exam is needed for a diagnosis, testing the quality and quantity of tear film, inspecting the ocular surface and considering the patient’s symptoms. Treatments might include artificial tears, eye drops that lubricate the eye, diet changes, drugs that reduce inflammation and, in more severe cases, surgery or procedures. The best treatment method relies on the root cause and severity of the condition.
Research on dry eye has progressed over time, leading to a broader understanding of the condition. Current medical literature and research often use the term DED to reflect this comprehensive understanding – studying inflammation, meibomian gland dysfunction, and the influence of the environment on the eye’s surface. By using the term DED, researchers aim to progress patient care by covering the myriad of factors that cause dry eye conditions.
What Causes Dry Eye Syndrome?
Dry Eye Disease (DED) usually falls into two main categories: evaporative dry eye and aqueous-deficiency dry eye. Evaporative dry eye happens when too much moisture evaporates from the surface of the eye. This can happen if the tear film (a protective coating that keeps your eyes lubricated) doesn’t have enough muco-aqueous components. On the other hand, aqueous deficiency is when there isn’t enough water on the surface of the eye due to autoimmune or other underlying conditions. Sometimes, a person can have a mixture of both types.
DED can be caused by various factors and often it is not limited to one. These can include local eye factors, systemic diseases, sociodemographic factors, environmental conditions, and causes like medications or surgeries.
These factors include a long list of both systemic (affecting the body as a whole) and topical (applied to a particular place on the body) medications. Some systemic medications include antihistamines, antidepressants, different cardiovascular-related drugs, hormonal medications, anti-inflammatory drugs, steroids, and medications that inhibit bodily secretions. An acne medication called isotretinoin can cause gland atrophy leading to dry eye. Eye drop medication to treat glaucoma or other similar drops that contain preservatives could also lead to dry eye.
Local skin conditions on or around the eyelids, such as rosacea or eczema, can also predispose to dry eye. DED can occur due to meibomian gland dysfunction, a common condition where the glands in your eyelids that produce the oils protecting your tear film don’t work properly.
In some cases, eye surgeries, chemical or thermal burns that scar the clear membrane covering the front of your eye, allergies, low androgen levels associated with menopause and other conditions can also exhibit dry eye symptoms.
Excessive computer or device usage that leads to reduced blinking; vitamin A deficiency which can lead to a dry-eye condition called xerophthalmia; decreased sensation in the cornea due to long-term contact lens wear, herpes virus infections, and other conditions; also contribute to dry eye.
Certain systemic diseases that affect the whole body like Sjogren syndrome, Graves’ ophthalmopathy, connective tissue disorders such as rheumatoid arthritis, lupus, thyroid disease, diabetes, and multiple sclerosis can lead to DED. Genetic diseases, nerve damage disorders, and gut imbalances could also raise the risk of dry eye.
Dry eye can be exacerbated by environmental factors, including exposure to irritants such as chemical fumes, cigarette smoke, strong winds, high temperatures, pollution, high altitude, and low humidity. Finally, certain behaviors and lifestyle habits such as smoking, alcohol use, poor sleep, unhealthy diet, and dislipidemia (abnormal amounts of lipids in the blood) can also lead to dry eye.
Risk Factors and Frequency for Dry Eye Syndrome
Dry eye is a condition that affects more women than men, due to hormone levels affecting certain eye glands. The older you get, the more likely you are to experience dry eye. Between 12% and 22% of women are shown to develop dry eye. However, the occurrence of dry eye in the entire world can vary. Depending on how it’s diagnosed, between 5% and 50% of people have been found to have dry eye in different studies.
- People who use visual terminals frequently have a high rate of dry eye, as much as 70%.
- It’s more common in Black and Asian people than in White people.
- Where you live, the climate, and the environment may also play significant roles.
- Evaporative dry eye is the most common type of dry eye.
- Sometimes, there might be a mismatch between the signs of dry eye and the symptoms. The signs are usually more common and varied than the symptoms.
Signs and Symptoms of Dry Eye Syndrome
Dry Eye Disease (DED) can cause a variety of symptoms, from mild to severe. Here is a list of potential symptoms:
- Stinging, burning, or a pressure-like feeling in the eyes
- A sensation of having sand, grit, or a foreign body in the eyes
- Excessive tearing, which may be surprising as dryness can lead to irritation, resulting in extra tear production
- Pain in or around the eye, ranging from sharp to dull
- Redness, which can be intensified by certain over-the-counter eye drops that temporarily reduce redness only to result in more noticeable redness when the effects wear off
- Blurry vision, with some people reporting seeing halos or glare around lights at night
- Fluctuating vision and difficulty reading
- A feeling of heaviness in the eyelids or trouble opening the eyes
- Excessive blinking and eyelid twitching
- Dryness making it hard for contact lens wearers to keep their lenses in
- Tired eyes, where closing the eyes brings some relief
- In severe cases, an inability to produce tears
These symptoms can vary significantly from person to person, so it’s always important to consult with a healthcare provider if you have any concerns about eye health.
Testing for Dry Eye Syndrome
Diagnosing Dry Eye Disease (DED) cannot be achieved through one single symptom or sign. It’s necessary to evaluate both the symptoms and signs of DED since at times, signs may be apparent without symptoms and vice versa.
Doctors often use verbal history and specifically designed questionnaires to identify the symptoms of DED. These questionnaires have been developed to spot symptoms of DED, monitor progress and responses to treatments. Questionnaires like Ocular Surface Disease Index (OSDI), Dry Eye Questionnaire (DEQ-5), and Symptoms Analysis in Dry Eye (SANDE) are commonly used in this process.
The stability of tear film or the time it takes for the tear film to break after a complete blink can be measured. This measurement is known as Tear film breakup time (TBUT). It is mostly conducted using a special microscope after adding a dye to improve the visibility of the tear film. If the tear film breaks in fewer than 10 seconds, it could indicate DED.
Assessing the volume of tears using the Tear Meniscus and the Schirmer Test is another way to diagnose DED. The Schirmer Test uses a paper strip to measure tear production while the patient’s eyes are closed. Guidelines suggest that wetting of less than 5 to 10 mm after 5 minutes can point towards DED.
A special dye, fluorescein, is used to assess the damage on the cornea while another staining agent, lissamine, is used to assess damage to the conjunctiva and the edges of the eyelids. Presence of more than a specific number of spots of staining can indicate DED
Gauging the redness in the conjunctiva, although not specific to DED, can provide further clues to help diagnosis. There are also tear film assays to measure the salt concentration in tears. Increased salt concentration in tears is usually associated with DED.
Evaluating the eyelids and the sebaceous glands located along the eyelid margin (Meibomian glands) is also an important part of the diagnosis process. Patients’ blinking pattern and eyelid closure can also provide further insights.
A detailed review and tests to look for underlying systemic diseases such as Sjogren syndrome, rheumatoid arthritis, lupus, Parkinson’s disease, androgen deficiency, thyroid disease, and diabetes might be necessary as these conditions are associated with DED.
Treatment Options for Dry Eye Syndrome
For treating Dry Eye Syndrome (DES), the steps taken may change based on how severe the disease is.
To start off, patients should understand the condition. They should tweak their environment to improve their eyes’ comfort. This could mean avoiding strong direct airflow like fans, reducing the time they spend looking at screens, taking frequent breaks from screens or even using a humidifier to moisten the air. Next up, it’s crucial to identify and stop using any substances that may worsen the condition, such as certain topical products or medications. Over-the-counter eye drops can provide some relief. Cleaning the eyelids with warm compresses and lid scrubs and taking oral supplements with essential fatty acids can also help.
These treatments are geared toward reducing the discomfort and signs of DES, restoring eye health, and improving the patient’s quality of life.
If these initial steps don’t offer enough relief, there are more treatment options to consider. Preservative-free eye drops, plugs for the eye’s tear ducts (the puncta), nighttime eye ointments or moisture goggles could all be valuable. There are also devices to warm up or express the meibomian glands (which produce an oil that prevents tears from evaporating). Intense pulsed light therapy, anti-inflammatory eye drops, or certain oral antibiotics could also be beneficial.
For cases that still don’t improve, there are even more treatment possibilities. Some patients may find relief from eye drops made from their own blood serum or from stimulating tear production with oral or topical secretagogues. Therapeutic contact lenses, amniotic membrane grafting (using a thin tissue layer from an amniotic membrane to heal the eye’s surface), surgery to permanently close the tear ducts, or tarsorrhaphy (partially sewing the eyelids together to narrow the eye opening and protect the eye) may also be options.
What else can Dry Eye Syndrome be?
Several health conditions can cause symptoms similar to dry eye disease (DED). Some of these can also lead to DED, including types of conjunctivitis (eye inflammation), keratitis (corneal inflammation), and others. It’s crucial to identify these underlying conditions, as treating them can slow down the progression of DED and prevent worsening of dry eye symptoms.
In diagnosing DED, doctors need to rule out several other conditions, including:
- Different types of eye inflammation (conjunctivitis) caused by allergies, viruses, bacteria, or parasites
- Anterior blepharitis (inflammation of the eyelid)
- Demodex blepharitis (a type of eyelid inflammation caused by a tiny mites)
- Cicatricial conjunctivitis (a severe form of eye inflammation that can scar the eye)
- Bullous keratopathy (a condition where the clear front surface of the eye, called the cornea, swells)
- Inflammation related to contact lens use
- Eyelid position problems (like entropion, where the eyelid folds inward, or ectropion, where it folds outward) or abnormalities (like trichiasis, where the eyelashes grow inward)
- Different types of corneal inflammation (keratitis)
What to expect with Dry Eye Syndrome
There’s not a lot of information available on what happens naturally over time to dry eye disease (DED), whether it’s treated or not. However, it’s often viewed as a chronic condition, meaning it’s long-lasting, but it can get worse at times due to certain triggers. If you develop dry eye after having surgery, like cataract or refractive surgery, it will often get better as time goes by. This could be related to the healing of the nerves in your cornea or because of decreased eye inflammation.
Possible Complications When Diagnosed with Dry Eye Syndrome
Dry eye disease (DED) can lead to a range of complications from mild to severe. Mild to moderate DED usually causes symptoms such as eye irritation or problems with sight. With more severe cases, there can be complications related to the cornea – the clear, front surface of your eye. These can include infectious keratitis (an inflammation of the cornea), ulceration (damage that causes a hole in the eye surface), and scarring, which could result in vision loss.
While it has not been definitively proven, research has also hinted at several non-eye related conditions that might be linked with DED. These include depression, sleep and mood disorders, dyslipidemia (abnormal amount of lipids in the blood), and migraines.
The common issues experienced by people with DED include:
- Eyes feeling irritated
- Visual disturbances
- Corneal complications (in severe cases)
- Inflammatory eye conditions
- Ulcers on the eye surface
- Scarring
- Losing vision (in severe cases)
- Possibly linked conditions like depression, sleep and mood disorders
- Dyslipidemia
- Migraines
Preventing Dry Eye Syndrome
It’s important to teach patients about changes they can make to their environment or behavior to help manage dry eye disease (DED). For instance, fans, air conditioners, and heating vents can make DED worse. Practices such as being conscious of how often they blink, or taking breaks from looking at screens can help minimize the dry eye effects of using digital devices. Using artificial tears can also help, and it might be beneficial to use contact lenses less frequently. Additionally, patients should be told about the role of diet in DED, including the potential benefits of supplements rich in essential fatty acids.
