What Causes Dry Eye Syndrome?

Introduction

Dry eye syndrome is one of the most common conditions affecting the eyes. Millions of patients deal with it every year. For some, the symptoms are mild and easily managed. However, for others, the symptoms can be long-lasting and severe. 

Most patients don’t realize that there are many different causes of dry eye syndrome. Many patients have more than one underlying cause. 

One of the best things most patients can do is understand the underlying causes and risk factors they have, and address them.

In this article, we’re going to provide the most comprehensive list anywhere on the internet of the causes of dry eyes. 

If you have one or more of these underlying causes, it’s important to discuss these with your doctor to help find the best way to treat it. 

Risk Factors and Causes of Dry Eyes

Many research studies have been done to determine risk factors and underlying causes of dry eye syndrome.

In some cases, the evidence is very strong. For example, we know that certain medications can directly cause dry eyes. 

In other situations, the research isn’t quite as clear. 

Let’s go through the many different causes that have been linked to dry eyes, and discuss home weak or strong the link is.

Here’s the broad list that we’ll discuss:

• Patient characteristics & habits: Age, gender, smoking, etc.
• Medications
• Medical Conditions 
• Eye history: Other eye problems, eye surgeries, eye treatments
• Eyelid history: eyelid conditions, eyelid surgeries
• Environmental factors
• Other

Patient Characteristics That Can Cause Dry Eye Syndrome

What about age, gender, race, habits, and lifestyle can result in dry eyes? Some of these you may be able to change, but not others. Let’s review some of the factors about you that could lead to or worsen dryness.

Age

Aging is a well-known risk factor for dry eyes. There are several reasons that aging increase the risk of dry eyes. 

It’s well known that the function of the meibomian glands decreases with age. These glands are responsible for a part of the tear film that keeps it from evaporating and coating the surface of the eye. As we age, these glands can become dysfunctional resulting in their “atrophy” or loss. 

When these glands are lost, it can be permanent. It is important to catch meibomian gland dysfunction early and takes steps to prevent it, such as doing warm compresses or having thermal compression treatments, such as Lipiflow. 

Gender

Women tend to be at greater risk for developing dry eyes than men.

The Women’s Health Study surveyed 39,876 women in the United States about dry eyes. They found that 5.7% of women younger than age 50 had dry eyes. This increased to 9.8% of women over age 75.

A similar study was performed for men in which the same definition of dry eyes was used. Researchers found that 3.9% of men aged 50-54 had dry eyes. This increased to 7.7% for men over age 80.

Smoking

Tobacco smoke irritates the surface of the eye. Research found tobacco smoke to break down the tear film, specifically the “lipid layer”, resulting in dry eye symptoms. 

Smoking affects both the smoker, as well as those exposed to secondhand smoke.

Alcohol

Alcohol was shown to be a risk factor for dry eyes in a 2016 study published in the International Journal of Ophthalmology.

Alcohol has a dehydrating effect which may result in dry eye symptoms. For heavy drinkers, peripheral nerve damage can occur. The researchers hypothesize that peripheral nerve damage caused by alcohol consumption may decrease corneal sensitivity leading to decreased tear production.

Caffeine 

Caffeine has been a controversial one. 

On one hand, caffeine has a diuretic effect, which can lea to dehydration. Some doctors and patients may believe there is a connection here that results in dry eyes.

However, there is research that shows the opposite may be true. 

Could caffeine actually be helpful for dry eyes?

A 2012 study published in the journal Ophthalmology found that caffeine actually increased tear production.

The Beaver Dam Study results published in 2000, which looked at dry eye risk factors, also found that caffeine had a protective effect against dry eyes.

Caffeine may have different effects on different people. However, overall, it looks like the evidence may currently be leaning in favor of caffeine having a protective effect against dry eyes. 

Medications That Can Cause Dry Eyes

There are many medications that have been linked to dry eyes. There are far too many to list every possible medication that’s linked to it. But there are some medications that have strong links. 

If you’re taking one of these medications, discuss with your doctors if it’s possible to switch to another medication. Sometimes there are alternatives. However, sometimes there are not, and the side effect of dry eyes needs to be managed with artificial tears and other treatments. 

Let’s discuss some of the most common medications that can cause or worsen dry eye symptoms.

Antihistamines

Antihistamines are commonly used in anti-allergy medications. These are some of the most common over-the-counter medications. Antihistamines are also available in eye drop formulations.

While antihistamines may decrease allergic symptoms such as a runny nose, they can also decrease tear production resulting in dry eyes.

Common over-the-counter antihistamines include medications such as:

• Claritin (loratadine)
• Zyrtec (cetirizine)
• Allegra (fexofenadine)

What if allergies are your cause of dry eyes?

This is where things can get tricky. Many patients have allergies that affect the glands that produce part of their tear film. In these patients, anti-allergy medications may actually be helpful.

As always, this is a reason to consult with your doctor if you have dry eye symptoms. In some patients, antihistamines can cause dry eyes, while in others, they can be an effective treatment. 

Antidepressants & Anti-Anxiety Medications

There are receptors on the surface of the eye that can be affected by these medications resulting in dry eyes.

The Beaver Dam Study is a research study that found a significant link between antidepressants, anti-anxiety medications, and dry eyes. 

Oral Corticosteroids

Oral corticosteroids are another tricky one. In some patients, the anti-inflammatory properties of steroids result in improved dry eye symptoms. 

In fact, there are certain types of dry eyes for which steroid eye drops are frequently recommended by doctors. 

However, in large population-based studies, oral corticosteroids were found to be a cause of dry eye syndrome.

Examples of oral corticosteroids are prednisone, methylprednisone, and dexamethasone.

Post-Menopausal Hormone Replacement Therapy / Estrogen

The Women’s Health Study looked at 25,665 postmenopausal women who provided information about their hormone replacement therapy.

This study found a significant link between hormone replacement therapy and dry eyes. The greatest risk was found in women who were taking estrogen alone. 

These hormone replacement therapies may result in the progression of meibomian gland dysfunction, tear film instability, and tear flow reduction. 

Botox

Believe it or not… Dry eye syndrome may result from botox injections. Researchers found that botox injections for crow’s feet, blepharospasm, or after periorbital surgery may result in dry eyes. 

Researchers believe that botox’s effect on the muscle that closes the eyes may lead to a poor blink mechanism and other eyelid problems. These eyelid abnormalities may result in tear film irregularities that may worsen over time. 

Medical Conditions That Can Cause Dry Eyes:

There are many medical conditions that can cause dry eyes. Let’s review some of the most common and potentially severe. 

• Allergies
• Auto-Immune Conditions
• Diabetes
• Rosacea
• Parkinson's Disease
• Viral Infections
• Graft-Versus-Host Disease (GVHD)
• Stevens-Johnsons syndrome
• Lymphoma
• Sarcoidosis
• Hemochromatosis
• Amyloidosis

Allergies - Allergic conjunctivitis & Allergic Blepharitis

Allergies are one of the most common medical conditions that can result in dry eyes. Allergies can cause dry eyes by affecting either the conjunctiva or the meibomian glands.

Allergic conjunctivitis results when an allergic reaction occurs in the conjunctiva of the eye. This results in red, irritated, and itchy eyes. 

Itching is the hallmark symptom of allergy.

When the conjunctiva is inflamed, the goblet cells responsible for making part of the tear film can be damaged or destroyed.

When allergic reaction occurs in the eye lid margin near the eyelashes, the oil glands which produce the lipid layer of the tear film can become blocked or damaged. Inflammation of the eyelid margin is called “blepharitis”. Therefore, allergy in this area is termed “allergic blepharitis”. 

The symptoms of allergic blepharitis include irritated and itchy eyes and eyelids. 

The symptoms of allergy may be seasonal, or they may be chronic if the allergen remains present.

While there are over-the-counter treatments for allergies, we recommend being evaluated by a doctor first.

Auto-Immune Conditions

Auto-immune conditions can affect the body in a variety of different ways. There are several autoimmune syndrome that are linked to dry eyes.

Sjogrens syndrome may be the most notable. In addition to dry eyes, it can cause dry mouth. In Sjogrens syndrome, inflammation of the lacrimal gland reduces tear production resulting in dryness. 

Other auto-immune conditions which have been linked to dry eyes include:

• Rheumatoid arthritis
• Lupus
• Ocular mucous membrane pemphigoid

By treating the underlying auto-immune condition, dry eye symptoms may improve. However, artificial tears and other treatments are often necessary.

Diabetes

There is evidence that suggests patients with diabetes are at greater risk for dry eyes, especially if their diabetes is poorly controlled. Compared to healthy patients, diabetics may have decreased corneal sensitivity and less stable tear films.

Research shows that diabetes results in damage to the small blood vessels supplying the lacrimal gland and the nerves that control it. 

Rosacea

Rosacea is a common skin condition that can result in redness, swelling, and small irregular blood vessel abnormalities.

These small blood vessel abnormalities can affect the oil glands in the eyelid resulting in blepharitis. 

There are a variety of treatments for rosacea and blepharitis, such as intense pulsed light (IPL).

Parkinson’s disease

Parkinson’s disease can impair blinking. Blinking is necessary to protect the eye and to spread tears across the eye surface.

When blinking is impaired the surface of the eyes dries out.

These patients in particular need frequent artificial tears, and often other treatments if severe. 

Lymphoma, sarcoidosis, hemochromatosis, amyloidosis

These conditions have something in common: They can have infiltration of the lacrimal glan which results in a decrease in tear production.

Once again, patients with this condition who have significantly decreased tear production may need very frequent artificial tears to manage their symptoms. 

Viral infections

Different viral infections can cause dry eyes. There are different mechanisms by which dryness occurs. For example, herpes simplex may impair the trigeminal nerve which senses dryness. Decreased tear secretion may result from hepatitis C. Virus which have been linked to dry eyes:

• Epstein-Barr
• HIV  /AIDS
• Hepatitis C
• Herpes Simplex

Graft Versus Host Disease (GVHD)

Graft versus host disease (GVHD) is a serious complication of stem cell transplantation. A high percentage of GVHD can have ocular issues.

Dry eyes are one of the most frequent ocular complications of graft versus host disease. 

The symptoms may be severe, resulting in pain, gritty sensation, blurred vision, and photophobia. 

Multiple research studies have shown that GVHD causes fibrosis or scarring of the lacrimal gland, and also disruption of the mucinous layer of the tear film. 

Stevens-Johnson syndrome (SJS)

Stevens-Johnson syndrome is a rare disorder of the skin and mucous membranes. The conjunctiva of the eye is a mucous membrane. When SJS affects the conjunctiva, it can result in pain, redness, inflammation, and disruption of the mucinous layer of the year film. Subsequent scarring can lead to long term or permanent severe dry eye. 

Treatment for SJS often needs to be aggressive and involves multiple specialists.  

Eye Problems That Can Cause Dry Eye Symptoms

Contact Lenses

No surprise here… Wearing something on your eye that moves around, rubs it all day, and blocks oxygen from getting to it will most certainly cause dry eye symptoms.

For most patients the symptoms are mild, and artificial tears are all you need. But for many patients they simply can’t tolerate the scratching of contacts.

Note: There is a small exception to this. There are certain specialty types of contacts called “scleral lenses” which can actually treat dry eyes. Scleral lenses are not standard soft contacts. They are a hard contact lens that has to be fit and prescribed by a specialist. 

Eye Drops With Preservatives

Preservatives are a great thing… except for a small percentage of patients in which they can cause irritation.

Preservatives allow eyedrops to remain safe and sterile for an extended period of time. This makes drops less expensive for patients, and reduces the risk of infection from contamination.

However, some patients can experience allergy or irritation from preservatives.  

Like other allergic reactions, itching is the hallmark. If you take an eyedrop, and find yourself with red, irritated, and itchy eyes afterwards, it could be an allergic reaction to something in the eyedrop. Notify your eye doctor to confirm this suspected diagnosis, and to consider preservative-free options.

Eye Surgery

All surgery results in swelling and inflammation. This is true whether you are having knee or hip surgery… or eye surgery.

When there is swelling and inflammation on the surface of the eye, the eye may feel irritated. 

Is this technically “dry eye”?... Sometimes yes… Sometimes no. 

For example, sometimes patients are feeling the healing incision from their procedure, and the tear film is perfect. Once the tiny incision heals, the irritation resolves.

Even though this may not technically be dry eye, the symptoms of irritation can be bothersome, and the management of these symptoms is similar. 

As another example, in cataract surgery, patients typically have a 2-3mm incision on the surface of the eye. Smaller than a papercut. Doesn’t even require a stitch. However, it can be irritating. Most patients should have artificial tears to help soothe the eye, and relieve these symptoms for the first few weeks after surgery.

Ocular surface diseases

When infections or inflammation involve the cornea or conjunctiva, they can result in short-term or long-term dry eye symptoms. 

Examples of diseases which can impact the ocular surface:

• Herpes simplex keratitis
• Varicella Zoster keratitis
• Ocular pemphigoid

These can all be severe, and require the management of an experienced eye doctor.

Eyelid problems

The eyelids are critical to maintaining a healthy tear film. They have numerous functions that are important to tear production, tear film stability, tear film uniformity, and tear drainage.

The blink reflex protects the eye from dryness. It required corneal nerves that sense dryness, and motor nerves to the muscles that close the eye. Further, a healthy blink requires transmission of the nerve signal to the muscle, adequate muscle tone, and proper eyelid anatomy to fully cover the ocular surface. 

If any part of this is dysfunctional, dryness can result. For example, there are many conditions that can cause eyelid malpositions, from age-related skin changes, to trauma and skin cancer.

Parkinson’s disease and Bells Palsy affect the nerves controlling eyelid closure and blink rate. 

Thyroid eye disease is common and can result in reduced coverage of the eyelids, leading to dryness from exposure of the cornea. 

Meibomian Gland Dysfunction or Blepharitis

Meibomian gland dysfunction (MGD), also known as “blepharitis”, is one of the most common causes of dry eyes. These glands are located in the eyelid near the eyelashes. They produce an oily part of the tear film that is necessary for it to coat the eye properly.

When these glands become dysfunctional, dryness results. 

MGD becomes more common as people age. Some other conditions can cause MGD, such as rosacea and allergy. 

Artificial tears, warm compresses, and lid scrubs are the main treatments for MGD, but there are many other options that can help if these don’t get you relief. 

Environmental factors

We’re all exposed to a variety of factors from the environment every day. From heating, cooling, fans, and more, let’s discuss some common environmental factors that can result in dry eyes.

Reduced Humidity In The Air (i.e. Dry Air)

Dry air can worsen dry eyes… No surprises here!

Air contains water. The amount of water vapor contained in air is called ‘humidity’. When humidity is low, the air is drier, which can lead to accelerated evaporation of tears, and drying of the eye surface.

Air plane cabins are one of the most notoriously low humidity environments that can dry eyes out. If you’re taking a long flight, bring a bottle or two of artificial tears is a smart way to stay ahead of dry eye symptoms. 

Increased wind exposure (fans, air conditioning / heating)

Currents of air blowing against the surface of the eye can spread and destabilize the tear film, and accelerate evaporation, leading to dry eyes.

We’re exposed to these environments all the time. Whether outside on a windy day, or in an office building with fans blowing, these air currents are important to be aware of. 

Reposition fans away from your eyes, or reposition yourself. If a vent in your office is aimed at your eyes, consider moving your chair or desk to face away from them.

There are many dry eye risk factors that can’t be modified. But this is one that often can. Do what you can by wearing sunglasses on a windy day, or making sure fans aren’t directed towards you. 

Poor CPAP Seal

CPAP’s are a common cause of dryness. No one is 100% successful at maintaining a perfect CPAP seal. And when this seal breaks, jets of air can sneak out of the mask. If this air is directed towards the eyes it can dry you out.

Do what you can to make sure you have a good fitting mask and deal. Considering a nasal CPAP may also be a better option for some patients. 

Eyelid hygiene & cosmetics

The list of facial cleansing and cosmetic products is endless. Many contain irritants to the eyelid margin or allergens that can cause inflammation. 

People respond differently to different products. 

Moreover, very few of these have been studied in extensive research trials to determine associations with dry eyes. 

However, doctors see patients all the time who have “switched to a new product” immediately before developing dry eye symptoms. 

It’s often hard to identify the exact chemical in the product for any individual. However, it’s important to be mindful that these products can sometimes cause or worsen symptoms. 

Wearing masks

Whether it’s related to COVID-19 or because of your work, many of us wear face masks. Because typical facemasks are a barrier to air flow, they can redirect airflow towards the eyes, resulting in dryness.

Computer work / Increased screen time

Digital device screen time is strongly linked to dry eyes. Research has shown that when people use the computer or digital devices they blink less. They also can have “incomplete blinks”. 

This is so common it’s been given the name “Computer Vision Syndrome”. 

So many of us have jobs that require staring at a screen all day. One of the best things you can do is stay ahead of the dryness.

Take breaks to refresh your eyes. Walk away from your screen every 15-20 minutes, and use artificial tears before and during long stretches of screen time. 

Summary

There you have it! That was a long list… to our knowledge, the most comprehensive discussion on the internet about the causes of dry eyes. 

Dry eyes is a common condition that can be caused by a variety of factors including aging, medications, environmental factors, and medical conditions. It is important to identify the underlying cause of your dry eyes and to take steps to address it to achieve lasting relief. Additionally, taking good care of your eyes by protecting them from environmental factors, using proper lighting, and taking regular breaks when working on a computer can help to reduce the risk of developing dry eyes.

Browse our other resources to learn more about all aspects of dry eyes, including treatment options.

If you are experiencing dry eyes, speak with your doctor about treatment options that may be available to you. Finding the underlying causes for your symptoms, using a high-quality artificial tear, and working with a good doctor can lead to the most effective treatments for your eyes.