If you've tried multiple artificial tears without lasting relief, the problem may not be that you haven't found the right eye drop. It may be that the underlying cause of your dry eye hasn't been identified. Dry eye disease is multifactorial. It develops when the tear film can no longer adequately lubricate and protect the ocular surface. For some patients, tears evaporate too quickly. Others don't produce enough tears. Many have a combination of both problems along with inflammation, eyelid disease, incomplete blinking, environmental factors, or other conditions that further destabilize the tear film. Understanding what's causing your dry eye is therefore much more useful than simply treating the symptom of dryness.
The Two Major Types of Dry Eye
Dry eye disease is generally divided into two major categories: evaporative dry eye and aqueous-deficient dry eye. However, these categories frequently overlap.
Evaporative Dry Eye
Evaporative dry eye occurs when tears evaporate too quickly from the ocular surface. One of the most common contributors is meibomian gland dysfunction (MGD). The meibomian glands are located within the eyelids and produce meibum, the oily component of the tear film that helps reduce evaporation. When these glands become obstructed or don't produce healthy oils, the tear film may become unstable and evaporate more rapidly. Eyelid disease, incomplete blinking, environmental exposure, and other factors can also contribute to evaporative dry eye.
Aqueous-Deficient Dry Eye
Aqueous-deficient dry eye occurs when the lacrimal glands don't produce enough of the aqueous component of the tear film. It may be associated with aging, certain medications, autoimmune disease such as Sjögren's syndrome, lacrimal gland dysfunction, or other systemic and ocular conditions.
Mixed Dry Eye
Many patients have mixed dry eye, meaning both evaporation and inadequate tear production contribute to their symptoms. For example, someone may have meibomian gland dysfunction causing excessive evaporation while simultaneously taking a medication that reduces tear production. This overlap is one reason symptoms alone usually can't tell us exactly what type of dry eye someone has.
What Is the Tear Film?
The tear film is much more complex than simply “water.” It contains lipid, aqueous, mucin, proteins, electrolytes, and other components that work together to create a smooth, stable surface over the eye.The meibomian glands provide oils that help limit evaporation. The lacrimal glands contribute the aqueous portion of tears, while mucins help tears spread and adhere properly across the ocular surface. Disruption anywhere within this system can contribute to tear-film instability and dry eye disease.
Common Causes of Evaporative Dry Eye
Evaporative dry eye is common and most often results from everyday factors rather than illnesses. The causes of evaporative dry eye include the following
Meibomian Gland Dysfunction
Meibomian gland dysfunction (MGD) is one of the most important contributors to evaporative dry eye. Healthy meibomian glands release clear oils with each complete blink. When gland function deteriorates, the oils may become thickened, reduced, or difficult to express.Over time, chronic gland dysfunction can also lead to structural gland changes or atrophy.
Because symptoms don't always correlate with the severity of gland dysfunction, evaluating the meibomian glands directly can provide information that symptoms alone cannot.
Blepharitis, Ocular Rosacea, and Demodex
Eyelid disease can significantly affect the tear film.
Blepharitis causes inflammation along the eyelid margins and may coexist with meibomian gland dysfunction.
Ocular rosacea can affect the eyelids, meibomian glands, tear film, and ocular surface, contributing to inflammation and evaporative dry eye.
Demodex blepharitis occurs when an excessive population of Demodex mites contributes to eyelid-margin inflammation. Characteristic cylindrical or collarette-like debris may be visible around the base of the eyelashes.
These conditions often overlap, which is why treating the eyelids can be an important part of treating dry eye.
Screens and Incomplete Blinking
Computer and smartphone use can significantly worsen dry-eye symptoms. During concentrated visual tasks, people tend to blink less frequently and may also blink incompletely. Because blinking redistributes the tear film and helps express oils from the meibomian glands, reduced or incomplete blinking allows the ocular surface to remain exposed for longer periods and can increase tear evaporation. Screen use may therefore trigger or worsen tear-film instability, particularly in someone already predisposed to dry eye.
Wind, Dry Air, Smoke, and Air Conditioning
Environmental conditions can dramatically affect tear evaporation. Wind, fans, air conditioning, low humidity, smoke, and prolonged air travel can all increase ocular-surface exposure or destabilize the tear film. This can be particularly noticeable in South Florida, where patients frequently move between hot, humid outdoor conditions and heavily air-conditioned indoor environments.
Incomplete Eyelid Closure
The eyelids protect the ocular surface and redistribute the tear film every time you blink. When the eyelids don't close completely during blinking or sleep, part of the ocular surface remains exposed. This may occur with conditions such as lagophthalmos, eyelid malposition, facial nerve dysfunction, thyroid eye disease, or after certain eyelid procedures. Chronic exposure can cause significant dryness, irritation, and ocular-surface damage.
What Causes Reduced Tear Production?
Aging
Dry eye becomes more common with age. Changes in lacrimal gland function, meibomian gland function, eyelid anatomy, hormones, medications, and systemic health can all contribute. Although age is an important risk factor, persistent dry-eye symptoms shouldn't simply be dismissed as a normal part of getting older.
Hormonal Changes
Hormones influence the lacrimal glands, meibomian glands, and ocular surface. Dry eye is more common in women, particularly during and after menopause, although the relationship between specific hormones and dry eye is complex. Pregnancy, hormonal medications, menopause, and other hormonal changes may influence symptoms in some patients.
Autoimmune and Systemic Disease
Certain systemic diseases can significantly affect tear production and ocular-surface health. Sjögren's disease is particularly associated with aqueous-deficient dry eye because autoimmune inflammation affects the lacrimal glands.
Other systemic conditions that may be associated with dry eye include:
- Rheumatoid arthritis
- Lupus
- Graft-versus-host disease
- Thyroid disease
- Diabetes
- Sarcoidosis
Dry eye is extremely common and does not automatically mean someone has an autoimmune disease. However, severe aqueous deficiency or dry eye accompanied by systemic symptoms may warrant additional medical evaluation.
Medications
A number of medications can contribute to dry-eye symptoms.
Examples include:
- Antihistamines
- Decongestants
- Certain antidepressants
- Some blood-pressure medications
- Isotretinoin and other retinoids
- Certain hormonal medications
- Other medications with anticholinergic effects
The effect varies considerably among patients. Never stop a prescribed medication because you suspect it may be contributing to dry eye without first discussing it with the healthcare professional who prescribed it.
The Role of Corneal Nerves in Dry Eye
The cornea is one of the most densely innervated tissues in the body, and its nerves play an important role in sensation, blinking, tear production, and ocular-surface health. Changes in corneal nerve function can therefore contribute to dry-eye disease or produce symptoms that overlap with dry eye. Reduced corneal sensation can occur with conditions such as neurotrophic keratitis, previous ocular surgery, certain viral infections, chronic ocular-surface disease, and other neurologic or corneal conditions. Conversely, some patients experience significant burning, pain, or light sensitivity despite relatively limited visible signs of dry eye because of abnormal or hypersensitive nerve signaling. This is one reason dry-eye disease cannot always be explained simply by how many tears someone produces.
What Makes Dry Eye Worse?
Some dry-eye risk factors can't be changed, including age, certain systemic diseases, and previous ocular surgery. Others can sometimes be modified.
For example, patients may benefit from:
- Taking regular breaks during prolonged screen use
- Practicing complete blinking
- Avoiding direct airflow from fans and air-conditioning vents
- Using a humidifier in particularly dry environments
- Treating underlying eyelid disease
- Removing eye makeup thoroughly
- Optimizing contact lens fit and ocular-surface health
- Reviewing potentially drying medications with the prescribing healthcare professional when appropriate
These measures can help reduce symptoms, but persistent dry eye often requires treatment directed at the underlying mechanism.
How a Dry Eye Evaluation Identifies the Cause
Two patients can describe virtually identical symptoms; burning, grittiness, watering, blurry vision and have very different underlying problems. That's why symptoms alone aren't enough to diagnose the mechanism of dry eye.
At Weston Contact Lens Institute, a dry eye evaluation may include examination of the ocular surface and eyelids, assessment of tear-film stability, evaluation of the meibomian glands, and other testing based on the patient's history and examination findings.
We look for factors such as:
- Tear-film instability
- Meibomian gland dysfunction
- Aqueous deficiency
- Blepharitis or Demodex
- Ocular rosacea
- Incomplete blinking or eyelid closure
- Ocular-surface inflammation
- Corneal abnormalities
The goal isn't simply to confirm that your eyes are dry. It's to determine why.
Treatment Depends on the Cause
Once we understand what's contributing to the dry eye, treatment can be individualized.For meibomian gland dysfunction and evaporative dry eye, treatment may include IPL, radiofrequency treatment, TearCare, LipiFlow, eyelid treatments, MIEBO, or a combination of approaches. Inflammatory dry eye may require prescription anti-inflammatory therapy. Patients who need additional tear volume or tear conservation may benefit from treatments such as Tyrvaya, LacriFill, or punctal plugs, depending on the underlying condition. More significant ocular-surface disease may require autologous serum or other biologic tears, amniotic membrane treatment, or specialty scleral lenses.
The best treatment isn't necessarily the strongest treatment. It's the treatment directed at the mechanism causing the problem.
Find Out What's Causing Your Dry Eye
Dry eye isn't one condition with one cause. It's a multifactorial disease that can result from tear evaporation, inadequate tear production, meibomian gland dysfunction, inflammation, eyelid disease, environmental exposure, medications, systemic disease, neurosensory abnormalities, or very commonly, a combination of several factors.
So the most useful question isn't simply, “What causes dry eye?” It's “What is causing my dry eye?”
At Weston Contact Lens Institute, we evaluate the tear film, meibomian glands, eyelids, cornea, and ocular surface to identify the factors contributing to each patient's symptoms and create an individualized treatment plan. Contact Weston Contact Lens Institute to schedule a dry eye evaluation. Patients closer to Miami can also be seen at our Miami office.
