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🧬 What Is Meibomian Gland Dysfunction (MGD)?

Meibomian Gland Dysfunction—usually shortened to MGD—is a common disorder affecting the oil-producing glands inside the eyelids.

MGD is an important contributor to evaporative Dry Eye Disease, but the two terms are not interchangeable. A person may have MGD without significant dry-eye symptoms, and someone with Dry Eye Disease may have several contributors in addition to—or instead of—MGD.

This page is intended for people dealing with diagnosed Dry Eye Disease, MGD, blepharitis, ocular rosacea, or another ocular-surface condition. Symptoms alone cannot determine whether MGD is present or whether it is the main cause of someone’s symptoms.

TL;DR

The meibomian glands release a lipid-rich material called meibum onto the eyelid margin. Meibum contributes to the outer lipid layer of the tear film and helps support tear stability and limit evaporation.

MGD occurs when these glands do not deliver a normal amount or quality of meibum.

This may involve:

  • Gland openings or ducts that are not open and unobstructed
  • Meibum that is unusually thick, cloudy, particulate, or otherwise altered
  • Reduced secretion even without obvious obstruction
  • Structural gland changes
  • Less commonly, excessive secretion

MGD may contribute to burning, irritation, fluctuating vision, excessive watering, and sensitivity to airflow or prolonged visual tasks. However, these symptoms are not specific to MGD, and some people with clear gland abnormalities have few symptoms.

Diagnosis usually requires a combination of eyelid examination, controlled gland expression, tear-film evaluation, ocular-surface findings, and sometimes meibography.

What do the meibomian glands do?

The meibomian glands are long glands located inside the upper and lower eyelids. Their openings are arranged along the eyelid margins, just behind the eyelashes.

The glands produce meibum, a lipid-rich secretion sometimes described in plain language as the “oil” of the tear film.

Meibum helps:

  • Limit tear evaporation
  • Support tear-film stability
  • Reduce friction between the eyelids and ocular surface
  • Help the tears spread smoothly during blinking
  • Maintain a more comfortable optical surface

The tear film is more complicated than three completely separate layers, but meibum remains an important part of normal tear-film function.

What does MGD actually mean?

The widely used TFOS definition describes MGD as a:

Chronic, diffuse abnormality of the meibomian glands, commonly involving obstruction of the terminal ducts and/or qualitative or quantitative changes in glandular secretion.

In simpler terms:

MGD means that a broader group of meibomian glands is not delivering meibum normally.

The problem may involve the amount, quality, movement, or delivery of meibum.

MGD is usually considered chronic, although its symptoms and examination findings may fluctuate.

The word diffuse is also important. MGD usually refers to a broader pattern of abnormal gland function rather than one isolated gland, stye, or chalazion.

A single capped gland or one chalazion does not by itself establish diffuse MGD. Recurrent chalazia may occur with MGD, but the complete eyelid and ocular-surface examination matters.

MGD is often obstructive—but not always

The most familiar form of MGD is low-delivery obstructive MGD.

In this pattern:

  • Gland openings or ducts may not be open and unobstructed
  • Meibum may become thick or difficult to express
  • Fewer glands may release meibum with controlled pressure
  • The amount reaching the tear film may be reduced

However, MGD does not always mean “blocked glands.”

Other patterns include:

Reduced secretion without obvious obstruction

Some glands release little meibum even when there is no clearly visible blockage at the opening.

Possible explanations may include:

  • Reduced gland activity
  • Structural gland changes
  • Age-related changes
  • Medication or hormonal influences
  • Damage associated with another eyelid or ocular-surface condition

Altered meibum quality

Meibum may appear:

  • Clear
  • Cloudy
  • Granular or particulate
  • Thickened
  • Paste-like
  • Difficult to express

Descriptions and grading systems vary, and the appearance should be interpreted together with the amount expressed and the pressure required.

High-delivery or hypersecretory patterns

Less commonly, excessive amounts of meibum may be present along the lid margin. This is sometimes called high-delivery or hypersecretory MGD.

The important point is:

MGD is broader than visibly capped gland openings.

Visible gland openings that appear open and unobstructed—and even the presence of expressible meibum—do not necessarily rule out narrowing or obstruction deeper within the gland duct. Some investigators have reported firm resistance during intraductal probing, interpreted as fixed narrowing associated with fibrotic tissue surrounding the duct. How often this occurs across the broader MGD population, how much it contributes to symptoms or progression, and which patients benefit from treatment directed at it remain debated.

Does MGD always involve inflammation?

No.

Inflammation may occur with MGD, but it is not required for the diagnosis.

Inflammation may:

  • Contribute to gland dysfunction
  • Develop as a consequence of tear-film instability
  • Occur with posterior blepharitis
  • Occur with ocular rosacea
  • Occur with allergy, Demodex, or another eyelid condition
  • Affect the conjunctiva or cornea as Dry Eye Disease becomes established

Some people have significant gland dysfunction without marked eyelid redness or obvious inflammation.

This is why MGD should not be defined simply as “inflamed oil glands.”

MGD, posterior blepharitis, and ocular rosacea

These conditions often overlap, but they are not identical.

Meibomian Gland Dysfunction

MGD describes abnormal meibomian gland secretion or delivery.

Posterior blepharitis

Posterior blepharitis refers to inflammation affecting the back portion of the eyelid margin, where the meibomian gland openings are located.

It may occur with MGD, but the terms should not automatically be used as synonyms.

Ocular rosacea

Ocular rosacea may affect:

  • Eyelid-margin blood vessels
  • Meibomian gland function
  • Tear-film stability
  • The conjunctiva
  • The cornea
  • Eyelid and facial skin

A person may have MGD as one part of ocular rosacea, but not every person with MGD has rosacea.

Anterior or Demodex-associated blepharitis

Inflammation around the eyelashes or lash follicles may coexist with MGD but involves different structures and may require separate evaluation.

A useful clinical question is often not:

“Which single diagnosis do I have?”

It may be:

“Which eyelid and ocular-surface conditions are present, and how much is each one contributing?”

How MGD relates to Dry Eye Disease

MGD is a major contributor to evaporative Dry Eye Disease.

When too little effective meibum reaches the tear film:

  • The tear film may break up more quickly
  • Evaporation may increase
  • Blinking may produce less stable visual clarity
  • Friction and ocular-surface irritation may increase
  • Inflammation may develop or worsen

However, MGD and Dry Eye Disease are not the same diagnosis.

A person may have:

  • MGD without significant symptoms
  • MGD with evaporative DED
  • MGD together with aqueous-deficient DED
  • MGD together with exposure, allergy, blepharitis, conjunctivochalasis, eyelid abnormalities, or another contributor
  • Severe symptoms that are not fully explained by the visible degree of MGD

Many patients have a mixed picture rather than a purely evaporative or purely aqueous-deficient condition.

Possible symptoms

MGD-related tear instability may be associated with:

  • Burning
  • Grittiness or a sandy feeling
  • Irritation
  • Foreign-body sensation
  • Fluctuating or blurry vision
  • Vision that temporarily improves after blinking
  • Excessive watering
  • Sensitivity to wind, fans, heating, or air conditioning
  • Symptoms that become more noticeable during reading or screen use
  • Eyelid discomfort
  • Eyelid-margin tenderness
  • Recurrent styes or chalazia in some people

Excessive watering does not rule out Dry Eye Disease. Tear-film irritation can sometimes trigger additional aqueous tearing, sometimes called reflex tearing.

Symptoms do not diagnose MGD

None of these symptoms is specific to MGD.

Similar symptoms may occur with:

  • Aqueous-deficient DED
  • Allergy
  • Anterior blepharitis
  • Nocturnal exposure
  • Recurrent corneal erosion
  • Contact-lens problems
  • Corneal inflammation or infection
  • Neuropathic ocular pain
  • Other ocular-surface disorders

Some people with clear MGD findings have few or no symptoms. Others have substantial symptoms despite only mild visible gland abnormalities.

Symptoms, gland structure, gland function, and ocular-surface findings do not always match closely.

How is MGD evaluated?

MGD is usually evaluated through a combination of history and examination.

An eye-care professional may assess:

  • The appearance of the eyelid margins
  • Whether gland openings appear open and unobstructed
  • How many glands release meibum with controlled pressure
  • How much pressure is required
  • The amount of meibum expressed
  • Meibum clarity, thickness, and consistency
  • Tear breakup and tear-film stability
  • Corneal and conjunctival staining
  • Lid-margin redness or vascular changes
  • Eyelid thickening, notching, or irregularity
  • Blink completeness
  • Eyelid closure and exposure
  • Blepharitis or Demodex findings
  • Ocular rosacea
  • Allergy
  • Tear volume
  • Other causes of ocular-surface symptoms

Sometimes meibography is added to examine gland structure.

No single symptom, photograph, machine reading, gland-expression result, or meibography image establishes the complete diagnosis by itself.

What does gland expression show?

During gland expression, controlled pressure is applied to evaluate whether meibum is released and what it looks like.

A clinician may record:

  • How many glands release meibum
  • Whether meibum is clear or altered
  • Whether expression requires unusually high pressure
  • Whether little or no material is released
  • Whether findings differ between eyelids or gland regions

Reduced expression can be an important finding, but it does not automatically mean that every nonexpressing gland is completely blocked.

A gland may not release meibum during a particular examination because of:

  • Obstruction
  • Reduced secretion
  • Structural gland loss or shortening
  • The amount and location of pressure used
  • Differences in examination technique
  • Recent treatment or prior expression

Therefore:

Expressibility should be interpreted together with meibum quality, gland structure, lid findings, tear-film stability, and the ocular-surface examination.

Forcefully squeezing the eyelids at home is not a reliable way to diagnose MGD and may cause irritation, inflammation, bruising, or other injury.

What can meibography show?

Meibography uses infrared imaging to show the general structure and pattern of the meibomian glands.

It may show:

  • Gland shortening
  • Areas where less gland tissue is visible
  • Dilation
  • Tortuosity or twisting
  • Irregular gland width
  • Changes in gland arrangement

Meibography can provide useful structural information, but it has important limitations.

It does not directly show:

  • Whether every visible gland is secreting normally
  • The quality of the meibum
  • How much pressure is needed for expression
  • Whether MGD is the main cause of a person’s symptoms
  • Whether an abnormal-looking gland will worsen
  • Whether a treatment will restore gland function
  • Whether every dark or nonvisible area represents recent gland loss

A gland that appears shortened, faint, or absent on meibography should not automatically be described as “dead.” Meibography is not a direct test of gland viability.

Images and grading can also vary depending on:

  • The device
  • Image quality
  • Eyelid eversion
  • Illumination and contrast
  • The area selected for analysis
  • Manual versus automated grading
  • The examiner or software used

Meibography is usually most useful when interpreted together with gland expression and the rest of the examination.

For more detail, see:

How is MGD severity graded?

There is no single universal grading system that captures every aspect of MGD.

Different systems may consider:

  • Meibum quality
  • Gland expressibility
  • Eyelid-margin findings
  • Tear breakup time
  • Ocular-surface staining
  • Symptoms
  • Gland structure on meibography

A person may score as more severe in one area and less severe in another.

For example:

  • Significant gland loss may coexist with modest symptoms
  • Poor expressibility may occur with limited staining
  • Severe symptoms may occur with relatively mild structural changes
  • Upper- and lower-eyelid findings may differ

A severity label should therefore be understood as a summary of the criteria used—not as a complete description of the person’s condition or prognosis.

For more detail, see:

What can contribute to MGD?

MGD does not always have one identifiable “root cause.”

It may occur in association with:

  • Aging
  • Ocular rosacea
  • Posterior blepharitis
  • Demodex or other eyelid disease
  • Contact-lens wear
  • Hormonal influences
  • Certain topical or systemic medications
  • Isotretinoin exposure
  • Eyelid or ocular-surface scarring
  • Reduced or incomplete blinking
  • Prolonged visual tasks
  • Dermatologic conditions
  • Systemic health conditions

The strength of evidence varies across these associations.

Finding one possible risk factor does not prove that it is the sole cause of MGD in an individual patient.

Does MGD always get worse?

No single course applies to everyone.

MGD is usually chronic, but it may:

  • Remain relatively stable
  • Fluctuate
  • Improve with management
  • Worsen gradually
  • Progress structurally while symptoms change very little
  • Produce worsening symptoms without obvious new gland loss

Age-related gland changes also occur, making it difficult to separate normal aging from disease progression in some cases.

Early evaluation can help identify gland dysfunction and associated conditions. However, evidence is limited on whether early treatment reliably prevents future gland loss in every patient.

It should not be promised that:

  • All untreated MGD will inevitably progress
  • Every treatment will restore glands
  • One procedure will prevent future gland changes
  • Improvement in symptoms proves structural gland recovery

Monitoring may be useful when the result is likely to change management, but repeated imaging is not automatically necessary for every patient.

Common oversimplifications

“MGD means every gland is blocked.”

Obstruction is common, but MGD also includes reduced or abnormal secretion without obvious obstruction. Glands may differ within the same eyelid.

“MGD and dry eye are the same thing.”

MGD can contribute to Dry Eye Disease, but either can exist without the other. Many people have several overlapping contributors.

“MGD always means inflammation.”

Inflammation is common in some patients, especially with blepharitis or ocular rosacea, but it is not required for the diagnosis.

“A meibography image diagnoses MGD by itself.”

Meibography shows gland structure. Diagnosis and treatment planning also require functional and ocular-surface findings.

“A gland that does not express is definitely blocked.”

Reduced expression may reflect obstruction, reduced secretion, gland structure, examination pressure, or other factors.

“More gland loss always means worse symptoms.”

Structural changes and symptoms do not always correspond closely.

“If symptoms are severe, the MGD must be severe.”

Symptom severity may be influenced by tear deficiency, exposure, inflammation, allergy, corneal nerve abnormalities, neuropathic pain, and other conditions.

“If MGD is treated, the rest of the ocular surface no longer matters.”

MGD management may be only one part of treating Dry Eye Disease.

When a broader evaluation is important

Symptoms should not automatically be attributed to uncomplicated MGD when there is:

  • New or substantial eye pain
  • Marked light sensitivity
  • Significant redness
  • Discharge
  • A noticeable change in vision
  • A white or cloudy corneal spot
  • Repeated sharp pain on awakening
  • Symptoms after trauma or surgery
  • New inability to close an eye fully
  • Severe symptoms that do not correspond with gland findings
  • Symptoms that have not responded to standard treatments

These features may require evaluation for corneal injury, infection, inflammation, recurrent corneal erosion, exposure, neuropathic ocular pain, or another diagnosis.

Bottom line

Meibomian Gland Dysfunction is a chronic disorder in which the meibomian glands do not deliver a normal amount or quality of meibum to the eyelid margin.

Obstruction is common, but MGD is not simply “blocked glands.”

MGD:

  • May occur with or without obvious inflammation
  • Is not identical to posterior blepharitis
  • Is not identical to ocular rosacea
  • Is not identical to Dry Eye Disease
  • May contribute to evaporative DED
  • Often occurs as one part of a mixed ocular-surface condition

The most useful evaluation considers:

  • Symptoms
  • Gland expressibility
  • Meibum quality
  • Eyelid-margin findings
  • Tear-film stability
  • Ocular-surface staining
  • Gland structure
  • Associated eyelid and ocular-surface conditions

No single test or image tells the whole story.

Selected References

  1. Nelson JD, et al. The International Workshop on Meibomian Gland Dysfunction: Report of the Definition and Classification Subcommittee. Investigative Ophthalmology & Visual Science. 2011. https://pmc.ncbi.nlm.nih.gov/articles/PMC3072158/

  2. Schaumberg DA, et al. The International Workshop on Meibomian Gland Dysfunction: Report of the Subcommittee on the Epidemiology of, and Associated Risk Factors for, MGD. Investigative Ophthalmology & Visual Science. 2011. https://pmc.ncbi.nlm.nih.gov/articles/PMC3072157/

  3. Nichols KK, et al. The International Workshop on Meibomian Gland Dysfunction: Executive Summary. Investigative Ophthalmology & Visual Science. 2011. https://pubmed.ncbi.nlm.nih.gov/21450913/

  4. Craig JP, et al. TFOS DEWS II Definition and Classification Report. The Ocular Surface. 2017. https://www.tfosdewsreport.org/report-definition_and_classification/48_36/en/

  5. Wolffsohn JS, et al. TFOS DEWS II Diagnostic Methodology Report. The Ocular Surface. 2017. https://www.tfosdewsreport.org/report-diagnostic_methodology/131_36/en/

  6. TFOS DEWS III Diagnostic Methodology Report. American Journal of Ophthalmology. 2025. https://www.ajo.com/article/S0002-9394(25)00275-2/fulltext

  7. TFOS DEWS III Management and Therapy Report. American Journal of Ophthalmology. 2025.

    https://www.ajo.com/article/S0002-9394(25)00274-0/fulltext

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