{"id":18021,"date":"2026-07-29T11:55:14","date_gmt":"2026-07-29T11:55:14","guid":{"rendered":"https:\/\/www.eyecliniclondon.com\/blog\/?p=18021"},"modified":"2026-07-29T11:59:47","modified_gmt":"2026-07-29T11:59:47","slug":"tear-biomarkers-dry-eye-diagnosis","status":"publish","type":"post","link":"https:\/\/www.eyecliniclondon.com\/blog\/tear-biomarkers-dry-eye-diagnosis\/","title":{"rendered":"How Tear Biomarkers Help Diagnose Dry Eye Disease"},"content":{"rendered":"

Dry eye disease may seem straightforward when your eyes feel gritty, sore, watery or tired, or when your vision occasionally becomes blurred. However, these symptoms can be caused by several different problems involving your tears, eyelids, oil glands, corneal nerves, or the surface of the eye.<\/p>\n

This is one reason why dry eye disease can be difficult to diagnose based on symptoms alone. You may have symptoms that are very similar to someone else’s, yet the underlying cause can be completely different. In some cases, significant damage to the eye surface may be present even when symptoms appear relatively mild.<\/p>\n

Tear biomarker testing can provide your eye specialist with additional information about your tear film and ocular surface. Rather than simply measuring tear quantity, selected tests may provide clues about inflammation, tear concentration and changes in tear composition. The findings must still be interpreted alongside your symptoms, examination results and other dry-eye tests before a diagnosis or treatment plan is made.<\/p>\n

What Are Tear Biomarkers?<\/h2>\n

A tear biomarker is a measurable biological feature that provides information about the health of your eyes and tear film. In dry eye disease, biomarkers can include substances found within your tears or measurements that help your eye specialist understand how well your tear film is functioning.<\/p>\n

Your tears are made up of much more than just water. They contain oils, proteins, enzymes, antibodies, electrolytes, mucins, growth factors, and other important components that work together to protect the surface of your eyes and support clear, comfortable vision.<\/p>\n

When dry eye disease disrupts this balance, some tear components may increase, decrease or function differently. Measuring selected changes may provide clues about inflammation, tear-film instability, reduced tear production or other disturbances affecting the ocular surface. However, biomarkers cannot usually determine the precise cause or subtype of dry eye without a wider clinical assessment.<\/p>\n

Why Dry Eye Diagnosis Can Be Complicated<\/h2>\n

Dry eye disease is not a single condition with one straightforward cause. You may have aqueous-deficient dry eye, where your eyes do not produce enough watery tears, evaporative dry eye linked to meibomian gland dysfunction, or a combination of both.<\/p>\n

A range of other factors can also contribute to dry eye symptoms. These may include incomplete blinking, eyelid inflammation, contact lens wear, hormonal changes, autoimmune conditions, previous eye surgery, certain medications, environmental factors, or changes in corneal nerve function.<\/p>\n

Because several causes can occur at the same time, diagnosing dry eye disease often requires a detailed assessment. Tear biomarkers can provide useful information, but your eye specialist will also consider your symptoms, tear film stability, eyelid health, ocular surface staining, and the results of other clinical tests.<\/p>\n

Why Symptoms Alone May Not Give the Full Answer<\/h2>\n

You may experience symptoms such as burning, grittiness, watering, sensitivity to light, tired eyes, or fluctuating vision. While these symptoms are important, they do not always reflect the level of tear film instability or eye surface damage seen during an examination.<\/p>\n

In some cases, you may have significant discomfort even when standard tests show only mild changes. This can happen when the corneal nerves become more sensitive or when symptoms have a neuropathic component.<\/p>\n

In other situations, your eyes may show clear signs of gland dysfunction, tear instability, or surface damage despite causing very few symptoms. Tear biomarker testing can provide additional objective information and help your eye specialist understand what is happening when symptoms and clinical findings do not appear to match.<\/p>\n

When Eye Symptoms Need Urgent Assessment<\/h2>\n

Dry eye usually causes symptoms such as irritation, grittiness, watering, or fluctuating vision rather than severe pain or sudden vision loss. However, some other eye conditions can feel similar at first and may need urgent assessment and treatment.<\/p>\n

You should seek urgent medical or eye-care advice if you develop a painful red eye, a red eye while wearing contact lenses, a sudden change in vision, strong sensitivity or pain when looking at light, severe headache with nausea and a red eye, an eye injury, chemical splash, embedded object, rapidly worsening symptoms, or thick discharge.<\/p>\n

If you develop a painful or unusually red eye, remove your contact lenses and avoid wearing them again until you have received appropriate advice. Prompt assessment can help identify the cause and ensure you receive the right treatment if a more serious eye problem is present.<\/p>\n

What Tear Osmolarity Can Reveal<\/h2>\n

Tear osmolarity measures the concentration of dissolved particles, including salts, within your tear film. If your tears evaporate too quickly or your eyes do not produce enough tears, the remaining tear film can become more concentrated.<\/p>\n

This increase in concentration, known as hyperosmolarity, can place stress on the cells that cover the surface of your eyes. Over time, it may trigger inflammation, reduce tear film stability, and contribute to the ongoing cycle of irritation and damage associated with dry eye disease.<\/p>\n

A small tear sample can be used to measure osmolarity during an eye examination. While the results can provide useful information, your eye specialist will interpret them alongside your symptoms and other clinical findings, as factors such as reflex tearing, eye drops, and environmental conditions can influence the reading.<\/p>\n

Understanding MMP-9 Testing<\/h2>\n

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Matrix metalloproteinase-9, commonly known as MMP-9, is an enzyme associated with inflammation and tissue remodelling on the ocular surface. A positive point-of-care test indicates that the amount of MMP-9 in the tear sample is above the test threshold. This can occur in some people with dry eye disease as well as in other inflammatory ocular-surface conditions.<\/p>\n

The result may provide useful additional information when your eye specialist is assessing ocular-surface inflammation. However, it does not measure every inflammatory pathway, establish the severity of dry eye by itself or automatically show which treatment will work best.<\/p>\n

A positive MMP-9 result does not automatically mean that dry eye disease is the only cause of your symptoms. The enzyme can also be elevated in other inflammatory eye conditions, and some people with dry eye may still have a negative result, which is why the test is always interpreted alongside the rest of your examination findings.<\/p>\n

Inflammatory Cytokines in the Tears<\/h2>\n

Cytokines are signalling proteins that help your immune system communicate and respond to inflammation. When inflammation develops on the surface of your eyes, the levels of certain cytokines and related molecules within your tears may change.<\/p>\n

Researchers have investigated inflammatory markers including interleukins, tumour necrosis factor, interferon-gamma and various chemokines. Associations have been observed between some of these markers and different forms or severities of ocular-surface disease. However, the results cannot currently identify a specific underlying condition or determine treatment when used on their own.<\/p>\n

Most cytokine testing is currently used in research rather than as a routine test in everyday eye clinics. However, these studies are helping specialists better understand why dry eye disease affects people differently and why certain treatments may work better for some patients than for others.<\/p>\n

Lactoferrin and Lacrimal Gland Function<\/h2>\n

Lactoferrin is a protective protein produced mainly by your lacrimal glands, which are responsible for making the watery layer of your tears. It helps defend your eyes against harmful microorganisms, supports the ocular surface, and plays an important role in maintaining healthy tears.<\/p>\n

Lower tear lactoferrin levels may provide supporting evidence of reduced lacrimal-gland function or aqueous-deficient dry eye. However, levels can be influenced by factors including age, tear collection and other ocular-surface conditions, and lactoferrin testing is not routinely used in every dry-eye clinic.<\/p>\n

Although lactoferrin can provide useful information, it is not a perfect stand-alone test. Your clinician will usually interpret the results alongside your symptoms, tear production measurements, eye surface findings, medical history, and other examination results to build a clearer picture of your condition.<\/p>\n

Common Tear Biomarkers and Their Current Roles<\/h2>\n\n\n\n\n\n\n\n\n\n\n
Test or Biomarker<\/strong><\/td>\nWhat It May Show<\/strong><\/td>\nImportant Limitation<\/strong><\/td>\n<\/tr>\n
Tear osmolarity<\/td>\nIncreased concentration of dissolved particles and loss of tear-film homeostasis<\/td>\nCan vary between measurements and must not be used as the sole diagnostic test<\/td>\n<\/tr>\n
MMP-9<\/td>\nRaised activity of an inflammatory enzyme on the ocular surface<\/td>\nCan be positive in other inflammatory eye conditions and negative in some people with dry eye<\/td>\n<\/tr>\n
Lactoferrin<\/td>\nPossible reduction in lacrimal-gland secretion or aqueous tear production<\/td>\nNot routinely tested in every clinic and affected by collection and patient factors<\/td>\n<\/tr>\n
Cytokines and chemokines<\/td>\nResearch information about inflammatory signalling<\/td>\nMost tests remain research-based and cannot determine a specific cause<\/td>\n<\/tr>\n
Tear proteins and peptides<\/td>\nChanges in protection, lubrication, inflammation and surface repair<\/td>\nDetailed analysis requires specialised laboratory methods<\/td>\n<\/tr>\n
Tear lipids<\/td>\nPossible biochemical changes linked to the oily tear layer and meibomian glands<\/td>\nClinical examination and meibomian-gland assessment remain necessary<\/td>\n<\/tr>\n
Oxidative-stress markers<\/td>\nResearch evidence of oxidative damage or altered antioxidant protection<\/td>\nTesting is not currently standardised for routine dry-eye care<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Biomarker results are most useful when combined with symptoms, tear-film assessment, ocular-surface staining and examination of the eyelids and meibomian glands.<\/p>\n

Protective Tear Proteins and Peptides<\/h2>\n

Your tears contain a wide range of proteins and peptides that help keep your eyes healthy and comfortable. These substances support lubrication, protect against microorganisms, regulate inflammation, and promote healing on the surface of your eyes.<\/p>\n

Research has shown that the balance of these protective components can change when dry eye disease develops. Some beneficial proteins may decrease, while proteins linked to inflammation and cellular stress may become more noticeable.<\/p>\n

By studying these changes, researchers hope to identify different types of dry eye disease more accurately in the future. At present, detailed protein analysis is mainly used in specialist research settings because it requires advanced laboratory testing and careful interpretation.<\/p>\n

Tear Lipids and Evaporative Dry Eye<\/h2>\n

The outer layer of your tear film contains oils produced by the meibomian glands in your eyelids. These oils help prevent your tears from evaporating too quickly and keep the tear film evenly distributed across the surface of your eyes between blinks.<\/p>\n

When these glands become blocked, inflamed, or damaged, the quality and quantity of the oils can change. As a result, your tears may evaporate more rapidly, leading to discomfort, fluctuating vision, and reduced tear film stability.<\/p>\n

Researchers are studying tear lipid biomarkers to gain a better understanding of evaporative dry eye. In the future, these biomarkers may help support other assessments, such as meibography, gland expression, blink analysis, tear break-up time testing, and examination of the eyelid margins.<\/p>\n

Oxidative Stress Biomarkers<\/h2>\n

Oxidative stress occurs when harmful reactive molecules build up and overwhelm your eye\u2019s natural antioxidant defences. This imbalance may contribute to inflammation, damage to the cells on the surface of your eyes, and disruption of the tear film, which can worsen dry eye symptoms.<\/p>\n

Researchers have identified certain molecules in tears that may show signs of oxidative damage or reduced protection against it. These biomarkers are being studied to understand how oxidative stress may contribute to dry eye linked with ageing, diabetes, autoimmune conditions, environmental exposure, contact lens use, and other health factors.<\/p>\n

At present, oxidative-stress biomarker testing is not part of most routine dry-eye assessments. These tests remain primarily research-based, and their role in diagnosing dry eye or selecting an individual treatment has not yet been established.<\/p>\n

How a Tear Sample Is Collected<\/h2>\n

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Tear biomarker testing usually requires only a very small sample of your tears. Depending on the test, your eye specialist may collect the sample from the lower tear meniscus using a small sampling tip, capillary tube, absorbent strip or another specialised device.<\/p>\n

The collection process is generally quick, although you may notice mild awareness around your lower eyelid. Care is taken during the procedure because touching the surface of your eye or causing extra watering can affect the accuracy of the sample.<\/p>\n

The way your tear sample is collected can have a significant impact on the results. Factors such as the collection method, sample amount, timing, storage conditions, temperature, and laboratory processing can all influence the final findings.<\/p>\n

Preparing for Tear Biomarker Testing<\/h2>\n

Your clinic may provide specific instructions before tear biomarker testing. Do not stop prescribed eye drops or other eye treatment unless your clinician has specifically advised you to do so. If a temporary change is needed, the clinic should explain which product to pause and when it is safe to restart it.<\/p>\n

Things such as contact lenses, eye make-up, rubbing your eyes, environmental conditions, and other eye tests carried out during the same visit can influence your tear sample. Your clinician may plan the order of tests carefully to reduce these effects and improve accuracy.<\/p>\n

Before testing, it is important to tell your specialist about your eye drops, medications, contact lens use, allergies, previous eye surgery, autoimmune conditions, and current symptoms. This information helps them understand your results more accurately rather than looking at a single test result in isolation.<\/p>\n

Clinical Tip<\/strong><\/p>\n

Bring an up-to-date list of all prescribed and non-prescribed eye drops, contact-lens products and medicines to your appointment. Tell the clinic when you last used each eye product and whether you have recently worn contact lenses.<\/p>\n

Do not change your normal treatment routine unless the clinic gives you specific instructions. The timing of drops, contact-lens wear, eye rubbing and other tests performed during the appointment can affect a tear sample, so following the clinic\u2019s preparation advice can make the result easier to interpret.<\/p>\n

Combining Biomarkers with Standard Dry Eye Tests<\/h2>\n

Tear biomarkers are most helpful when they are used alongside a complete dry eye assessment. Your clinician may ask about symptoms such as discomfort, watering, blurred vision, screen use, contact lens wear, environmental triggers, and how dry eye affects your daily activities.<\/p>\n

Your eye specialist may also check tear stability, tear production, staining on the eye surface, eyelid closure, blink quality, meibomian gland function, tear meniscus height, and the health of your eyelid margins. Additional imaging may be used to examine the meibomian glands and better understand the condition of your tear film.<\/p>\n

No single test can show every aspect of dry eye disease, which is why a combined approach is important. By looking at biomarkers alongside other clinical findings, your specialist can better identify the factors contributing to your symptoms and create a more personalised treatment plan.<\/p>\n

Evidence Note<\/strong><\/p>\n

The 2025 TFOS DEWS III report defines dry eye as a multifactorial, symptomatic disease involving loss of homeostasis of the tear film and\/or ocular surface. Its diagnostic approach combines symptom screening with objective evidence of tear-film or ocular-surface disturbance and emphasises the importance of considering alternative diagnoses.<\/p>\n

Research into MMP-9, osmolarity and other tear biomarkers shows that these measurements can provide useful additional information. However, study results vary, individual biomarkers do not detect every case, and testing methods are not yet fully standardised. Biomarkers should therefore support, rather than replace, a comprehensive clinical assessment.<\/p>\n

Clinical Guidance Note<\/strong><\/p>\n

Current clinical guidance supports diagnosing dry eye through a combination of symptoms, relevant medical and eye history, and clinical examination. Assessment may include tear-film stability, ocular-surface staining, tear production, eyelid health, blinking and meibomian-gland function.<\/p>\n

Tear osmolarity, MMP-9 and other biomarker tests may be available in selected specialist clinics, but they are supplementary tests rather than mandatory investigations for every patient. A normal result does not necessarily exclude dry eye, while a raised result does not confirm that dry eye is the only condition present.<\/p>\n

Persistent symptoms, diagnostic uncertainty, significant ocular-surface changes or failure to respond to initial care may require further assessment by an optometrist or ophthalmologist.<\/p>\n

Identifying Aqueous-Deficient Dry Eye<\/h2>\n

Aqueous-deficient dry eye develops when your lacrimal glands do not produce enough of the watery part of your tears. You may experience symptoms such as grittiness, burning, soreness, fluctuating vision, or discomfort that becomes more noticeable as the day goes on.<\/p>\n

Your eye specialist may use tear-quantity measurements, tear-meniscus height and ocular-surface staining to assess whether reduced aqueous tear production is present. Osmolarity can provide evidence of disturbed tear-film homeostasis, while lactoferrin testing may offer supporting information about lacrimal-gland secretion in selected settings. Neither test identifies aqueous-deficient dry eye when used alone.<\/p>\n

Recognising reduced tear production can help guide your treatment plan. Management may include conserving your natural tears, reducing inflammation, supporting tear production, protecting the surface of your eyes, and checking for any underlying health conditions when needed.<\/p>\n

Identifying Evaporative Dry Eye<\/h2>\n

Evaporative dry eye occurs when your tear film loses moisture too quickly, causing your eyes to become dry and uncomfortable. Factors such as meibomian gland dysfunction, reduced blinking, incomplete eyelid closure, prolonged screen use, contact lens wear, and changes in the tear oil layer can all contribute.<\/p>\n

Tear biomarkers may provide supporting information about inflammation or changes in tear composition, but they cannot diagnose evaporative dry eye on their own. Your specialist will primarily examine your eyelids, blinking and meibomian glands, including the gland openings, oil quality, eyelid position, tear break-up time and, where appropriate, gland structure.<\/p>\n

Identifying evaporative dry eye correctly can help ensure you receive the right treatment approach. Instead of relying only on artificial tears, your management plan may include eyelid care, treatment for blocked glands, reducing inflammation, adjusting your environment, and improving blinking habits.<\/p>\n

Supporting More Targeted Treatment<\/h2>\n

Tear biomarker results may provide supporting information about processes such as inflammation or loss of tear-film homeostasis, but they do not reliably identify the dominant cause or independently select treatment. Your specialist will interpret the result alongside your symptoms, disease severity, eyelid and meibomian-gland findings, medical history and previous treatment response.<\/p>\n

A single biomarker result does not automatically determine your treatment. Your specialist will also consider your symptoms, disease severity, examination findings, medical history, previous treatments, and any factors that may affect which options are suitable for you.<\/p>\n

Monitoring Changes During Treatment<\/h2>\n

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In selected specialist or research settings, repeat biomarker testing may provide additional information about changes occurring on the ocular surface during treatment. For example, a change in an inflammatory marker may suggest that one biological pathway is responding, but it should not be treated as proof that the condition has resolved.<\/p>\n

However, changes in biomarkers do not always mean that all your symptoms will improve immediately. Factors such as nerve sensitivity, surface healing, tear stability, eyelid health, and environmental triggers can improve at different speeds.<\/p>\n

For this reason, follow-up appointments usually include both clinical tests and a discussion about how your eyes feel and function. Researchers are continuing to study which biomarkers are most useful for tracking treatment response and long-term dry eye changes.<\/p>\n

Current Limitations of Tear Biomarkers<\/h2>\n

Tear biomarkers can provide useful information, but they are not perfect diagnostic tools. A raised inflammatory marker may be linked with different eye surface conditions, while someone with dry eye disease may still have a normal result on a particular day.<\/p>\n

Your tear composition can change due to several factors, including blinking, reflex watering, contact lens use, eye drops, humidity, sleep, hormones, overall health, and the way the sample is collected. This natural variation can make results more difficult to interpret.<\/p>\n

Another challenge is that testing methods are not yet fully standardised for every biomarker. As a result, your specialist needs to consider the test results alongside your symptoms, examination findings, and medical history rather than relying on a single measurement.<\/p>\n

Research Insight<\/strong><\/p>\n

Tear biomarker research is moving towards broader molecular patterns rather than relying only on individual markers. Approaches such as proteomics, lipidomics and metabolomics may help researchers define different biological patterns within dry eye disease.<\/p>\n

In the future, combining these forms of information may help classify dry-eye mechanisms and investigate which treatments are more likely to benefit particular patient groups. Artificial intelligence may also support research by recognising complex relationships between molecular findings, clinical features and treatment responses.<\/p>\n

Although these developments are promising, many are still being studied and are not yet part of routine care. Further research, including larger clinical studies and more standardised testing methods, is needed before biomarker-guided treatment becomes widely available.<\/p>\n

Myth vs Fact<\/h2>\n\n\n\n\n\n\n\n\n\n\n\n\n
Myth<\/strong><\/td>\nFact<\/strong><\/td>\n<\/tr>\n<\/thead>\n
One biomarker test can confirm dry eye disease.<\/td>\nDiagnosis requires symptoms, examination and appropriate clinical tests rather than one result.<\/td>\n<\/tr>\n
A normal MMP-9 result rules out dry eye.<\/td>\nSome people with dry eye have a negative MMP-9 result because not every case involves detectable elevation of this marker.<\/td>\n<\/tr>\n
A positive MMP-9 result proves that dry eye is the cause.<\/td>\nMMP-9 can also be raised in other inflammatory ocular-surface conditions.<\/td>\n<\/tr>\n
High tear osmolarity identifies the exact type of dry eye.<\/td>\nOsmolarity can indicate disrupted tear-film homeostasis but does not independently identify the cause.<\/td>\n<\/tr>\n
Biomarker testing replaces examination of the eyelids and glands.<\/td>\nEyelid, blink and meibomian-gland assessment remain essential, particularly in evaporative dry eye.<\/td>\n<\/tr>\n
All tear biomarkers are routinely available.<\/td>\nOsmolarity and MMP-9 may be available in selected clinics, while many cytokine, protein, lipid and oxidative tests remain research-based.<\/td>\n<\/tr>\n
Biomarker results automatically determine treatment.<\/td>\nResults may add useful context, but treatment also depends on symptoms, examination findings, severity, medical history and previous response.<\/td>\n<\/tr>\n
Improvement in a biomarker guarantees that symptoms will disappear.<\/td>\nSymptoms, nerve sensitivity, tear stability and surface healing may change at different rates.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Key Takeaways<\/h2>\n