Meibomian Glands: The Nerve Fiber Layer of the Anterior Segment

Meibomian Glands: The Nerve Fiber Layer of the Anterior Segment

Many new options are available for testing and treatment of ocular surface disease.

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By Leslie E. O’Dell, OD

A dry eye disease (DED) epidemic is upon us. You can choose to recognize this and actively seek out patients to treat or you can miss an opportunity for practice growth by ignoring it. If you look, you will find that the majority of your patients have some stage and type of dry eye disease. Ocular surface disease (OSD) is a complicated process involving adequate quantity and quality of tears to maintain a healthy ocular surface. There have been many advances over the years in defining this disease, in the diagnostic tests available, and in treatment options to help our patients who experience what are often life-altering symptoms. There is still much to learn, but maybe we do not have to reinvent the wheel.

PARALLELS: DED AND GLAUCOMA

The same philosophies used in the understanding of glaucoma can be applied to OSD. Reviewing the history of glaucoma and the challenges faced in defining, diagnosing, and treating the disease could help to enhance our understanding of OSD and drive needed research.

The concept of high intraocular pressure and its relationship to glaucoma dates back to Demours in France in 1818.1 Optic neuropathy, the modern definition of glaucoma, was introduced by Drance only in 1973—155 years later.2

Korb first introduced the idea of meibomian gland dysfunction (MGD) in 1980,3 and the term meibum was coined by Nicolaides et al in 1981.4 Let us hope it does not take 155 years to achieve a better understanding of DED!

Figure 1. Transillumination of the lower lid.  Although hard to photograph the changes seen in the meibomian gland structure, when viewing with the slit lamp it is easy to see gland dropout.  

The same shift seen with glaucoma, from a disease of IOP to that of optic nerve damage or optic neuropathy, is beginning to evolve with dry eye disease. Through the efforts of the Dry Eye Workshop and the International Workshop on Meibomian Gland Dysfunction, there has been a fundamental change in our understanding of the main type of dry eye from that of an aqueous deficiency to that of an evaporative one.5,6

 

Figure 2. According to its manufacturer, the LipiView II now images meibomian glands with Dynamic Meibomian Imaging, simultaneously employing noncontact surface illumination and high-definition transillumination to provide the most detailed gland images available (A, B). Atrophy is easily identified (C).

STRUCTURE VERSUS FUNCTION

Diagnosing and treating glaucoma depends on the relationship of structure and function. This determines when a patient is diagnosed with glaucoma and influences treatment for that patient. Understanding this relationship can lead to improvements in glaucoma detection and the management of individual patients.7

We are now learning more about how this structure-function relationship relates to the meibomian glands. Diagnostic testing is available to measure the structure of the meibomian glands through manual evaluation, transillumination of the lid at the slit lamp, meibography, and interferometry (Figure 1).

In early glaucoma, patients are asymptomatic as the nerve fiber layer is dropping out. In dry eye patients the same is true. They can be asymptomatic in the early stages as the meibomian glands are slowly changing, becoming truncated, and eventually atrophying. When is the best time to treat? Should we really be treating only once symptoms begin? In glaucoma management, that concept is long outdated.

DIAGNOSTIC TESTING

When you see a patient you think is at risk for glaucoma for the first time, what is your treatment plan? It is safe to assume you would schedule a return visit to start a battery of diagnostic tests to aid in the diagnosis of glaucoma, and over time you would evaluate the stability of the disease under treatment. For glaucoma suspects, there are known risks associated with glaucoma that guide follow-up examinations.

The same can now be done for the patient with dry eye. Gone are the days of handing an artificial tear supplement to the patient as he or she leaves your office. It is time to embrace the new treatments and diagnostic tests available. Hand the patient an artificial tear that is best suited for the appropriate deficiency, whether aqueous or evaporative, and take the next step: Schedule a return visit to evaluate how it is working.

As part of that follow-up, you can start to lay the foundation from which you will be able to evaluate the effectiveness of your treatments. What are the risk factors for MGD: inadequate blink? That would make every person using a computer or smartphone at risk or a MGD suspect. Should they all be monitored? We need to find the right balance of when to test these patients and the gold standards for diagnosis.

What test will become the equivalent of the visual field for dry eye patients? Meibomian gland evaluation with the Korb Meibomian Gland Evaluator (TearScience) provides standardized pressure to evaluate the function of the meibomian gland with normal blinks.

What will become the dry eye equivalent of structural analysis with a retinal nerve fiber layer analyzer? Meibography, first introduced in 1977 by Tapie, is a method to directly visualize the meibomian gland structure.8 This technology is available with the Keratograph 5M (Oculus). TearScience will have a similar technology available in 2015 with the introduction of LipiView II (Figure 2).

What about overall risk assessment, as with high intraocular pressure, pachymetry, and gonioscopy? There are many diagnostics available, such as tear osmolarity testing (TearLab), MMP-9 inflammatory marker testing (InflammaDry; Rapid Pathogen Screening), and interferometry with LipiView (TearScience) or TearScan (Advanced Tear Diagnostics). All of these tests measure the tear film dynamic and components of the tear to evaluate for tear film dysfunction.

BACK TO BASICS

Relying solely on diagnostic tests, clinicians may either over- or under-diagnose glaucoma; the same is true for dry eye disease with the new diagnostics introduced since 2008.

With all new diagnostic tests there is a learning curve, as glaucoma specialists have encountered in recent decades. These tests can enable us to educate dry eye patients better, but they must be used in conjunction with a good clinical evaluation.

For example, tear osmolarity is a wonderful addition to aid in diagnosis and track improvement in ocular surface health. But much like “red disease” with optical coherence tomography and optic nerve evaluation,9 in which testing falsely influences treatment due to limitations of the normative database, the osmolarity number could influence one to treat an evaporative dry eye patient for aqueous deficiency or vice versa. Hyperosmolar tears can be present in all types of DED.

THE VALUE OF A REGISTRY

Perhaps we need to change our thinking toward outcome-based medicine to better determine which DED treatments are working and to drive innovation in developing new treatments.

The use of clinical registries to track and analyze patient outcomes is a relatively new concept gaining traction throughout medicine. “Right now, eye care providers have no idea how effective their treatments actually are, or how what they are doing compares with what other providers are doing,” said Jim Grue OD. “That is the fundamental concept upon which outcome-based care is built. This affords all practitioners the opportunity to gravitate toward the most effective diagnostic and therapeutic processes to achieve the best patient outcomes. It requires information that providers have never had, but this is exactly what a registry provides.”

In the end, we are all trying to improve quality of life for our patients. Research shows that both glaucoma and dry eye have a negative impact on patients’ quality of life, and both have been correlated with depression.10,11 We have all seen this first hand when we take the time to listen and consider the specific symptoms dry eye patients are experiencing. We must continue to search for answers that will further improve our understanding of DED. It is a real disease with real consequences, and it is not going away. Although some progress has been made recently, it is time that DED received the recognition, research, and collaboration among all types of eye care practitioners that it deserves.

If you have an interest or comment on the ideas in this article or an interest in participating in a DED registry with www.eyecareregistries.com, please contact me via e-mail at the address below. 

Leslie E. O’Dell, OD, is a specialist in the treatment of dry eye disease at The May Eye Care Center & Associates in Hanover, Pennsylvania. She is a consultant to TearScience. Dr. O’Dell may be reached at helpmydryeyes@gmail.com.

1. Mantzioros N. The history of the meaning of the word glaucoma. www.glaucoma.org. Accessed November 5, 2014.

2. Morgan RW, Drance SM. Chronic open-angle glaucoma and ocular hypertension. Br J Ophthalmol. 1975;59(4):211-215.

3. Korb DR, Henriquez AS. J Am Optom Assoc. 1980;51:243-251.

4. Nicolaides N, Kaitaranta JK, Rawdah TN, et al. Meibomian gland studies: comparison of steer and human lipids. Invest Ophthalmol Vis Sci. 1981;20(4):522-536.

5. The definition and classification of dry eye disease: report of the Definition and Classification Subcommittee of the International Dry Eye Workshop (2007). Ocul Surf. 2007;5(2):75-92.

6. Nichols KK, Foulks GN, Bron AJ, et al. The international workshop on meibomian gland dysfunction: executive summary. Invest Ophthalmol Vis Sci. 2011;52(4):1922-1929.

7. Sharma P, Sample PA, Zangwill LM, Schuman JS. Diagnostic tools for glaucoma detection and management. Surv Ophthalmol. 2008;53(suppl1):S17-S32.

8. Tapie R. Etude biomicroscopique des glandes de meibomius. Ann Ocul (Paris). 1977;210:637-48.

9. Chong GT, Lee RK. Glaucoma versus red disease: imaging and glaucoma diagnosis. Curr Opin Ophthalmol. 2012;23(2):79-88.

10. Kong X, Yan M, Sun X, et al. Anxiety and depression are more prevalent in primary angle closure glaucoma than in primary open-angle glaucoma [published online ahead of print November 14, 2013]. J Glaucoma. doi: 10.1097/IJG.0000000000000025.

11. Labbé A, Wang YX, Jie Y, et al. Dry eye disease, dry eye symptoms and depression: the Beijing Eye Study. Br J Ophthalmol. 2013;97(11):1399-1403.

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