dry eye dx and tx

Nonobvious MGD—an Enigma No More

BY DONALD R. KORB, OD, & CAROLINE A. BLACKIE, OD, PHD

Meibomian gland dysfunction (MGD) has traditionally been considered an infectious disorder with obvious signs of inflammation, hypersecretion, and purulent excreta. However, it is now understood that obstructive—rather than infectious—MGD is the most common form and that obstructive MGD is the most common cause of evaporative dry eye (Lemp et al, 2007). This paradigm shift is exemplified by the Tear Film and Ocular Surface Society's (TFOS) statement that "Meibomian gland dysfunction may be the leading cause of dry eye syndrome throughout the world," (TFOS newsletter, 2010) and by the initiation of an International Workshop and evidence-based 2010 report on MGD.

There Often are Few Signs

Our research, building on a key finding from 30 years ago (Korb and Henriquez, 1980) establishes that the majority of obstructive MGD cases are non-obvious. Nonobvious obstructive MGD (NOMGD) is a hyposecretory disorder in which lid inflammation and other signs of pathology are minimal or absent altogether (Blackie et al, 2010). This is in contrast to the traditional concept of MGD as a hypersecretory disorder with obvious signs of infection and inflammation. If there are no obvious lid or meibomian gland (MG) orifice changes, or even when lid changes such as mild serration of the lid margins or mild lid margin inflammation occur, obstruction might not be expected with no co-existing significant MG orifice changes and surrounding inflammation. Diagnostic expression of the gland is therefore vital for diagnosis.

Diagnosis May Prevent Dry Eye

We developed an instrument for standardized MG diagnostic expression that applies a force approximating that of a deliberate blink to determine individual MG functionality and whether an adequate number of glands are functional to maintain ocular surface integrity (Korb and Blackie, 2008). Forceful expression helps determine whether individual glands have the potential to be functional.

Because NOMGD is likely the precursor to obvious obstructive MGD, diagnostic meibomian gland expression for diagnosis of NOMGD in routine eye exams is necessary to diagnose and treat dry eye and also to offer early intervention for prevention. The ever-increasing use of computers appears to result in NOMGD at a young age, making the diagnosis and treatment of obstructive dysfunction in its early nonobvious stages critically important for decreasing the prevalence and severity of dry eye in later years.

Because NOMGD occurs in the absence of obvious hallmark signs of inflammation and infection, the recent use of the term "posterior blepharitis" as a synonym for MGD is inappropriate. Hopefully their use as synonyms will disappear from the contemporary vernacular and literature.

Recognizing that NOMGD is a significant factor across the entire spectrum of dry eye will accelerate research in the diagnosis, treatment, and prevention of all forms of obstructive MGD. We predict that evaluating for NOMGD with diagnostic expression will become as commonplace as the basic diagnostic tear film stability and ocular staining tests are in the clinical evaluation of dry eye. Recognizing NOMGD's importance is a key step for both clinical practice and research to enhance the diagnosis, management, and, ultimately, the prevention of dry eye disease. CLS

For references, please visit www.clspectrum.com/references.asp and click on document #175.

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Dr. Korb is co-founder and chief technical officer at TearScience and co-founder and director of research of Korb Associates. He holds more than 30 U.S. patents and is in private practice. Dr. Blackie is a charter member of the Ocular Surface Society of Optometry (OSSO). She is a clinical research scientist for TearScience as well as for Korb Associates.