Meibomian Gland Dysfunction: All You Need to Know
By Eric Papas, PhD, MCOptom, DipCL, FAAO
For most clinicians and many researchers, sorting through the available literature to glean key information on a condition of interest presents an unappealing prospect and at best is a major chore. Even when an individual has the time, skills, and resources to conduct a meaningful search, it is not easy to be confident that the discovered details are up-to-date, relevant, comprehensive, and reflect the state of current thinking in that particular field. With that background, if a large group of international experts was ready to perform this daunting task for us, it's a fair bet that most of us would happily accept.
Accordingly, the news that one such group endeavor has recently been completed should be very welcome, particularly when the subject is meibomian gland dysfunction (MGD), a condition that has great importance for many practitioners and patients due to its association with symptoms of ocular dryness and discomfort.
Undertaking the Workshop
The International Workshop on Meibomian Gland Dysfunction began to take shape in late 2008 when, under the auspices of the Tear Film and Ocular Surface Society, an initial steering committee met. During this first meeting, the committee laid out the terms of reference for the activities to come and identified a set of key individuals who would carry out the work. These people, who were all experts on an international scale in various aspects of the field, were invited to join a series of subcommittees, each under a chairperson, which divided the task into the following seven areas for in-depth study:
• Definition and Classification of MGD, Anatomy
• Physiology and Pathophysiology of the Meibomian Gland
• Tear Film Lipids and LipidProtein
• Epidemiology of, and Associated Risk Factors for, MGD
• Evaluation, Diagnosis and Grading of Severity of MGD
• Management and Therapy of MGD
• Design and Conduct of Clinical Trials
Within each of these groups, the objective was to assemble an overview of the existing knowledge, current at that point in time, and present it in a form that would be accessible to clinicians, researchers, educators, and other concerned groups. In total these authoritative teams involved more than 50 individual members from 12 countries.
As an adjunct to this, an Industry Liaison Committee was also formed to facilitate communication and consultation with appropriate and interested industrial organizations.
Over the next several months, the expert subcommittees met face-to-face as well as by telephone and Skype to hammer out the contents of their reports. While it was obviously anticipated that a comprehensive and thorough literature review would form the basis of this activity, there was also an expectation and indeed the hope that the assembled experts would engage in energetic discussion, argument, and disagreement while working toward, and ultimately achieving, a consensus view.
By May 2009, each subcommittee had produced a draft report, and these were tabled and reviewed at a meeting of the entire Workshop group held just after the Association for Research in Vision and Ophthalmology (ARVO) annual meeting in Florida. All Workshop members were subsequently given the opportunity to review and comment on not only their own section, but also on the work of the other subcommittees before the “final” drafts were submitted to a Writing Committee in April 2010. This group had the task of identifying areas of duplication or those that needed to be balanced among sections before returning the reports for one last reading and approval by the various subcommittees.
The culmination of this gargantuan activity was the publication of the full report in a special issue of the journal Investigative Ophthalmology and Vision Science (Asbell et al, 2011; Geerling et al, 2011; Green-Church et al, 2011; Knop et al, 2011; Nelson et al, 2011; Nichols, 2011; Nichols et al, 2011; Schaumberg et al, 2011; Tomlinson et al, 2011) in May. Pending the release of the IOVS issue, the report findings began to be disseminated in the form of presentations given at several conferences around the world. These included the American Academy of Optometry, British Contact Lens Association, Asia Pacific Academy of Ophthalmology Congress, and ARVO, among others. At each of these meetings, members of the Workshop delivered a series of short lectures covering each of the subcommittee reports and answered questions from the assembled delegates.
MGD and Contact Lenses
While the entire report document will be of interest to many in the ophthalmic community, Contact Lens Spectrum readers may be particularly drawn to the pages dealing with epidemiology and associated risk factors (Schaumberg et al, 2011). Given the similarly increased frequency of dry eye disease among the elderly, it probably comes as no great surprise to discover that aging is one of the major factors associated with MGD.
Perhaps more unexpected is the evidence for ethnic variation, with studies conducted in Asian countries such as Japan, China, and Thailand reporting markedly higher rates of MGD compared to studies done in predominantly Caucasian populations. Thus, MGD prevalence in these countries exceeds 60 percent among those over 40 years of age.
Turning to contact lenses, despite the view held by many practitioners that lens wear is associated with a heightening of MGD problems, it turns out that there have been rather few studies in this area. While those that do exist generally indicate a small excess frequency of MGD among contact lens wearers, the size of this bias is quite small. On average, only about 6 percent more contact lens wearers have MGD than do non-wearers, which is not of statistical significance. Nevertheless, one particular measure of meibomian gland disease, namely gland dropout, does seem to be quite markedly affected by the presence of contact lenses and, intriguingly, it doesn't matter whether the lenses are made from rigid or soft materials. Longer exposure to either type is associated with greater degrees of observed dropout in both the upper and lower eyelids.
Given a result like this, it might be expected that there would be plenty of symptomatic complaints among those lens wearers who do have clear signs of meibomian gland dropout, but this does not seem to be the case. One way to interpret this apparent contradiction is that there is considerable redundancy in meibomian gland function, meaning that only a relatively small number of active glands are required to provide a normal tear film and to prevent the onset of symptoms. For those individuals who do suffer from discomfort and dryness related to MGD, actively treating the condition with lid scrubs and massage does appear to provide some benefit.
The suspicion of a link between MGD and contact lens-induced papillary conjunctivitis (CLPC) remains unproven based on available evidence. While there are studies that report high levels of association between these conditions, others are much less supportive. While admittedly somewhat frustrating, this equivocation demonstrates one of the strengths of the Workshop proceedings in that the participants have clearly defined those areas in which information is either lacking or is of a contradictory or unconvincing nature. Researchers are thus in a good position to use this report as a lens to focus their efforts in relevant and useful directions. CLS
For references, please visit www.clspectrum.com/references.asp and click on document #188.
Associate Professor Papas is executive director of Research & Development and director of Post Graduate Studies, Brien Holden Vision Institute and Vision Cooperative Research Centre, and senior visiting fellow, School of Optometry & Vision Science, University of New South Wales, Sydney, Australia. He has received research funds from Ciba Vision, Alcon, AMO, and Allergan. You can reach him at firstname.lastname@example.org.