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Methods using a combination of non-invasive thermal treatments and meibomian gland expression seem to be particularly effective.
The existence of the meibomian glands (MGs) has been recognised since the time of Galen, in the 2nd century CE.1 They are named after Prof. Heinrich Meibom (1639-1700), who was the first to dissect and describe them. However, their obstructive pathology was first defined only in 1977, by McCulley and Sciallis,2 and named meibomian gland dysfunction (MGD) by Korb and Henriquez in 1980.3
By the late 1990s and early 2000s, the importance of lipids produced by the MGs for the tear film homeostasis was fully appreciated, as was the role played by MGD in the pathogenesis of dry eye disease (DED).4
MGD includes an array of MG disorders, ranging from congenital to acquired. The common denominator for these disorders is the change in tear film composition that results in ocular discomfort, visual disruption and evaporative dry eye. Congenital factors; ageing; hormonal imbalance; diet; medications; contact lens wear; trauma; inflammation; and even the ocular surface’s microbiome have been implicated in the aetiology of MGD.
In MGD, due to reasons not fully known, meibum (the lipid-rich secretion that the MGs add to the tear film) exhibits a higher phase-transition temperature than normal.5 In addition, in MGD, meibum lipids become more saturated and contain less-branched chain hydrocarbons and more protein, therefore becoming more viscous. Thus, the delivery of meibum to the lid margin is impeded.6
Historically, therapies for MGD have consisted mainly of mechanical application of heat, lid hygiene and massage of the eyelid.7 All of these methods are intended to facilitate the secretion of lipid products at the ocular surface by unclogging gland orifices and “softening” the meibum.8
In addition, lipid-based artificial tears and meibomian gland expression (MGX) have been advocated as efficient. Nevertheless, because many of these methods are time-consuming and can be uncomfortable,9 they are impeded by low patient adherence and have limited effectiveness, especially in more advanced stages of the disease.
When bacterial colonisation is present, oral agents of the tetracycline family (tetracycline, doxycycline and minocycline) have also been found to improve the clinical picture in MGD. However, these therapies need to be given over long periods (usually months) and, therefore, in addition to low patient adherence, they can often be contraindicated for some patients or, if indicated, can lead to adverse effects that limit their success.10
In 2010, a method was proposed for inserting stainless steel probes, up to 6 mm in size, directly into the meibomian gland orifices, with immediate relief in lid tenderness following treatment and improvements lasting 4 weeks.11
The discovery that a therapeutic temperature level of 41°C applied at the tarsal conjunctiva is critical for the effective liquefaction and clearance of meibum obstructions has prompted more efforts to optimise methods to deliver targeted, controlled, noninvasive thermal treatments at this level. In 2005, intense pulse light (IPL) therapy was proposed as an efficient method of treating MGD in patients with DED, due to its thermal effect that facilitates meibomian gland secretion by softening meibum.12
In 2017, a report from the Tear Film and Ocular Surface Society’s Dry Eye Workshop II proposed IPL/MGX as a method to be used in MGD treatment.13 Nevertheless, many cases are refractory to this type of treatment and there are no clinical guidelines for using IPL/MGX in MGD, although it has been proposed that this method could be more efficient in early stages of the disease.9
There are many other devices on the market designed for delivering therapeutic levels of heat and pressure to the eyelids to melt altered meibum and to clear meibomian gland obstruction. These are summarised in the Table.14
Among the methods listed in the Table, the TearCare system, the most recent such device to enter the market, includes a blink-assisted device that applies heat to the eyelids in patients suffering from MGD, DED and/or blepharitis. The TearCare software and sensor technology enable tight control as well as the maintenance of a maximised external eyelid temperature of up to 45°C for 15 minutes.16 Because the device allows patients to blink during the procedure, it is comfortable to wear.
SmartLids, which is the TearCare system’s eyelid-worn, open-eye, blink-assisted technology (see Figure), is designed to offer conformance and adherence across the entire geography of eyelids and to deliver targeted thermal energy to the underlying MGs. It also allows complete removal of liquefied meibum with a tailored gland-by-gland approach under optimal visualisation.
A recently published, 1-month follow-up study demonstrated that a single TearCare treatment resulted in statistically and clinically significant improvements of all signs of DED in patients with MGD. This result was equivalent in its safety and effectiveness profile to the LipiFlow treatment.16 Moreover, this study showed that TearCare offered significantly better symptomatic relief compared with LipiFlow, as measured by the proportion of subjects achieving Ocular Surface Disease Index improvement by at least one severity category, and as reflected in the reduced need for use of lubricating drops.
In the attempt to control MGD, many treatments have been tried with various success rates. Methods using a combination of non-invasive thermal treatments and MGX, such as TearCare, seem to have gained particular advantages.