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Dry eye disease (DED) affects nearly Americans. This multifactorial condition, characterized by rapid tear evaporation or decreased tear production, can cause symptoms from eye irritation and pain to visual problems.

"In my practice, most patients with DED have contributing meibomian gland dysfunction [MGD]," Selena Friesen, OD, a board member of Fighting Blindness Canada and optometrist in Winnipeg, Manitoba, told 乌鸦传媒, noting that the rate is approximately 86%.

This specialized sebaceous gland in the superior and inferior tarsal plates of the eyelids secretes a lipid known as meibum as the eye blinks, which evenly spreads across the ocular surface, explained a review paper in the .

"A large proportion of patients who have symptoms such as dryness, burning, aching, and visual fluctuations have some degree of MGD and tear film instability, called evaporative dry eye, because the tears are unstable -- as opposed to a less common problem, aqueous tear deficiency, where there is a deficit in tear production," Anat Galor, MD, professor of ophthalmology at the University of Miami and a spokesperson for the American Academy of Ophthalmology, told 乌鸦传媒. However, the two can occur concomitantly, and MGD can even be entirely asymptomatic, she noted.

Diagnosis

Common exams for MGD include tear break-up time, phenol red thread test for tear production, and meibography, which is imaging of the glands by inverting the upper and lower eyelids, noted Sudhir Verma, a PhD student at the University of Houston College of Optometry, in an interview. "Meibography will give you the best visualization of the glands and can determine if there is gland dropout, atrophy, or even distortion of glands."

Galor added: "We also look at plugging of the glands, and/or inflammation of the eyelid margin. It's also helpful to squeeze the eyelid to express the glands and evaluate the consistency of the meibum. We want to see motor oil; if the meibum is granular or has a toothpaste-like consistency, that is suggestive of MGD."

Foam on the eyelid is suggestive of an unhealthy oil component to tears or an unstable tear film, she pointed out.

Friesen said the number one cause of MGD in her practice is blepharitis. "We naturally have bacteria living on our lashes and lids; but if their numbers increase, the result is inflammation and misfunctioning meibomian glands."

Computer screen usage is also a well-known cause of dry eye. The blinking rate is reduced while using screens, leading to stagnant oils and tear evaporation, she noted. "Another cause of gland loss that seems to surprise my patients is eye rubbing. I recently identified a 12-year-old old boy on my meibographer with total drop out and loss of a meibomian gland on his lower eyelid from eye rubbing."

Contact lens use is also common with meibomian gland dropout, Galor noted. "And the data suggest that it is due to the contact lenses, not just an association," she said. "Many conditions that cause inflammation of periocular skin, such as uncontrolled rosacea, seborrheic dermatitis, and allergies, are also under the MGD umbrella. You're never going to get the eyes under control if you don't treat the periocular skin."

Friesen pointed out that many common medications, including birth control pills, isotretinoin (Accutane), antidepressants, antihistamines, and blood pressure medications alter the quality of the meibum or reduce the vitality of the glands.

She cautioned that eyelash growth serums and anti-aging serums damage the meibomian glands: "Latisse, a common eyelash growth serum, is 0.03% bimatoprost. This prostaglandin analog is used in a higher concentration to treat glaucoma. We counsel our patients of the possibility of obstructive meibomian gland disease before starting , but patients exposed through over-the-counter products are normally not aware of the many side effects."

Retinol, retinoids, and retinyl palmitate in anti-aging serums also destroy meibomian glands. These products include instructions to avoid applying to the eyelids, but the product can migrate to the lid area while sleeping, Friesen cautioned.

Non-preserved artificial tears are the usual initial treatment for mild MGD. Other measures include application of hot, dry heat for 10 minutes, said Friesen. "Older studies were promoting 45°C [113°F], but more recent studies are stating 40°C [104°F] is the ideal temperature to melt the hardened oils (meibum)."

Achieving therapeutic levels of omega-3 fatty acids also helps, she added, but it is very difficult to do this by diet alone. Friesen said it's important to know the mg of eicosapentaenoic acid and docosahexaenoic acid as well.

In and cleaning solutions for the eyelid, topical or oral antibiotics such as doxycycline or azithromycin are commonly used, Galor said, noting that data suggest that symptoms and MGD parameters improve with antibiotic use.

"The teaching is that the effect of antibiotics is due to an improvement in meibum composition and decreased inflammation," said Galor. "But it may be partly that the antibiotic is changing the ocular surface bacteria and that this secondarily changes the meibum."

For moderate to severe MGD, Friesen noted that intense pulsed light (IPL) therapy -- a dermatological treatment for vascular lesions, acne, and rosacea -- uses thermal energy to coagulate blood vessels: "IPL likely improves DED signs and symptoms by inhibiting inflammatory mediators at the eyelid margin vessels and in the tear film."

Athermal low-level light therapy can be used in addition to IPL for added benefit, she pointed out. "Photobiomodulation of the meibomian glands triggers endogenous heating of both eyelids by activating the cellular production of adenosine triphosphate." Meibomian glands can then be expressed after treatment, she added.

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