Meibomian Gland Dysfunction

Meibomian gland dysfunction (MGD) is a chronic, diffuse abnormality of the meibomian glands, usually obstruction of the terminal ducts and altered meibum quality, that leads to tear film instability, ocular surface inflammation, and evaporative dry eye. It is the commonest cause of evaporative dry eye and the leading cause of dry eye worldwide.

• There are about 25 meibomian glands in the upper lid and 20 in the lower lid, and they secrete the lipid layer that slows tear evaporation. In MGD the secretion is thickened, turbid, or toothpaste like, and over time glands drop out and atrophy.
• Mechanisms: hyperkeratinisation of the duct epithelium, raised meibum melting point, bacterial lipases and lid margin bacteria altering lipid composition, inflammation, and age or androgen related change.
• Types: low delivery (hyposecretory, with atrophy or obstruction) and high delivery (hypersecretory, seborrhoeic, with foamy tears), plus mixed forms.
• Risk factors: age, male sex, Asian ethnicity, rosacea, seborrhoeic dermatitis, atopy, contact lens wear, long screen use, isotretinoin, menopause and anti-androgen therapy, chronic blepharitis, and Demodex infestation.

• Burning, grittiness, foreign body sensation, fluctuating vision that clears with blinking, redness of the lid margins, and symptoms worst in the morning and with screens or air conditioning.
• Lid signs: capped or plugged gland orifices, pouting orifices, telangiectatic vessels crossing the lid margin, lid margin thickening and irregularity, lash debris, and recurrent chalazia.
• Expression of the gland produces thick, opaque, or toothpaste like secretion, or no secretion; foam at the lid margin or in the tear meniscus.
• Corneal staining inferiorly, reduced tear break up time, and in advanced disease dropout of glands on meibography, corneal vascularisation, and recurrent marginal keratitis.
• Associated rosacea features: facial flushing, papules, and telangiectasia.

• Diagnosis is clinical, supported by symptom scores and lid assessment.
• Tests: meibum quality and expressibility grading with moderate digital pressure over 5 glands of the central lower lid; tear break up time (below 10 seconds is abnormal); fluorescein and lissamine green staining; lid margin evaluation under magnification; meibography (infrared imaging showing gland loss and shortening); lipid layer interferometry; tear osmolarity (above 308 mOsm/L suggests hyperosmolar disease).
• Examine for Demodex (collarettes at the lash base, lash epilation microscopy with more than 3 mites per lash), bacterial blepharitis, and rosacea.
• Differential diagnosis: aqueous deficient dry eye, allergic conjunctivitis, chronic anterior blepharitis, sebaceous gland carcinoma (unilateral, recurrent chalazion, lash loss), and ocular cicatricial pemphigoid.

• Stepwise treatment, with chronic maintenance because MGD is not curable:
  • Education, avoidance of aggravating factors, screen breaks, and increased blinking.
  • Warm compresses at 40 to 45 degrees Celsius for 10 minutes once or twice daily, followed by firm lid massage toward the lid margin, and lid margin cleansing (hypochlorous acid 0.01 to 0.02 percent spray or wipes, or dilute baby shampoo).
  • Preservative free artificial tears, preferably lipid containing formulations, four to six times daily; perfluorohexyloctane drops one drop four times daily for evaporative disease.
  • Oral omega-3 fatty acids (eicosapentaenoic and docosahexaenoic acids, 1 to 2 g daily), though the benefit is modest.
• Anti-inflammatory and antimicrobial therapy for moderate or inflammatory disease:
  • Oral doxycycline 100 mg daily for 4 to 12 weeks, or 40 mg modified release daily for 12 weeks, taken with food and a full glass of water (avoid in pregnancy, breastfeeding, and children under 8 years); oral azithromycin 500 mg daily for 3 days repeated monthly for 3 cycles, or erythromycin 250 mg twice daily, as alternatives.
  • Topical azithromycin 1.5 percent drops twice daily for 2 days then once daily for 12 days, or azithromycin 1 percent ointment to the lid margins at night for 2 to 4 weeks.
  • Short courses of topical corticosteroid (loteprednol 0.5 percent or fluorometholone 0.1 percent twice daily for 1 to 2 weeks) for flares; topical ciclosporin 0.05 percent twice daily for 3 to 6 months or longer.
• Procedures for obstructive disease: thermal pulsation (about 12 minutes of heating at about 42.5 degrees Celsius to the inner lids with compression), intense pulsed light (3 to 4 sessions at 3 to 4 week intervals, particularly with rosacea and telangiectasia), manual expression, and intraductal probing for refractory cases.
• Treat associated conditions: rosacea (oral doxycycline, topical metronidazole 0.75 percent or ivermectin 1 percent to the face), Demodex blepharitis (lotilaner 0.25 percent drops twice daily for 6 weeks, or tea tree oil lid scrubs), and chalazia.
• Follow up every 4 to 8 weeks initially and then every 3 to 6 months; step up therapy if symptoms or signs persist.
• Complications: chronic dry eye, recurrent chalazia, corneal vascularisation and scarring, and contact lens intolerance.