MGD is very common in oily skin and older individuals and is the main cause of hyper-evaporative dry eye. It can be broadly classified into obstructive and non-obstructive types. Etiology】 Recent studies have shown that in the early stages of MGD, the lipid composition of the secreted lid glands is abnormal, manifested by an increase in free fatty acids, which form foam that affects the stability of the tear film, a decrease in wax esters, and an increase in cholesterol esters, which increase viscosity and obstruct the ducts, thus providing the necessary substrate for bacterial colonization. Some studies have found that cholesteryl esterase and fatty wax esterase from Staphylococcus epidermidis can break down lid gland lipids, forming metabolites that irritate the eyelid margin and exacerbate ocular discomfort in MGD patients.MGD patients often suffer from tear deficiency, leading to tear film instability, accelerated tear film evaporation rates, and increased tear osmolarity. In addition, risk factors leading to MGD include lupus erythematosus, rosacea, etc. Clinical manifestations】 Most commonly seen in the elderly, but there is no significant gender difference, colder zones and the incidence is higher than in warmer climates, symptoms are non-specific including eye redness, burning sensation in the eye, foreign body sensation, dryness, irritation, itching, visual fatigue, fluctuating vision, and tearing. The lid margin is often thickened and may be accompanied by signs of erythema and hyperkeratosis, permanent vasodilation from posterior to anterior in the posterior layer of the lid margin, bulging and distorted lid gland openings with white keratin blockage, and foamy, granular, or toothpaste-like secretions when squeezed. The lesion progresses with a yellow mucus-like discharge from the lid gland, and after years of lid inflammation, there is extensive atrophy of the lid gland. Other common accompanying signs include chalazion, conjunctival calculi, conjunctival congestion, papillary hyperplasia, punctate staining of the cornea, and in severe cases, corneal vascular opacification and corneal ulceration with ectropion. In cases of unilateral recalcitrant lid gland dysfunction with persistent inflammation in the same area of the eyelid margin and surrounding anatomic abnormalities (e.g., loss or distortion of eyelash follicles), adipocytic carcinoma should be considered. There are no uniform diagnostic criteria. MGD can be diagnosed based on (1) absence of the lid gland (2) abnormalities of the lid margin and lid gland opening (3) changes in the quantity and quality of lid gland secretions, and any of the above signs combined with symptoms. Treatment] 1. Physical cleaning of the eyelid: Pay attention to eyelid hygiene. If the lid gland is blocked, apply a hot compress to the eyelid for 5-10 minutes to soften the lid gland secretions, then place a finger on the skin surface of the eyelid relative to the lid gland, rotating it while pushing toward the lid margin to expel the secretions. A non-irritating shampoo or special solution such as boric acid solution can be used to clean the local eyelid margin and eyelashes. Early morning cleaning of the eyelids is more effective due to the accumulation of scales at night. 2. Oral antibiotics: Doxycycline 50mg orally, 2 times/day. It needs to be taken continuously for several weeks to take effect and it needs to be maintained for several months. Common side effects are sensitivity to light and causing enamel abnormalities, so use with caution in children under 8 years of age, pregnant and lactating women. 3. Application of topical medications: These include antibiotic eye drops for blepharitis, short-term glucocorticoid eye drops, and preservative-free artificial tears. Topical 1% metronidazole cream or 1% clindamycin lotion is effective in controlling the infection of the facial skin of rosacea. In patients with seborrheic dermatitis, shampoos containing antiseborrheic agents such as selenium disulfide or tar may be used to cleanse the skin of the head. In recent years, we have started to try topical androgen therapy for MGD. 3% testosterone grease strips 10mm long and 2mm wide are placed in the upper and lower conjunctival vault 3 times/day, and the symptoms, tear film lipid layer thickness, and tear film rupture time improve significantly after 2-3 months, but the long-term efficacy remains to be further observed.