Examining Meibomian Gland Structure and Function in Patients With Demodex Blepharitis
Findings from a retrospective analysis highlight the association between Demodex blepharitis and meibomian gland structure and function.
Cecelia Koetting, OD, FAAO, DipABO and Elizabeth Yeu, MD
Cataract and Refractive Surgery Today 
Meibomian gland disease (MGD) is defined as dysfunction of meibomian glands (e.g. obstruction, atrophy, or poor-quality meibum) that leads to tear film disruption, visual disturbance, and ocular discomfort.1 Inflammation from Demodex mites may cause serious consequences, like Demodex blepharitis and MGD. When discussing MGD, it’s important to include consideration of concurrent Demodex blepharitis. According to a study published in 2022, 58% of US patients (n = 595/1032) who visited an eye care clinic and underwent a slit-lamp examination, regardless of chief complaint, had Demodex blepharitis, including consultations for cataract or refractive surgery.2 A retrospective study by Cheng et al reported a positive rate of Demodex infestation in MGD patients (89%; n = 103 eyes of 52 patients) compared to control (43%; n = 62 eyes of 31 non-MGD patients).3 In a separate single-center study, Bhandari et al concluded that the incidence of Demodex infestation was 60% for patients with MGD (n = 60) and 18% for control (n = 50).4 Finally, Lim Bon Siong et al reported that the overall incidence of Demodex blepharitis was 85% for MGD patients (n = 65) and 34% for control patients (n = 50).5 Although Demodex blepharitis may be asymptomatic in a small proportion of patients (≤1% in one prospective observational study of 515 patients; n = 4), most patients (98.3%) reported two or more symptoms.6 Symptoms can stem from Demodex mites triggering inflammation leading to swollen eyelid margins, reduced gland openings, and compromised meibum flow.7,8 Additionally, Demodex infestation may be an important contributor to inflammatory MGD and can lead to structural and functional changes in the meibomian glands.8 Symptoms from Demodex blepharitis and MGD can impact tear film stability and ocular surface integrity, and may also lead to altered biometry and abnormal corneal topography measurements, which can potentially affect cataract or refractive surgery planning and increase the risk of postoperative dissatisfaction.9-12 Therefore, evaluation for Demodex blepharitis should be considered when managing MGD, particularly in patients undergoing such procedures. Study Rationale and Design In early 2025, we published a study in the Journal of Cataract and Refractive Surgery to answer one primary question: How do structural and functional measures of MGD compare in eyes with moderate-to-severe Demodex blepharitis (collarette grades 2–4) versus those with collarette grade 0? For this retrospective, single-center, observational study, we examined case records of 438 patients ≥18 years with available data for collarettes and MGD signs (e.g., telangiectasia, meibum expressibility, meibum quality, meibography).8 Collarettes were graded per eyelid on a 0 to 4 scale: Grade 0: 0 to 2 lashes/eyelid with collarettes. Grade 1: 3 to 10 lashes/eyelid with collarettes. Grade 2: >10 to <1/3 (~50) lashes/eyelid with collarettes. Grade 3: ≥1/3 to <2/3 (~100) lashes/eyelid with collarettes. Grade 4: ≥2/3 (~150) lashes/eyelid with collarettes.
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