Which statement best describes Meibomian gland dysfunction's role in evaporative dry eye?

• A. Aqueous tear deficiency is the major evaporative dry eye cause
• B. Meibomian gland dysfunction is the major evaporative dry eye cause
• C. Nocturnal lagophthalmos is the major evaporative dry eye cause
• D. Parkinson's disease is the major evaporative dry eye cause

Answer: (B)

Meibomian gland dysfunction is the main driver of evaporative dry eye because it disrupts the lipid layer that shields the tear film from rapid evaporation. The outer lipid layer, produced by the Meibomian glands, slows tear loss and helps stabilize the tear film. When glands are dysfunctional, lipid quality or quantity declines, the tear film becomes unstable and evaporates more quickly, leading to the classic signs of evaporative dry eye such as burning, irritation, and rapid tear breakup. Aqueous tear deficiency, by contrast, reduces the overall tear volume rather than the rate of evaporation, so it’s not the primary cause of evaporative dry eye. Nocturnal lagophthalmos can worsen evaporation through exposure, but it’s not the leading cause in most cases. Parkinson's disease is not a primary driver of evaporative dry eye.