Which of the following is the LEAST likely etiology of Evaporative Dry Eye?

• A. MGD
• B. Sjogren's syndrome
• C. Nocturnal lagophthalmos
• D. Parkinson's disease

Answer: (B)

Evaporative dry eye happens when the tear film evaporates too quickly, usually because the lipid layer is deficient or the eye is exposed. Meibomian gland dysfunction reduces the lipid layer, so tears evaporate faster. When eyelids don’t fully close at night, as in nocturnal lagophthalmos, the exposed surface loses tears to evaporation. Parkinson’s disease can slow blinking or cause incomplete blinking, disrupting tear film distribution and increasing evaporation risk.

Sjogren’s syndrome, on the other hand, mainly causes dry eye by destroying the lacrimal glands and reducing tear production (aqueous deficiency). While some patients can have mixed features, the dominant mechanism is decreased tear volume rather than increased evaporation, making Sjogren’s syndrome the least likely cause among the options.