Like some other fats, meibum becomes hard when it becomes cold. When meibum hardens it loses it’s fluidity. As a result the tear film stiffens, creating gaps in the oily layer of the tear film that lead to evaporative dry eye.
Forced air and heat needed in cold climates lowers humidity causing dry air, which is destabilizing to tear film.
Meibomian lipid films and the impact of temperature
Butovich IA, Arciniega JC, Wojtowicz JC
Investigative Ophthalmology & Visual Science
2010 Nov;51(11):5508-18. doi: 10.1167/iovs.10-5419. Epub 2010 Jul 7.
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