The reason why you should ditch the AC and put on MCG...

[Milo007]

A useful study that shows the effect of a dessicating environment on tear film parameters.

Perhaps this confirms why dry eye patients must use moisture chamber glasses (MCG) to arrest further damage and provide an ideal environment for the glands to heal.

This also votes against living or working in air conditioned spaces. Also explains why there is increasing prevalence of dry eyes - Not only digital screens are to be blamed but most people spend a lot of time in air conditioned spaces.

[hopeful_hiker]

Absolutely. Pretty sure low humidity was one of the kickstarters to my dry eye. Even 40% humidity is low for me. I would say 50% is needed for me at a minimum indoors. Somehow I did not feel as bad in a desert-like grasslands (about 25-30%) as I do at my AC’d office (even if I am not on the computer).

I am curious about tear production. They mention that tear production also changed but don’t specify how in the article preview. I assume it declined? Although it could increase to compensate for evaporation?

[Milo007]

Absolutely. Pretty sure low humidity was one of the kickstarters to my dry eye. Even 40% humidity is low for me. I would say 50% is needed for me at a minimum indoors. Somehow I did not feel as bad in a desert-like grasslands (about 25-30%) as I do at my AC’d office (even if I am not on the computer).

I am curious about tear production. They mention that tear production also changed but don’t specify how in the article preview. I assume it declined? Although it could increase to compensate for evaporation?

Yes hopeful_hiker. I am having a hard time in winter and the humidity here has dropped to below 30%. Usually the humidity remains at >80% here year round.

Regarding AC I can't tolerate air conditioning since it dries up my eyes really quickly and after about an hour I feel as if my eyes are not producing enough lipids or tears. Maybe inflammation worsen the parameters like tear production, LLT TBUT etc by affecting the glands after some exposure to low humidity air conditioned spaces.

They are talking about a decrease in tear production I am sure because they say after eyes are exposed to a dessicating environment for sometime the tear parameters mimicked that of a dry eye patient. And that indicates they have made the study on patients having normally functioning glands. Imagine if someone with normally functioning glands develop signs of a typical dry eye patient after few hours of exposure to a low humidity environment what effect would such an environment have on existing dry eye patients whose glands are already compromised to some degree!

If a few hours of exposure to a low humidity environment can develop signs of dry eyes in normally functioning eyes then it's not hard to imagine the effect on them on a long term basis (a few years or maybe even months).

[Milo007]

Somehow I did not feel as bad in a desert-like grasslands (about 25-30%) as I do at my AC’d office (even if I am not on the computer).

Temperature of the tear film is also a factor. Since I am a science graduate I can tell you the rate of evaporation is influenced mainly by two factors :

1. The relative humidity of the ambient air i.e., the vapor pressure or partial pressure of water vapor in the surrounding air.

2. The temperature of the tear film as the evaporating medium. More precisely the saturation pressure of the aqueous component of tear at the temperature of the tear film.

The larger the difference is between the two the greater will be the rate of evaporation.

Now it's upto how the body varies the temperature of the ocular surface and hence the tear film in cold, warm or hot ambient conditions. It might be so that when the climate is low in temperature the body tries to warm it up more and the tear film temperature (the ocular surface temperature) increases slightly which will enhance the rate of evaporation as explained above.

[Milo007]

Although it could increase to compensate for evaporation?

Yes it would increase the production of the aqueous component of tears initially (reflex tearing) but thinking on a long term basis it would result in a decrease in the production of the aqueous component of tears.

This is because of two things :

1. The constant dessication stress would result in inflammation and the inflammatory mediators generated on the ocular surface would cause inflammation of the lacrimal glands. Inflammation of the lacrimal gland will eventually decrease its functionality and result in permanent damage as scarring on a long term basis.

2. An overdrive of the lacrimal glands to compensate for tear volume loss at the ocular surface would make the lacrimal glands fatigued over time and it will move on to a period of quiescence (resting) often when the production of the aqueous component of tear will subside resulting in more inflammation and cascade of events again affecting the lacrimal glands adversely (also the meibomian glands).