Dry eye explanation

[brd888]

Dr Holly,
Your descriptions of dry eye tend to be highly technical. What do you think of the following "dumbed-down" description?

"Dry eye is a group of conditions each characterized by loss of water from the tear film sufficient to increase the amount of salt relative to the amount of water. As a result, the tear film becomes too concentrated, and as it does, its "osmolarity" increases. I think most of us will remember "osmosis" from our high school chemistry class. Well, that's what happens in dry eye--when the tear film becomes more concentrated it pulls water out of the surface of the eye, making it dry. "

Regards,
Bruce

[Redbirdi]

Thanks Bruce! I really hope Dr. Holly makes a comment on this.

I have no idea how to explain "dry eye" in the simplist layman terms either. I would really appreciate a simple yet accurate way of doing such.

Rose

[Frank Holly PhD]

Dr Holly,
Your descriptions of dry eye tend to be highly technical. What do you think of the following "dumbed-down" description?

"Dry eye is a group of conditions each characterized by loss of water from the tear film sufficient to increase the amount of salt relative to the amount of water. As a result, the tear film becomes too concentrated, and as it does, its "osmolarity" increases. I think most of us will remember "osmosis" from our high school chemistry class. Well, that's what happens in dry eye--when the tear film becomes more concentrated it pulls water out of the surface of the eye, making it dry. "

Regards,
Bruce

Hello, Bruce:

Your explanation is based on the hypothesis of Dr. Gilbard who assumes that an increase in tear film osmolality causes the dry eye symptoms. What I am teaching is that ocular dewetting is the basic cause of the majority of the dry eye case and osmotic processes have little to do with it.

I hope you agree with me that whatever one remembers from science taught in high school cannot be a decisive factor in creating an explanation for dry eyes.

When you write: "when the tear film becomes more concentrated it pulls water out of the surface of the eye, making it dry " you are creating a paradox. When the tear film pulls water out of the eye surface it becomes more dilute, right? How can that make the underlying surface drier?

Please read my posts on the fallacies and verities in tear film physiology. I think two of them are dealing with this very fallacy!