Could Different Drops Counteract Each Other?

[Randal]

Dr. G:

I noticed in another thread ("Medicamentosa") that you mentioned, "TheraTears are hypotonic," and, "An artificial tear with a high oncotic pressure would behave as if it were hypertonic." I use Dakrina as a wetting drop for my contacts first thing in the morning and Dwelle at night time (both of which have high oncotic pressure), but throughout the day I've been using TheraTears.

Do the hypotonic effects of the one cancel out the hypertonic effects of the other?

Also, I'm not quite clear when one would want the effects of hypotonicity and when hypertonicity would be better. Can you elaborate a bit?

Thank you so much.

Randal

[DrG]

Randal,

That statement was directed toward patients who use multiple doses of artificial tears on an hourly basis, where in the presence of a compromised epithelium the effect may be the opposite of therapeutic.

The idea of using hypertonic tears derives from the notion that dry eyes lead to a hypertonic tear film. Jeff Gailbard takes this further, and states that the long term effects of a hypertonic environment leads to inflammation and tissue distruction, if I have understood him correctly.

For a discussion of oncotic pressure as it relates to dry eye and the orginal formulations of Dr. Frank Holly, I refer to this link. His opinion appears to be that the loss of barrier function is a key component in the pathogenesis of corneal surface disease.

I am going to resist being dragged into a debate between these two learned men. Both have compelling arguments along with research. Whether one or the other works better in a particular situation probably depends on a number of factors, including just how much the corneal integrity has been compromised. In severe damage, I would go with the drops with the higher oncotic pressure, as this will act to reverse edema. Where the barrier function is not intact, I would wonder about using hypotonic tears. But, in fact, this is a complex physics problem involving many non-quantified and changing variables.

[Randal]

In severe damage, I would go with the drops with the higher oncotic pressure, as this will act to reverse edema. Where the barrier function is not intact, I would wonder about using hypotonic tears.

What would be the symptoms that would allow an individual to know whether the barrier function is intact or not? That is, how would this differ from other causes of dry eye? (Obviously, I'm looking for clues that will point me toward the right type of eye drops.)

Thank you.

Randal

[DrG]

The presence of punctate keratopathy, i.e. fluorescein staining, SPK, etc., would be a good indicator that the cornea is compromised. These are signs rather than symptoms.

[Randal]

One last question, please: When you said, "Where the barrier function is not intact, I would wonder about using hypotonic tears," did you mean the use of hypotonic tears in this instance would be a good idea, or you would wonder why anyone would use them in this instance (i.e., a not so good idea)?

Thank you.

Randal

[DrG]

One last question, please: When you said, "Where the barrier function is not intact, I would wonder about using hypotonic tears," did you mean the use of hypotonic tears in this instance would be a good idea, or you would wonder why anyone would use them in this instance (i.e., a not so good idea)?

I meant that it may not be a good idea to use too much of them.

Drs. Holly and Gilbard are both very passionate about their eyedrops. Dr. Holly seems more concerned about the barrier function, whereas Dr. Gilbard talks about the effects of hypertonicity and inflammation. There is no artificial tear on the market that comes close to having the constituents of real tears.

My advice is to use what feels the best and then don't over-use it. As I said before, and I will say it again, if you are using A/T more than once/hour, then you should be pursuing another avenue of treatment such as plugs, bandage lenses, goggles, and other therapies. Simply flooding an irritated eye with hypotonic tears may not be good for the epithelium if it is already significantly damaged.

[Randal]

Great Advice

Dr. G:

Thank you for your well-reasoned and balanced answers, particularly about avoiding overuse of artificial tears. You have taught me, and I'm sure so many others, quite a bit from your postings.

Randal