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Sticking is wetting
Perhaps this is a good place here to put my two cents worth. When I first started to study tear film physiology (1969) the concept of wetting was not even thought of. It is still somewhat of a mystery to many. I will try to clarify it here.
Wetting a solid can be done by any liquid even though the liquid is usually water. Wetting really means that the water molecules will be attracted to the solid surface not only to each other. If the water molecules are attracted to the solid surface more than to each other, we talk about complete wetting.
To form a thin aqueous film over the eye surface the artificial tear has to wet the surface completely.
These eye drops achieve complete wetting of even water-repelling surfaces due to the fact that they contain a mixture of two polymers that are similar to each other, attract water but have certain locations along the polymer chain where there are little "suction cups" distributed in a certain pattern. These suction cups can attach to a water-repelling surface such as the dry eye surface - via hydrophobic bonding - and hold down the polymer chain for a long period of time. Since the majority of sites on the polymer chain is water attracting, this process will stabilize the tear film over the eye surface. This is very important because the ocular surface cells cannot tolerate being exposed to the atmosphere.
The formulators of the other eye drops on the market do not seem to realize what complete wetting is, how to achieve it, or even whether that is important at all.
By implications, perhaps this also explains why these drops are found to be effective with contact lenses. The drops makes the contact lens surface also more wettable.
The high oncotic pressure unique to Dwelle and Dakrina are also important in healing the epithelium. But this is another topic altogether.
I hope this will help some.
Perhaps this is a good place here to put my two cents worth. When I first started to study tear film physiology (1969) the concept of wetting was not even thought of. It is still somewhat of a mystery to many. I will try to clarify it here.
Wetting a solid can be done by any liquid even though the liquid is usually water. Wetting really means that the water molecules will be attracted to the solid surface not only to each other. If the water molecules are attracted to the solid surface more than to each other, we talk about complete wetting.
To form a thin aqueous film over the eye surface the artificial tear has to wet the surface completely.
These eye drops achieve complete wetting of even water-repelling surfaces due to the fact that they contain a mixture of two polymers that are similar to each other, attract water but have certain locations along the polymer chain where there are little "suction cups" distributed in a certain pattern. These suction cups can attach to a water-repelling surface such as the dry eye surface - via hydrophobic bonding - and hold down the polymer chain for a long period of time. Since the majority of sites on the polymer chain is water attracting, this process will stabilize the tear film over the eye surface. This is very important because the ocular surface cells cannot tolerate being exposed to the atmosphere.
The formulators of the other eye drops on the market do not seem to realize what complete wetting is, how to achieve it, or even whether that is important at all.
By implications, perhaps this also explains why these drops are found to be effective with contact lenses. The drops makes the contact lens surface also more wettable.
The high oncotic pressure unique to Dwelle and Dakrina are also important in healing the epithelium. But this is another topic altogether.
I hope this will help some.
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