Under normal conditions, healthy human tears are composed mainly of water (98%), together with mineral salts, proteins and lipids.
Their osmolarity (concentration of salts) is about 300 mOsm/l and they have neutral pH (about 7).
In principle, the composition and characteristics of artificial tears should imitate those of natural tears, but this is not always ideal.
Why should artificial tears not be identical to healthy natural tears?
We often talk about hypotonic and isotonic moisturising drops. These terms refer to the tonicity of the formula, that is, the concentration of salts in the liquid.
We say that artificial tears are hypotonic when their osmolarity is below that of healthy natural tears, and isotonic when the osmolarity is the same.
Also, in dry eye, tears are usually hyperosmolar, because there is less fluid so the concentration of salts is greater. This can damage the eye.
What happens when two solutions with different osmolarity (such as tears in dry eye and artificial tears) are separated by a semi-permeable membrane (such as the corneal-conjunctival epithelium)?
A physical phenomenon called osmosis takes place, in which water flows through the semi-permeable membrane from the solution with the lowest concentration to the one with the highest concentration; in this case, from the artificial tears to the natural tears. Both solutions end up with the same concentration, creating a balance.
For this reason, it is advisable for artificial tears to be hypoosmolar (with osmolarity below 300 mOsm/l).
Acuaiss Dual contains two humectants, each with outstanding properties, which complement each other very well: hyaluronic acid and hydroxyethylcellulose. Their osmolarity of 260 mOms/l is slightly hypotonic, to restore balance in the eyes.
Acuaiss Dual is available in the form of drops, for mild dry eye, with 0.13% hyaluronic acid and 0.10% hydroxyethylcellulose:
It is also available in gel form for moderate-severe dry eye, with 0.30% hyaluronic acid and 0.10% hydroxyethylcellulose:
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