Hyaluronic acid is an excellent humectant and is used for its therapeutic properties in various fields of medicine, such as ophthalmology or aesthetic medicine. It is a polymer distributed in chain form. The molecular weight of hyaluronic acid is measured in millions of daltons: the figure indicates the size of the molecules and whether the chains are longer or shorter.
It might seem strange but in preparations to relieve dry eye, high molecular weight hyaluronic acid gives the best results because it lubricates the eye better and inhibits inflammation. In skin care products, on the other hand, low molecular weight hyaluronic acid is more effective because it penetrates the epidermis better and gives good hydration.
There is no exact figure defining the optimal molecular weight of hyaluronic acid in humectant eye drops, but a high molecular weight is recommended, that is, above 900,000-1,000,000 daltons.
Why?
One of the most surprising properties of hyaluronic acid is its viscoelasticity, that is, its capacity for changing its viscosity with movement. At rest, hyaluronic acid is viscous and, with movement, it becomes fluid.
This characteristic is ideal for humectant drops because it means that a viscous substance that hydrates the cornea and remains on it for a long time does not lead to damage from friction or blurred vision because it becomes fluid with movement (blinking).
The higher the molecular weight of the hyaluronic acid, the greater its viscoelasticity.
This means that if a high molecular weight hyaluronic acid is chosen for the formulation of humectant drops, excellent results can be achieved without using a high concentration. Such a product will have outstanding viscoelasticity and hydration properties and will also be very comfortable for the user.
Hyaluronic acid can be produced with different molecular weights:
All the variables are important.
Hyaluronic acid has an enormous water retention capacity, making it the best humectant known. The higher the concentration of hyaluronic acid in a product, the greater its hydration capacity will be. But care must be taken because high concentrations of hyaluronic acid can cause blurred vision.
The greater the molecular weight, the greater the viscoelasticity, that is, the longer it remains in the eye.
An ideal formulation should combine the variables in the best possible way to get the desired results: a product that hydrates the eye and remains for a long time on the cornea, is comfortable to use, and does not cause blurred vision.
Another consideration is that there are different types of hyaluronic acid on the market: it can come from different sources and can be produced in various ways. Most hyaluronic acid used in the industry today is produced by biotechnology (microbial fermentation) because this is biocompatible with the human body and there is less risk of biological contamination than with hyaluronic acid of animal origin.
All the products in the Acuaiss family contain hyaluronic acid.
Acuaiss Wipes and Acuaiss Eye Bath are recommended for the hygiene and care of eyes and eyelids.
Acuaiss Roll-on lifts tension from the area of the eye contour.
Acuaiss Spray & Go is a spray for open eyes to fight digital eye strain.
All the artificial tears in the Acuaiss line (Acuaiss Moisturizing Drops, Acuaiss Dual Drops, Acuaiss Ultra and Acuaiss Dual Gel) contain high molecular weight hyaluronic acid at different concentrations and provide immediate relief for all dry eye symptoms, without causing blurred vision.
● Chang WH, Liu PY, Lin MH, Lu CJ, Chou HY, Nian CY, Jiang YT, Hsu YH. Applications of Hyaluronic Acid in Ophthalmology and Contact Lenses. Molecules. 2021 Apr 24;26(9):2485. doi: 10.3390/molecules26092485. PMID: 33923222; PMCID: PMC8123179.
● Fallacara A., Baldini E., Manfredini S., Vertuani S. Hyaluronic Acid in the Third Millennium. Polymers. 2018;10:701. doi: 10.3390/polym10070701