If someone were to ask you what sunscreen has in common with eye surgery, we wouldn’t fault you for not knowing. Not many do. The answer is hyaluronic acid. That might not sound too interesting at first, but this substance is quite amazing. In fact, it’s in your eyes right now—and your knees. We produce it naturally, and for decades, it’s been the focus of many theoretical and proven applications for human health.
What is Hyaluronic Acid?
Hyaluronic acid (HA), also known as hyaluranon and as the compound sodium, hyaluronate, is a naturally occurring polymer that can be found in all tissues and fluids of the body. HA can be found in higher concentrations in the skin, the vitreous (the jelly-like substance inside the eye), the umbilical cord, and the synovial fluid found in the body’s synovial joints (Price et al. 2005; Papakonstantinou, Roth, and Karakiulakis 2012).
The substance was first identified in 1934 when it was extracted and isolated from the vitreous humor of cows’ eyeballs. Later, a Hungarian chemist, Endre Balazs, Ph.D, pioneered a method of extracting pure hyaluronic acid from the comb of a rooster (American Academy of Ophthalmology).
Since its discovery, hyaluronic acid has been studied at great length for its possible applications. Its unique properties have proven it to be an effective agent in various medical fields, from cosmetic surgery to orthopedics, and especially in tissue engineering (Price et al. 2005). It is also an essential ingredient in products used for some ophthalmic surgeries and for addressing certain symptoms of dry eye disease.
The Functions of Hyaluronic Acid
Within the human body, hyaluronic acid functions to hydrate, lubricate the joints, fill certain spaces, and provide material through which cells are able to travel. It also plays a role in wound healing and is synthesized at a greater rate during tissue repair. Hyaluronic acid activates inflammatory cells that enhance immune response and the response to injuries of fibroblasts and epithelial cells (Papakonstantinou, Roth, and Karakiulakis 2012).
One of the most unique properties of hyaluronic acid is its superior ability to bind and retain water molecules (Papakonstantinou, Roth, and Karakiulakis 2012). This, along with its anti-inflammatory properties, make hyaluronic acid ideal for many cosmetic applications.
Of the total hyaluronic acid found in the human body, 50% is concentrated in the skin (Papakonstantinou, Roth, and Karakiulakis 2012). Many of the attributes we associate with youthful or healthy skin, such as its resilience and pliability, are due in large part to the moisture-retaining properties of hyaluronic acid.
As we age, the epidermal concentration of hyaluronic acid progressively reduces. In women, this concentration goes from 0.03% in 19- to 47-year-olds to just 0.007% for 70-year-olds (Wiest and Kerscher 2008).
The skin is further protected by larger concentrations of hyaluronic acid due to the substance’s abilities to protect cells from damage caused by free radicals (Wiest and Kerscher 2008). For these reasons, hyaluronic acid is used as an ingredient in many cosmetic products that offer an “anti-aging” effect. It is an integral component of the extracellular matrix of the skin and serves several functions (Wiest and Kerscher 2008):
- increases water-binding capacity
- influences cell motility
- protects cells from free radicals
- promotes cell-to-cell communication
- exhibits anti-inflammatory properties and promotes wound healing
Hyaluronic Acid and its Role in Eye Health
Many of the aforementioned properties make hyaluronic acid particularly well suited for ophthalmic applications.
Hyaluronic acid and OVDs
Hyaluronic acid was part of the first OVD (ophthalmic viscosurgical device) to be put into clinical practice. Balazs first suggested its possible use in ophthalmic surgery, theorizing that it could act as a replacement for the vitreous in the human eye (American Academy of Ophthalmology).
In 1979, Healon (sodium hyaluronate 1%, Pharmacia) became the first licensed OVD, and in the same year, doctors began using it in human cataract surgery. To this day, hyaluronic acid is still the most common molecule used in OVDs, and its applications in ophthalmic procedures are still being researched and expanded (American Academy of Ophthalmology).
Hyaluronic acid and dry eye disease
Dry eye disease, a common condition affecting the ocular surface, is caused by instabilities in the tear film or issues with the tear-producing glands. As a result, those suffering with dry eye can experience deficiencies in the production of tears and the ability of those tears to function properly. The condition can cause chronic discomfort, visual blurring, inflammation and damage to the surface of the eye (Adler 2015).
Read more about dry eye disease in our three-part blog series during the month of September.
The most common therapy for dry eye is treatment with artificial tears, which aim to reestablish the moisturizing, lubricating, and protective properties of a healthy tear film (Aragona et al 2002). A wide variety of polymers has been used in formulating these lubricants, but, since its introduction as an ingredient, hyaluronic acid has gained special prominence and widespread use.
Hyaluronic acid is naturally occurring, and it exhibits excellent biocompatibility and unique viscoelastic properties, all of which make it a desirable ingredient in tear- replacement products (Kaya et al 2015).
The high viscosity of artificial tears containing hyaluronic acid leads to longer-lasting effects for patients, as the substance is able to reside on the eye’s surface longer than many other formulations. Hyaluronic acid has also been shown to increase tear film thickness (Kaya et al 2015).
In addition to its value in providing moisture and lubrication, hyaluronic acid has been shown to promote healing on the surface of eyes damaged by severe dry eye disease. Patients with cases of severe dry eye can experience damage to the corneal and conjunctival epithelia (the outer layer of cells on the cornea and inside of the eyelids, respectively), which may be improved by hyaluronic acid’s ability to promote epithelial healing (Aragona et al 2002).
That’s not quite all there is to know about hyaluronic acid, especially as researchers continue to study it and expand its potential applications. For now, it might be overkill to call it a “miracle” substance or a “fountain of youth,” but for those sufferers of osteoarthritis, dry eye, and other ailments, whose lives have been improved by hyaluronic acid, it can at least be called “amazing.”
Paragon BioTeck, Inc., offers a product portfolio for the diagnosis, management, and treatment of ocular conditions, including dry eye, as well as products to maintain proper eyelid hygiene. The ilast® Lid Hygiene System is scientifically formulated to soothe and moisturize the dry, irritated skin around the eye. Comfortear® Punctum Plugs and Comfortear® Lacrisolve™ 180 Absorbable Punctum Plugs provide occlusion therapy for the treatment of symptoms associated with dry eye disease, which may result from allergies, cataracts, or contact lens intolerance. Patients who are unsure whether dry eye treatment is right for them should talk with their eye doctor.
Citations:
- Adler, Richard. “Understanding Dry Eye Syndrome.” All About Vision. 2015.
- Aragona, Pasquale et al. “Long Term Treatment with Sodium Hyaluronate-Containing Artificial Tears Reduces Ocular Surface Damage in Patients with Dry Eye.” The British Journal of Ophthalmology. 2002.
- “Characteristics and Chemistry.” American Academy of Ophthalmology. 2012.
- “Glossary of Eye Care Terms – E-H.” All About Vision. 2016.
- “History.” American Academy of Ophthalmology. 2012.
- Kaya, S., Schmidl, D., Schmetterer, L., Witkowska, K. J., Unterhuber, A., Aranha dos Santos, V., Baar, C., Garhöfer, G. and Werkmeister, R. M. “Effect of hyaluronic acid on tear film thickness as assessed with ultra-high resolution optical coherence tomography.” Acta Ophthalmol. 2015.
- Papakonstantinou, Eleni, Michael Roth, and George Karakiulakis. “Hyaluronic Acid: A Key Molecule in Skin Aging.” Dermato-endocrinology. 2012.
- Price, R.D., S. Myers, I.M. Leigh, and H.A. Navsaria. “The role of hyaluronic acid in wound healing: assessment of clinical evidence.” PubMed. 2005.
- Wiest, L. and Kerscher, M. “Native hyaluronic acid in dermatology – results of an expert meeting.” JDDG: Journal der Deutschen Dermatologischen Gesellschaft. 2008.
