Ingredient type could play a role in future artificial tear selection

Many options are available when it comes to artificial tears; some better than others. I would argue that, typically, most optometrists would say they look to prescribe artificial tears that contain the ingredients povidone, trehalose, carboxymethylcellulose, and hyaluronic acid (HA). What many optometrists may not be aware of, however, is that there are different types of HA. Until recently, I didn’t know this either.

Here, I discuss what HA does, the types of HA, and what this information may mean when it comes to prescribing artificial tears.

WHAT HA DOES

HA is a naturally occurring, hydrophilic, glycosaminoglycan disaccharide biopolymer found within the tear film.^1,2 The rich hydroxyl-groups attract water molecules, thickening and stabilizing the tear film. This helps to reduce evaporation and, thus, resultant damage to the ocular surface.² Additionally, HA is shown to improve corneal re-epithelization.²

In artificial tears, this ingredient helps increase the natural tears’ viscosity. This leads to increased tear film stability, tear retention time, tear break-up time (working to optimize ocular surface hydration), and lubrication.^1,2 Studies show that artificial tears containing HA have therapeutic benefits, including corneal epithelial healing (mentioned above), improvement of the ocular surface function, and goblet cell density.²

TYPES OF HA

Let’s put our chemistry hats on for a moment to discuss the different types of HA and why this information is important.

HA comes in different molecular weights: High molecular weight (MW) HA and Low MW HA. High MW HA acts as an anti-inflammatory mediator, and low MW HA acts as a pro-inflammatory mediator.²

Additionally, formulations and variations of HA impact the artificial tears’ behavior by altering the drops’ viscosity and level of shear thinning (ability for a tear to spread on the cornea with blinking).^2,1

Something else to keep in mind: Artificial tears formulated with different MW of HA and polydispersion index (PDI, evenness of MW distribution) may be better suited to treat different stages or types of dry eye disease.^1,2 An example would be a patient with grade 2+ diffuse corneal superficial punctate keratitis, indicating epithelial damage and an increased amount of ocular surface inflammation. This patient would benefit from an artificial tear that contains high MW HA and low PDI. Unfortunately, at this time MW of HA is not indicated on the label of tears, nor is there a table to quickly reference.

NOW WHAT?

As further studies provide more data, OD thinking may change to incorporate HA type as a prescribing deciding factor in particular patients. This is a new scientific approach. OM

REFERENCES

1. Hynnekleiv L, Magno M, Vernhardsdottir RR, et al. Hyaluronic acid in the treatment of dry eye disease. Acta Ophthalmol. 2022 Dec;100(8):844-860. doi: 10.1111/aos.15159.
2. Aragona P, Simmons PA, Wang H, Wang T. Physicochemical properties of hyaluronic acid–based lubricant eye drops. Transl Vis Sci Technol. 2019;8(6):2. doi: 10.1167/tvst.8.6.2.

DR. KOETTING practices in Denver, Colo. She is a fellow of the American Academy of Optometry, diplomate of the American Board of Optometry, an active member of AOA, and a speaker and consultant for multiple companies. Follow her on Instagram at Dr_Jazz_Hands, or email her at Dr.CeceliaKoetting@gmail.com.