Different Types of Artificial Tears
Finding eye drops that help treat dry eyes can be a real challenge. There are many brands and products on the market, all containing different ingredients.
The composition of eye drops may seem complicated at first glance. A bit of background knowledge will help you find the right eye drops for your needs. In this article, you’ll learn about the individual ingredients and what to look out for.
The use of preservatives in eye drops is very controversial. They are added because of their antibacterial properties. On one hand, this makes sense since everything that comes in contact with the eye should be as sterile as possible to avoid germ contamination.
On the other hand, preservatives can irritate the cornea and conjunctiva, and therefore damage the eye in the long run. Eyes that are already irritated through dryness are especially sensitive. Some preservatives can even destabilize the tear film and thus aggravate dry eyes.1
For this reason, you should opt for preservative-free artificial tears, especially if using them for extended periods.
Preservatives are not compatible with contact lenses. That’s because the fluid remains between the contact lens and the cornea, thereby irritating the cornea.2
Commonly used preservatives include cetrimide, benzalkonium chloride, polyhexanide (PHMB), polidronium chloride, sodium chlorite, and edetate disodium (EDTA). Read the ingredient label to check whether your eye drops contain one of these ingredients. Preservative-free eye drops are usually labeled as such.
To avoid contamination, eye drops without preservatives are packaged in special bottles. They are designed in a way that the fluid can come out, but nothing can come in from the outside. The package insert provides information about how long the eye drops can be used after the bottle has been opened.
Preservative-free eye drops are also available in single-use vials that can be used for 24 hours after opening. If you are concerned about germ contamination, these are a great option.
Buffers to Maintain pH Balance
Eye drops contain buffers that help to keep the pH stable. The most commonly used are phosphate or citrate buffers. However, when the cornea is already irritated, phosphate buffers can lead to calcification (accumulation of calcium salts), thereby causing impaired vision.3 People whose cornea is damaged in any way should therefore choose a product without phosphate buffer.
Tear Film Stabilizing Polymers
Polymers are added to artificial tears in order to stabilize the tear film. The main difference between them is their viscosity. The higher the viscosity, the longer the eye drops stay in the eye. This makes more viscous eye drops particularly suitable for severe dry eyes. However, one disadvantage is that viscous eye drops can temporarily disturb vision.
The following polymers are commonly used in eye drops:
Mucus Layer Stabilizing Polymers
The tear film consists of three layers. The inner mucus layer protects the cornea and facilitates the eyelid movement over the ocular surface. It also provides protection from bacteria and other germs. The mucous layer also helps the tear film to spread evenly across the eye and remain stable.
The following mucous layer stabilizing polymers are found in artificial tears:
Povidone and PVA
FreshKote preservative-free lubricating eye drops are an example of povidone and PVA containing eye drops.6
Cellulose derivatives and carbomers
GenTeal Tears preservative-free lubricant eye drops contain the cellulose derivative Hypromellose.9
Hyaluronic acid is usually added to artificial tears in the form of sodium hyaluronate. Hyaluronic acid is also produced in the body and is found naturally in the eye, making it a well-tolerated ingredient. Hyaluronic acid binds to water, leading to high viscosity. It also promotes the regeneration of the cornea.10,11 Products with a high hyaluronic acid concentration are therefore suitable for severe symptoms.
Hylo-Forte preservative-free lubricating eye drops are an example of hyaluronic acid containing eye drops.12
Guaraprolose is a derivative of guar gum. This agent is fluid when bottled but becomes viscous as soon as it comes into contact with the eye, so it stays in the eye for a long time and is suitable for moderate to severe symptoms.13
Systane Ultra preservative-free lubricant eye drops contain guaraprolose.14
Some eye drops contain multiple polymers, which can increase the efficacy for some people. However, because any ingredient can lead to intolerances, it may be better to try a product with a single polymer before trying one with multiple polymer combinations.
Lipid Layer Stabilizing Agents
The lipid layer forms the outer layer of the tear film and prevents the evaporation of tear fluid. Lipid layer instability is a common cause of dry eyes, in which case lipid-containing artificial tears can be an effective treatment.15
Lipid-containing eye drops are most effective for individuals with a meibomian gland dysfunction (the gland that produces the oily secretions of the lipid layer).
These eye drops may additionally contain mucous layer stabilizing polymers.
Soothe XP Emollient lubricating eye drops contain mineral oil to stabilize the lipid layer.16
Dexpanthenol is a vitamin B5 derivative. It promotes the regeneration of the cornea and conjunctiva and is also hydrates the eye. However, studies assessing the efficacy of dexpanthenol for the treatment of dry eye disease are inconclusive.17 In some cases, dexpanthenol can cause side effects such as itching and burning.
Glycerin, Propylene Glycol, & Polyethylene Glycol
These ingredients are sometimes added to eye drops because they help the polymers to stay in the eye for longer.18
Eyebright is a plant extract that is said to have anti-bacterial and anti-inflammatory properties. The therapeutic benefit for dry eyes is not clear.19
Vitamin A is vital for eye health and function. While acute vitamin A deficiency is rare in western countries, mild deficiency is not uncommon and can contribute to dry eyes. You can ensure you get enough vitamin A by taking a vitamin supplement, and vitamin A containing eye drops can support dry eye therapy.20,21
Dry eyes trigger inflammatory responses, which in turn cause more dryness. Anti-inflammatory ingredients can help break this vicious cycle.22 Cyclosporine A has anti-inflammatory properties23 and also promotes tear fluid production, which is a positive side effect for people with dry eyes.24
Corticosteroids (cortisone-like chemicals) are also anti-inflammatory.25
Antibacterial and Antiviral Ingredients
Takeaway: Artificial Tears Are Very Diverse
There are many different eye drops on the market, containing various ingredients and ingredient combinations. How well tolerated and efficient these different products are will depend on the individual.
1. Walsh K, Jones L. The use of preservatives in dry eye drops. Clinical Ophthalmology. 2019;Volume 13:1409-1425. doi:10.2147/OPTH.S211611
2. Markoulli M, Kolanu S. Contact lens wear and dry eyes: challenges and solutions. Clinical Optometry. 2017;Volume 9:41-48. doi:10.2147/OPTO.S111130
3. Kompa S, Redbrake C, Dunkel B, Weber A, Schrage N. Corneal calcification after chemical eye burns caused by eye drops containing phosphate buffer. Burns. 2006;32(6):744-747. doi:10.1016/j.burns.2006.01.003
4. Guillon M, Maissa C, Pouliquen P, Delval L. Effect of Povidone 2% Preservative-free Eyedrops on Contact Lens Wearers With Computer Visual Syndrome: Eye & Contact Lens: Science & Clinical Practice. 2004;30(1):34-39. doi:10.1097/01.ICL.0000101489.13687.9A
5. Calles JA, Bermúdez J, Vallés E, Allemandi D, Palma S. Polymers in Ophthalmology. In: Advanced Polymers in Medicine. ; 2015:147-176. doi:10.1007/978-3-319-12478-0_6
6. FreshKote Preservative Free Lubricant Eye Drops (solution) Eyevance Pharmaceuticals. https://www.drugs.com/otc/1283407/freshkote-preservative-free-lubricant-eye-drops.html. Accessed December 16, 2019.
7. Solomonidou D, Cremer K, Krumme M, Kreuter J. Effect of carbomer concentration and degree of neutralization on the mucoadhesive properties of polymer films. Journal of Biomaterials Science, Polymer Edition. 2001;12(11):1191-1205. doi:10.1163/156856201753395743
8. Verma DrS. Polymers in designing the mucoadhesive films: A comprehensive review. International Journal of Green Pharmacy. 2018;12(2). doi:10.22377/IJGP.V12I02.1783
9. | gentealtears.com. https://gentealtears.myalcon.com/eye-care/genteal/products/genteal-moderate-preservative-free/safety-information/. Accessed December 16, 2019.
10. Guillaumie F, Furrer P, Felt-Baeyens O, et al. Comparative studies of various hyaluronic acids produced by microbial fermentation for potential topical ophthalmic applications. Journal of Biomedical Materials Research Part A. 2009;9999A:NA-NA. doi:10.1002/jbm.a.32481
11. DeLuise VP, Peterson WS. The use of topical Healon tears in the management of refractory dry-eye syndrome. Annals of ophthalmology. 1984;16(9):823-824. http://www.ncbi.nlm.nih.gov/pubmed/6508097. Accessed November 21, 2019.
12. HYLO Forte | Scope Ophthalmics. http://www.scopeophthalmics.com/hylo/hyloforte. Accessed December 16, 2019.
13. Ubels J, Clousing D, van Haitsma T, et al. Pre-clinical investigation of the efficacy of an artificial tear solution containing hydroxypropyl-guar as a gelling agent. Current Eye Research. 2004;28(6):437-444. doi:10.1080/02713680490503787
14. SYSTANE® ULTRA Preservative-Free Eye Drops | systane.com. https://systane.myalcon.com/eye-care/systane/products/systane-ultra-preservative-free/. Accessed December 16, 2019.
15. Lee S-Y, Tong L. Lipid-Containing Lubricants for Dry Eye. Optometry and Vision Science. 2012;89(11):1654-1661. doi:10.1097/OPX.0b013e31826f32e0
16. Soothe® XP Preservative-Free Lubricant Eye Drops from Bausch + Lomb. https://www.sootheeyedrops.com/products/soothe-xp-presFree.html. Accessed December 16, 2019.
17. Islam MH. Effect of D-Panthenol on Corneal Epithelial Healing after Surface Laser Ablation. J Ophthalmol. 2018:6537413-6537413.
18. de Campos A. The effect of a PEG versus a chitosan coating on the interaction of drug colloidal carriers with the ocular mucosa. European Journal of Pharmaceutical Sciences. 2003;20(1):73-81. doi:10.1016/S0928-0987(03)00178-7
19. Assessment Report on Euphrasia Officinalis L. and Euphrasia Rostkoviana Hayne, Herba. www.ema.europa.eu. Accessed November 21, 2019.
20. Alanazi SA, El-Hiti GA, Al-Baloud AA, et al. Effects of short-term oral vitamin A supplementation on the ocular tear film in patients with dry eye. Clinical Ophthalmology. 2019;Volume 13:599-604. doi:10.2147/OPTH.S198349
21. Kobayashi TK, Tsubota K, Takamura E, Sawa M, Ohashi Y, Usui M. Effect of Retinol Palmitate as a Treatment for Dry Eye: A Cytological Evaluation. Ophthalmologica. 1997;211(6):358-361. doi:10.1159/000310829
22. Pflugfelder SC, de Paiva CS. The Pathophysiology of Dry Eye Disease. Ophthalmology. 2017;124(11):S4-S13. doi:10.1016/j.ophtha.2017.07.010
23. Turner K, Pflugfelder SC, Ji Z, Feuer WJ, Stern M, Reis BL. Interleukin-6 Levels in the Conjunctival Epithelium of Patients with Dry Eye Disease Treated with Cyclosporine Ophthalmic Emulsion. Cornea. 2000;19(4):492-496. doi:10.1097/00003226-200007000-00018
24. YOSHIDA A, FUJIHARA T, NAKATA K. Cyclosporin A Increases Tear Fluid Secretion via Release of Sensory Neurotransmitters and Muscarinic Pathway in Mice. Experimental Eye Research. 1999;68(5):541-546. doi:10.1006/exer.1998.0619
25. Pflugfelder SC, Maskin SL, Anderson B, et al. A randomized, double-masked, placebo-controlled, multicenter comparison of loteprednol etabonate ophthalmic suspension, 0.5%, and placebo for treatment of keratoconjunctivitis sicca in patients with delayed tear clearance. American Journal of Ophthalmology. 2004;138(3):444-457. doi:10.1016/j.ajo.2004.04.052
26. Zhang Z, Yang W-Z, Zhu Z-Z, et al. Therapeutic Effects of Topical Doxycycline in a Benzalkonium Chloride–Induced Mouse Dry Eye Model. Investigative Opthalmology & Visual Science. 2014;55(5):2963. doi:10.1167/iovs.13-13577
27. Magnuson RH. Gentamicin Sulfate in External Eye Infections. JAMA: The Journal of the American Medical Association. 1967;199(6):427. doi:10.1001/jama.1967.03120060125030
28. Spertus CB, Mohammed HO, Ledbetter EC. Effects of topical ocular application of 1% trifluridine ophthalmic solution in dogs with experimentally induced recurrent ocular canine herpesvirus-1 infection. American Journal of Veterinary Research. 2016;77(10):1140-1147. doi:10.2460/ajvr.77.10.1140