Preservative Free Eye Drops – Can They Help You?
One of the most common questions we hear from patients is “Why do my eyes burn when I put in my eye drops?” First off, if you experience burning eyes you should always be examined by an eye care professional. That being said it may not be the medicine in your eye drops causing the stinging but it may in fact be the preservative causing the irritation.
In this article we’ll look at:
- Common preservatives used in eye medications
- Possible side effects of these preservatives
- Why you might benefit from a preservative free eye drop
- How are preservative free eye drops packaged – including single use packaging and preservative free eye drops in a bottle
Why do some Eye Drops have Preservatives?
Benzalkonium chloride (BAK) is a commonly used preservative in eye medications.
It works well to stop germs from growing, but it can actually damage and irritate the eye – especially if used several times a day. BAK has a detergent-like effect – like the soap you use to wash your greasy dishes.
And the tear film that coats and hydrates your eye has natural fatty particles in it that we called lipids.
So just like dish soap can cut through fatty grease, BAK can disrupt the fatty components of our eye’s tear film. And without those lipid components in our tears, our eyes will actually dry out faster through evaporation. This can lead to dry eye. (Reference: https://bjo.bmj.com/content/86/4/418.long )
Plus, BAK can damage the outermost epithelial cell layer of the cornea and conjunctiva: this can also potentially cause or aggravate symptoms of dry eye. An eyeball damaged by Benzalkonium chloride cannot make or keep a proper layer of hydrating tears. (Reference Link: https://onlinelibrary.wiley.com/doi/10.1111/j.1755-3768.2008.01250.x )
This inadequate tear film causes the symptoms of dry eye such as stinging and watery eyes: your eye is trying to overcompensate for the lack of a proper tear film by pumping out excess watery tears in a desperate attempt to coat and hydrate the eyeball.
Dry eye can be caused by multiple factors, but the preservatives in many eye drops is at least part of the reason many glaucoma patients also have dry eye disease. The Glaucoma Research Foundation claims that between 40-50% of patients with glaucoma will also have dry eye. (Reference link: https://www.glaucoma.org/treatment/dry-eyes-and-glaucoma-double-trouble.php )
So, when patients ask, can Benzalkonium chloride burn and sting my eyes? The short answer is yes it can, and the risks go up if you use it frequently.
The preservative Benzalkonium chloride should be avoided if possible. And this is especially true for patients requiring regular, frequent dosing of their eye drops.
Other Newer Preservatives
Benzalkonium chloride is not the only preservative available.
There are other newer preservatives such as:
- Polyquaternium-1 (commonly called Polyquad)
- Sodium chlorite (Purite)
- Sodium perborate (GenAqua)
- Zinc chloride (SofZia)
A few of these are marketed as being ‘disappearing preservatives’: meaning they break down into non-toxic molecules when they’re exposed to your body’s tears, air or light.
All of the newer preservatives listed above work to stop microbes from growing in your eye drops, and they may be better tolerated than Benzalkonium chloride, but they too can cause irritation and stinging in some patients.
Do they make Preservative Free eye drops?
Yes, thankfully they now make preservative-free eye drops that you can use and avoid the potential side effects of eye drop preservatives.
Manufacturers still ensure the medicine isn’t contaminated by microbes, but they do it without adding a chemical preservative.
Remember the preservative is in there only to kill off any bacteria that may get into the medicine AFTER the bottle is opened by the patient.
But what if we can prevent the bacteria from getting in there…then we won’t need a preservative!
The two most common approaches to creating preservative-free eye drops is by either putting the medicine into sealed single-dose vials, or to put the medicine into smartly designed multidose bottles.
Ultimately what they’re trying to do is stop the bacteria and other germs from invading the medicine after the bottle is opened. If the germs never get into the medicine, you don’t have to worry about how to kill them.
How are preservative free eye drops packaged?
Putting eye medication into single-dose, single use plastic packaging is one way to avoid contamination without adding a preservative.
You open the sealed plastic vial, instill the medication into your eye, and then throw out the vial. These are not multidose drops…they are one and done, and since they are sealed by the manufacturer before you open it, it doesn’t have time to get contaminated.
Some eye medications are only available in single-dose vials.
But some smart scientists and designers have created multi-dose preservative-free eye drops in a bottle. Say goodbye to single use plastics.
These multidose bottles are designed to have a one-way valve (so medicine goes out and nothing comes back in), or they’re designed with a filter to stop bacteria from getting into the bottle.
(Reference: https://ondrugdelivery.com/using-intelligent-design-deliver-safe-multi-dose-eye-drops/ )
These design improvements – both the one-way valve and the specialized filter – mean that you can get preservative free eye drops in a multidose bottle that will prevent the backflow of bacteria into the bottle.
Voila, no preservative, and you’ve got multiple doses in one bottle so less plastic waste.
Are preservative free eye drops better tolerated than preserved eye drops?
Yes, most patients will tolerate a preservative free eye drop better than a preserved eye drop.
A study from 2002 showed patients experienced less adverse events of their eyes when using a preservative free drop versus a preserved eye drop. (Reference: https://bjo.bmj.com/content/86/4/418.long)
They had less stinging, reduced dry eye symptoms, less tearing, less irritation upon putting in the drops, and reduced incidence of itchy eyelids when switched to preservative-free drops compared to using preserved drops.
(Reference: https://bjo.bmj.com/content/86/4/418.long )
Switching to a preservative free eye drop can make a big difference in a patient’s quality of life and helping ensure they use their eye drops as prescribed.
Patients experiencing burning, stinging or irritation from their eye drops may be reacting to the preservative in the eye drop, and not necessarily the medication itself.
The preservatives in eye drop medications are effective at killing off bacteria that may get into the bottle once opened, but these chemical additives can come at a cost of patient tolerability.
And a medication won’t work if you can’t take it.
Benzalkonium chloride – the most commonly used preservative in eye drops – has been shown to cause damage to the outer layer of cells that coat your eye resulting in stinging, burning and other symptoms of dry eye.
If you experience any stinging or irritation when you use your eye drops consult your eye care professional. They may be able to recommend or prescribe preservative free eye drops in a bottle or single use vials, so you can take the medicine into your eye without getting the preservative.
And keep in mind that if you are switched to a preservative-free formulation it may take several weeks for your eye to feel better: you may still experience some slight stinging initially. This is because your use of a preserved eye drop may have slightly damaged your eye, and this damage to your corneal and conjunctival epithelial cells may take some time to heal.
A qualified eye care professional like your optometrist or ophthalmologist will be able to help you on your journey to improved eye health.
Disclaimer: Please note this article is not to be taken as medical advice and is solely for informational purposes. Please see your healthcare provider for diagnosis and treatment.