Preservative-free eye drops for dryness: who needs them, and what to do when drops are not enough

On this page

1. Why do eye drops contain a preservative?
2. What can a preservative do to the eye?
3. Who especially needs to choose preservative-free drops?
4. What do preservative-free drops look like?
5. A few questions to ask before buying
6. When are lubricating drops no longer enough?
7. What does a dry eye specialist check?
8. The bottom line

If you use eye drops several times a day and your eyes still stay red, burning or sensitive, part of the problem may be inside the bottle itself. On this page we explain what a preservative does in drops, why it may irritate the eye surface, who especially needs to choose preservative-free drops, and when it is no longer a question of which drop to buy but of needing an examination.

Why do eye drops contain a preservative?

An opened bottle of drops is exposed to air, fingers and eyelashes. A preservative is meant to prevent bacteria and fungi from growing inside the bottle, so that it can be used for weeks after opening. This is an important goal: a contaminated drop may cause an eye infection.

The most common preservative in eye drops is benzalkonium chloride (BAK for short). It is very effective against bacteria, and for exactly the same reason it is not gentle on the cells of the eye either.

What can a preservative do to the eye?

BAK works like a detergent: it damages cell membranes. When it comes into contact with the eye surface again and again, it may damage the top layer of cells of the cornea (the clear window at the front of the eye) and of the conjunctiva (the thin membrane covering the white of the eye). Comprehensive reviews of the topic, such as the one by Baudouin and colleagues, have also described a drop in the number of goblet cells (cells in the conjunctiva that produce the mucus in the tears) and an increase in signs of inflammation.

This damage depends on the dose. One drop in the morning will almost never be the problem. But someone who uses drops many times a day, for months and years, or who combines several different medicines that all contain a preservative, builds up significant exposure. In some people this leads to a frustrating cycle: the eye is dry, they use more drops, the preservative irritates more, and the dryness gets worse.

There are also "softer" preservatives, which break down on contact with the eye or with light. They are usually better tolerated than BAK, but they do not suit everyone either, and for a particularly sensitive eye it is sometimes better to avoid preservatives altogether.

Who especially needs to choose preservative-free drops?

• People who use lubricating drops many times a day. When use is frequent, professional guidelines prefer preservative-free drops.
• Patients with glaucoma (a disease in which the optic nerve is damaged, usually because of high pressure inside the eye). Glaucoma drops are usually given for life, and many of them contain BAK. In some patients this causes dryness and redness. Do not stop the drops; instead, talk to your eye doctor about alternatives.
• Soft contact lens wearers. Soft lenses may absorb preservative and keep it in contact with the eye for longer.
• After eye surgery, for example cataract surgery or surgery to correct vision so you no longer need glasses, when the eye surface is healing and sensitive, and several types of drops are often used at the same time.
• People with moderate to severe dryness, an autoimmune disease such as Sjögren's syndrome, or a known sensitivity to preservatives.

What do preservative-free drops look like?

There are two common forms, and the difference between them is about convenience of use:

• Single-dose vials (small ampoules). You open one, put in the drops and throw it away according to the instructions in the leaflet. This is the older, simpler form.
• A preservative-free multi-dose bottle. These bottles are built with a valve or filter that stops air and bacteria from getting back in, so they can be used for several weeks, according to what is written on the package. An example of this type is explained on the page about lubricating drops with hyaluronic acid.

The drops themselves contain a range of ingredients: hyaluronic acid, carboxymethylcellulose (CMC), lipid emulsions and more. A Cochrane review of over-the-counter lubricating drops found that they may improve symptoms, but no single drop was found to be clearly better than the others. So the choice is personal, and sometimes requires trying two or three types.

A few questions to ask before buying

• Does the package say "preservative-free"? If not, look in the list of ingredients for names such as benzalkonium chloride. If you are not sure, ask the pharmacist.
• When do you need the drops? Thin drops suit daytime use because they hardly blur. A gel or thick drops last longer, but blur vision for a few minutes, so many people use them before sleep.
• Do you wear contact lenses? Check in the leaflet whether the drop is suitable for use with lenses.
• Do you use other regular drops? Tell the eye doctor or the pharmacist about all your drops, so that the total amount of preservative can be worked out and to check that there is no duplication.

If a particular drop causes strong burning, redness or itching every time you use it, stop it and get advice. This may be a sign of sensitivity to one of the ingredients.

When are lubricating drops no longer enough?

Preservative-free drops are the right step, but they still treat a symptom: they add fluid to the eye for a short time. They do not fix the reason why the eye dries out. Here are signs that it is worth looking into it further:

• You need to use drops many times a day, and the relief lasts only a few minutes.
• Your vision blurs and clears on and off, especially at a screen or when reading.
• Your eyelids are red, sticky or swollen in the morning.
• The dryness is getting worse even though you have switched to preservative-free drops.
• You have a general medical condition or take medicines known to cause dryness (see medicines that cause dry eyes).

In most people with dry eye, the problem is not just a lack of fluid. Often the oily layer of the tears is faulty because the meibomian glands (the oil glands in the eyelid margins) are blocked, and then the tears evaporate too quickly. In other cases there is inflammation of the eyelid margins, or genuinely low tear production. Each of these conditions has a different treatment.

What does a dry eye specialist check?

At the appointment we go through all the drops and medicines you use, including preservatives. Then dry eye tests are done: a symptom questionnaire, a slit lamp examination (a microscope for examining the eye), measuring the break-up time of the tear film with fluorescein dye, staining that shows damage to the eye surface, measuring tear production, and checking the meibomian glands and eyelid margins.

A plan is built according to the findings. Among the treatments at the Dry Eye Clinic in Haifa:

• When the problem is in the meibomian glands: meibomian gland expression at the clinic, and sometimes IPL treatment (broad-spectrum pulsed light).
• When there are deposits and inflammation of the eyelid margins: eyelid margin cleaning with BlephEx.
• When tear production is low: punctal plugs, which help tears stay in the eye for longer.
• In severe dryness, for example in Sjögren's: autologous serum eye drops made from the patient's own blood, without preservative.
• When the surface of the cornea is damaged and not healing: a bandage contact lens that protects the eye like a bandage.

In addition, the eye doctor may prescribe anti-inflammatory drops or other medical treatment as needed. The aim is for you to need fewer drops, not more. You can read about anti-inflammatory drops and who they suit on the prescription eye drops for dry eye page.

The bottom line

If you use a lot of drops, switch to preservative-free drops. If that is not enough either, it does not mean you "need to get used to it". It is a sign that it is worth understanding exactly what is happening in the eye, so that the cause is treated and not just the feeling.

Want a basic explanation first?For basic information on artificial tears: the guide on the Mitzmutz site

Frequently asked questions

Are drops with preservatives harmful for everyone?

No. Occasional use, a few times a day, is usually well tolerated. The problem appears mainly when drops are used many times a day, over a long period, or when several types of drops are used at the same time.

I use glaucoma drops. Can I stop them because they dry my eyes?

No. Do not stop glaucoma drops on your own. Talk to your eye doctor: some of the medicines have a preservative-free version, and there are also other ways to relieve the dryness.

How long can I use a single-dose vial after opening it?

Follow the product leaflet. Most single-dose vials are meant for one use or for one day only, because they contain nothing that protects against contamination.

I use drops every hour and my eyes are still dry. What does this mean?

It is a sign that it is worth finding out what is causing the dryness. Often the problem is in the oil glands of the eyelids or is inflammation, and lubricating drops alone do not treat this. An examination by a dry eye specialist can point to the right treatment.

Sources

1. Baudouin C, Labbé A, Liang H, Pauly A, Brignole-Baudouin F. Preservatives in eyedrops: the good, the bad and the ugly. Prog Retin Eye Res. 2010;29(4):312-334.
2. Gomes JAP, Azar DT, Baudouin C, et al. TFOS DEWS II iatrogenic report. Ocul Surf. 2017;15(3):511-538.
3. Jones L, Downie LE, Korb D, et al. TFOS DEWS II Management and Therapy Report. Ocul Surf. 2017;15(3):575-628.
4. Pucker AD, Ng SM, Nichols JJ. Over the counter (OTC) artificial tear drops for dry eye syndrome. Cochrane Database Syst Rev. 2016;2:CD009729.
5. Akpek EK, Amescua G, Farid M, et al. Dry Eye Syndrome Preferred Practice Pattern®. Ophthalmology. 2019;126(1):P286-P334.

The information on this site is general only. It is not medical advice and does not replace an examination by an eye doctor.