When are eye drops drying?
1. When they're preserved.
#1 evil preservative is, of course, benzalkonium chloride (BAK). BAK is toxic to the cornea. It has been documented to harm the eye in seven different ways. Prolonged exposure is the main risk factor for damage from BAK.
BAK is present in:
- almost all prescription eyedrops (but since you don't take most Rx drops for very long, that shouldn't be a big deal... unless you do take it for a long time)
- almost all over-the-counter allergy drops (which isn't tragic unless you continue to take them long term)
- almost all over-the-counter redness reliever drops (which isn't necessarily tragic but... in conjunction with the redness rebound factor, and the fact that redness relievers so often become addictive, can very easily become tragic)
- some over-the-counter lubricant drops (which makes NO SENSE WHATSOEVER and frankly no one in their right might should ever recommend or use a BAK preserved lubricant eye drop)
There are other preservatives, like polyquad, which is present in many lubricant drops. Toxicity may be less than BAK, but is still present. Why would you expose yourself to it long term?
Then there are "disappearing" preservatives, like sodium perborate, which are supposed to dissipate on contact with the eye. The problem with that theory is that it assumes you have a healthy tear film. When you don't, the preservative may be irritating.
2. When the drug itself is drying.
So which ones are drying? We don't necessarily know.
It would be so nice if we could just say "This one is drying."
But according to TFOS DEWS II, it really is very complicated to figure out what drugs are drying. There are a ton of technical factors that add "noise" to the evaluation, such as:
- Clinical trials usually exclude people with dry eye. (People diagnosed with dry eye have a better understanding of what dry eye is and what it feels like, so they are more reliable in understanding and reporting dry eye symptoms.)
- Most studies focus on drops for glaucoma or ocular hypertension, which are usually preserved.
- Most studies on any prescription drops are drops that are preserved, so it becomes impossible to distinguish the effect of the preservative from the effect of the drug.
- Clinical trials even of glaucoma drugs tend to exclude people on other drugs at the same time or who have dry eye, blepharitis or allergy.
- The type of drop (ointment, suspension, emulsion) may play a role that we don't know.
- Chemical properties (pH, hypotonicity) might affect the tear film too.
- It is actually pretty hard to distinguish between things that happen on their own and things that are truly drug-induced.
Clinically, it remains difficult to discriminate between spontaneous changes in OSD and iatrogenic effects. Symptoms and timing of conjunctival allergy induced by the instillation of eyedrops can be evocative, but simple conjunctival congestion or papillary conjunctivitis may be observed with or without eczema. Delayed allergic reactions can also occur, often mimicking blepharitis with low-grade inflammation. Similarly, it can be very difficult to differentiate corneal staining due to DED, either preexisting or iatrogenic, from toxic epitheliopathy or corneal melting, like those induced by overuse of anesthetics or NSAIDs. With so many confounding factors, the relationships between eyedrops and ocular inflammation, tear instability or ocular surface staining, are often difficult to assess, especially when the treatment is mandatory for a severe and/or sight-threatening condition. This is particularly the case in glaucoma, where long-term, often life-long, treatments are required.
All that to say, please do not assume that every drop on the list below really IS drying! It's more like, they *might* be drying for some people. You can scroll down for an actual list of which drugs are *thought* to potentially be drying.
Which drops are and aren't drying?
Most prescription eye drops are drying - because of the preservatives, at least
Because most prescription drops are preserved with BAK, about which we have TONS of clinical data proving them to be toxic.
If it's a short course - a few weeks - it's probably not an issue at all, unless of course you're allergic.
If you have no choice but to take a BAK-preserved prescription eye drop, talk with your doctor about the lowest (least frequent) dosage you can be on, and whether it may be possible to get a preservative-free equivalent compounded.
Preservative-free prescription drops may not be drying.
The only problem is finding them! There are a few preservative-free glaucoma drops on the market now, but for most other prescription drops (steroids, antibiotics, mydriatics, etc.), if you are in the US, they will not be available. You may be able to get them compounded, which may be expensive and inconvenient but at least an option. If you already have dry eye, that may be the right investment.
Many over-the-counter eye drops are drying - because of the preservatives.
All about the BAK.
Most unpreserved over-the-counter drops AREN'T drying.
Don't interpret that to mean they're any good. But at least they're not drying.
I have heard so many people talking about how they use only preservative free lubricants, as though that's some kind of virtue.
I'm sorry, but preservative-free is not a virtue, it's simply the absence of a vice. It doesn't mean the lubricant itself is any good. Keep drop and preservative in two different parts of your brain.
MY top priority for awareness: Glaucoma drops
Are you using a glaucoma eye drop?
Do you have an elderly family member who is using a glaucoma eye drop?
Please, seek out preservative-free glaucoma drops. Talk to the glaucoma specialist about available alternatives. Talk to the corneal specialist about how to prevent or address dry eye.
Glaucoma eye drops are the #1 prescription drug dry eye risk, because (1) most of them contain BAK and (2) all glaucoma eye drops are used at least once daily. Prolonged exposure to BAK is drying.
The Drying Drop List
Types of drops
Adrenergic agonist drugs
- Carbonic anhydrase inhibitors
Agents used to treat allergies
Mydriatics and cyclopegics
- Benzalkonium chloride
Topical and local anesthetics
Topical ocular NSAIDs
Some additional ingredients
- Glyceryl monostearate
- Lauroyl sarcosine
- Octylphenol polymethylene
- Poloxamer 188
- Poloxamer 407
- Polyethylene glycol 300
- Polyethylene glycol 400
- Polyethylene glycol 4000
- Polyethylene glycol 8000
- Polyoxyethylene-polyoxypropylene 1800
- Polyoxyl 35 castor oil
- Polyoxyl 40 hydrogenated castor oil
- Polyoxyl 40 stearate
- Polypropylene glycol
- Polysorbate 20
- Polysorbate 60
- Polysorbate 80
- Propylene glycol
- Sorbitan monolaurate
- Triton 720
- Benzyl alcohol
- Cetyl alcohol
- Edetate disodium
- Phenylethyl alcohol
- Sodium sulfate
- Sodium sulfite
- Sodium bisulfate
- Sodium bisulfate
- Sodium metabisulfite
- Sodium thiosulfate