Last Updated: July 2026 | Reviewed by Dr. Davinder Sidhu, OD
Most people who come in frustrated with their eye drops have already tried switching brands, but almost no one looks at the one ingredient those bottles shared, because it isn't the medicine. It's the preservative.
[Image: real photo of a preservative-free multidose bottle next to a strip of single-use vials on the clinic counter, phone photo fine]
The preservative is there for the bottle, not for you
Benzalkonium chloride, (BAK) has one job, keep the inside of a dropper bottle sterile after you've opened it and squeezed it a hundred times. It's perfect, It's a disinfectant, a detergent by design, and it kills whatever gets back into the bottle.
The part the box never says is that you're rinsing your cornea with that disinfectant every time you use the drop. Your eye just happens to be standing where it lands, and the outermost cells of the cornea are built from the same kind of membranes BAK is designed to break apart. It also thins the oily layer of the tear film, the layer that slows your tears evaporating.
The evidence against BAK is old news in clinics
Jaenen (2007) surveyed over 9,000 patients on daily preserved versus preservative-free drops and the preserved group reported burning, stinging and dry eye sensation at almost double the rate. Baudouin (2010) pulled the mechanism together, and by 2017 the TFOS DEWS II report was listing preservative exposure as a recognized cause of iatrogenic dry eye, dryness caused by the treatment itself.
None of this makes preserved drops poison. Once or twice a day on a healthy eye, your own tears flush the BAK out before it builds up, and you'd never know the difference. The problem is arithmetic on a dry eye: less tear volume to rinse with, more drops per day to rinse away. Six doses a day onto a surface that never cleared the first one. The people who rely on eye drops are the exact people whose eyes can't clear the preservative in them.
What your eyes get back when the preservative is gone
A retired 62-year-old from Vernon came in last winter after three years of drugstore drops, five or six times a day through every furnace season. Two weeks after moving her to a preservative-free hyaluronic acid drop, the morning sting she'd assumed was "just her eyes now" had mostly gone. Nothing else changed.
That's the first thing you buy with preservative-free: the surface finally gets to recover between doses instead of taking a fresh hit of disinfectant with each one. Comfort stops being a twenty-minute rental.
The second thing is freedom on frequency. There's no real ceiling on a preservative-free tear. A brutal day of highway driving or harvest dust or fourteen hours in front of spreadsheets, use them ten times, nothing builds up.
Third, contact lenses. A soft lens soaks up preservative and holds it against the cornea for the rest of the wear day. Preservative-free drops over contacts are a non-issue.
And fourth, for the last fifteen years of artificial tear development, hyaluronic acid formulas, trehalose, the lipid emulsions for evaporative dry eye, nearly all of it shipped preservative-free, because the companies doing serious tear research concluded BAK was indefensible in a drop meant for daily use.
Where preserved drops are still fine
Twice a month on long drives? Buy whatever's on sale, the preserved bottle won't hurt you and I won't pretend otherwise. The case for preservative-free is a frequency case, and if you barely use drops, you're not in it.
Run the money math per drop, not per bottle
The comparison looks bad for preservative-free: about $13 for a preserved bottle at Shoppers against $23 to $33 for a preservative-free one. That's the wrong comparison. A Hyabak bottle holds around 300 drops and lasts up to three months after opening, which puts it under 8 cents a drop, and the preserved bottle only stays cheaper if it works, meaning you don't go back for a second and third one. The brand-switchers from the top of this page weren't saving money. They were buying the cheap bottle repeatedly.
Side rant, if the bottle in your glove box promises to "get the red out," it's not an artificial tear at all, it's a vasoconstrictor, and long-term use makes the redness worse. Bin it.
Picking a first bottle without overthinking it
Read the medicinal ingredient line. If your eyes feel dry and gritty through the day, start with plain hyaluronic acid, it binds water to the surface and lasts between blinks; I-Drop Pur has 0.18% viscoadaptive version and Hyabak is the budget route into the same ingredient. If dryness comes with screen marathons or your eyes feel worse by evening, Thealoz Duo adds trehalose, which protects the surface cells themselves rather than just wetting them. If your tears seem to evaporate fast (burning more than gritty, worse in wind and dry heat), a lipid-based drop like Systane Complete Preservative-Free targets the evaporation layer.
Uncertain which pattern is yours? That's what an optometrist visit answers in ten minutes, and the Canadian Association of Optometrists keeps a plain-language dry eye explainer if you want the neutral version. Or browse the preservative-free range we stock and start with the cheapest bottle that matches your symptom, you can get precise later.
About the Reviewer
Dr. Davinder Sidhu is an optometrist based in British Columbia with a focus on dry eye management and preservative-free solutions. Learn more at TheGenuwineOD.com or follow him on Instagram and Facebook.
