What Are the Long-Term Side Effects of Latanoprost?

Latanoprost is one of the most widely used daily drops for glaucoma and high eye pressure, and many people stay on it for decades. Most of its long-term side effects are changes you can see in the mirror rather than harm to your sight. A few of those visible changes can be permanent, which makes the question worth asking before years of use rather than after.¹ Serious effects inside the eye are uncommon and tend to cluster in people with specific risk factors.

Longer, Darker Lashes and a Red Eye

Eyelashes on the treated eye can grow measurably longer within 2 weeks of starting the drops.² In one group of users, average lash length rose from about 5.8 mm to 6.6 mm over 10 weeks.³ Noticeable lash changes appeared in about a third of users by 3 months and nearly half (46%) by 1 year.⁴ Lashes can also become darker and thicker.⁵

Day to day, the longer lashes may curl, tangle, or brush against your glasses. Using drops in only one eye can leave the two sets of lashes looking different. Trimming the lashes can even out the length; ask your eye doctor how to do it safely near the eye.

You can cut down on uneven changes. After putting the drop in, wipe any excess off the eyelid skin and lashes. Use one drop only, since more just runs onto the skin. If only one eye is being treated, ask your doctor whether that is truly unavoidable.

Redness is one of the most common side effects of this group of drops.⁶ Latanoprost causes less redness than the similar drugs bimatoprost and travoprost.⁷ Still, redness and other eye side effects are a leading reason people stop or switch their glaucoma drops.⁸ If redness bothers you, tell your eye doctor rather than quietly skipping doses.

Iris and Eyelid Skin Darkening

The drops can slowly darken the iris, the coloured part of the eye.⁹ They make the pigment cells in the iris produce more melanin, the same pigment behind skin colour.¹⁰ The front layer of the iris builds up extra pigment and thickens.¹¹ In one group of treated people, about 7 in 10 developed a visible colour difference between their eyes.¹² The change is added pigment, not damage, so it is not harmful in itself.

Mixed-colour eyes, such as hazel or green-brown, change most noticeably. Evenly dark brown eyes rarely show a visible change, and evenly blue eyes are less prone than mixed ones. The change develops over months to years, not overnight.

The main clear disadvantage is a colour difference between the eyes when only one eye is treated.¹³ This darkening is likely to be permanent or to fade only very slowly.¹⁴ If you have light or mixed eyes and need drops in one eye only, ask about this before starting.

To track changes yourself, take a well-lit close-up photo of both eyes before you begin. Repeat it every few months in the same light, and bring the photos to check-ups so your doctor can compare. Iris change does not affect vision, so it is not a reason to stop without advice.

Eyelid skin can darken with ongoing use.¹⁵ This darkening can fade after the drops are stopped.¹⁶ Rarely, the skin around the eye becomes lighter instead.¹⁷

Sunken Upper Eyelids and Facial Changes

Over time the drops can cause loss of fat around the eye, which deepens the upper lid crease and flattens lower lid bags.¹⁸ In people newly starting latanoprost, a deeper upper lid appeared in about 6% by 6 months.¹⁹ In people already using it, about 4 in 10 had some of these signs and about 1 in 6 had a deeper upper lid.²⁰ With bimatoprost the figures were far higher, with 8 in 10 having a deeper lid.²¹ With latanoprost these changes can take years, about 6 years on average, to appear.²²

Changes can include a droopier lid and a smoother, more hollow look around the eye.²³ A hollow lid can make one eye look sunken or tired. It can also make eye-pressure measurements and future eye surgery a little harder. Younger people seem less affected by fat loss, and photos side by side help you spot slow change.

The changes can partly reverse. A year after stopping these drops, the deep lid crease improved in most people and lower lid bags partly returned.²⁴ If hollowing bothers you, switching drugs is a real option to discuss. Your doctor may offer a different drug class, such as timolol, and will recheck eye pressure a few weeks after a switch. Stopping on your own risks silent vision loss.

Dry, Gritty, Stinging Eyes and the Preservative Question

Standard latanoprost contains a preservative, benzalkonium chloride (BAK), which can irritate the eye surface; you may see it on the label.²⁵ Preservative-free latanoprost caused less stinging, burning, itching and stickiness.²⁶ It also caused less redness while lowering pressure just as well.²⁷ People found these drops easier to keep using.²⁸

The drug itself may still affect the oil glands of the eyelids. In mice, even preservative-free latanoprost began clogging these glands within 4 weeks.²⁹ In lab studies, latanoprost caused inflammation in gland cells.³⁰ This comes from animal and lab work, so how much it affects people is not known.

Signs of dry eye or eyelid gland trouble include burning, grittiness, or vision that clears with blinking. Lid margins may be crusty or sticky in the morning. Symptoms are often worse with screens or heating. Warm compresses and lid cleaning are common simple remedies.

Preservative-free drops often come in single-use vials, and they may cost more or need specific prescribing. They are worth asking for if you have dry eye or use several drops.

Rare Serious Effects Inside the Eye

Latanoprost has been linked to cystoid macular edema (CME), swelling at the centre of the retina that blurs reading vision.³¹ In one group of 94 users, about 2% developed it.³² It has mostly been seen after cataract surgery, including in eyes with other risk factors.³³ It has also occurred with preservative-free drops years after a routine cataract operation.³⁴ The swelling cleared within weeks of stopping the drops, and came back in one person who restarted.³⁵

Latanoprost may also trigger uveitis, inflammation inside the eye causing pain, redness and light sensitivity.³⁶ About 6% of patients in the same group of 94 developed it.³⁷ The risk seems higher in people with past uveitis or eye surgery, though it can happen without them.³⁸ Tell your eye doctor about any past eye surgery or inflammation before starting.

Mild redness or stinging in the first days is common and is not the same as inflammation inside the eye. Swelling at the centre of the retina usually brings blurring or distortion of reading vision without pain, so it can be missed if you only watch for discomfort. Make a prompt appointment if you notice blurred or wavy central vision, straight lines looking bent, new eye pain, sensitivity to light, or a red eye worse than your usual redness.

If you are having cataract surgery, tell the surgeon you use latanoprost. Some surgeons pause the drops around surgery, and anti-inflammatory drops are sometimes added afterwards. Do not stop on your own without a pressure plan.

Effects on the Rest of the Body and Other Eye Tissues

Most of each drop drains through the tear duct into the nose and throat and is absorbed there.³⁹ After a year of daily use, levels in the blood were too low to detect in most people.⁴⁰ Body-wide side effects such as headache, facial rash or heart effects are rare.⁴¹ To reduce what reaches the body, press the inner corner of the eye for one to two minutes after the drop and close the eye gently instead of blinking hard.

Over years, the cornea, the clear front window of the eye, may become slightly thinner, by about 4 to 5 micrometres.⁴² This showed up only after about 2 years of use.⁴³ Your doctor may remeasure corneal thickness because it affects how pressure readings are interpreted.⁴⁴ A thinner cornea can make pressure read lower than it really is. The change is small and not harmful to sight itself, and it is checked with a quick painless test.

Cataracts may also be a consideration: in one comparison, people on this drug group needed cataract surgery earlier than people without glaucoma, but later than people on timolol-type drops.⁴⁵

Does Latanoprost Keep Working for Years

Latanoprost keeps lowering eye pressure with no sign of wearing off over prolonged use.⁴⁶ After 5 years it kept pressure down and preserved side vision in about 70% of treated eyes.⁴⁷ It works in normal-tension and angle-closure glaucoma too.⁴⁸

Missed doses matter more than side effects. Glaucoma damage is silent and permanent, and only a small share of people keep refilling steadily for a full year. Dosing in the evening, tied to a routine, helps. So do phone reminders or a drop log. Your doctor may add or change drugs if pressure creeps up despite use, if visual field tests show progression, or if side effects make you skip doses.

Latanoprost in Children and Compared With Similar Drops

Long-term latanoprost did not affect eye development in children with glaucoma.⁴⁹ Children had fewer side effects than adults, with no cases of eyelid hollowing.⁵⁰ Darker lashes, though, were more common in treated children.⁵¹

In one comparison, about 16% on latanoprost had significant side effects versus about 41% on bimatoprost or travoprost.⁵² Bimatoprost caused more redness than latanoprost.⁵³

At a review, useful questions include whether your iris or eyelid is changing in photos, whether preservative-free drops would suit you, and whether one-eye treatment is avoidable. Ask too what to do if hollowing appears.