Understanding the Answer to 'What are the side effects of glaucoma eye drops?'

October 8, 2025 •

4 min read

As of 2022, an estimated 4.22 million people in the U.S. were living with glaucoma [1.11.1]. For many, treatment involves prescription eye drops, but it's crucial to understand the answer to: what are the side effects of glaucoma eye drops? [1.2.1]

Quick Summary

Glaucoma eye drops can cause local side effects like redness, stinging, and eye color changes, as well as systemic effects like fatigue and slowed heart rate [1.2.1, 1.4.1]. The specific side effects vary by medication type.

Key Points

Vary by Type: Side effects differ significantly among medication classes like prostaglandin analogs, beta-blockers, and alpha-agonists [1.2.1, 1.2.5].
Local vs. Systemic: Effects can be local (eye redness, stinging, color change) or systemic (fatigue, slowed heart rate, dry mouth) [1.2.1, 1.10.4].
Prostaglandins Cause Cosmetic Changes: The most common class, prostaglandin analogs, can cause eyelash growth and permanent darkening of the iris and eyelid skin [1.2.4].
Beta-Blockers Affect Heart and Lungs: Beta-blockers can cause systemic issues like low blood pressure, fatigue, and breathing difficulties, especially in those with pre-existing conditions [1.4.1].
Management is Possible: Minimizing systemic absorption by closing the eye and pressing on the tear duct after application can reduce side effects [1.8.3, 1.8.4].
Communication is Crucial: Always discuss side effects with your doctor, as they may be able to switch medications or suggest alternatives [1.8.2].
Allergies Are Common with Alpha-Agonists: Alpha-adrenergic agonists have a relatively high likelihood of causing an allergic reaction in the eye [1.5.3].

The Role of Eye Drops in Glaucoma Management

Glaucoma is a group of eye conditions that damage the optic nerve, often caused by abnormally high pressure inside your eye (intraocular pressure or IOP) [1.2.4]. It is a leading cause of irreversible blindness worldwide [1.11.4]. Prescription eye drops are typically the first line of treatment, designed to lower IOP by either reducing the amount of fluid the eye produces or by helping fluid drain more effectively [1.2.5]. While essential for preserving vision, these medications can come with a range of side effects, which differ depending on the class of drug prescribed [1.2.1].

Prostaglandin Analogs

This is the most commonly prescribed class of glaucoma medication, used once daily [1.2.4]. They work by increasing the outflow of fluid from the eye [1.3.3].

Local Side Effects: The most common effects include eye redness, stinging, and itching [1.3.3]. Over time, they can cause permanent changes, such as darkening of the iris (especially in hazel or green eyes), increased growth and darkening of eyelashes, and darkening of the skin around the eyelids [1.3.2, 1.2.4]. Some patients experience a sunken-eye appearance (periorbital fat atrophy) or blurred vision [1.3.2, 1.3.3].
Systemic Side Effects: These are uncommon but can include flu-like symptoms or joint and muscle pain [1.3.1].
Examples: Latanoprost (Xalatan), Travoprost (Travatan Z), Bimatoprost (Lumigan) [1.2.4].

Beta-Blockers

Beta-blockers work by reducing the production of fluid in the eye and may be prescribed for once or twice-daily use [1.4.1].

Local Side Effects: These can include stinging, burning, redness, and blurry vision [1.2.2, 1.4.2].
Systemic Side Effects: Beta-blockers are absorbed into the bloodstream and can have significant systemic effects. These include fatigue, slowed heart rate (bradycardia), lower blood pressure, and shortness of breath, particularly in those with asthma or COPD [1.4.1, 1.10.4]. Other reported effects are depression, dizziness, and reduced libido or impotence [1.3.2, 1.4.1].
Examples: Timolol (Timoptic), Betaxolol (Betoptic S) [1.4.1].

Alpha-Adrenergic Agonists

These medications both reduce fluid production and increase its outflow [1.2.4]. They are often prescribed for use two or three times a day [1.2.4].

Local Side Effects: A key issue with this class is a relatively high rate of allergic reaction, causing red, itchy, and swollen eyes [1.5.3]. Dilated pupils and a feeling of something being in the eye can also occur [1.3.2, 1.2.5].
Systemic Side Effects: The most common are dry mouth and nose, fatigue, drowsiness, and headache [1.5.3, 1.2.4]. They can also affect blood pressure and heart rate [1.2.4].
Examples: Brimonidine (Alphagan P), Apraclonidine (Iopidine) [1.2.4].

Carbonic Anhydrase Inhibitors (CAIs)

Available as both eye drops and oral pills, CAIs reduce the production of fluid in the eye [1.2.4]. The drops are typically used two or three times daily [1.2.4].

Local Side Effects (Drops): Stinging, burning, and general eye discomfort are common [1.3.3]. Blurred vision and dry eyes can also occur [1.5.1, 1.2.5].
Systemic Side Effects (Pills): The oral form has more pronounced side effects, including a metallic taste (especially with carbonated drinks), tingling in the hands and feet, fatigue, frequent urination, and kidney stones [1.2.4, 1.6.2].
Examples: Dorzolamide (Trusopt), Brinzolamide (Azopt) [1.2.4].

Rho Kinase Inhibitors

This newer class of medication increases fluid outflow by targeting the trabecular meshwork, the eye's primary drainage system [1.7.2]. It is prescribed for once-daily use [1.2.4].

Local Side Effects: The most frequent side effect is eye redness (conjunctival hyperemia) [1.7.3]. Other common effects include stinging or pain upon instillation, small bleeds on the white of the eye (conjunctival hemorrhages), and deposits on the cornea (corneal verticillata) that typically don't affect vision [1.7.2, 1.7.3].
Systemic Side Effects: Systemic side effects are not commonly associated with this class [1.8.1].
Example: Netarsudil (Rhopressa) [1.2.4].

Comparison of Glaucoma Eye Drop Side Effects


Medication Class	Common Local Side Effects	Common Systemic Side Effects
Prostaglandin Analogs	Redness, stinging, eyelash growth, iris & skin darkening, sunken eyes [1.3.3, 1.9.2].	Rare; may include flu-like symptoms [1.3.1].
Beta-Blockers	Stinging, blurry vision [1.4.2].	Fatigue, slowed heart rate, low blood pressure, difficulty breathing [1.4.1].
Alpha-Adrenergic Agonists	Allergic reaction (red, itchy eyes), dry mouth, fatigue, drowsiness [1.5.3, 1.2.4].	Dry mouth, fatigue, headache, changes in blood pressure [1.5.3].
Carbonic Anhydrase Inhibitors	Stinging/burning, metallic taste [1.2.4, 1.6.1].	Tingling in hands/feet, fatigue, frequent urination (especially with pills) [1.2.4].
Rho Kinase Inhibitors	Eye redness, corneal deposits, small bleeds on the eye's surface [1.3.3, 1.7.3].	Generally well-tolerated systemically [1.8.1].
Miotic/Cholinergic Agents	Smaller pupils, blurred or dim vision, headache, eye pain [1.12.1].	Rare; may include sweating and salivation [1.12.3].

Managing and Minimizing Side Effects

While side effects can be frustrating, there are techniques to manage them. To minimize the amount of medication absorbed into your bloodstream, which causes most systemic side effects, press your finger on the corner of your eye near the nose (nasolacrimal occlusion) for one to two minutes after instilling the drop and keep your eyes closed [1.8.3, 1.8.4]. Wiping away any excess medication from your eyelid is also helpful [1.8.3].

If you use multiple types of eye drops, wait at least five minutes between each one [1.8.3]. Never change your dosage or stop your medication without consulting your doctor [1.8.4]. Some side effects may decrease over time as your body adjusts [1.2.2]. If side effects persist or are intolerable, your doctor may switch you to a different medication, a preservative-free formulation, or suggest alternative treatments like laser therapy [1.3.3, 1.8.1].

Conclusion

Glaucoma eye drops are a vital tool in preventing vision loss. However, they are not without potential side effects, which range from mild local irritation to significant systemic issues [1.2.1]. Understanding the specific side effects associated with your prescribed medication is key. Open communication with your ophthalmologist is essential to find a treatment that effectively controls your eye pressure while minimizing adverse effects, ensuring you can adhere to your therapy long-term. Always report any new or bothersome side effects to your healthcare provider.

For more information from a trusted source, visit the Glaucoma Research Foundation.

Frequently Asked Questions

Yes, prostaglandin analogs, a common type of glaucoma medication, can cause permanent darkening of the iris, particularly in people with hazel, green, or light brown eyes [1.3.2, 1.2.4].

Fatigue and drowsiness can be a systemic side effect of several types of glaucoma drops, most notably beta-blockers and alpha-adrenergic agonists, which can be absorbed into the bloodstream [1.4.1, 1.5.3].

Yes, a mild and temporary stinging, burning, or itching sensation is a common side effect for many types of glaucoma eye drops, including prostaglandins, alpha-agonists, and carbonic anhydrase inhibitors [1.2.2, 1.3.3].

No, you should never stop or change your medication regimen without first consulting your eye doctor. Abruptly stopping treatment can lead to a dangerous increase in eye pressure. Your doctor can work with you to find a more tolerable alternative [1.8.4, 1.8.2].

To minimize systemic side effects, gently close your eyes for one to two minutes after instilling the drop and press on the inner corner of your eye by the nose. This prevents the medication from entering the tear duct and bloodstream as quickly [1.8.3, 1.8.4].

Side effects like increased eyelash growth, which are common with prostaglandin analogs, are generally reversible and will diminish if you stop using that specific medication [1.8.2].

Eye redness is a potential side effect of almost all glaucoma medications, but it's most common with prostaglandin analogs and Rho kinase inhibitors [1.2.1, 1.3.3]. The severity can vary by specific drug and individual. If redness is a major concern, discuss preservative-free options or other medication classes with your doctor [1.8.1].