What are the recommended first‑line and alternative eye drop therapies for glaucoma, including their indications and contraindications?

Eye Drops for Glaucoma

Prostaglandin analogs are the first-line eye drop therapy for glaucoma because they provide the most effective IOP reduction (20-30%), require only once-daily dosing, and are well-tolerated with minimal systemic side effects. 1

First-Line Therapy: Prostaglandin Analogs

The 2021 American Academy of Ophthalmology guidelines explicitly state that prostaglandin analogs are "often considered as initial medical therapy" for glaucoma 1. Network meta-analyses confirm that prostaglandin analogs (PGAs) provide the best IOP-lowering effect among all monotherapy regimens 2.

Specific agents include:

• Latanoprost
• Bimatoprost
• Travoprost
• Tafluprost

Key advantages:

• Once-daily dosing (improves adherence)
• Most efficacious IOP reduction
• No absolute contraindications
• Minimal systemic side effects

Side effects to counsel patients about:

• Conjunctival hyperemia (redness)
• Iris pigmentation changes (permanent)
• Periocular skin darkening
• Eyelash growth and darkening
• Prostaglandin-associated periorbitopathy (deepening of eyelid sulcus)

Second-Line Alternatives

Beta-Blockers (e.g., Timolol, Betaxolol)

Use when prostaglandins are contraindicated, not tolerated, or refused by the patient 1.

IOP reduction: 20-25%

Dosing: Once or twice daily (avoid nighttime dosing—associated with nocturnal hypotension and potential visual field progression) 1

Critical contraindications:

• Asthma or chronic obstructive pulmonary disease (COPD)
• Heart block (second or third degree)
• Bradycardia
• Congestive heart failure
• Caution in diabetes (may mask hypoglycemia symptoms) 3

Important distinction: Cardioselective beta-blockers (betaxolol) minimize but do not eliminate pulmonary risks 1.

Systemic absorption warning: Topical timolol can cause bradycardia requiring pacemaker implantation in some patients 3. Educate patients on nasolacrimal occlusion or eyelid closure after instillation to reduce systemic absorption 1, 4.

Alpha-2 Adrenergic Agonists (e.g., Brimonidine)

IOP reduction: 15-20%

Dosing: 2-3 times daily

Side effects:

• Ocular allergy (common—up to 15% develop allergic conjunctivitis)
• Dry mouth
• Fatigue
• Avoid in children under 2 years (CNS depression risk)

Topical Carbonic Anhydrase Inhibitors (Dorzolamide, Brinzolamide)

IOP reduction: 15-20%

Dosing: 2-3 times daily

Contraindications:

• Sulfonamide allergy (absolute)

Side effects:

• Metallic taste
• Ocular stinging/burning
• Corneal edema (rare)

Rho Kinase Inhibitors (Netarsudil)

IOP reduction: 10-20%

Mechanism: Increases trabecular outflow, decreases episcleral venous pressure

Side effects:

• Conjunctival hyperemia (very common—up to 50%)
• Corneal verticillata
• Conjunctival hemorrhage

No contraindications listed 1

Combination Therapy Algorithm

If target IOP is not achieved with monotherapy:

1. Add a second agent from a different class (e.g., prostaglandin + beta-blocker)
2. Consider fixed-combination drops to improve adherence (reduces drop burden) 1, 4, 5
3. Avoid monocular trials—they are poor predictors of long-term efficacy due to asymmetric IOP fluctuations and contralateral effects 1, 4, 5

Common fixed combinations:

• Latanoprost/timolol
• Travoprost/timolol
• Dorzolamide/timolol
• Brimonidine/timolol

Target IOP Strategy

Initial target: 20% reduction from baseline mean IOP 1

Adjust downward if:

• Progressive optic nerve damage occurs despite achieving target
• Baseline IOP is markedly elevated (20% may be insufficient)

Adjust upward if:

• Patient stable for prolonged period with low IOP
• Side effects necessitate medication reduction

Critical Adherence Considerations

Nearly 45% of glaucoma patients take fewer than 75% of prescribed doses, even with once-daily medications 4, 5. To improve adherence:

• Link drop administration to daily activities (e.g., brushing teeth)
• Provide written medication schedules
• Use fixed combinations when multiple drops needed
• Consider preservative-free formulations for patients with ocular surface disease 6
• Ensure patients can physically instill drops (assess dexterity, especially in elderly) 4, 5
• Address cost barriers directly

Special Populations

Pregnancy:

• Prostaglandins: Category C
• Beta-blockers: Labetalol and metoprolol considered safe 3
• Carbonic anhydrase inhibitors: Category C (avoid if possible)

Patients with cardiovascular disease: Avoid or use caution with beta-blockers; prostaglandins are preferred 3.

Patients with pulmonary disease: Absolutely avoid nonselective beta-blockers; prostaglandins are first-line 1.

Common Pitfalls to Avoid

• Do not dose beta-blockers at night—associated with visual field progression 1
• Do not use monocular trials to assess medication efficacy 1, 4, 5
• Do not overlook systemic absorption of topical beta-blockers—teach nasolacrimal occlusion 1, 4
• Do not ignore adherence barriers—directly address cost, dexterity issues, and complexity of regimen 4, 5
• Do not prescribe carbonic anhydrase inhibitors to patients with sulfa allergy 1