Intraocular pressure (IOP) is a major risk factor for the development of glaucoma-related optic neuropathy. Primary open-angle glaucoma (POAG) is the most common type of glaucoma in patients of European or African descent. Reducing IOP is currently the only FDA-approved treatment to prevent glaucoma in ocular hypertensive (OHT) patients and to prevent or delay glaucomatous progression in POAG patients.

Managing elevated IOP is usually done through medication. The most popular types of pharmaceuticals to treat glaucoma include beta blockers, carbonic anhydrase inhibitors (CAIs), alpha agonists, miotics, and prostaglandin analogues (PGs). In eye drop form, PGs are the strongest IOP-lowering medications for treating POAG and OHT. 

Three of the most commonly prescribed PGs are:

• 0.005% latanoprost 
• 0.004% travoprost
• 0.03% bimatoprost (synthetic PG)

Over the past several years, few studies have been conducted to compare the efficacy and tolerance of different PGs, and their results have been inconsistent. In a 2019 meta-analysis of randomized controlled trials (RCTs), researchers compared results concerning the efficacy and safety of these three popular PGs in treating patients with POAG or OHT.*

What they did

Seventeen studies, involving a total of 2,433 participants, were included in the analysis. Patients had either POAG or OHT and were age 18 or older, with an average age of 52 to 68 years. There were no restrictions based on sex, race, or region. 

Treatment efficacy was determined by the average IOP reduction from baseline to endpoint. Safety and tolerability were analyzed based on such side effects as: 

• Conjunctival hyperemia (eye redness) 
• Discomfort (itching, eye irritation, foreign body sensation)
• Growth of lashes

What they found

Results of the study comparisons revealed that:

• Bimatoprost showed greater efficacy in lowering IOP in the third month; lower tolerability and higher incidence of eye redness than travoprost; and similar incidence (new case) rates of discomfort and lash growth as travoprost.
• Travoprost showed a higher risk of eye redness and lash growth compared to latanoprost.
• Latanoprost showed similar efficacy to travoprost in lower IOP, but latanoprost was better tolerated.

What it means

Overall, bimatoprost was more effective in controlling IOP compared to latanoprost and travoprost, though it also resulted in a higher incidence of side effects. The higher concentration of the drug was associated with both of these outcomes. The fewest side effects occurred in patients treated with latanoprost. 

Limitations of this meta-analysis include the short duration of the trials (few lasted longer than six months) and the small sample sizes of all but four of the studies. Despite these limitations, there were clear differences in both efficacy and tolerability between the medications. Both factors heavily influence patient adherence and outcomes. 

While there are no definitive guides to direct ophthalmologists in the use of PGs, these results may be useful for optimizing treatment strategies for individual patients. 

*Tang, W., Zhang, F., Liu, K., & Duan, X. (2019, July). Efficacy and Safety of Prostaglandin Analogues in Primary Open-Angle Glaucoma or Ocular Hypertension Patients. Medicine. https://journals.lww.com/md-journal/fulltext/2019/07260/efficacy_and_safety_of_prostaglandin_analogues_in.78.aspx

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