A large observational study published in August 2026 in the British Journal of Ophthalmology has found that men taking tadalafil for urinary symptoms associated with an enlarged prostate experienced a higher rate of glaucoma over a five-period compared to similar patients who did not use phosphodiesterase type 5 inhibitor drugs. Tadalafil, widely recognized as the active ingredient in Cialis for treating erectile dysfunction, is also prescribed to manage urinary urgency and frequency linked to benign prostatic hyperplasia (BPH).
New Study Links Tadalafil Use to Higher Glaucoma Risk
The research examined anonymized electronic health records from the multinational TriNetX database. Following statistical matching, investigators evaluated 36,927 tadalafil users alongside 36,927 men who were not taking a PDE5 inhibitor. Over follow-up periods lasting as long as five years, glaucoma was diagnosed in 3.93% of the tadalafil users, compared to 3.16% of the non-users.
Understanding the Relative Risks and Eye Health Outcomes
While the study reported a 22% higher relative risk of overall glaucoma among patients taking the medication, researchers emphasized that this figure does not mean 22 out of every 100 users developed the condition. The actual five-year rates remained below 4% in both observed groups. However, the analysis identified several related ocular outcomes that moved in the same direction:
- Glaucoma overall: 22% higher risk associated with tadalafil
- Ocular hypertension: 32% higher risk
- Primary open-angle glaucoma: 33% higher risk
- Starting glaucoma treatment: 33% higher risk
Investigators found no statistically significant association between tadalafil use and low-tension glaucoma or primary angle-closure glaucoma. Furthermore, the statistical signal persisted in analyses focusing specifically on men aged 50 and older, White participants, and individuals presenting with multiple underlying health conditions.
Dosing Distinctions and Limitations in Causation
Dosing regimens for tadalafil vary depending on the condition being treated. While erectile dysfunction can be managed with an as-needed dose often starting at 10 mg or through daily dosing, BPH is typically treated with 5 mg once daily. Because participants in the British Journal of Ophthalmology study were taking the medication for lower urinary tract symptoms involving long-term, ongoing use, findings apply most directly to older men receiving continuous treatment for urinary problems rather than occasional use before sexual activity.
Because the research was observational, investigators noted that the study cannot establish causation or prove that tadalafil itself directly caused the increased eye risks. The study was supported by the Taichung Veterans General Hospital in Taiwan under grant number TCVGH-1152201B.
Clinical Context and Recommendations for Patients
PDE5 inhibitors function by increasing signaling involving nitric oxide and cyclic guanosine monophosphate (cGMP), a pathway that relaxes smooth muscle and alters blood flow to produce vascular effects. Because blood flow and pressure regulation are critical inside the eye, experts have proposed hypotheses involving temporary changes in intraocular pressure or blood circulation around the optic nerve.
An expert discussing the findings noted that changes in eye pressure or optic nerve perfusion could potentially contribute to injury in susceptible individuals. For patients taking Cialis, particularly on a daily basis or over extended periods, researchers advise that the sensible response is heightened awareness rather than panic, supporting closer eye monitoring especially for those who already exhibit glaucoma risk factors such as a family history of the disease or elevated pressure inside the eye.
