People who take tadalafil (Cialis) long-term may need regular eye health monitoring.
Tadalafil (Cialis), a medication widely known for treating erectile dysfunction, is also prescribed for urinary urgency and frequency associated with an enlarged prostate. A large comparative study published online in the British Journal of Ophthalmology has found that men receiving the drug for these symptoms had a higher likelihood of developing glaucoma, a serious eye condition that can damage vision.
The researchers say the findings support careful eye monitoring for patients who take tadalafil long term for this purpose, particularly those who already have glaucoma risk factors, including a family history of the disease or elevated pressure inside the eye (ocular hypertension).
Tadalafil belongs to a group of medications called phosphodiesterase type 5 inhibitors (PDE5i), which also includes sildenafil (Viagra). Previous research has associated these drugs with several eye conditions involving structures such as the optic nerve and the macula, the part of the retina responsible for sharp, detailed vision.
Evidence specifically connecting PDE5i drugs with glaucoma, however, has remained inconsistent and inconclusive. The uncertainty is especially relevant for tadalafil when it is prescribed for lower urinary tract symptoms because treatment commonly involves taking the medication every day over long periods.
Long-term use raises a safety question
To investigate that possible connection, researchers examined whether tadalafil, a long-acting PDE5i, was associated with an increased risk of glaucoma when used to manage urinary symptoms caused by an enlarged prostate (benign prostatic hyperplasia).
They analyzed anonymized records from 73,854 men aged 40 or older in the TriNetX Analytics Network (Global Collaborative Network). Half had received tadalafil or another PDE5i for their urinary symptoms for periods of up to five years (between January 2012 and December 2022), while the other half had not been prescribed these medications.
The researchers compared the two groups over five years, examining the likelihood of developing glaucoma, ocular hypertension, or beginning treatment for glaucoma.
To make the groups more comparable, the men were matched according to factors that could potentially influence the results. These included age, ethnicity, smoking, alcohol-related disorders, cardiovascular disease, diabetes, cancer, high cholesterol, kidney function, obesity, chronic obstructive pulmonary disease (COPD), and prescribed medications.
Tadalafil users showed higher eye risks
The analysis found that men prescribed tadalafil were 22% more likely to develop glaucoma than those who had not received the drug. They were also 32% more likely to develop ocular hypertension, 33% more likely to develop primary open angle glaucoma–the most common form of the disease—and 33% more likely to begin glaucoma treatment.
Additional analysis found that the associations remained among patients who developed glaucoma within 1, 3, or 6 months after beginning tadalafil treatment. Similar patterns were consistently seen among patients aged 50 and older, White patients, and people with various underlying health conditions included in the analysis.
The study cannot establish causation
Because the research was observational, it cannot demonstrate that tadalafil itself caused the increased eye risks. The researchers also identified several limitations, including their inability to account for changes in medication prescriptions and actual drug use over time or for new underlying health conditions that developed during the study period.
Most participants were White, which also limits how confidently the findings can be applied to men from other ethnic backgrounds.
Nevertheless, they write: “These findings suggest that chronic PDE5 inhibition may influence ocular physiology, warranting further mechanistic investigation.”
But they emphasize: “These findings do not contraindicate tadalafil use but highlight the importance of baseline ophthalmic assessment and regular follow-up, particularly in patients with pre-existing glaucoma, ocular hypertension, a family history of glaucoma, high myopia [shortsightedness], or those requiring long-term therapy.”
Reference: “Risk of glaucoma among patients using tadalafil for lower urinary tract symptoms: a multinational cohort study” by Yun Hsia, Chien-Yun Tsai, Sheng-Chun Hung, Jun-Peng Chen, Ssu-Yu Pan, Hui-Ju Lin, I-Jong Wang, Chien-Hsiang Weng, Mi-Hyun Nam and Chien-Chih Chou, 4 August 2026, British Journal of Ophthalmology.
DOI: 10.1136/bjo-2026-329957
This study was supported by the Taichung Veterans General Hospital, Taiwan (grant number: TCVGH-1152201B).
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