The case for tadalafil has long been clear: proven efficacy for erectile dysfunction and enlarged prostate symptoms, backed by decades of clinical use. A study now published in the British Journal of Ophthalmology, covering nearly 74,000 men, complicates that picture. Men who took the drug were 22% more likely to develop glaucoma than those who did not, surfacing a visual risk that patients rarely associate with the medication.
An international research team compared roughly 37,000 men prescribed tadalafil against a matched group not using phosphodiesterase type 5 inhibitors, the drug class that includes Eli Lilly's Cialis, following both cohorts for up to five years. The risk gradient sharpens at the subtype level: men on tadalafil were 32% more likely to develop elevated intraocular pressure, and 33% more likely to develop primary open-angle glaucoma, the most common form of the disease.
The read-through to patient risk compounds when you factor in how glaucoma actually presents. Dr. Valerie Kattouf of the Illinois Eye Institute, who was not involved in the study, said the condition typically carries no visual symptoms in its early stages, with peripheral vision loss arriving gradually enough that meaningful damage often precedes any patient-reported change. Kattouf identified a higher-risk subset worth watching: men with a family history of glaucoma, pre-existing elevated eye pressure, or severe nearsightedness. For long-term daily tadalafil users in that group, she said, closer ophthalmological monitoring and a comprehensive baseline eye exam are warranted.
The counterargument is the one the researchers put forward themselves. This is observational research. The study identified an association between tadalafil use and glaucoma rates; it did not establish a causal mechanism. The team also acknowledged it could not account for changes in medication use or new health conditions that developed during the follow-up period. The researchers were explicit: the findings do not support discontinuing the medication.
On balance, this study does not move prescribing patterns on its own. What it does is define a monitoring obligation for a specific patient subset. The line to watch is how Eli Lilly responds. Fox News Digital contacted the manufacturer of Cialis for comment, and no response had been received at time of publication.