Cialis Linked to 22% Higher Glaucoma Risk in Study of 74,000 Men, Researchers Say Link Is Not Yet Proven

A large study published in the British Journal of Ophthalmology found men taking tadalafil for urinary symptoms tied to an enlarged prostate had a higher rate of glaucoma diagnoses than men who didn't take the drug. Tadalafil is the generic name for Cialis, one of the most widely prescribed erectile dysfunction drugs in the country.

Researchers led by Chien-Chih Chou of Taichung Veterans General Hospital in Taiwan pulled records on 73,854 men age 40 and older from the TriNetX Analytics Network, a global health records database, according to SciTechDaily. About half had been prescribed tadalafil or a similar drug for lower urinary tract symptoms between 2012 and 2022. The other half hadn't.

Over five years of follow-up, men on tadalafil were 22% more likely to develop glaucoma, 32% more likely to develop high eye pressure, and 33% more likely to develop primary open-angle glaucoma, the most common form of the disease, according to the study as reported by SciTechDaily, MedPage Today, and The Independent. Those men were also 33% more likely to start glaucoma treatment.

Glaucoma is a leading cause of irreversible blindness worldwide. It typically damages the optic nerve gradually, often destroying peripheral vision before a patient notices anything is wrong.

Not proof of cause and effect

Every outlet covering this study, including Fox News, The Independent, and MedPage Today, is careful to note the same thing: this is an observational study. It shows a statistical association. It does not prove tadalafil causes glaucoma.

Dr. Stephen Freedland of Cedars-Sinai Medical Center in Los Angeles, who wasn't involved in the research, told MedPage Today the study has real limitations worth taking seriously. Men prescribed tadalafil for urinary symptoms may differ from men who aren't in ways researchers couldn't fully account for.

"We know tadalafil is used not just for LUTS, but also for ED," Freedland said, using the medical shorthand for erectile dysfunction. "Thus, whether it is the medicine itself or the fact that these men were deemed to need tadalafil is unknown."

Freedland raised a specific example: high blood pressure raises the risk of both erectile dysfunction and glaucoma. The researchers adjusted for whether a patient had hypertension, he said, but not for how severe it was. That means men with worse hypertension could be driving both their ED diagnosis and their glaucoma risk, with tadalafil as an innocent bystander.

Freedland also flagged the actual size of the effect. "The absolute effect, if real, was small," he told MedPage Today. "A less than 0.8% increased risk over 5 years." He said requiring routine eye exams for every man starting tadalafil "is a huge burden on our health system" for that level of risk, and said his own recommendation on eye care wouldn't change based on whether a patient was starting the drug.

A 22% relative increase sounds dramatic. An 0.8% absolute increase over five years is different, and both figures are accurate at the same time.

A conflicting study exists too

MedPage Today reported something none of the other outlets mentioned: a separate study using the same TriNetX database, presented at the Association for Research in Vision and Ophthalmology meeting, found the opposite result. Researchers at the University of Miami reported a protective effect against glaucoma in men prescribed PDE5 inhibitors, the drug class that includes both Cialis and Viagra, for erectile dysfunction specifically.

That's a direct contradiction sitting in the same body of research, using the same database. Fox News, The Independent, and SciTechDaily don't mention it. This shows the science on PDE5 inhibitors and eye health is genuinely unsettled, not converging on one answer.

What the study's authors actually recommend

Chou and his co-authors were not sweeping in their conclusions. "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, or those requiring long-term therapy," they wrote, according to MedPage Today.

Dr. Valerie Kattouf, an optometrist at the Illinois Eye Institute who wasn't involved in the study, told Fox News Digital that glaucoma "especially in its early stages often does not present with visual symptoms." She recommends a baseline comprehensive eye exam for anyone taking the drug regularly, with closer monitoring for people who already have risk factors like a family history of glaucoma or severe nearsightedness.

Nobody in this reporting, including the study's own authors, is telling men to stop taking Cialis. The unresolved question is whether future prospective trials, the kind that could actually test cause and effect rather than just association, will confirm the Taiwan findings, back the Miami group's opposite result, or land somewhere in between.