August 5, 2026, 3:46 pm | Read time: 4 minutes
In Germany, several million men suffer from erectile dysfunction. Medications like Viagra can help. However, a large-scale Taiwanese study has now shown that a widely used potency drug ingredient may increase the risk of a dangerous eye disease.
Estimates suggest that around three to five million men in Germany are affected by erectile dysfunction.1 Colloquially, this is referred to as impotence or an erection disorder. In addition to numerous dubious methods, effective medications like Viagra with the active ingredient Sildenafil and Cialis with the active ingredient Tadalafil have been available for years.
A recent study with nearly 74,000 participants has now shown a link between the long-term use of Cialis with the active ingredient Tadalafil and an increased risk of the eye disease glaucoma.2 This is concerning because this serious eye disease can destroy the optic nerve and lead to blindness.
How Do Sildenafil and Tadalafil Work?
The so-called phosphodiesterase type 5 inhibitors (PDE-5 inhibitors) like Sildenafil and Tadalafil are approved and widely used for the treatment of erectile dysfunction. They are marketed under brand names such as Viagra and Cialis. Their effect is similar: They lead to the relaxation of vascular muscles, which expands the blood vessels. This, in turn, promotes blood flow in the penis, allowing men to achieve and maintain an erection more easily. The effect of Sildenafil occurs more quickly but lasts only four to five hours. With Tadalafil, the maximum effect is reached a bit later, but it lasts up to 36 hours. Tadalafil is also prescribed in small regular doses to older men over 40 for bladder and urinary tract issues.
What Did the Current Study on Potency Drugs Investigate?
The aim of the study was to investigate a possible link between the use of Tadalafil and the risk of the eye disease glaucoma.
For this purpose, data from the TriNetX database was used. This is an international data pool for research purposes. From this pool, men over the age of 40 who suffered from bladder and urinary tract issues between 2012 and 2022 were selected. These issues included sudden urge to urinate, delayed bladder emptying, or a weak urine stream.3
The focus was particularly on men who take Tadalafil daily for these urinary tract issues, rather than only as needed for erectile dysfunction. Individuals with a history of glaucoma were excluded. The participants were then divided into a Tadalafil group and a non-PDE-5 inhibitor group. Of the 73,854 participants, 36,927 took Tadalafil, while the control group consisted of another 36,927 participants who did not take PDE-5 inhibitors for treatment. The control group was matched to the Tadalafil group in terms of age, ethnicity, comorbidities, kidney function, and concomitant medication.
How Tadalafil Increases the Risk of Glaucoma
The data analysis showed that men who took Tadalafil for bladder and urinary tract issues had a 22 percent higher risk of developing glaucoma. The likelihood of suffering from ocular hypertension (increased intraocular pressure) was 32 percent higher. The risk that glaucoma treatment had to be initiated was also 33 percent higher. However, the increased risks mentioned here affect men over 50 who have taken Tadalafil regularly for up to five years.
“The use of Tadalafil for lower urinary tract symptoms was associated with a significant increase in the risk of glaucoma, ocular hypertension, primary open-angle glaucoma, and the initiation of glaucoma treatment in a large, multinational real-world cohort,” the Taiwanese researchers state in their study.
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What Do the Results Mean for Men Who Regularly Take Potency Drugs?
This is not the first study to link PDE-5 inhibitors like Tadalafil and Sildenafil with eye diseases. A study review from 2021 already showed that phosphodiesterase type 5 inhibitors can cause side effects on the eyes.4 These include the following:
- Changes to the eye surface
- Increased intraocular pressure
- Glaucoma
- Uveitis
- Non-arteritic ischemic neuropathy
- Chorioretinopathy
- Retinal occlusion
- Changes in the visual field
The Taiwanese researchers therefore warn that long-term treatment with PDE-5 inhibitors could affect eye physiology. They recommend that patients who take Tadalafil long-term undergo increased ophthalmological monitoring, especially if risk factors for glaucoma are present.
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Limitations of the Study
It should be noted that this study had several limitations. For example, most participants were white, so the results may not be applicable to men of other ethnic backgrounds. Additionally, changes in medication intake or the occurrence of other underlying conditions that could increase the risk of glaucoma were not considered.
Finally, the participants were generally not healthy. About 40 percent of them suffered from high blood pressure and another 40 percent from high cholesterol levels. Therefore, additional chronic conditions could also have an impact on the increased risk of glaucoma.
It is important to note: The study shows a statistical correlation but does not yet provide definitive proof that Tadalafil is the sole cause of the eye damage.