Some men who take Viagra (sildenafil) experience a strange visual twist – everything looks blue – in a surreal effect called cyanopsia.
It is supposed to help below the belt. But for some men, Viagra comes with a surprising visual twist — everything suddenly looks blue.
This bizarre side effect is called cyanopsia, a condition where the world appears bathed in a bluish tint. And while it usually fades after a few hours, some men have reported prolonged vision changes lasting days — even weeks.
What is going on?
What is Cyanopsia?
Cyanopsia means “seeing blue.” It is not unique to Viagra; patients who undergo certain cataract surgeries or take other drugs like digoxin have also reported it.
But sildenafil (the active ingredient in Viagra) seems to have a unique link.
Sildenafil belongs to a group of drugs called PDE5 inhibitors, designed to increase blood flow by blocking the enzyme phosphodiesterase type 5. However, the drug also affects a closely related enzyme, PDE6, found in the retina.
PDE6 is expressed in the rod and cone photoreceptor cells in the retina. In the presence of sildenafil, mild inhibition of PDE6, rod sensitisation can occur, causing cyanopsia.
In other words: sildenafil messes with how your eyes interpret light. The result? A short-lived world cast in shades of blue.
Case Reports of Cyanopsia with Sildenafil Use
The study published by Turkish researchers in 2020 reported 17 cases of men who took 100mg sildenafil (the maximum dose) and developed prolonged visual disturbances. These included:
- Cyanopsia (blue-tinted vision)
- Photophobia (light sensitivity)
- Blurred vision
- Dilated pupils
- Red-green colour blindness
Many of these men had no prior eye disease, were healthy, and had taken the drug recreationally. While most side effects go away within 5 hours, these men were still experiencing problems 1-2 days after taking the medication, with some taking as long as 3 weeks for the eyes to adjust.
Why Some People Are More Vulnerable
Not everyone sees blue after taking Viagra. So what makes some people more susceptible? Experts believe metabolism plays a role.
Sildenafil is usually broken down in the liver. But some men may metabolise the drug more slowly, allowing it to linger longer in the bloodstream.
In the Frontiers study, all the affected men took the same batch of sildenafil. Yet only a few developed prolonged side effects, hinting at individual differences in drug processing.
There is also a dose-response link: the higher the dose, the greater the chance of visual disturbances. Starting with a lower dose may have meant less severe side-effects.
Can Cyanopsia be Dangerous?
In most cases, no. The effect wears off as the drug clears from the body.
Cyanopsia does not affect life expectancy or long-term quality of life. While some people may notice mild symptoms like light sensitivity, these are typically brief and do not significantly disrupt daily routines.
Individuals with cyanopsia may also experience blurred vision or increased sensitivity to bright light, making brightly lit settings feel uncomfortable.
What To Do If You Experience Cyanopsia After Taking Sildenafil
If you notice a bluish tint to your vision after taking sildenafil, do not panic. It is most likely temporary cyanopsia, especially if it occurs within a few hours of the dose.
But seek medical attention if:
- The vision changes persist beyond 24 hours
- You experience loss of central or peripheral vision
- You see flashing lights, or have eye pain
- You notice difficulty distinguishing red and green
Your doctor may refer you to an ophthalmologist for retinal imaging and colour vision tests.
The Takeaway
Viagra is one of the most studied and widely used drugs in the world. Its effects on sexual performance are well known, but its effects on sight are often overlooked. Furthermore, it is also one of the most counterfeited drugs in the world.
Cyanopsia may be harmless in most cases, but it reveals just how interconnected our body systems are, and how a drug meant for one function can end up affecting something else in unexpected ways.
For men who use sildenafil regularly or recreationally, especially from unregulated or online sources, it is a reminder: what seems like a quick fix could come with consequences you did not see coming.
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External References
- Ausó, E., Gómez-Vicente, V., & Esquiva, G. (2021). Visual Side Effects Linked to Sildenafil Consumption: An Update. Biomedicines, 9(3), 291. https://doi.org/10.3390/biomedicines9030291
- Chao, Jonathan T; Omari, Amro A; Herrera, Amanda; Siegel, Les I; Siegel, Michael J. Persistent cyanopsia following non-diffractive extended depth-of-focus intraocular lens implantation. Indian Journal of Ophthalmology – Case Reports 3(2):p 346-348, Apr–Jun 2023. | DOI: 10.4103/ijo.IJO_1283_22
- Karaarslan C. (2020). Ocular Side Effects of Sildenafil That Persist Beyond 24 h-A Case Series. Frontiers in neurology, 11, 67. https://doi.org/10.3389/fneur.2020.00067
