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Viagra Blindness Mechanism

- September 17, 2020 | January 31, 2025 - admin

Viagra ‘may cause visual disturbance’ in some men

“Viagra may permanently damage vision some men, study,” reports The Guardian. However, the news is based on research conducted on mice.

The research suggests the medication may not be suitable for men who carry a gene mutation associated with the inherited eye retinitis pigmentosa.

Researchers found that Viagra (the brand for the drug sildenafil) caused visual disturbances in mice genetically engineered to carry a single copy of the retinitis pigmentosa mutation.

It took two weeks for the mice’s visual response to return to normal.

The researchers state that this has human implications, 1 50 men are believed to be of retinitis pigmentosa.

Retinitis pigmentosa is a hereditary condition that causes a progressive loss of light reception and outer fields of vision, leading to tunnel vision and blindnessDespite The Guardian’s headline, Viagra did not cause permanent damage the mice’s eyes and all of the mice in the study recovered. Additionally, the doses used were between and 50 times the equivalent recommended dose for men.

However, you should stop taking sildenafil citrate and seek immediate medical advice if you suddenly develop eye or eyesight problems.

The origin of the story is a study conducted by researchers from the School of Optometry and Vision Science at the University of New South Wales, the Centre for Eye Health in Sydney, the University of Melbourne in Australia, and the University of Auckland in Zealand. The study was funded by the National Health and Medical Research Council of Australia and published in the peer medical journal Experimental Eye Research. While Guardian accurately reported the study its headline suggested more permanent visual damage than the study actually found and implied that the research had been conducted on humans rather than mice.

What kind of research was this?

This study investigated the effects of sildenafil (commonly known as Viagra) on the retina of mice. Temporary visual disturbances such as blurred vision, increased light sensitivity, and color changes have been reported by some individuals after taking sildenafil.

Previous research in humans found that 50% of healthy men who take at least double the maximum recommended dose of sildenafil experience temporary visual disturbances (200mg rather than the recommended 25mg to 100mg).

The researchers aimed to determine if the effect of sildenafil on vision was greater in individuals susceptible to retinal damage, as is that 1 in 50 men are carriers of a single copy of a gene for one of several degenerative retinal conditions but have normal vision.

To test this theory, researchers used mice genetically engineered to be carriers of the degenerative condition retinitis pigmentosa and examined their susceptibility to visual disturbances.

Retinitis pigmentosa is a hereditary condition that causes progressive loss of light reception and the outer fields of vision, leading to tunnel vision and blindness.

Most individuals with the condition have defects in both. Some individuals with just one gene can be affected, though most have normal vision and are considered to have “carrier status.”

The research involved genetically engineered mice for retinitis pigmentosa, which had normal retinal structure and function as assessed by electroretinography (ERG). ERG uses electrodes to measure how the retina responds to visual stimulations, such as flashing lights.

However, there were molecular differences in the rod cells of the mice (which detect light,, and movement), making them more sensitive to light than normal mice. The researchers suggest that this increased sensitivity also made their sight more susceptible to degeneration.
The researchers heavily anesthetized normal mice carrier mice using ketamine and measured their to detect flashes of light in a dark by ERG.
The mice were also injected with doses of sildenafil (5 to 50 times higher than the equivalent recommended dose for humans), and researchers repeated the ERG after one hour.
Some mice were given a dose20 times higher, and the ERG was performed after one hour, two days, or two weeks. They performed same experiment using a saline injection as a.
The mice then euthanized, and their retinas were examined using several laboratory processes.

What were the basic results?

In normal mice, photoreceptor response as sildenafil dose increased (this termed a “dose-dependent” response). For the mice given 20 times the equivalent human dose, this decreased response resolved by day two, although at bright light levels a ERG response was still apparent.
Although there was a decrease in photoreceptor response for the carrier mice after one hour, this was smaller than that seen in normal mice. Sildenafil also increased the response to light of the inner retinal neurons, especially in bright light.
For the mice given 20 times the equivalent human dose, this response did not improve until two weeks later.
 the carrier mice, there were increased levels of cyto C a molecule that indicates cell death, but there was no sign of cell change in retinal thickness in any of the mice retina.

How did the researchers interpret the results?

The researchers concluded that in normal, sildenafil caused a reduced electroretinogram (ERG) response that resolved within 48 hours.
In mice that were carriers for the degenerative condition retinitis pigmentosa but had normal sight, the reduced ERG response took two weeks to return to normal, and there was an increase in a molecule that indicates cell death.
The researchers concluded that this may mean sildenafil could cause retinal degeneration.
They stated that, “The results of this study are significant considering approximately 1 in 50 people are likely to be carriers of recessive traits leading to retinal degeneration.”

Conclusion

This study examined the effects of sildenafil (Viagra) on the retinas mice. It demonstrated that genetically engineered mice with retinitis pigmentosa carrier status are more susceptible to temporary visual disturbances than normal.
These carrier mice also exhibited increased levels of the chemical cyto C, an indicator of cell death.
However, there was no evidence of cell loss or changes in retinal thickness in any of the mice., this research did not prove that sildenafil causes permanent retinal degeneration, as the changes were reversible in all mice.
It should be emphasized that the smallest amount of sildenafil used these experiments was five times the equivalent recommended dose for men, so it is unclear whether similar results would be seen at normal dose levels.
The product information for sildenafil states that its safety has not been determined for people with hereditary degenerative retinal disorders, so it is not recommended for this group.
However, this is only problematic for men who carry a single copy of the gene, although they might not be aware this because it does not cause problems.
Studies conducted over a longer period would be useful to determine if sildenafil causes retinal degeneration or permanent visual changes, and whether these types of symptoms or changes are more likely in people with status for a degenerative retinal condition.
If you experience a sudden decrease or loss of, stop taking sildenafil and contact your doctor immediately.

Analysis by Bazian
Edited by NHS Website