In 2005, the FDA requested that Pfizer add a warning to Viagra that the drug may possibly lead to sudden blindness. Before you become worried that taking Viagra may make you blind, it is important that you understand why this may occur and what the risk factors are.
It is common for Viagra to cause some changes to vision. About 3% of patients in clinical trials using 25-50 mg of Viagra experienced unusual changes to their eyesight. The incidence of vision changes increased to 11% with the 100 mg dosage of Viagra. These changes included blurriness, haziness, increased sensitivity to light, and seeing a bluish color. With 100-200 mg dosages of Viagra, some patients also were unable to discriminate between blue and green colors. Viagra did not, however, cause changes to vision clarity, contrast, or pupil response. These possible vision side effects from Viagra are due to a temporary effect occurring on the retina. They are not related to the risk of sudden blindness.
The FDA asked for the blindness warning on Viagra due to a condition called NAION, or nonarteritic anterior ischemic optic neuropathy. This condition is a sudden blindness which is caused by damage to the optic nerve from not getting enough blood. In 2005, it was discovered that 38 men taking Viagra had experienced NAION. Note that this amount is incredibly low when you take into account that Viagra had then by used by over 23 million men worldwide.
Whether Viagra was the cause of NAION in these cases is unknown. That is because NAION occurs in 1000-6000 people yearly in the US alone. Some of the risk factors for NAION occurring are diabetes and cardiovascular problems. These factors are also two of the main causes of erectile dysfunction as well. The reason why the FDA linked the cases of NAION with Viagra was because the patients experienced the sudden loss of vision within hours of taking Viagra. This makes it seem very plausible that the cases of NAION are linked to Viagra use. However, there is currently no proof that Viagra caused the blindness.
In response to the risks of blindness with Viagra, Pfizer released a statement where they said, “There is no evidence showing that NAION occurred more frequently in men taking Viagra than men of similar age and health who did not take Viagra. NAION is the most common acute optic nerve disease in adults over age 50 and it shares a number of common risk factors with erectile dysfunction: age over 50, high blood pressure, high cholesterol, diabetes. Most of the reported cases in which NAION has occurred in men taking Viagra have involved patients with underlying anatomic or vascular risk factors associated with the development of NAION.”
Even though the chances of NAION occurring from Viagra are very, very rare, this risk should still be taken seriously. If you have any of the risk factors for NAION (especially “crowded” optic nerve or general cardiovascular risk factors), then you should talk to your doctor about whether it is safe for you to use Viagra.