1) "The first problem comes because Viagra happens to have a spillover effect. It blocks PDE5, but it also has an effect on PDE6. It turns out that PDE6 is used in the cone cells in the retina, so Viagra can have an effect on color vision. Many people who take Viagra notice a change in the way they perceive green and blue colors, or they see the world with a bluish tinge for several hours. For this reason, pilots can't take Viagra within 12 hours of a flight."
Source and further information:
http://health.howstuffworks.com/viagra5.htm
2) "Researchers at the University of Minnesota say that they have diagnosed a condition called non-arthritic ischemic optic neuropathy (NAION) in a group of men who took the erectile dysfunction drug Viagra. NAION is also known as a stroke of the eye. The condition occurs when blood flow to the optic nerve is interrupted, injuring the nerve and causing permanent vision loss.
The researchers studied seven patients regarding Viagra and blurred vision, all men between the ages of 50 and 69. All of the patients took Viagra and blurred vision and vision loss developed within 36 hours of taking Viagra. It has been known for several years that Viagra use can cause temporary color change in patients' vision, but this new condition appears to be permanent."
Source and further information:
http://www.adrugrecall.com/viagra/blurred-vision.html
Further information:
http://en.wikipedia.org/wiki/Naion
http://en.wikipedia.org/wiki/Sildenafil
- "Pfizer may update Viagra packaging with vision warning":
http://www.encyclopedia.com/doc/1G1-132814336.html
- "Eye side effects of Medications":
http://www.agingeye.net/visionbasics/eye&meds.php
