The study involved 244 men, ages 30 to 65, taking either Pfizer Inc.’ Viagra, Eli Lilly & Co.’s Cialis or a placebo. The chemicals in Viagra and Cialis act on compounds in the blood vessels of the penis, allowing for more blood flow that can lead to an erection, according to background information in the study.

 

The men had comprehensive vision exams at the beginning and at the end of the study, including electroretinography (ERG, a test used to detect diseases of the retina).

  

The study found no significant differences between those who took the erectile dysfunction drugs or the placebo on ERG, vision function tests, pressure within the eyeball, or assessments of the anatomy of the eye.

“The average patient should be relieved these drugs don’t cause significant visual dysfunction. And he can be comfortable taking them in the long-term,” said Raj Maturi, an author of the Lilly-funded research and an ophthalmologist at the Indiana University School of Medicine in Indianapolis.

 

Viagra and Cialis each had global sales of more than $1 billion in 2008. According to data by the National Institutes of Health, about 6.2 percent of U.S. men are unable to achieve an erection, with rates rising to 16.7 percent in ages 60 to 69.