A new study has laid to rest fears that Viagra may pose a long-term threat to men's sight.
There were huge concerns that Viagra, and its competitor drug sold in the United States as Cialis, might prove harmful after some men reported blurred and blue-tinged vision.
However, the results of the six-month study have revealed that such drugs have no side effects on sight.
The drugs treat erectile dysfunction by blocking an enzyme in the blood flowing to the penis.
And, thus, doctors feared that these drugs could also act on similar compounds in the retina in the eye that receives and transmits images, reports the China Daily.
The study was conducted on a total of 244 healthy men, aged 30 to 65, some with mild erectile dysfunction.
Almost 85 of those men took a daily dose of five milligrams of Cialis, 77 took 50 milligrams of Viagra manufactured by Pfizer, and 82 received a placebo.
Among the 194 men who completed the study and eye examinations, no significant differences were found in vision between those taking the drugs and the placebo groups.
"Our results indicate that there is no cumulative damage or effect of clinical significance for either 5 milligrams of tadalafil (Cialis) or 50 milligrams of sildenafil (Viagra) taken daily for six months," said the report.
The study has been published in the Archives of Ophthalmology.