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Temporary burry vision has been reported on patients taking Viagra and similar drugs for erectile dysfunction (ED). In addition, some people also suggest other visual complications if these drugs are taken for a long term. On the other hand, a new study argues that these medications will never cause permanent eyesight impairment. 

In general, there are two types of medicines that are commonly used to inhibit selective phodiesterase type 5 (PDE5). Chemical sildenafil citrate is sold as Viagra and tadalafil as Cialis. By interfering with the action of PDE5 on the blood vessel in the penis, these medicines can effectively treat ED. Unfortunately, these drugs at the same time are suspected to affect the similar compounds in the retina of the eye. 

This suspicion leads to the randomized placebo-controlled study conducted by William H. Cordell of the Lilly Research Lab and his colleagues. Recruiting totally 224 healthy male participants, the study was carried out in order to assess the change in retina among men taking Viagra or Cialis. 85 of the subjects were randomly assigned to take 5mg of tadalafil every day for six months, and another group of 77 men was asked to take 50mg of sildenafil on a daily basis for a same period. In similar, 82 individuals took a placebo. In order to figure out potential changes in their retinas, researchers performed comprehensive ophthalmic tests on these subjects, before, during and after treatment. 

Nine men discontinued the study due to an adverse event, including two in the placebo group, one in the tadalafil group and six in the sildenafil group. In final, 194 participants finished the study. Researchers conducted eletroretinography, visual function tests and measurements of intraocular pressure on these individuals who completed the study. The result showed that there were no significant differences between treatment and placebo groups. In addition, researchers found no abnormalities suggesting drug toxicity.