John R. Nordlund, M.D., Ph.D., is the owner of the Williamsburg Retina Center, a full-time practice specializing in diagnosis and treatment of retinal diseases and glaucoma. He is a former University of Virginia School of Medicine faculty member and has fellowship training in both medical retina from the Mayo Clinic and glaucoma from The Johns Hopkins School of Medicine.

Erectile Dysfunction Treatments May Be Linked to Vision Loss by John R. Nordlund, M.D., Ph.D. Published: June 2006 For the millions of men who suffer from erectile dysfunction (ED), medications such as Viagra, Levitra and Cialis have proven to be effective treatments. Now, due to recent reports, some physicians believe the same medications used to treat erectile dysfunction may cause vision loss, possibly blindness. This brings up the centuries-old question: Can sex really make a man go blind? Last year the U.S. Food and Drug Administration (FDA) issued a news release advising physicians about the potential risk of Viagra, Levitra, and Cialis causing a vision disorder known as nonarteritic anterior ischemic optic neuropathy (NAION). The FDA has received a total of 43 reports claiming varying degrees of vision loss, including blindness. Of the claims, 38 men had used Viagra, four had taken Levitra, and, in one case, Cialis was reported to have caused significant vision loss. However, there is no evidence that one drug presents a higher risk than another. The difference in the number of reported cases represents the difference in the number of dosages used for each of the medications. Researchers think NAION is caused by decreased blood flow to the small arterioles that supply the optic nerve with oxygen-rich blood. The disruption of blood flow usually results in permanent damage to the optic nerve that the patient recognizes as a visual field defect and decreased vision. Patients at risk for NAION are typically over 45 years of age and have systemic diseases like heart disease, hypertension, diabetes mellitus, elevated cholesterol, and sleep apnea. Tobacco use is also a risk factor. Many patients who develop NAION have an anomalous optic nerve head that is most easily seen on a dilated retinal examination. This finding, called a “disc-at-risk,” is characterized by smaller than usual optic nerve head and a small depression in the center of the nerve head, known by ophthalmologists as a small cup-to-disc ratio. Patients who develop NAION in one eye are more likely to have a recurrence. In 20 to 25 percent of patients, the second event may occur in either eye months, or even years, after the first occurrence. Viagra, Levitra and Cialis are all known as type five phosphodiesterase (PDE-5) inhibitors and are used to treat erectile dysfunction. By allowing a molecule known as cyclic GMP to accumulate, these medications can prolong a man’s erection by relaxing smooth muscles and increasing blood flow. Some studies show that these drugs increase blood flow to the optic nerve; therefore, it’s not clear why a drug that causes vasodilation (dilation of blood vessels), resulting in increased blood flow, would be associated with a condition like NAION, which is caused by decreased blood flow to the optic nerve. There are at least 13 types of phosphodiesterases in the human body. Each has a specific function depending on its location. PDE-6, for example, is found in the photoreceptors of the retina. Some PDE inhibitors have known ocular side effects. One common effect is a change in color discrimination (the ability to distinguish certain colors), especially after receiving high dosages, resulting from cross-reactivity of PDE-5 inhibitors with certain PDEs found within the body. Patients using Viagra, Levitra and Cialis frequently describe changes in color discrimination, mostly in the blue-green spectrum. Fortunately these changes are reversible and are simply the result of PDE-5 inhibitors blocking the activity of PDE-6. Reports of patients without erectile dysfunction suffering visual-field defects shortly after taking test dosages of PDE-5 medications are puzzling, given that several studies show that Viagra actually increases blood flow to the optic nerve. These conflicting findings demonstrate how much we still have to learn about erectile dysfunction (ED) medications and how they affect the mechanisms of the entire body, including the eye. What patients should know: Some investigators believe that Viagra, Levitra or Cialis may increase the risk for developing NAION, especially in patients who have already suffered a heart attack. There have been 43 reported cases of NAION in approximately 29 million men who used Viagra, Levitra or Cialis – an estimated annual incidence of less than 0.025 cases per 100,000 persons. Patients with systemic risk factors for developing NAION who want to use one of these medications may want to visit an ophthalmologist to determine if they also have ocular risk factors including the “disc-at-risk.” Nearly all cases of NAION among patients using PDE-5 inhibitors (ED medications) occurred in patients who already had risk factors for developing NAION. All patients with previous vision loss in one eye (caused by NAION) have a higher risk of developing NAION in the other eye. They should probably not use PDE-5 inhibitors. Anyone who develops vision problems while taking these medications should stop taking the medication and consult an ophthalmologist.

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