Viagra may cause irreversible colour vision deficiency

High doses of Sildenafil citrate (Viagra), a popular medication used for erectile-dysfunction can cause irreversible damage to a person’s colour vision

High doses of Sildenafil citrate (Viagra), a popular medication used for impotence or erectile-dysfunction can cause irreversible damage to a person’s colour vision, according to a study by researchers at  Mount Sinai Health System in the US.

Viagra has been used safely for many years in a wide range of doses and age groups. It has been used in premature infants with pulmonary hypertension and also in elderly with erectile dysfunction. It works by relaxing the smooth muscle cells around blood vessels so that the vessels can easily fill with blood, which is how it helps both erectile dysfunction and pulmonary hypertension.

Researchers based their study on a 31 year old patient who arrived at an emergency clinic complaining of red-tinted vision in both eyes that persisted even after two days of taking a high dose of liquid sildenafil citrate. He reported that his symptoms began shortly after taking a dose of liquid sildenafil citrate, which was much more than the recommended 50mg dose, sold under the brand name Viagra.

The researchers identified microscopic injury to the cones of the retina, the cells which are responsible for colour vision

Sildenafil citrate can occasionally cause visual disturbances with normal dosage, but symptoms typically resolve within 24 hours. The patient was then diagnosed with persistent retinal toxicity linked to the high dose of medication damaging the outer retina.

The researchers identified microscopic injury to the cones of the retina, the cells which are responsible for colour vision and his tinted vision has not improved despite various treatments for more than a year.

“To actually see these types of structural changes was unexpected, but it explained the symptoms that the patient suffered from,” said Richard Rosen, Director of Retina Services at New York Eye and Ear Infirmary of Mount Sinai (NYEE).

“While we know coloured vision disturbance is a well-described side effect of this medication, we have never been able to visualize the structural effect of the drug on the retina until now,” said Rosen.

“Our findings should help doctors become aware of potential cellular changes in patients who might use the drug excessively, so they can better educate patients about the risks of using too much,” he added.