Ocular Syphilis: STD That Can Cause Blindness Is on the Rise

An illustration of the Treponema pallidum bacterium, which causes the disease syphilis, on the surface of human skin. Reports from around the world suggest that a growing number of syphilis cases are leading to an inflammatory eye disease. iStock

Increasing numbers of people in industrialized countries are at risk from permanent damage to their vision as a result of the sexually transmitted disease syphilis, an international team of researchers warned in a study published in the journal Scientific Reports.

Syphilis rates in many nationshave been on the rise in recent years. Occurrences in the United States, for example, have more than doubled from 2.1 cases per 100,000 people in 2000 to 7.5 cases per 100,000 in 2015, according to the Centers for Disease Control and Prevention (CDC). This is the highest rate of reported syphilis cases in the U.S. for approximately 20 years.

And reports from around the world suggest that a growing number of syphilis cases are leading to an inflammatory eye disease, known as ocular syphilis, which can cause redness, blurry vision and in the worst cases, partial or total vision loss, if not treated in a timely manner.

"Ocular syphilis means eye infection with the syphilis bacteria, which is called Treponema pallidum," Justine Smith, a co-author of the study from the College of Medicine and Public Health at Flinders University, told Newsweek. "The disease most often shows up in the eye as a condition called uveitisinflammation inside the eyebut actually syphilis can affect any tissue of the eye and cause a lot of different manifestations."

"Syphilis most often affects the back part of the inside of the eye, which includes the retina," she said. "Usually a person with ocular syphilis that is causing uveitis of the back of the eye, will suffer a loss of vision."

In the latest study, researchers from Flinders and the University of São Paulo (USP), in Brazil, observed four medical centers in Brazil for two-and-a-half years, finding that ocular syphilis cases had increased more than eight times in this period compared to the past decade.

In total, the team identified 127 patients, with 87 of those suffering inflammations in both eyes. Many had suffered complications including retinal detachmentwhich occurs when the thin layer at the back of the eye (retina) becomes loose. More than half of the patients had lost vision to below levels that would be required to drive.

According to the researchers, the findings in Brazil are a reflection of the re-emergence of syphilis in general, and now ocular syphilis.

"The 1990s and 2000s indicated that ocular syphilis was a rare diagnosis, accounting for less than 2 percent of all cases of uveitis [inflammation inside the eye]," co-author of the study, Joao Marcello Furtado from USP, said in a statement.

"More recent reports describe cohorts of up to 85 patients with ocular syphilis in the Americas, countries in Europe, and parts of Australasia which shows it's not only a problem in Brazil," Furtado says.

The syphilis infection itself often goes unnoticed because many of its symptoms, such as sore throat, headache and skin rash, resemble those of other common illnesses.

The same goes for ocular syphilis—likely explaining why many patients in the study often didn't present to doctors for some months after developing the problem. Furthermore, practitioners are no longer accustomed to seeing syphilis, according to Smith, so the cause of any symptoms is often missed.

"When ocular syphilis goes untreated or is treated late, the damage done to internal components inside the eye may be permanent," Smith said in the statement. "However, symptoms often can be reversed entirely with early treatment."

In light of their findings, the researchers recommend that doctors refer any syphilis patients with eye complaints to ophthalmologists.

"There is no longer a stigma associated with syphilis," Furtado said. "Anyone can be exposed and infected, so early detection is increasingly important."

A number of factors, including high-risk sexual practices, an increase in global travel and the use anti-HIV medications, which affect the immune system, have been implicated in the increased incidence of syphilis cases around the world.