Eye infections can steal sight, but early diagnosis can save vision
· Medical Xpressedited by Lisa Lock, reviewed by Andrew Zinin
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Rising rates of infectious eye diseases are putting more people at risk of preventable vision loss, prompting researchers to call for greater awareness of the warning signs and the importance of early treatment.
Two new reviews led by Flinders University examine ocular syphilis and ocular toxoplasmosis, conditions that can damage the retina and lead to permanent sight loss if they are not diagnosed and treated promptly.
Both diseases can mimic other eye conditions, creating diagnostic challenges that may delay treatment. Common symptoms include blurred vision, floaters, eye inflammation and sudden changes in eyesight.
The first review, published in the Journal of Ophthalmic Inflammation and Infection, shows that syphilis is resurging globally, with cases increasing from around 8 million in 1990 to 14 million in 2019. Alongside this rise, eye specialists are reporting more cases of ocular syphilis, a potentially blinding infection that occurs when the bacterium responsible for syphilis affects the eye.
The second review, published in Progress in Retinal and Eye Research, finds that ocular toxoplasmosis remains the leading worldwide cause of infectious inflammation at the back of the eye. It is caused by the parasite Toxoplasma gondii, which infects up to 30% of the global population. Although many people never develop symptoms, the parasite can remain dormant for years before reactivating and damaging vision.
Senior author Justine Smith, an internationally recognized ophthalmologist and professor at FHMRI Eye & Vision at Flinders University, says understanding how these infections affect the eye is critical to reducing preventable blindness.
"The encouraging message is that many people can retain good vision if these infections are recognized and treated early," says Smith.
The reviews highlight the consequences of delayed diagnosis. Research on ocular syphilis shows vision outcomes worsen when treatment is postponed, while more than half of reported cases of ocular toxoplasmosis in immunocompromised patients were initially misdiagnosed, increasing the risk of serious complications.
Associate professor João Furtado, from the University of São Paulo, says greater awareness among both the public and health care professionals can help prevent avoidable sight loss.
"People often assume blurred vision, floaters or other sudden visual changes will go away on their own, but these symptoms can sometimes signal a serious eye infection," says Furtado. "Prompt assessment is essential because delays can significantly increase the risk of permanent vision loss."
People with weakened immune systems, including those living with HIV, receiving cancer treatment, taking immune-suppressing medications or recovering from organ transplantation, should be particularly vigilant because some eye infections can progress more aggressively and cause greater damage.
Smith says regular eye examinations and timely reporting of vision changes can play an important role in protecting sight.
"Don't ignore a sudden change in your vision," she says. "Although there can be many causes, infectious eye diseases are often treatable, and the best outcomes usually come when they are diagnosed early."
More information
Liam M. Ashander et al, Putative mechanisms of ocular inflammation in syphilis, Journal of Ophthalmic Inflammation and Infection (2026). DOI: 10.1186/s12348-026-00638-2
Elke O. Kreps et al, Ocular toxoplasmosis in the immunocompromised patient, Progress in Retinal and Eye Research (2026). DOI: 10.1016/j.preteyeres.2026.101523
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OphthalmologyCommon illnesses & PreventionInfectious diseases Provided by Flinders University Who's behind this story?
Lisa Lock
BA art history, MA material culture. Former museum editor, paramedic, and transplant coordinator. Editing for Science X since 2021. Full profile →
Andrew Zinin
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