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.1,2
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.
Syphilis is resurging globally, with cases increasing from around eight million in 1990 to 14 million in 2019.1 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 encouraging message is that many people can retain good vision if these infections are recognised and treated early
Meanwhile, ocular toxoplasmosis remains the leading world-wide cause of infectious inflammation at the back of the eye.2 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 causing damage to vision.
Senior author and internationally recognised ophthalmologist Professor Justine Smith, from FHMRI Eye and Vision at Flinders University, said understanding how these infections affect the eye is critical to reduce preventable blindness.
“The encouraging message is that many people can retain good vision if these infections are recognised and treated early,” said Prof Smith.
Consequences of Delayed Diagnosis
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, said greater awareness among both the public and healthcare 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,” said Assoc Prof 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.
Prof Smith said regular eye examinations and timely reporting of vision changes can play an important role in protecting sight.
References
- Ashander LM, Furtado JM, Smith JR, et al. Putative mechanisms of ocular inflammation in syphilis. J Ophthalmic Inflamm Infect. 2026 Sep 15;16(1):57. doi: 10.1186/s12348-026-00638-2.
- Kreps EO, Furtado JM, Smith JR. Ocular toxoplasmosis in the immunocompromised patient. Prog Retin Eye Res. 2026 Sep 1;115:101523. doi: 10.1016/j.preteyeres.2026.101523.
