Ocular syphilis is a manifestation of the sexually transmitted infection syphilis, which is caused by the bacterium Treponema pallidum. This condition occurs when the infection spreads to the structures of the eye. It is not a separate disease but a complication of a systemic infection. Due to its potential to mimic other eye conditions and cause serious complications, it requires prompt medical evaluation.
Visual Signs and Symptoms
The visual signs of ocular syphilis are diverse, which has led to it being called “the great imitator” as its symptoms can resemble many other ocular diseases. Symptoms can develop in one or both eyes and may range from mild to severe. Common complaints include blurred or decreased vision, eye pain, and redness.
A frequent manifestation is uveitis, which is inflammation of the uveal tract—the middle layer of the eye that includes the iris, ciliary body, and choroid. When the front of the uvea is affected (anterior uveitis or iritis), it can cause eye pain, redness, and sensitivity to light, known as photophobia. Inflammation in the middle part (intermediate uveitis) often leads to floaters and blurred vision.
Inflammation in the back of the eye, such as posterior uveitis or retinitis, can cause symptoms like floaters, blind spots, and flashes of light. A specific finding in syphilitic posterior uveitis can be acute posterior placoid chorioretinopathy (APPC), which involves yellowish lesions at the back of the eye. The optic nerve can also become inflamed (optic neuropathy), leading to a rapid decline in vision. In some cases, the cornea may be affected, a condition called interstitial keratitis, causing pain, tearing, and decreased vision due to corneal clouding.
Connection to Systemic Syphilis
After entering the body, typically through sexual contact, the spirochete bacteria can multiply and spread through the bloodstream to distant organs, including the eyes. This can happen at any stage of the disease—primary, secondary, latent, or tertiary—though it is commonly associated with the secondary stage.
The presence of ocular syphilis is often considered a form of neurosyphilis, indicating the infection has invaded the central nervous system. The bacteria can cross the blood-brain and blood-ocular barriers, which are protective mechanisms that shield the brain and eyes from pathogens. The resulting inflammation is what causes damage to ocular tissues.
Individuals with ocular syphilis may also have other signs of systemic syphilis. These can include the characteristic rash of secondary syphilis, which often appears on the palms of the hands and soles of the feet, or the more severe organ damage associated with tertiary syphilis. However, ocular involvement can sometimes be the first and only clear sign of the underlying infection.
The Diagnostic Process
Diagnosing ocular syphilis involves a detailed eye examination combined with laboratory testing. An eye doctor performs a comprehensive ophthalmologic exam to look for signs of inflammation like uveitis, retinitis, or optic neuropathy, using specialized instruments to view the internal structures.
Serological testing is used to detect the presence of syphilis in the blood. Two types of blood tests are used: non-treponemal (like VDRL or RPR) and treponemal (like FTA-ABS or TP-PA). Non-treponemal tests detect antibodies present during an active infection, while treponemal tests detect antibodies specific to Treponema pallidum and usually remain positive for life. A combination of these tests is needed to confirm an active infection.
If ocular syphilis is suspected, a lumbar puncture, or spinal tap, may be performed to collect a sample of cerebrospinal fluid (CSF). The CSF is then analyzed for evidence of syphilis infection, which helps confirm a diagnosis of neurosyphilis and determine the correct course of treatment.
Treatment and Recovery
The standard treatment for ocular syphilis is the same as for neurosyphilis, requiring a course of antibiotics to eliminate the Treponema pallidum bacteria. The recommended regimen is intravenous (IV) aqueous crystalline penicillin G, administered for 10 to 14 days. This treatment requires hospitalization to ensure the medication is delivered consistently.
Intravenous delivery is necessary because the IV route ensures that a high concentration of penicillin crosses the blood-ocular and blood-brain barriers. For patients with a penicillin allergy, alternative treatments may be considered, but desensitization to penicillin is often preferred due to its superior efficacy.
The prognosis for recovery depends on how quickly the condition is diagnosed and treated. With early antibiotic therapy, many visual symptoms like inflammation and blurred vision can be improved or reversed. However, if treatment is delayed, permanent damage can occur, such as optic atrophy, retinal scarring, or glaucoma, which can lead to irreversible vision loss.