What Is Ocular Syphilis?

Introduction

Ocular syphilis is caused by a sexually transmitted infection called syphilis spreading to the eyes.^1,2,3 Syphilis can affect most organ systems in the body, causing various symptoms and health problems.^1,2 Ocular syphilis causes inflammation of the eyes, resulting in vision loss and sometimes irreversible blindness.^1,2 In some cases, ocular syphilis can be the only sign of infection from syphilis, so it must be diagnosed properly and not mistaken for another inflammatory eye disease.¹

Over the last decade, there has been a substantial increase in ocular syphilis cases that have caused vision impairments or blindness, the most since the 1990s.¹ Studies from 2018-2020 have reported an increase in ocular syphilis occurrence and that syphilis has increased globally.^1,4,5 Clearly, this infection is an ongoing issue that needs attention.

Cause and transmission

Syphilis is caused by a bacterium called Treponema pallidum.^1,5,6 The bacterium enters the body during sexual contact with an infected person through syphilis sores, which are breaks in the skin.^1,4-6 These are usually painless and not noticed by the infected person. After transmission of syphilis, there are four stages of the infection: primary syphilis, secondary syphilis, latent syphilis, and tertiary syphilis.^1,3,6,8 Ocular syphilis can occur at any time during these stages.^1,3,6,7

Symptoms

Symptoms of ocular syphilis can initially occur anywhere from 2 weeks to 6 months after infection.^5,6,9 Symptoms can often go unnoticed for many years or may not be a cause of concern for many people.^1,2 The symptoms are caused by inflammation of different parts of the eye. Ocular syphilis most commonly causes uveitis, which is inflammation in the middle layer of the eye.^2,3,6,7,9,10 It may also cause syphilis sores on the tear ducts and inflammation or blockage of blood vessels in the eyes.^2,3,5 The symptoms of these are often mistaken for another inflammatory eye disease, resulting in misdiagnosis.^1,6 

Symptoms include:^1,7,10

• Blurred vision
• Vision loss/blindness
• Redness of the eye or surrounding eye
• Eye pain
• Ulcers on eyelids
• Floaters (small, dark shapes across your vision)

Diagnosis

The diagnosis of ocular syphilis involves both clinical evaluation and laboratory tests.^1,8 A simple blood test to see if the bacteria are in your system will determine if you have syphilis.⁸ Then, eye tests, performed by an optometrist, are needed to see if the infection has progressed to ocular syphilis.⁵ These tests include:^5,7,10

• Visual acuity test
• Tonometry (measures intraocular pressure)
• Slit lamp examination
• Dilated posterior eye examination

Sometimes the symptoms of ocular syphilis are what prompt the diagnosis of a syphilis infection.⁴ If you are diagnosed with uveitis or another inflammatory eye disease and suspect you may have syphilis, it is important to request a test for syphilis.^1,4

Often, when people are diagnosed with ocular syphilis, they also have other complications of a syphilis infection.^2,5 A lumbar puncture can be used to diagnose other complications of syphilis, including neurosyphilis (see complications section).^2,5 During a lumbar puncture a needle is inserted between the vertebrae in the lower back to collect cerebrospinal fluid.²

Groups at risk

There are groups of people that have more recorded cases than the rest of the population and that are at a statistically higher risk of contracting syphilis. The most obvious high-risk group of people are those who have unsafe sex -- not using a condom.^4,8 This risks their exposure to the bacteria on the syphilis sores of infected people.⁶ Unsafe sexual contact combined with global travel also increases the risk of ocular syphilis.⁵ So, practising safe sex and being aware of the risks is very important to avoid the complications of syphilis, such as ocular syphilis.

There have also been higher numbers of cases of syphilis in men who have sex with men.^1,4,5 Studies have shown that this group of people is up to 180 times more likely to contract syphilis than women.^1,4 

One study found that increasing age increases the risk of ocular syphilis.¹ A strong link has also been found between the occurrence of human immunodeficiency virus (HIV) and ocular syphilis.^1,4,5 These studies have found that having HIV does not affect the outcome of ocular syphilis treatment.^1,5 There is ongoing research being done on the occurrence of these infections and how they affect the symptoms that patients experience.^1,5

If you aren’t in a high-risk group and have contracted syphilis, it is less likely that your symptoms will be diagnosed as syphilis.² So if you have symptoms of inflammatory eye disease or think you may have ocular syphilis, it is important to get tested for syphilis, even if you aren't in one of these groups.²

Treatment

Ocular syphilis and systemic syphilis can be treated with the antibiotic penicillin, which kills the bacteria that cause the infection.^1,5 There are alternative antibiotics if you are allergic to penicillin, except if you are pregnant.⁹ If this is the case, you will need to be desensitised to penicillin so that you can take enough to cure the infection.⁹ 

In some cases, corticosteroids are also used to treat ocular syphilis by reducing inflammation in the eyes and preventing further vision impairment while the antibiotic kicks in.^1,5 This may be administered through a localised injection, either orally or topically.⁵

Complications

Untreated ocular syphilis can cause conditions in the eye that further affect vision. It can cause cataracts, where cloudy patches appear over the lens of the eye, causing blurred vision.⁵ It can also cause ocular hypertension, which is a buildup of fluid in the eye, causing increased pressure and potential vision loss.^3,5

A very serious complication of syphilis that is often associated with ocular syphilis is neurosyphilis.^1,2,9 Neurosyphilis is when the infection reaches the central nervous system (brain and spinal cord) and neurological symptoms occur.^1,2,9 There are often cases where patients have both types of syphilis, so it is important to be tested for neurosyphilis with a cerebrospinal fluid examination if you have ocular syphilis.^1,2,8

Another serious complication of syphilis for pregnant women is that it can be passed on to the infant and cause serious health implications, including ocular syphilis.⁴

Prognosis

When it comes to ocular syphilis, getting treatment early is very important to prevent complications or further damage to the eyes and vision.^2,6 So if you believe you may have it, don't wait; book into a clinic to get tested and treated right away. 

If diagnosed early and treated with antibiotics, ocular syphilis has good outcomes, with many cases reporting improvements in impaired vision.^1,5 If syphilis is diagnosed before any ocular syphilis symptoms occur, it is likely there will be no effect on vision at all. 

If ocular syphilis is diagnosed late and there is already significant vision impairment or blindness, then unfortunately, it is unlikely that vision will be repaired.⁵ Delays in treatment due to misdiagnosis or inappropriate treatment of the eye inflammation can worsen the outcome and permanent vision damage, as well as other complications of the syphilis infection itself.⁵

Prevention

The only way to prevent the transmission of syphilis is through safe sex, like the use of a condom.⁹ It is important to get tested for syphilis and other sexually transmitted illnesses (STIs) at least every 6 months while you are sexually active, particularly when you have multiple sexual partners.^4,8 This is very important, as early diagnosis may prevent syphilis from progressing past the primary stage and prevent an ocular syphilis infection completely.⁴

It is also important to communicate openly about sexual health and STI checks with any sexual partners before engaging in sex. Education is extremely important in the prevention of syphilis infection.⁵ It is also important that general practitioners are regularly educated on recognising the symptoms and the high-risk groups to prevent misdiagnosis.⁵ These things can prevent infections of syphilis and, as a result, will prevent ocular syphilis and other syphilis complications.⁴

If you have already been infected with syphilis, it is important that you do not engage in any sexual activity before you have been treated and cured of the infection. It is also very important that you inform any sexual partners you have had in the 3-6 months before your diagnosis, that they also need to be tested and treated for syphilis.^4,6,9

Summary

Ocular syphilis is caused by the spread of a syphilis infection to the eye. Ocular syphilis can manifest at any stage of an infection. To prevent vision damage, blindness, and other complications, early diagnosis and treatment are crucial. Diagnosis relies on the recognition of symptoms, particularly of inflammatory eye diseases like uveitis, by general practitioners and sexual health clinics. Treatment of ocular syphilis involves antibiotics and sometimes corticosteroids to reduce inflammation in the eye. Practising safe sex, getting tested regularly, and open communication play a pivotal role in the prevention or early diagnosis of ocular syphilis.