Infective Uveitis

Infective uveitis is inflammation of the middle layer of the eye caused by germs like viruses, bacteria, fungi, or parasites. It accounts for 15 to 20 percent of uveitis cases in the United States and requires early treatment to prevent vision loss.

Table of contents

• What Is Infective Uveitis?
• What Causes Infective Uveitis?
• Signs and Symptoms
• How Is It Diagnosed?
• Treatment
• Importance of Early Treatment

What Is Infective Uveitis?

Infective uveitis is inflammation of the uvea, the middle layer of your eye. The uvea includes the iris (the colored part of your eye), the ciliary body (which controls the eye’s lens), and the choroid (which brings nutrients to the retina)^[1][2]. When germs like viruses, bacteria, fungi, or parasites infect one or more of these structures, it causes infective uveitis.

Infective uveitis is one of the most common causes of uveitis in the United States and worldwide. According to research, infectious causes account for between 15 and 20 percent of all uveitis cases in certain parts of the United States. At specialized eye care centers, this proportion can be even higher, ranging from 26 to 35 percent^[1]. The condition can affect people of all ages, though it is most common in adults between the ages of 20 and 60^[2][5].

Infective uveitis can affect different parts of the eye. When inflammation occurs in the front of the eye, affecting the iris and ciliary body, it is called anterior uveitis. When it affects the back of the eye, including the choroid and sometimes the retina, it is called posterior uveitis. If all three parts of the uvea are inflamed, the condition is known as panuveitis^[2].

What Causes Infective Uveitis?

Infective uveitis develops when germs enter the eye and cause inflammation. Different types of germs can cause this condition, including viruses, bacteria, fungi, and parasites^[3][5].

Viruses are the most common infectious cause of uveitis, accounting for about 39 percent of cases^[5]. The most frequent viral causes include herpes simplex virus (HSV), which also causes cold sores; varicella-zoster virus (VZV), which causes chickenpox and shingles; and cytomegalovirus (CMV)^[1][3][12]. HSV and VZV are responsible for approximately 8 percent of all uveitis cases^[1].

Bacteria that cause other serious infections can also lead to uveitis. The bacteria that cause syphilis and tuberculosis are known to trigger eye inflammation^[3][12]. Syphilitic uveitis has increased in prevalence over the last decade^[1].

Parasites are another important cause of infective uveitis. Toxoplasmosis, caused by the parasite Toxoplasma gondii, is the most common cause of retinitis (inflammation of the retina) in people with healthy immune systems^[3]. People can acquire this parasite from cats or contaminated food. Another parasitic infection called toxocariasis can also cause eye inflammation^[1].

Fungi can cause uveitis as well, particularly in people with weakened immune systems. Fungal species that may lead to eye infections include Candida (which causes candidiasis) and Aspergillus (which causes aspergillosis)^[2][12].

Infection-related uveitis usually affects only one eye at a time, which helps doctors distinguish it from other types of uveitis that affect both eyes^[2][12].

Signs and Symptoms

The symptoms of infective uveitis depend on which part of the eye is affected. The warning signs often come on suddenly and can get worse quickly^[4].

When the front part of the eye is inflamed (anterior uveitis), you might experience eye pain, redness, and sensitivity to light (called photophobia). Your vision may become blurred, and your pupil may change shape from a circle to an irregular form. You might also notice the white part of your eye becoming swollen^[1][2][3].

Viral infections like HSV or VZV that cause anterior uveitis have some specific signs. These include elevated pressure inside the eye, decreased sensation in the cornea (the clear front part of your eye), and patches of iris tissue that look different or damaged^[1][3].

When the back part of the eye is affected (posterior uveitis), the symptoms are different. You may notice an increase in floaters (dark spots that seem to float in your field of vision), or the floaters you already have may become more noticeable. You might experience gaps or missing sections in what you can see, and your vision overall may decrease^[2][12].

For toxoplasmosis, a common parasitic infection affecting the back of the eye, symptoms include floaters and decreased vision. These can be caused by cells floating in the gel-like substance inside your eye or by lesions and scars on your retina. Sometimes the front of the eye becomes involved as well, leading to eye pain, redness, and sensitivity to light^[3].

How Is It Diagnosed?

Diagnosing infective uveitis requires a thorough eye examination by a specialist. Because infectious uveitis can look similar to other types of eye inflammation that are not caused by infection, doctors must be very careful in their evaluation^[1].

An eye specialist will conduct a complete eye exam that usually includes several tests. They will assess your vision and how your pupils respond to light. They will measure the pressure inside your eye using a test called tonometry. A specialized microscope called a slit lamp is used to examine the front of your eye in detail, looking for microscopic signs of inflammation. The doctor will also dilate (widen) your pupil with eye drops to examine the back of your eye^[4][11].

Advanced imaging techniques can help with diagnosis. These may include color photography of the inside of your eye, optical coherence tomography (OCT) to map the layers of your retina and look for swelling, and special dye-based tests called fluorescein angiography or indocyanine green angiography that show swollen blood vessels inside your eye^[4][11].

Laboratory tests are crucial for identifying the infectious cause. Blood tests can detect antibodies or signs of specific infections. For toxoplasmosis, doctors test for antibodies against Toxoplasma gondii in your blood^[3]. Testing for syphilis and tuberculosis is recommended for all uveitis patients because these infections are treatable causes^[3].

Sometimes, doctors need to analyze fluid from inside the eye itself. This can be tested using molecular diagnostic testing, which identifies the genetic material of germs and helps confirm which infection is causing the problem^[1][10].

In some cases, your eye doctor may refer you to another healthcare professional for a general medical examination and additional laboratory tests if they suspect an underlying condition is contributing to your eye problem^[4][11].

Treatment

The treatment of infective uveitis depends on which germ is causing the infection. Early and aggressive treatment with medicines that fight the specific infection is essential for protecting your vision^[1].

For viral infections caused by HSV or VZV, treatment includes antiviral medicines taken by mouth. Common antiviral drugs include acyclovir and valacyclovir. These medicines stop the virus from multiplying. In addition to antiviral drugs, doctors prescribe eye drops containing steroids to reduce inflammation and special drops to help your pupil relax and reduce pain. If the pressure inside your eye becomes elevated, additional eye drops may be needed to lower it^[3][13].

For toxoplasmosis, treatment is recommended when the infection affects important structures of the eye like the area responsible for sharp central vision (called the macula) or the optic nerve. Multiple drugs are used together, including pyrimethamine, sulfonamides, and clindamycin. In some cases, oral steroids are added, but these should never be used alone without medicines to fight the parasite. For severe cases threatening central vision, medicines may be injected directly into the eye. Toxoplasmosis can come back, so some patients need long-term preventive treatment^[3][13].

For small infections in the outer edges of the retina that do not threaten important visual structures, doctors may choose to watch the condition carefully without immediate treatment. These cases should start to improve slowly over one to two months^[3].

The route of treatment varies based on the infection. Medicines can be given as eye drops applied to the surface of the eye, as oral pills or liquids, or as injections into or around the eye. Each method has advantages and limitations. Eye drops and injections around the eye work well for the front of the eye but may not reach the back effectively. Oral medicines work throughout the body but may not achieve high enough concentrations inside the eye. Direct injection into the eye (intravitreal therapy) allows high concentrations of medicine to reach the back of the eye, bypassing natural barriers that protect the eye but also limit medicine penetration^[10].

In many cases, a combination of treatments targeting the infection and reducing inflammation is necessary. The specific medicines, doses, and duration of treatment are tailored to each patient’s condition^[10].

Importance of Early Treatment

Infective uveitis is one of the most visually devastating causes of uveitis. Without treatment, it can lead to permanent scarring of the eye, vision loss, or total blindness^[1]. Uveitis is the third leading cause of blindness in the United States^[2].

Early identification and treatment are crucial for visual recovery and preservation. The key to early identification is a combination of maintaining a high level of suspicion, recognizing certain clinical features, using advanced imaging techniques, and obtaining samples for laboratory testing to identify the infectious agent^[1].

Because infectious uveitis can often look like other types of eye inflammation that are not caused by infection, having detailed knowledge of how different infections appear and using appropriate diagnostic tests are essential for proper management^[1].

If you experience symptoms like eye pain, redness, sensitivity to light, blurred vision, or an increase in floaters, you should see an eye doctor promptly. Do not delay seeking care, as early treatment significantly improves the chances of preserving your vision^[2][4].