Uveitis is inflammation of the uvea, the middle layer of the eye wall which contains the iris, ciliary body, and choroid. Posterior uveitis specifically involves the inflammation of the uveal tract behind the lens, encompassing the choroid, the retina, and the vitreous humor. Because the retina and optic nerve, structures responsible for sight, are directly adjacent to the inflammation, uncontrolled posterior uveitis can rapidly lead to vision impairment.
Recognizing the Signs
The inflammation in the posterior segment often causes symptoms that manifest as disturbances in the visual field. A frequent complaint is the sudden onset of floaters, which are small specks or cloud-like shapes that drift across the line of sight. These are inflammatory cells and debris released from the inflamed tissues into the vitreous humor.
Patients may also notice blurry or hazy vision, even if the eye appears externally normal. In some cases, the inflammation can trigger photopsia, which are brief flashes or streaks of light. These visual symptoms typically develop without associated pain because the back of the eye lacks the dense concentration of pain receptors found in the front.
The severity of vision loss depends directly on how close the inflammation is to the macula, the small central part of the retina responsible for sharp, detailed central vision. Even subtle inflammation near this area can cause a significant drop in visual acuity.
Categorizing the Causes
The underlying reason for posterior uveitis is broadly separated into two main groups: infectious and non-infectious causes. Identifying the correct category is a foundational step, as mismanaging an infectious case can compromise the patient’s vision. Infectious agents are responsible for a significant portion of cases globally, with common culprits including parasites like Toxoplasma gondii, which causes toxoplasmosis.
Viral infections are also a frequent cause, particularly the herpes virus family, such as Cytomegalovirus (CMV), Herpes Simplex Virus (HSV), and Varicella Zoster Virus (VZV). Systemic bacterial infections like tuberculosis can manifest as inflammation in the posterior segment of the eye. These infections often require specific antimicrobial therapy to eradicate the causative pathogen.
The non-infectious category encompasses conditions where the body’s immune system mistakenly attacks its own tissues, resulting in autoimmune or autoinflammatory responses. Systemic diseases like sarcoidosis, characterized by the growth of inflammatory cells, frequently affect the eyes. Other examples include Behçet’s disease, which causes inflammation of blood vessels, and Vogt-Koyanagi-Harada (VKH) disease, which targets melanocytes. If the inflammation is isolated to the eye with no identifiable systemic cause, the condition is often labeled as idiopathic.
Confirming the Diagnosis
An ophthalmologist begins the diagnostic process with a comprehensive eye examination, including a dilated fundus examination to visualize the retina, choroid, and vitreous. Slit lamp microscopy is used to detect inflammatory cells and debris in the anterior chamber and vitreous, a phenomenon known as vitritis. These initial steps confirm the presence and location of the inflammation.
Specialized imaging techniques provide detailed anatomical information and help track disease progression and treatment response. Optical Coherence Tomography (OCT) creates cross-sectional images of the retina, allowing the detection of macular swelling or fluid accumulation. Fluorescein Angiography (FA) involves injecting a fluorescent dye into the bloodstream to highlight areas of abnormal blood vessel leakage or non-perfusion in the retina and choroid.
To identify the specific underlying cause, a systemic workup is often required, particularly when the uveitis is bilateral or recurrent. This workup typically involves blood tests to check for markers of autoimmune diseases or exposure to infectious agents. A chest X-ray may be ordered to screen for conditions like tuberculosis or sarcoidosis. For definitive identification of an infectious agent, a sample of the vitreous humor can be taken for Polymerase Chain Reaction (PCR) testing, which amplifies and detects the genetic material of pathogens.
Treatment Strategies
The management of posterior uveitis is guided by the underlying cause, with the primary goals being to reduce inflammation, preserve existing vision, and prevent structural damage. For non-infectious forms, corticosteroids are the first-line treatment due to their anti-inflammatory effects.
Corticosteroids can be administered as topical eye drops, though this method is less effective for deep posterior inflammation. More direct delivery methods include periocular or intraocular injections of steroids, which provide high concentrations of the medication directly to the affected tissues. For severe or widespread inflammation, systemic corticosteroids taken orally may be required.
However, long-term systemic steroid use carries a risk of side effects, including cataracts and glaucoma, which necessitates careful monitoring. If the inflammation is chronic, severe, or requires prolonged steroid use, treatment progresses to non-steroidal immunosuppressive drugs, sometimes called disease-modifying anti-rheumatic drugs (DMARDS). These medications, which include agents like methotrexate or azathioprine, help modulate the immune system more broadly.
Biologic therapies, a newer class of drugs, target specific molecules involved in the inflammatory cascade and are reserved for the most resistant cases, helping to reduce the long-term dependency on high-dose steroids.
When the diagnosis confirms an infectious cause, the treatment shifts to specific anti-infective medications. This involves administering antibiotics for bacterial infections, antivirals for herpes-related uveitis, or antiparasitic drugs for toxoplasmosis. The anti-infective treatment is often combined with a short course of corticosteroids to control the immediate inflammatory damage, but only after the pathogen is being effectively targeted. In rare cases, surgical intervention, such as a vitrectomy, may be necessary to remove persistent inflammatory debris or to address complications like retinal detachment.