Endogenous endophthalmitis is a rare but serious infection that occurs inside the eye. This condition arises when infectious microorganisms, such as bacteria or fungi, travel through the bloodstream from another part of the body and reach the eye.
Sources of Infection and Risk Factors
Common primary sources include liver abscesses, which are collections of pus in the liver, and endocarditis, an infection of the heart’s inner lining, often involving heart valves. Other potential origins include urinary tract infections, pneumonia, or even skin abscesses and cellulitis. These microorganisms enter the bloodstream, a condition known as bacteremia or fungemia, and then circulate throughout the body, eventually seeding the ocular tissues.
Certain individuals face a higher likelihood of developing this eye infection due to specific underlying health conditions or circumstances. Diabetes mellitus is a significant risk factor, particularly when accompanied by ophthalmic manifestations. A weakened immune system, often due to conditions like HIV/AIDS, lymphoma/leukemia, or the use of immunosuppressive medications, also increases susceptibility. Intravenous drug use is another recognized risk factor, as it can introduce pathogens directly into the bloodstream.
Patients undergoing recent major surgeries, especially those involving indwelling catheters, are also at increased risk. Prolonged hospital stays, particularly in intensive care units, further elevate the chances of developing endogenous endophthalmitis.
Ocular Signs and Symptoms
Once microorganisms reach the eye, they cause a range of noticeable signs and symptoms. Individuals often experience severe eye pain, which can be sudden in onset and progressively worsen. The affected eye typically appears significantly red, often accompanied by general redness of the white part of the eye.
Vision loss is a common and concerning symptom, frequently described as sudden and progressive. Patients might also report an increase in “floaters,” which are small specks or strands that drift across the field of vision, or heightened sensitivity to light, known as photophobia. A distinct sign that can be observed is a hypopyon, which is a visible accumulation of white blood cells forming a yellowish-white layer in the lower part of the front chamber of the eye, between the iris and the cornea. Other manifestations can include swollen eyelids, watery eyes, and a cloudy appearance of the cornea.
The Diagnostic Process
Diagnosing endogenous endophthalmitis involves a careful assessment by an ophthalmologist, often starting with a comprehensive eye examination. A dilated eye exam is performed to allow the doctor to view the back of the eye, including the retina and vitreous, which is the clear gel filling the eye. This examination helps identify inflammation, exudates, or infiltrates within the eye.
When the view to the back of the eye is obscured by significant inflammation or haziness, a B-scan ultrasound is an invaluable diagnostic tool. This imaging technique uses sound waves to create detailed images of the eye’s internal structures, revealing vitreous inflammation, membranes, exudates, or even retinal detachment. To identify the specific microorganism causing the infection, a vitreous tap is frequently performed, where a small fluid sample is carefully withdrawn from the vitreous cavity.
This fluid sample is then sent for laboratory analysis, including Gram stain and culture, to grow and identify the bacteria or fungus and determine its susceptibility to various medications. In cases of endogenous endophthalmitis, blood cultures are also taken to detect the systemic infection originating elsewhere in the body. While intraocular cultures are highly specific, their positivity rate can vary, with vitreous samples showing better yields than aqueous samples.
Medical and Surgical Treatments
Treating endogenous endophthalmitis is an emergency that typically requires immediate medical intervention and often hospitalization to manage both the eye infection and the underlying systemic source. The primary medical approach involves administering antibiotics or antifungals. Systemic treatment, given intravenously or orally, targets the infection throughout the body, including the original source. For bacterial infections, broad-spectrum intravenous antibiotics like vancomycin combined with a third-generation cephalosporin or aminoglycoside are commonly used.
In addition to systemic therapy, medication is delivered directly into the eye through intravitreal injections. For bacterial infections, common intravitreal antibiotics include vancomycin (1.0 mg/0.1 mL) and ceftazidime (2.25 mg/0.1 mL) to achieve high concentrations at the site of infection. For fungal infections, intravitreal amphotericin B (5-10 µg/0.1 mL) or voriconazole (100 µg/0.1 mL) may be administered. These injections help to directly reduce the microbial load within the eye.
Surgical intervention, specifically a pars plana vitrectomy, is often a necessary component of treatment, particularly in cases of severe vitritis or declining vision. During a vitrectomy, the infected vitreous gel is carefully removed from the eye, which helps to reduce the number of microorganisms and inflammatory mediators. This procedure also allows for a larger, more comprehensive sample for culture and can improve the penetration of intravitreal medications. Vitrectomy can also address complications such as retinal detachment.
Prognosis and Visual Outcomes
The long-term visual outlook for individuals with endogenous endophthalmitis is often guarded and varies significantly depending on several factors. The type and virulence of the infecting microorganism play a substantial role, with fungal infections caused by yeasts generally having a better prognosis than bacterial infections, and mold infections often leading to the least favorable outcomes. For instance, approximately 56% of patients with yeast-related endogenous endophthalmitis may achieve vision of 20/200 or better, compared to about 41% for bacterial cases and 33% for mold infections.
The patient’s overall underlying health and immune status also influence the recovery. Perhaps the most impactful factor is how quickly the diagnosis is made and aggressive treatment is initiated. Delay in treatment can lead to more severe inflammation and damage, increasing the likelihood of permanent vision loss. While some degree of permanent vision reduction is common, rapid and comprehensive medical and surgical management can help preserve the eye and maintain some functional vision.