Endophthalmitis is a serious infection of the eye’s inner fluids, the aqueous and vitreous humors. When bacteria or fungi enter these spaces, they trigger an inflammatory response that can compromise vision. This condition is a medical emergency due to its potential for rapid and severe vision loss.
Causes and How It Develops
Endophthalmitis can arise from external sources, known as exogenous endophthalmitis, or from infections spreading within the body, termed endogenous endophthalmitis. Exogenous cases are the most common and often occur after eye surgery, such as cataract surgery, or following a penetrating eye injury.
Post-surgical infections often involve Staphylococcus epidermidis, entering through surgical incisions or contaminated instruments. Trauma, especially involving organic matter, can introduce bacteria and fungi like Bacillus cereus.
The infection can also develop without a direct breach of the eye’s outer layers, such as in severe contact lens keratitis or after procedures like scleral buckling, where pathogens from the ocular surface or adjacent tissues may spread into the eye. Once inside, these infectious agents multiply and release toxins, leading to inflammation and accumulation of inflammatory cells and exudates within the aqueous and vitreous humors. This process can quickly damage delicate eye structures, including the retina.
Endogenous endophthalmitis is less common (2% to 15% of cases) and results from microorganisms traveling through the bloodstream from a distant infection site to the eye. It is frequently associated with systemic conditions like diabetes, weakened immune systems, or indwelling catheters. Fungi, particularly Candida species, are a common cause, though bacteria like Klebsiella pneumoniae (especially in East Asia) and Staphylococcus species can also be responsible. These pathogens typically lodge in the choroid due to its rich blood supply, then spread into the subretinal space and vitreous cavity.
Identifying the Symptoms
Symptoms often appear rapidly, typically within one to six days after an eye injury or surgery. A significant decrease in vision is common, reported by over 90% of patients, ranging from blurred vision to severe loss of light perception.
Intense eye pain is another frequent symptom, though about 25% of individuals may not experience it. Symptoms can include eye redness, eyelid swelling, and sensitivity to bright light (photophobia). Patients may observe white or yellow discharge from the eye, a cloudy cornea, or a visible layer of white cells, called hypopyon, in the lower anterior chamber.
Diagnosis and Treatment
Diagnosis begins with a thorough eye examination by an ophthalmologist, including visual acuity checks, slit lamp examination, and intraocular pressure assessment. If the back of the eye (fundus) cannot be clearly seen due to inflammation, an ocular ultrasound may be performed to identify vitreous inflammation, retinal detachment, or foreign objects following trauma.
To identify the specific microbe, a sample of the eye’s fluid is collected. This typically involves a vitreous tap (aspirating vitreous humor with a fine needle) or an anterior chamber tap for aqueous humor. Vitreous samples generally yield more accurate culture results. These samples are sent for microbiological analysis (Gram stain and cultures) to determine the type of bacteria or fungi and their susceptibility to medications. For endogenous endophthalmitis, blood cultures and other systemic tests may also be performed to locate the primary infection source.
Treatment for endophthalmitis is an emergency and should begin as soon as the condition is suspected, even before culture results are available. The primary approach involves injecting broad-spectrum antibiotics directly into the vitreous cavity, typically vancomycin and ceftazidime, to combat Gram-positive and Gram-negative bacteria. For fungal infections, intravitreal antifungals like amphotericin B or voriconazole are used. Systemic antibiotics are generally recommended for endogenous endophthalmitis, as the infection originates elsewhere, but their routine use in exogenous bacterial endophthalmitis is less clear.
In severe cases, especially when vision is significantly impaired (e.g., light perception only), a vitrectomy may be performed. This surgical procedure removes the infected vitreous gel, reducing microbial load and inflammatory substances. Vitrectomy can improve the effectiveness of injected medications and allow for better visualization of the retina. Repeat intravitreal injections may be necessary if initial treatment does not show sufficient improvement within 24 to 48 hours.
Expected Outcomes and Recovery
The prognosis for endophthalmitis varies widely, depending on factors such as the infection’s cause, the microorganism type, initial visual acuity, and how quickly treatment begins. Early diagnosis and prompt treatment are associated with better visual outcomes. Eyes infected with more aggressive bacteria, such as Streptococcus species, tend to have a poorer prognosis.
Even with appropriate treatment, only about 39% of patients may recover vision better than 20/400. Factors like advanced age and poor initial visual acuity are associated with a worse visual prognosis. Complications can include retinal detachment, chronic pain, and in rare, severe cases, surgical eye removal (enucleation or evisceration).
Recovery can be prolonged, with pain and redness potentially improving within days, but vision problems often persisting for weeks or months. Regular follow-up appointments with an ophthalmologist are necessary to monitor recovery, manage ongoing inflammation, and address potential long-term complications. Patients may require additional injections or surgical interventions if the infection recurs or if vision does not improve as expected.