What is Bacterial Endophthalmitis?
Bacterial endophthalmitis is an infection that takes hold within the very core of the eye, specifically affecting the internal fluids—the vitreous humor, which is the large gel-like body that gives the eye its shape, and the aqueous humor in the front chamber. When bacteria breach the eye’s protective outer layers, they multiply rapidly in this sterile environment. This invasion triggers a swift and overwhelming inflammatory cascade as the body’s immune cells rush in to combat the microbes. The resulting accumulation of pus and inflammatory byproducts is profoundly toxic to the eye’s delicate internal structures, particularly the light-sensing retina, and can quickly lead to catastrophic vision loss.
Causes:The development of this severe intraocular infection hinges on the successful entry of bacteria past the eye's formidable protective walls. The primary events that facilitate this microbial invasion are:
- Breach During Ocular Surgery (Exogenous): This is the most frequent origin of the infection. A necessary surgical incision, typically for cataract removal, retinal repair, or glaucoma procedures, momentarily compromises the integrity of the globe. This breach can allow common bacteria from the patient's own eyelids or tear film to be introduced into the sterile interior of the eye.
- Introduction via Penetrating Trauma (Exogenous): An accident that results in a puncture or rupture of the eyeball creates a direct, uncontrolled pathway for infection. The foreign object responsible for the injury physically carries bacteria from the outside environment through the cornea or sclera and deposits them deep within the eye.
- Seeding from a Systemic Infection (Endogenous): In this much rarer scenario, bacteria from a serious infection located elsewhere in the body—such as a heart valve infection (endocarditis) or a liver abscess—enter the bloodstream. These circulating pathogens can then travel to the eye and cross the blood-ocular barrier to establish a secondary infection site.
While this infection is rare, certain circumstances dramatically elevate an individual's vulnerability to developing this sight-threatening condition. The primary situations that predispose a person to bacterial endophthalmitis are:
- A History of Recent Intraocular Surgery: Having undergone a procedure that involves an incision into the eyeball is the single most significant predisposing factor. The risk is highest in the immediate days and weeks following common operations such as cataract removal, corneal transplantation, or glaucoma filtering surgery.
- Experiencing a Penetrating Ocular Injury: Any trauma that physically breaches the protective outer wall of the eye (the cornea or sclera) creates a direct portal for bacterial entry. The risk is compounded if the injury involves a contaminated foreign object, such as a piece of metal or organic matter.
- Impaired Systemic Immune Defenses: Individuals with a compromised immune system are at a higher risk for the rarer, blood-borne (endogenous) form of the disease. This includes patients with uncontrolled diabetes, those receiving immunosuppressive therapy after an organ transplant, or individuals with indwelling intravenous catheters.
