Endophthalmitis is an inflammatory condition of the eye, specifically the intraocular cavities – inside the eye is the aqueous humor between the cornea and lens, and the vitreous humor between the lens and retina. The inflammation can be either infectious or non-infectious, though the most common cause is infection. The source can also be endogenous (another body part as the source) or exogenous (external source directly impacting the eye). The condition may be as subtle as small white nodules on the lens, iris, retina or choroid – or it can be evident inflammation of all structures in the eye with or without discharge (called exudate).
Endogenous infectious causes
Endogenous endophthalmitis can also be referred to as metastatic. The infectious agent spreads from an infection in another distant part of the body, such as the heart (endocarditis) or nervous system (meningitis). Bacteria (both Gram-negative and Gram-positive) and fungi are both potential causes, though Gram-positive bacteria are the most common bacterial strains involved, including Streptococcus species, Staphylococcus epidermidis and Staphylococcus aureus. According to studies, fungal infections may cause more than 50 percent of endogenous cases. Because of the blood-ocular barrier, the condition is rare and accounts for less than 15 percent of endophthalmitis cases according to Medscape, but when it does occur it can lead to blindness. Intravenous and intravitreal antibiotics are used against bacterial causes of the disorder.
Exogenous infectious causes
Exogenous endophthalmitis is caused by direct inoculation of the eye, which can occur during surgery, penetrating trauma or with the introduction of foreign bodies. Any event or procedure that compromises the eyeball structure can result in the introduction of pathogenic material, such as keratotomy. According to Medscape, post-cataract endophthalmitis is the most common exogenous form, though less than 1 percent of cataract surgeries have this complication. Less than 15 percent of penetrating intraocular trauma results in endophthalmitis. Gram-negative bacterial strains are the most common causes of infection from penetrating injury, including Pseudomonas, Escherichia coli, and Enterococcus.
Non-infectious causes of endophthalmitis
Non-infectious endophthalmitis is also called sterile endophthalmitis. Sources of inflammation in the eye can include toxic agents or retention of material (e.g., lens) after surgery. Recent therapies for eye conditions that involve intravitreal injection, such as macular degeneration, can also cause inflammation. In one case study in 2003, the inflammation was found to be caused by a cellular reaction and to resolve on its own. However, intravitreal injection can also introduce infectious agents.
Determining the cause of inflammation
Cultures of the intraocular fluid can determine for certain whether the eye inflammation is caused by a cellular reaction that may resolve on its own or the introduction of a pathogenic agent. Endophthalmitis can be caused by infectious or non-infectious culprits, and determining the source will help treat the condition. As such, the guidelines for diagnosing the condition and other similar conditions of the eye are under constant scrutiny.