50.1 Features
50.1.1 Endogenous Endophthalmitis
Endogenous endophthalmitis results from the hematogenous spread of microorganisms (bacteria, fungi, or mycobacteria) from distant foci to intraocular structures and accounts for 2 to 8% of all cases of endophthalmitis.
Risk factors:
Recent hospitalization.
Diabetes mellitus.
Immunosuppression.
Intravenous drug use.
Others: Indwelling catheters, urinary tract infection, organ abscesses, and endocarditis.
Causative organisms:
Several series have identified fungal organisms as the culprit in the majority of cases (in developed countries). The most commonly isolated fungal species is Candida, followed by Aspergillus.
In bacterial endogenous endophthalmitis, gram-positive species (Staphylococci and Streptococci) predominate in isolates from Western countries, whereas gram-negative strains (especially Klebsiella) are the main culprit in East Asian countries. Bacterial endogenous endophthalmitis is more common than fungal causes in East Asian countries. Klebsiella infections are associated with rapid progression of the disease and poor visual outcome.
Endophthalmitis following intravitreal injection of anti-vascular endothelial growth factor (anti-VEGF) agent or steroid is rare (i.e., <1 per 1,000 injections) and typically occurs acutely following the procedure.
Risk factors:
Talking, coughing, and sneezing should be avoided during the injection procedure. Studies have suggested that potential ocular surface contamination with oral flora may be a risk factor.
The use of povidone-iodine to sterilize the ocular surface is recommended as a preinjection sterilizing agent.
The use of bladed lid speculums, the hemisphere of injection, conjunctival displacement, and type of anti-VEGF agent have not been definitively shown to alter risk.
The use of postoperative antibiotics has not been shown to decrease the risk of postinjection endophthalmitis and was shown to increase the rate of antibiotic resistance.
Causative organisms:
Coagulase-negative Staphylococcus and Streptococcus species are the most common isolates in postinjection endophthalmitis.
50.1.2 Sterile Endophthalmitis
Noninfectious endophthalmitis, also referred to as sterile endophthalmitis or postinjection vitritis, is believed to be an inflammatory reaction to a drug or drug delivery vehicle. Although hypopyon, fibrin in the anterior chamber, and pain are less common, all vitreous inflammation postintravitreal injections must be suspected as infectious endophthalmitis.
Toxic anterior segment syndrome following intraocular surgery has a similar presentation to sterile postoperative inflammation (limbus to limbus corneal edema, frequently presents without pain, less vitritis compared to infectious endophthalmitis); however, this inflammation is usually greatest on postoperative day 1, whereas an infectious endophthalmitis typically presents after 2 or more days. The etiology is unknown but is believed to be a severe inflammatory immune response to various factors introduced during the procedure (e.g., detergents, residual viscoelastic, and preservatives).
50.1.3 Postcataract Surgery Endophthalmitis
Endophthalmitis following cataract surgery is a rare but feared complication.
Incidence:
Reported worldwide to be 0.03 to 0.2%.
Risk factors:
Posterior capsular rupture.
Manual intracapsular and extracapsular cataract extraction.
Clear corneal incisions, silicone intraocular lenses, male gender, and age greater than 85 years have also been identified as risk factors.
Causative organisms:
The source likely originates from ocular surface and/or skin flora.
Coagulase-negative Staphylococcus is the most commonly isolated organism, followed by Staphylococcus aureus and Streptococcus species.
Chronic postoperative endophthalmitis is rare and occurs more than 6 weeks after surgery. These infections are typically due to indolent bacteria such as Propionibacterium acnes, Staphylococcus epidermidis, or fungi, such as Candida or Aspergillus. Patients are generally misdiagnosed as having chronic or recurrent uveitis postcataract surgery due to their indolent course.
50.1.4 Bleb-Related Endophthalmitis
During a filtering glaucoma surgery, a bleb is created and as a result, the aqueous humor is only separated from the external environment by a thin conjunctival barrier. When this barrier is disrupted, this allows for the introduction of bacteria into the bleb (i.e., blebitis) and ultimately into the eyes (bleb-related endophthalmitis [BRE]). The onset of BRE may be early (<1 month postoperatively) or delayed (>1 month).
Incidence: Approximately 1%.
Risk factors: Nasally or inferiorly located bleb due to increased exposure to the tear film, bleb leakage, use of antimetabolites, blepharitis, and bleb revisions.
Causative organisms:
One-third of cases are attributed to Streptococcus species, followed by Staphylococcus and gram-negative species.
Early BRE is most commonly from coagulase-negative Staphylococcus and S. aureus.
Delayed-onset BRE is attributed to more virulent microorganisms, such as Streptococcus and Haemophilus species.
Glaucoma drainage implants, such as Ahmed glaucoma valve or Baerveldt glaucoma implant, have also been associated with endophthalmitis; the major risk factor is conjunctival erosion over the tube.
Commonly isolated organisms include Staphylococcus species, Streptococcus pneumoniae, and Pseudomonas aeruginosa.
50.1.5 Post-Trauma Endophthalmitis
After penetrating injury or globe rupture, inoculation of the intraocular tissue with foreign material may result in a particularly fulminant manifestation of endophthalmitis.
Incidence:
Incidence of trauma-related endophthalmitis ranges from 0 to 16.5%.
Risk factors:
Presence of intraocular foreign body (IOFB), injury occurring in a rural setting, ruptured lens capsule, contaminated injury with organic matter, delayed repair of globe, and vitreous prolapse through wound.
Causative organisms:
Coagulase-negative Staphylococci and Streptococci species.
Bacillus, Pseudomonas, Klebsiella, and Clostridium species are seen and are associated with a fulminant and rapid progression.
Soil contamination and IOFB are associated with a higher incidence of Bacillus infections.
Polymicrobial infections are also more common with penetrating globe injuries compared to other causes of endophthalmitis.
Aspergillus species are the most prevalent fungal cause of post-traumatic endophthalmitis.
50.2 Symptoms
Eye redness, pain, photophobia, floaters, and decreased vision in the setting of ocular trauma, ocular surgery, intravitreal injection, or systemic illness (e.g., fever, chills, nausea, vomiting, and other signs associated with the underlying systemic etiology) may be present in endophthalmitis.
50.2.1 Exam Findings
Signs of various types of endophthalmitis include vitreous haze/cell, anterior chamber inflammation, vitreous exudates, visible arteriolar septic emboli, uveal tissue abscesses (▶ Fig. 50.1), hypopyon (▶ Fig. 50.2), whitened bleb with surrounding conjunctival injection (▶ Fig. 50.3), and necrotizing retinitis.
Fig. 50.1 Color fundus photograph following partial treatment of methicillin-sensitive Staphylococcus aureus endophthalmitis with resolving vitritis and a persistent yellow–white choroidal abscesses.
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