Endogenous endophthalmitis accounts for a minority of cases (1). Predisposing conditions include immune deficiency, immune suppression, diabetes mellitus, chronic renal failure, IV drug abuse, and patients receiving hyperalimentation. These patients can develop endophthalmitis without prior ocular disease. Such cases may be bilateral, increasing both the impact on the patient and the management difficulties. Systemic workup and therapy play an extensive role in the management of these patients and require infectious disease consultation. Metastatic infection accounts for approximately 8% of endogenous bacterial endophthalmitis. At times, vitrectomy is indicated in this patient group but is quite difficult because of the associated anesthesia risk and the potential bilaterality of the disease. Eyes with endogenous endophthalmitis have increased penetration of systemic antibiotics through breakdown of the blood-retinal barrier, and intravenous antibiotics may be sufficient to treat the disease if the intraocular inflammation is not severe. On the other hand, whenever bilateral endogenous endophthalmitis is diagnosed and rapid progression of the diseases is noticed or one of the eyes has progressed to severe visual loss, the authors often recommend vitrectomy for the less involved eye to prevent bilateral blindness. Adequate coordination with the infectious disease consultants is paramount. If the patient has a known systemic infection, the appropriate intravitreal antibiotic therapy can be chosen. If the infectious agent has not been identified, vitrectomy can permit isolation of the bacteria and guide systemic treatment.

Ocular trauma (2,3) accounts for approximately 20% of bacterial endophthalmitis (4,5). Ocular surgery (6, 7, 8) accounts for the vast majority (˜70%) as it facilitates the introduction of organisms into the eye. Management of trauma cases usually requires vitreous surgery and may involve removal of intraocular foreign bodies. While conventional surgical wisdom suggests removal of any implanted materials if infection occurs, this logic does not apply to the IOL. Removal of an IOL, especially in an endophthalmitis case, has a risk of iris avulsion, endothelial trauma, intraocular bleeding, choroidal expulsive hemorrhage, and retinal detachment. Vitrectomy with intraocular antibiotics without implant removal can be successful in a high percentage of cases. This is probably because the smooth surface of the lens implant coupled with the high fluid throughput of vitrectomy removes all organisms on the lens surface, but organisms may remain in the peripheral capsular bag.

Fortunately, the incidence of acute postoperative endophthalmitis remains relatively low. Extracapsular cataract surgery with or without an IOL insertion carries an incidence of 0.072% (9). Vitrectomy (0.051%) and penetrating keratoplasty (0.11%) have a far less risk than the insertion of a secondary IOL (0.30%). Sutureless clear corneal incisions and temporal placement of phacoemulsification incisions may have an increased risk of postoperative infectious endophthalmitis (10). The most frequent organisms include coagulase-negative Staphylococcus, Staphylococcus aureus, Streptococcus species, and Gram-negative bacteria.

Delayed-onset, post-cataract surgery endophthalmitis is most often caused by Propionibacterium acnes, coagulase-negative Staphylococcus, or Candida. In the setting of P. acnes endophthalmitis, inflammatory plaque and associated capsule must be removed at a minimum; in most instances, the IOL must be removed as well (11).

The incidence of trauma-related endophthalmitis varies with or without the presence of a retained foreign body. Following a penetrating injury, the incidence of endophthalmitis ranges from 3.2% to 7.4%. With a retained foreign body, the incidence jumps to 6.9% to 13% (metallic—7.2%, nonmetallic—7.3%, organic—6.3%). The most frequent organisms include Bacillus sp., Staphylococcus sp., and Streptococcus sp.

Streptococcus, coagulase-negative Staphylococcus, and Haemophilus are the most common organisms in delayed-onset filtering bleb-related cases. Immediate vitrectomy intervention is mandatory in these often rapidly deteriorating cases.

Therapeutic intravitreal injections with anti-vascular endothelial growth factor (VEGF) compounds are widespread but fortunately produce a low incidence of postinjection endophthalmitis when meticulous sterile technique is utilized. Fortunately, the incidence of endophthalmitis after intravitreal triamcinolone injections, although higher than anti-VEGF compounds, appears to be low (˜0.1%-0.9%) (12,13).