A complete history and physical examination are critical in diagnosing and treating bacterial endophthalmitis in a timely and effective manner. Prompt and effective diagnosis can be the difference between a lifetime of vision or a lifetime of blindness. The most common symptom of endophthalmitis that patients will complain of is decreased vision. Eye pain, discharge, or red-eye are also common but may be present or absent in different cases of bacterial endophthalmitis. The timeline of symptoms can also serve as a clue to healthcare providers whether the patient is suffering from a bacterial etiology versus a fungal etiology. 

Bacterial endophthalmitis presents in a much more acute timeframe, often within days of a penetrating event; versus fungal endophthalmitis, which has a much more subacute presentation, worsening over days to weeks. Healthcare providers should inquire about a history of ocular surgery, ocular injections, or any penetrating ocular injury that are often present in exogenous endophthalmitis. Healthcare providers should also inquire about systemic symptoms such as fevers, chills, recent infections, recent surgery, recent hospitalization for sepsis, recent antibiotic use, intravenous drug use, that are often present in endogenous endophthalmitis cases.[1]

Exogenous Endophthalmitis

Patient presentation is most commonly unilateral and can vary, ranging from asymptomatic to symptoms of a painful eye, conjunctival injection, photophobia, corneal edema, iritis, vitritis, anterior chamber cells, floaters, or reduced vision. On examination, a hypopyon, which represents a layer of white blood cells in the anterior chamber, can occur in most cases of bacterial endophthalmitis and up to 80% of postcataract cases. Funduscopic examination reveals intraocular inflammation, which often obscures the view of the retina with white blood cells that create a "hazy" look. The type of intraocular inflammation can also be a clue, with bacterial endophthalmitis having diffuse intraocular inflammation. In contrast, fungal endophthalmitis will present with "clumps" of inflammation in the aqueous or vitreous. Using ultrasound B-scan can help identify vitritis, or chorioretinal infiltrates.[1] Vitreous fluid obtained via vitrectomy has a higher diagnostic yield than vitreous fluid from needle biopsies. If a patient contracts endophthalmitis from anti-VEGF intravitreal injections, vitreous culture is helpful in the prognosis of visual outcomes, but not necessarily influential in the clinical course.[12] Aqueous humor tap is the lowest yielding fluid to culture, most likely due to the increased distance from the nidus of infection. Blood cultures yield true-positive results in approximately a third of cases.[13] whereas polymerase chain reaction can identify both bacterial and fungal culture-negative cases.[14] 

Endogenous Endophthalmitis 

Endogenous endophthalmitis is most often unilateral, but up to a third of cases have bilateral involvement. Diagnosing endogenous endophthalmitis requires a high degree of suspicion with the presence of systemic risk factors. However, a clinical diagnosis of endogenous endophthalmitis is always difficult as it has a high false-negative rate, and multiple clinic visits may be required to confirm the diagnosis. Some patients may present asymptomatically while symptomatic patients might present with symptoms such as hypopyon, vitritis, conjunctival injection, corneal edema, iritis, anterior chamber cells, or reduced visual acuity. White infiltrate originating in the choroid and protruding into the vitreous cavity is a key diagnostic finding of endogenous endophthalmitis. The presence of endogenous endophthalmitis is generally not a major concern in patients with life-threatening sepsis secondary to a bacterial etiology, and hence the diagnosis of endogenous endophthalmitis may be delayed with other morbidities under acute management. A 2015 study helped stratify the likelihood of endogenous endophthalmitis as a diagnosis[15]:

• Positive endogenous endophthalmitis
  • Uveal tissue abscesses
  • Hypopyon greater than 1.5 mm
  • Vitreous exudates
  • Visible arteriolar septic emboli
  • Necrotizing retinitis
  • Perivascular hemorrhages with inflammatory
  • Panophthalmitis
  • Corneal infiltrates of ulcer
• Possible endogenous endophthalmitis
  • Hypopyon greater than 1.5 mm
  • Vitreous haze with no visible exudates
  • Chorioretinal lesions
  • Optic neuritis
  • White reflex in neonates
  • Scleritis
• Probable endogenous endophthalmitis
  • Conjunctival injection or chemosis
  • Anterior chamber inflammation but no hypopyon
  • Absence of vitreous haze
  • Lid edema 
  • Fever

Bacterial endophthalmitis necessitates prompt and early management with intraocular antibiotics often combined with a pars plana vitrectomy. Patients should be hospitalized and have broad-spectrum intravenous, topical, and potentially intravitreal antibiotics initiated after collecting the appropriate cultures. The antibiotic of choice should be determined once the etiology of the infection is verified, and once cultures come back, the clinician can make appropriate changes to antibiotic therapy. Patients should receive topical cycloplegic such as atropine 1% twice daily, and topical prednisolone acetate 1% every 1 to 6 hours. Intravitreal antibiotics offer higher intraocular concentrations of antibiotics and can be a consideration if they cover the correct etiology. Intravitreal antibiotics include ceftazidime 2.2 mg, vancomycin 1 mg, and amikacin 0.4 mg. The susceptibility of gram-positive bacteria was highest to vancomycin. Pars plana vitrectomy is beneficial because it reduces the infective and inflammatory load as well as providing material for diagnostic studies.

Periocular injections or subtenon injections can also be options if necessary.[11] A current study showed the most common isolate in cases of endophthalmitis following evisceration was Streptococcus pneumoniae, followed in order by Aspergillus and Pseudomonas aeruginosa, respectively.[11] Endophthalmitis can convert to panophthalmitis if the infection spreads to the sclera and the Tenon capsule.[3] Regarding panophthalmitis, the affected eye usually needs to undergo evisceration or enucleation, with studies suggesting the evisceration rate of panophthalmitis ranges from 14.3% to 23.2%.[3] All isolates showed susceptibility to ceftazidime and levofloxacin, and all MIC 90s for isolates in the current period compared with isolates from 1987 to 2001 remained identical. Despite early and appropriate treatment, outcomes were generally poor with a high rate of enucleation.[16] Intravenous drug users are given aminoglycosides and clindamycin to cover the most likely causative organism, bacillus cereus.

The differential diagnosis of bacterial endophthalmitis include:

• Endogenous fungal endophthalmitis
• Retinochoroidal infection
• Noninfectious posterior or intermediate uveitis
• Neoplastic conditions such as large cell lymphoma or retinoblastoma

Studies on endophthalmitis resulting from Streptococcus pneumoniae suggest a poor visual outcome. Miller et al., in their study on pneumococcal endophthalmitis, reported 3/27 (11.11%) eyes required evisceration. Pseudomonas endophthalmitis has a high enucleation rate with one study suggesting that 64% endophthalmitis caused by Pseudomonas will end up with evisceration and enucleation. Similarly, high evisceration rates post Pseudomonas endophthalmitis were also seen in other studies.[17][11] One study found risk factors that are strongly associated with evisceration or enucleation include endogenous endophthalmitis, corneal ulcer, older age, poor initial visual acuity, female gender, and delayed treatment. However, patients with traumatic or postoperative endophthalmitis were less likely to be eviscerated or enucleated. Multivariate analysis indicates that patients suffering from a corneal ulcer, endogenous endophthalmitis, and poor initial visual acuity were much more likely to require evisceration or enucleation.[3]

Complications of bacterial endophthalmitis:

• Panophthalmitis
• Corneal ulcer
• Orbital cellulitis
• Loss of vision
• Retinal detachment

The use of intracameral cefuroxime following cataract surgery reduced the incidence of postoperative endophthalmitis. Additional risk factors associated with endophthalmitis after cataract surgery included clear corneal incisions (CCI) and the use of silicone intraocular lenses (IOL).[14] A study reviewing 45954 cataract procedures performed by the same surgeon discovered that the incidence of postoperative endophthalmitis could be reduced by 72% if the patient had pretreatment with periocular penicillin injections and topical chloramphenicol-sulphadimidine. The efficacy of this method had confirmation by a concurrent masked, randomized study of 6618 cataract operations that demonstrates that topical regimen alone was as ineffective as penicillin prophylaxis alone.[13] Prevention of postcataract endophthalmitis is a difficult topic to study, given the low incidence. In addition to the appropriate wound construction, a combination of antibiotics and povidone-iodine provide a reasonable approach in reducing the risk of this rare but severe infection.[18]

Bacterial endophthalmitis frequently poses a diagnostic dilemma. These patients may exhibit non-specific signs and symptoms such as blurry vision, eye pain, or leukocytosis. Bacterial endophthalmitis may be due to either endogenous or more commonly exogenous causes, such as traumatic or surgical. Although the slit-lamp exam may reveal that the patient has endophthalmitis, the etiology is difficult to ascertain without proper diagnostic studies. While the ophthalmologist is almost always involved in the care of patients with bacterial endophthalmitis, it is essential to consult with an interprofessional team of specialists and other providers that include infectious disease, pharmacology, and the patient's primary care provider.

Nurses are also vital members of the interprofessional group, as they will monitor the patient's status. The pharmacist will ensure that the patient receives the right antibiotics as well as cycloplegic and steroid eye drops, and perform dose checking and medication reconciliation, reporting any issues to the interprofessional team. Nursing can counsel on the appropriate dosing and administration of medications and answer patient questions, as well as charting treatment progress, and reporting any issues to the clinician managing the case. Without providing a proper history, the ophthalmologist may not be sure what to look for or what additional diagnostic exams may be needed. This problem gets even more complicated when immunocompromised patients present with bacterial endophthalmitis. The outcomes of bacterial endophthalmitis depend on the cause. However, to improve outcomes, prompt consultation with an interprofessional group of specialists is recommended. [Level V]