Bacterial Endophthalmitis

Etiology

Bacteria are not present in the vitreous or aqueous humor of a healthy eye, but seeding into the eye can occur from an exogenous or endogenous source (see Table 1). The most common cause of bacterial endophthalmitis is exogenous seeding from the exterior ocular surface during penetrating ocular trauma, surgery, or intraocular injections. Although rare, bacterial endophthalmitis can also result from hematogenous spread from infections elsewhere in the body or intravenous drug use (see Image. Etiologic Classification of Bacterial Endophthalmitis).[14]

Risk Factors

Specific risk factors have been associated with preoperative, intraoperative, and postoperative stages:

Preoperative 

• Blepharitis or lid abnormalities [15]
• Application of 2% xylocaine gel before povidone-iodine [16]
• Diabetes mellitus [17]
• Advanced age
• Immunocompromised status [18]

Intraoperative 

• Poor sterile technique [19]
• Posterior capsular rupture
• Vitreous loss and wound leak
• Use of intracameral miotics/staining dyes and epinephrine
• Contamination during the mixing of compounded medications

Postoperative 

• Postoperative wound leak
• Nonsilicon intraocular lens type

The second most common cause of endophthalmitis is post-intravitreal injection, with coagulase-negative staphylococci and streptococci as the primary pathogens. Penetrating eye trauma is the third most common cause and constitutes anywhere from 2% to 15% of all cases of endophthalmitis.[20] Coagulase-negative staphylococci predominate in this category, but other bacteria, such as Bacillus, gram-negative bacilli, and fungi, can cause infection.

Bleb-related endophthalmitis is the fourth most common cause, with bacterial etiology in descending order of S pneumoniae, enterococci, and Haemophilus influenzae. The fifth most common cause of endophthalmitis-keratitis is corneal penetration by infectious organisms. However, 50% of keratitis-related cases are due to fungi, with S aureus, streptococci, and Pseudomonas causing a minority of these infections. Endogenous blood-borne endophthalmitis is the rarest cause, with Klebsiella pneumoniae being the most common pathogen, followed by Candida, Streptococcus, S aureus, and E coli.[10][21]

In postoperative endophthalmitis, most cases (48%–70%) are caused by coagulase-negative staphylococci. Gram-positive bacteria, including S aureus and streptococcal and enterococcal species, have been identified as causative agents in such instances. In the context of ocular trauma, the incidence of endophthalmitis is notably higher, with reported rates between 3% and 17%.[22] The incidence of endophthalmitis following ocular trauma has shifted from coagulase-negative staphylococci to other staphylococcal species and to Bacillus cereus. Notably, B cereus is 10 times more prevalent in post-traumatic endophthalmitis than in post-surgical cases.[23]

Endogenous endophthalmitis, also called metastatic endophthalmitis, emerges from the spread of infectious organisms to the eye from other sites within the body. Although less common than its postoperative or post-traumatic counterparts, accounting for only 2% to 8% of all endophthalmitis cases, endogenous endophthalmitis presents a significant risk of bilateral infection, occurring in 15% to 25% of such cases.

Fungal pathogens cause approximately half of all endogenous endophthalmitis cases, with Candida albicans the primary fungal pathogen, accounting for 75% to 80% of fungal cases. On the other hand, gram-negative bacteria are associated with 32% to 37% of endogenous endophthalmitis cases. Infections caused by gram-negative organisms are concerning due to their association with poor outcomes and their difficulty in treating.[24]

Table 1. Etiologies of Bacterial Endophthalmitis

Cataract surgery is the single most important cause of bacterial endophthalmitis. Approximately 40% to 80% of endophthalmitis cases are caused by cataract surgery; of these cases, 70% are caused by coagulase-negative staphylococci, 10% by Staphylococcus aureus, and 9% by streptococci (see Table 2).

Table 2. Classification of Bacterial Endophthalmitis by Microbial Type

Epidemiology

Cataract surgery and intravitreal injections are the leading causes of endophthalmitis. However, endophthalmitis remains a relatively rare complication in the modern antibiotic era. Among patients undergoing cataract surgery, approximately 0.05% to 0.2% develop postoperative endophthalmitis, with most contemporary large database studies reporting rates closer to 0.03% to 0.1% in centers that use intracameral antibiotics.

Traumatic penetrating eye injury can result in bacterial endophthalmitis in 1% to 18% of patients, depending on the extent of globe disruption, contamination with organic matter, presence of intraocular foreign bodies, and delay in primary wound repair. Hematogenous bacterial endophthalmitis is the rarest form, with reported incidence rates ranging from 0.04% to 0.4%, and is commonly associated with intravenous drug use, diabetes mellitus, immunosuppression, malignancy, prolonged hospitalization, indwelling catheters, or systemic infections requiring intravenous antibiotic therapy.[11] Systemic infections involving the liver, lungs, heart, brain, or urinary tract are the most common.

Epidemiologic trends have evolved alongside changes in ophthalmic practice patterns. In the 1990s, infection rates following cataract surgery were estimated at approximately 0.1% (1 in 1000 surgeries). During the early 2000s, some reports documented a transient increase to approximately 0.2% (1 in 500 surgeries), possibly related to clear corneal incision techniques and increased surgical volume. However, results from more recent studies suggest that rates stabilize or decline with the widespread adoption of intracameral antibiotic prophylaxis. Despite its rarity, cataract surgery remains the largest contributor to the absolute number of postoperative endophthalmitis cases, given the sheer number of procedures performed worldwide.[13]

Globally, postoperative endophthalmitis accounts for approximately 40% to 80% of cases in developed nations, whereas post-traumatic endophthalmitis contributes 2% to 15% in many Western countries. In contrast, post-traumatic cases represent a significantly larger proportion in certain developing regions, ranging from 40% to 60% of all reported endophthalmitis cases, particularly in parts of Egypt, India, and China. This geographic variation reflects differences in occupational hazards, agricultural exposure, access to immediate surgical repair, and variations in healthcare infrastructure.[25]

The epidemiology of endophthalmitis has also shifted due to the exponential increase in intravitreal injections for retinal diseases, including neovascular age-related macular degeneration, diabetic macular edema, and retinal vein occlusion. The per-injection risk of endophthalmitis is low, generally estimated at 0.02% to 0.05%, but the cumulative procedural volume has led to a measurable rise in post-injection cases in tertiary referral centers. In some institutions, post-injection endophthalmitis now rivals or exceeds the number of post-cataract surgery cases. Streptococcal species appear more common in post-injection cases than in postoperative cataract cases, potentially due to contamination from oral flora.[26]

Age distribution varies by etiology. Postoperative endophthalmitis predominantly affects older individuals, reflecting the age demographic undergoing cataract surgery and intravitreal injections. The mean age in postoperative series typically ranges from 65 to 80.

Conversely, post-traumatic endophthalmitis is more common in younger populations, particularly men in the second to fifth decades of life, due to occupational exposure, agricultural injuries, and higher rates of mechanical trauma. Pediatric traumatic endophthalmitis is also reported, particularly in rural settings, where delayed presentation and limited access to care contribute to higher complication rates.[27]

Sex distribution similarly reflects underlying risk exposure. Postoperative endophthalmitis generally demonstrates no significant sex predilection, as cataract surgery is performed across both sexes with comparable frequency in aging populations. However, post-traumatic endophthalmitis shows a marked predominance, often accounting for 70% to 90% of cases in trauma-related series. This bias in men is attributed to occupational and environmental risk factors. Endogenous endophthalmitis does not demonstrate a consistent sex predilection but is more frequent in patients with systemic comorbidities, including diabetes mellitus and intravenous drug use, conditions that may have variable demographic patterns across regions.[3]

Microbiological epidemiology also demonstrates regional variability. In North America and Europe, gram-positive organisms, particularly coagulase-negative Staphylococcus species, remain the most common pathogens in postoperative cases. Streptococcus species and gram-negative bacilli are associated with more severe clinical presentations and worse visual outcomes. In East Asia, particularly in Taiwan and parts of China, Klebsiella pneumoniae is a leading cause of endogenous endophthalmitis, often associated with pyogenic liver abscess. In agricultural regions worldwide, Bacillus cereus is a common pathogen in post-traumatic endophthalmitis and is associated with rapid progression and poor prognosis.[26]

The incidence of endogenous endophthalmitis remains low compared to exogenous forms, accounting for approximately 2% to 15% of all cases in most large case series. However, this proportion may be higher in regions with increased prevalence of systemic infections, liver abscesses, or poorly controlled diabetes. Bilateral involvement is more common in endogenous cases than in exogenous forms.[28]

Temporal trends suggest that while improved aseptic technique and prophylaxis have reduced the relative risk per procedure, the growing number of intraocular interventions globally has maintained the absolute burden of disease. Advances in surgical technology, antibiotic prophylaxis strategies, and sterile technique have improved outcomes, but endophthalmitis continues to pose a significant threat to vision due to its rapid progression and inflammatory sequelae.[29]

In summary, bacterial endophthalmitis is an uncommon but severe ocular infection with epidemiologic patterns that vary by geography, age, sex, and underlying etiology. Postoperative cases predominate in developed countries with high surgical volume, whereas post-traumatic cases account for a larger proportion in developing regions. Older adult populations are primarily affected in postoperative and injection-related cases, while younger males are disproportionately represented in trauma-related disease. Endogenous cases remain rare but are strongly associated with systemic comorbidities. Understanding these epidemiologic patterns is critical for prevention strategies, early recognition, and optimized clinical management worldwide.[30]

Pathophysiology

Exogenous seeding is the most common cause of bacterial endophthalmitis (see Image. Pathogenesis of Bacterial Endophthalmitis). Disease development depends on host and pathogen factors, as well as inoculum size (see Table 3). Pathogen factors play a particularly critical role in the pathogenesis of bacterial endophthalmitis (see Table 4).

Bacteria such as coagulase-negative staphylococci typically colonize the conjunctiva and can be introduced to the inner ocular cavity during surgery, injections, or trauma. After cataract surgery, research results have shown that one-third of patients' aqueous humor samples tested positive for coagulase-negative staphylococci. However, only 0.1% to 0.2% of cataract surgeries result in bacterial endophthalmitis. These numbers highlight how host factors, such as the immune response, can clear a small bacterial inoculum. However, a larger inoculum size has been shown to overload the immune system, leading to infection.[31][32][33]  

Bacteremia is a rare cause of bacterial endophthalmitis, but when it does occur, Klebsiella pneumoniae is usually the culprit. The mucoviscosity-associated gene A endows K pneumoniae serotypes K1 and K2 with a mucopolysaccharide capsule that allows hypermucoviscosity. K pneumoniae is a common cause of pyogenic liver abscess in Southeast Asia, in part due to this virulence mechanism. As many as 7% of patients with K1 or K2 Klebsiella pneumoniae liver abscess will experience hematogenous spread to their retina. Experimental mouse models confirm that eyes injected with Klebsiella strains exhibiting the hypermucoviscosity (HMV) phenotype show greater retinal functional loss and inflammation than eyes injected with HMV-negative strains.[34]

Bacillus cereus can cause posttraumatic endophthalmitis, particularly in patients with intravenous drug use. B cereus is a major pathogen that can cause fulminant endophthalmitis. Quorum-sensing by Bacillus initiates toxin release and migration, contributing to the rapid deterioration of the retina and the destructive course of Bacillus endophthalmitis. The virulence factors of Bacillus species that trigger this destruction include membrane-damaging toxins such as hemolysins, sphingomyelinases, and phospholipases. The quorum-sensing–dependent phospholipase C regulator acts as a transcriptional regulator to control virulence factor production. Neutrophil recruitment and C-X-C motif chemokine ligand 1 lead to inflammation and retinal damage in Bacillus endophthalmitis.[35]

In bleb-related endophthalmitis, S pneumoniae is the most common pathogen; this organism can cause severe endophthalmitis. The virulence factors that appear to contribute to pathogenesis include exotoxins and enzymes such as pneumolysin and autolysin, as well as a polysaccharide capsule that prevents phagocytosis. S pneumoniae uses pneumolysin to inhibit host responses involved with antibody synthesis and lymphocyte proliferation. Studies have found that initial tissue damage is less severe when infected with pneumolysin-deficient S pneumoniae vs pneumolysin-producing strains within the first 24 hours of the disease.[36][37] Components of the cell wall of S pneumoniae cause inflammation, resulting in the characteristic clinical symptoms.[38]

Pseudomonas aeruginosa endophthalmitis causes rapid tissue necrosis due to toxins such as pyocyanin, pyoverdin, exotoxin A, and elastase. These toxins disrupt membrane and epithelial barriers, leading to cytotoxicity.[38] This aggressive toxin-mediated damage contributes to rapid clinical deterioration and is associated with poor visual outcomes despite prompt treatment.

Table 3. Pathophysiology of Bacterial Endophthalmitis

IL-1, interleukin 1; IL-2, interleukin 2; TNFα, tumor necrosis factor alpha; PMNs, polymorphonuclear leukocytes; RAPD, relative afferent pupillary defect

Table 4. Most Common Pathophysiologic Findings in Bacterial Endophthalmitis

Histopathology

Histopathologic examination of bacterial endophthalmitis reveals a series of pathological changes within the intraocular tissues. The process begins with bacterial infiltration of the eye, triggering an acute inflammatory response. The key histopathological features observed in cases of bacterial endophthalmitis are as follows:

• Inflammatory infiltrate: The vitreous cavity typically shows an infiltration of polymorphonuclear leukocytes, indicative of an acute inflammatory response. In response to the infection, the retina and choroid may also exhibit infiltration by inflammatory cells, including lymphocytes, macrophages, and plasma cells.[39]
• Suppurative changes: Areas of suppuration may occur with the formation of abscesses within the vitreous body or the retina. Necrotizing inflammation can occur, characterized by tissue destruction and necrotic debris.[40]
• Vascular changes: Endophthalmitis can lead to vasculitis of the choroidal and retinal vasculature. Vascular occlusion and hemorrhages may be present due to the inflammation.[41]
• Fibrin exudation: Fibrin deposition is noted within the vitreous cavity and anterior chamber; this process may progress to a hypopyon, characterized by the layering of white blood cells in the anterior chamber.[42]
• Retinal detachment: Progressive inflammation can lead to separation of the sensory retina from the underlying retinal pigment epithelium.[43]
• Tissue damage and necrosis: Bacterial infection and the host immune response can lead to retinal and uveal tissue damage, with focal-to-confluent areas of necrosis.[44]
• Granulomatous reaction: In some cases, particularly with certain bacteria, a granulomatous response is observed, characterized by the formation of granulomas containing multinucleated giant cells.
• Fibrosis and scarring: Over time, the inflammation can lead to fibrosis and scarring within the eye, which can have long-term effects on vision.[45]
• Infiltration of the optic nerve: In severe cases, the optic nerve may show signs of inflammation and infiltration, potentially leading to optic atrophy.[46]
• Biofilm formation: Some bacteria can form biofilms on intraocular lenses or other implanted devices within the eye; this phenomenon enables resistance to immune cells and antibiotics.[47]

Clinicians should note that the histopathological features of bacterial endophthalmitis can vary with bacterial virulence, the host's immune status, and the duration of infection prior to treatment. Early and effective intervention is crucial in preventing the severe histopathological changes associated with this condition.

Toxicokinetics

The key toxicokinetic features of the bacteria most commonly implicated in bacterial endophthalmitis are outlined below. Understanding these aspects is crucial for effectively managing bacterial endophthalmitis, as they directly influence treatment strategies and outcomes. The goal is to maximize the local concentration of antibiotics to control the infection while minimizing inflammatory damage from bacterial toxins and the immune response.[48]

• Absorption: In bacterial endophthalmitis, bacterial toxins and inflammatory mediators are produced locally in the eye and are not absorbed in the traditional sense but can diffuse into adjacent ocular tissues.[49]
• Distribution: Bacterial toxins are typically confined to the intraocular compartments, particularly the vitreous and aqueous humor. The inflammatory response to these toxins can cause the breakdown of the blood–ocular barrier, leading to potential leakage and more widespread distribution of inflammatory cells and mediators.[45]
• Metabolism: Bacterial toxins are not metabolized in the same way as drugs. Instead, toxins may be neutralized by antibodies or broken down by enzymes in the ocular fluids, or they may persist, contributing to ongoing inflammation and damage.[50]
• Excretion: Bacterial toxins and inflammatory debris are removed from the eye by phagocytosis and possibly through the trabecular meshwork and the canal of Schlemm, which are part of the eye's natural drainage system.
• Local toxicity: The virulence factors of the bacteria damage ocular tissues, leading to the characteristic signs of endophthalmitis, including vitreous clouding, retinal edema, and uveal tract inflammation.[51]
• Pharmacokinetics of antibiotics: Intravitreal injection enables high local drug concentrations while bypassing systemic circulation, thereby reducing systemic toxicity. The half-life of antibiotics in the vitreous may be prolonged due to the vitreous body's relatively avascular nature and the slow turnover of vitreous fluid.[52]
• Response to treatment: The efficacy of antibiotic therapy for endophthalmitis can be influenced by bacterial cell wall permeability, biofilm formation, and antibiotic resistance.[53]

History and Physical

A thorough history and comprehensive ocular examination are fundamental in the early diagnosis and timely management of bacterial endophthalmitis. Because the disease can progress rapidly and lead to irreversible visual loss within hours to days, clinicians must maintain a high index of suspicion, particularly in patients presenting with recent ocular procedures or systemic infection. Early recognition significantly influences visual prognosis.

History

The hallmark symptom of bacterial endophthalmitis is a sudden decrease in vision, reported in nearly all cases (see Image. Approach to History in Suspected Bacterial Endophthalmitis). The visual decline is typically rapid in onset and may progress over hours to 1 to 3 days in acute postoperative or post-traumatic cases. Pain is common in bacterial infections but may vary in intensity depending on the organism's virulence. Redness, photophobia, lid swelling, floaters, and purulent discharge may also occur. However, the absence of severe pain does not exclude the diagnosis.[54]

The timeline of symptom onset provides valuable diagnostic clues.[55] Acute bacterial endophthalmitis typically presents within 2 to 7 days following surgery or injection. Hyperacute presentations (within 24–48 hours) may suggest highly virulent organisms such as Streptococcus or Bacillus. Chronic postoperative endophthalmitis (eg, Cutibacterium acnes) may present weeks to months later with recurrent inflammation. In contrast, fungal endophthalmitis usually demonstrates a subacute course, with gradual vision decline over days to weeks (see Table 5).[26]

A targeted history should include:

• Recent intraocular surgery (especially cataract surgery)
• Recent intravitreal injection
• History of open globe trauma
• Filtering bleb from glaucoma surgery
• Contact lens wear
• Recent antibiotic use
• Systemic infections (endocarditis, liver abscess, pneumonia, urinary tract infection)
• Intravenous drug use
• Diabetes mellitus
• Immunosuppression or malignancy
• Recent hospitalization or indwelling catheters [10]

In endogenous endophthalmitis, systemic symptoms such as fever, malaise, chills, or recent bacteremia are often present, although ocular symptoms may be the initial manifestation.[54]

Physical Examination

A complete ophthalmic examination should be performed urgently (see Table 6).

Visual acuity

Visual acuity often ranges from reduced Snellen vision to light perception or, in severe cases, no light perception. Initial visual acuity is an important prognostic indicator (see Image. Examination-Based Suspicion of Bacterial Endophthalmitis).[56]

External examination

• Eyelid edema
• Conjunctival chemosis
• Diffuse conjunctival injection
• Purulent discharge (occasionally)

Slit lamp examination

• Anterior segment findings include:   
  • Corneal edema (due to inflammatory endothelial dysfunction)
  • Anterior chamber cells and flare
  • Hypopyon (layered leukocytes in the anterior chamber)
  • Fibrin formation
  • Posterior synechiae
  • Reduced red reflex [13]
• Posterior segment examination
  • Fundus visualization may be limited due to dense vitritis. When visible, findings may include:
    • Vitreous haze
    • Retinal hemorrhages
    • Retinal infiltrates
    • Retinal necrosis
    • Optic disc hyperemia

B-scan ultrasonography

If the fundus view is obscured, B-scan ultrasonography is essential and typically reveals:

• Low to moderate reflective echoes within the vitreous cavity
• Membranous strands
• Retinal detachment in advanced cases
• Choroidal thickening [2]

Table 5. Key Historical Features of Endophthalmitis

Table 6. Physical Examination Findings in Bacterial Endophthalmitis

Red Flag Findings Suggesting Severe Disease

• Light perception, vision, or worse
• Rapid progression within 24 hours
• Marked hypopyon
• Severe vitritis obscuring the fundus
• Relative afferent pupillary defect
• Associated orbital signs (suggesting panophthalmitis)

Evaluation

Because bacterial endophthalmitis progresses rapidly, evaluation and treatment must occur concurrently rather than sequentially. Bacterial endophthalmitis is primarily a clinical diagnosis, and management should never be delayed while awaiting laboratory confirmation (see Image. Diagnostic Approach to Bacterial Endophthalmitis). However, microbiological, imaging, and systemic investigations are essential to confirm etiology, guide antimicrobial therapy, and evaluate systemic sources in endogenous cases (see Image. Diagnostic Pathway for Suspected Bacterial Endophthalmitis). Timely diagnostic sampling before intravitreal antibiotic administration improves culture yield but must not delay treatment (see Table 7).

Immediate Clinical Evaluation

When endophthalmitis is suspected, immediate clinical evaluation should include:

• Documentation of the best corrected visual acuity
• Slit lamp examination for anterior chamber inflammation and hypopyon
• Dilated fundus examination (if view possible)
• B-scan ultrasonography if the posterior view is obscured
• Immediate vitreous or aqueous sampling [3]

Management decisions are guided by presenting visual acuity, as supported by the Endophthalmitis Vitrectomy Study and American Academy of Ophthalmology Preferred Practice Patterns:

• Patients with vision better than light perception → vitreous tap and inject
• Patients with light perception only → consider immediate pars plana vitrectomy [57]

Table 7. Ocular Diagnostic Investigations for Suspected Bacterial Endophthalmitis

Microbiological Evaluation

Vitreous sampling (gold standard)

Vitreous biopsy provides the highest diagnostic yield (see Table 8). Vitreous samples obtained during vitrectomy have a higher diagnostic yield than needle aspiration.

• Needle aspiration (tap)
• Vitreous cutter sampling during vitrectomy [56]

Aqueous humor sampling

Aqueous sampling has lower sensitivity than vitreous sampling because it is farther from the primary site of infection. However, an aqueous sample may be helpful when a vitreous tap is not feasible.

Guideline recommendations 

• Obtain an intraocular specimen before antibiotics when feasible.
• Start empiric intravitreal antibiotics immediately (vancomycin + ceftazidime).
• Consider early vitrectomy if the presenting visual acuity is light perception.[58]

Microbiologic results may provide prognostic information and guide targeted therapy, although initial management is empiric and should not be delayed.

Table 8. Microbiological Testing for Bacterial Endophthalmitis

Imaging Evaluation

Imaging plays a complementary role in the evaluation of bacterial endophthalmitis, particularly when clinical examination is limited or when complications are suspected (see Table 9).

B-scan ultrasonography

B-scan ultrasonography is indicated when media opacity prevents visualization of the fundus.

Typical findings:

• Low to medium reflective echoes in vitreous
• Membranous strands
• Retinal detachment
• Choroidal thickening [9]

Orbital computed tomography

Orbital computed tomography is indicated in cases of suspected:

• Trauma
• Intraocular foreign body
• Panophthalmitis [11]

Optical coherence tomography 

This is useful when media clarity permits visualization of the posterior segment and detailed assessment of retinal structure.

Typical findings:

• Hyperreflective vitreous opacities (in mild cases)
• Retinal thickening or edema
• Disruption of retinal layers
• Subretinal or intraretinal fluid
• Epiretinal membrane or inflammatory debris

Table 9. Imaging Modalities for Bacterial Endophthalmitis

Systemic Evaluation (Endogenous Cases)

If endogenous endophthalmitis is suspected, systemic workup is mandatory (see Table 10). Blood cultures may be positive in a subset of cases and should be obtained prior to systemic antibiotic administration when feasible (see Image. Evaluation Pathway for Endogenous Bacterial Endophthalmitis).

Recommended investigations:

• Complete blood count 
• Blood cultures (2–3 sets)
• Liver function tests
• Urine culture
• Chest x-ray
• Echocardiography (if endocarditis is suspected)
• Abdominal ultrasound or computed tomography (if liver abscess is suspected) [13]

Table 10. Systemic Workup in Suspected Endogenous Endophthalmitis

National and International Guideline Highlights

American Academy of Ophthalmology

• Immediate intravitreal broad-spectrum antibiotics
• Vitreous sampling before antibiotics, if possible
• Early vitrectomy for light perception vision
• Systemic antibiotics in endogenous cases [59]

Endophthalmitis Vitrectomy Study

• Vitrectomy improves outcomes in cases of light perception.
• Tap-and-inject is acceptable for visual acuity better than LP.[3]

Royal College of Ophthalmologists (United Kingdom)

• Do not delay treatment for microbiology.
• Consider local resistance patterns.
• Intracameral prophylaxis is recommended in cataract surgery.

Key Points in Evaluation

• Endophthalmitis is a clinical emergency.
• Diagnosis is primarily clinical, with microbiologic testing used to confirm etiology.
• Vitreous sampling provides the highest yield.
• B-scan is essential when the fundus is not visible.
• Systemic evaluation is mandatory in cases of suspected endogenous origin.
• Treatment should not be delayed while awaiting laboratory results.[13]

Treatment / Management

Bacterial endophthalmitis necessitates prompt and early management with intraocular antibiotics, often combined with a pars plana vitrectomy. Patients should be hospitalized, and broad-spectrum intravitreal, topical, and potentially intravenous antibiotics should be initiated after appropriate cultures are collected. Intravitreal antibiotics offer higher intraocular concentrations and include ceftazidime 2.2 mg, vancomycin 1 mg, and amikacin 0.4 mg.

The antibiotic of choice should be selected based on the suspected etiology, and once cultures return, the clinician can adjust antibiotic therapy.[60] Patients should receive a topical cycloplegic, such as atropine 1%, twice daily, and topical prednisolone acetate 1% every 1 to 6 hours. PPV is beneficial because it reduces the infective and inflammatory load and provides material for diagnostic studies.[61](B3)

Current Antibiotic Regimen

Contemporary therapeutic protocols for bacterial endophthalmitis typically include direct intravitreal antibiotic administration. Ceftazidime, dosed at 2.2 mg per 0.1 mL, provides broad-spectrum coverage against gram-negative bacteria. Conversely, at a dose of 1.0 mg per 0.1 ml, vancomycin is used for its broad coverage of gram-positive pathogens, with a 99% susceptibility rate among gram-positive organisms implicated in endophthalmitis. However, cases of vancomycin-resistant Enterococcus causing endophthalmitis have been reported, indicating that the effectiveness of traditionally used antibiotics varies with the emergence of resistance.[62] For endogenous endophthalmitis, systemic antibiotic administration is standard. 

Ceftazidime, a third-generation cephalosporin, has historically shown complete susceptibility among gram-negative ocular isolates. Nonetheless, resistance has been documented, with a subset of gram-negative endophthalmitis cases exhibiting resistance to amikacin and ceftazidime. Structural advancements within the cephalosporin class have enhanced their efficacy against gram-negative bacteria, with both second- and third-generation cephalosporins demonstrating this improved activity.[63](A1)

Intravitreal ceftazidime is generally regarded as safer compared to aminoglycosides, with toxicity observed only at elevated concentrations. Clinical evidence suggests a significant reduction in the risk of endophthalmitis when cefuroxime, a second-generation cephalosporin, is administered intracamerally as a surgical prophylactic. The synergistic potential of antibiotic combinations, particularly vancomycin paired with either amikacin or ceftazidime, should be considered when managing rapidly progressing infections such as endophthalmitis. However, the necessity is debated because intravitreal injections achieve high local concentrations.[64]

Fluoroquinolones are another promising class for the treatment of endophthalmitis, especially later generations, which exhibit robust activity against a broad spectrum of ocular pathogens. The ability of fluoroquinolones to cross the ocular barrier without intravitreal injection underscores their value in specific clinical scenarios. Although primarily indicated for ocular surface infections, their use for endophthalmitis is considered off-label. Experimental studies have confirmed the safety and effectiveness of intravitreal fluoroquinolones in eliminating intraocular infections, suggesting that intravitreal administration of these and other antibiotics can be effective when immediate, adequate bactericidal concentrations at the site of infection are required.[65]

However, the use of fluoroquinolones for surgical prophylaxis or for the treatment of postoperative endophthalmitis remains contentious. The penetration of fluoroquinolones into ocular tissues varies widely, with moxifloxacin showing superior intraocular penetration compared to gatifloxacin in topical administration. Despite the efficacy of topical moxifloxacin in experimental models, the ability of fourth-generation fluoroquinolones to achieve bactericidal concentrations in the vitreous remains inconsistent.[66] Notably, gatifloxacin has been discontinued for systemic use due to its association with dysglycemia.

Anti-Inflammatory Drugs

Intraocular inflammation, a crucial component of the host defense mechanism against infection, can inflict retinal damage. Intravitreal introduction of bacterial cell wall components provokes a significant inflammatory response within the ocular environment. This reaction typically results in only transient, reversible functional impairment of the retina, but given the potential for the inflammatory response to cause permanent damage within the eye, intravitreal corticosteroids may be administered strategically to mitigate immune-mediated injury. This method can serve as an additional therapeutic strategy alongside antibiotic treatment.[67]

The clinical and experimental literature presents a divergent viewpoint on the utility of intravitreal corticosteroids in the context of endophthalmitis. While the safety profile of dexamethasone following intravitreal injection is well established clinically, with no evidence of retinal toxicity, its efficacy remains a point of contention. Disparate clinical findings have been reported, with some studies suggesting that intravitreal dexamethasone may be beneficial, whereas others argue its utility is negligible.[68]

Experimental investigations into the role of intravitreal steroids in bacterial endophthalmitis have similarly yielded inconsistent outcomes. Some studies' results support the efficacy of combined dexamethasone and antibiotic therapy in managing inflammation, while others report no significant advantage. Furthermore, combinations of intravitreal prednisolone and antibiotics did not reduce inflammation in experimental Bacillus endophthalmitis compared with antibiotic therapy alone. Although a definitive consensus has not been reached, corticosteroids, such as dexamethasone 0.4 mg, are frequently used as adjuncts in the management of endophthalmitis, reflecting a preference for their anti-inflammatory properties in combination with antibiotic regimens.[69]

Role of Vitrectomy

In advanced presentations of endophthalmitis, pars plana vitrectomy is frequently employed to excise necrotic microorganisms, compromised cellular material, and deleterious inflammatory by-products from the vitreous cavity. This intervention enhances optical clarity and diffusion within the posterior segment, expediting the restoration of visual function. Minimally invasive approaches to vitrectomy, such as 23- and 25-gauge systems, have gained favor in recent years. Nonetheless, the inherent complexity of PPV entails certain procedural risks, even with these refined techniques.[1](B3)

The Endophthalmitis Vitrectomy Study led to increased use of vitrectomy for therapeutic purposes in endophthalmitis (see Image. Visual Acuity–Based Treatment Algorithm for Bacterial Endophthalmitis). Early vitrectomy improved visual acuity outcomes for patients with hand motion or light perception deficits. The postulated mechanisms underlying the efficacy of vitrectomy in such scenarios include a breach of the blood–ocular barrier, which may enhance the intraocular penetration of systemic antibiotics. A synergistic approach of immediate intravitreal antibiotics coupled with PPV is recommended for endophthalmitis secondary to ocular trauma with retained intraocular foreign bodies. This strategy, including timely foreign body removal, has been associated with significant visual recovery in most cases, although a subset of patients may experience visible decline after these interventions.[70](B3)

Similarly, the prognosis for endophthalmitis secondary to ocular procedures other than cataract surgery appears to benefit from expeditious vitrectomy, especially when initial conservative management is ineffective. In endogenous endophthalmitis, the temporal aspect of vitrectomy plays a pivotal role, with early surgical intervention correlating with improved outcomes. The consensus within clinical literature increasingly supports immediate vitrectomy alongside appropriate intravitreal antibiotic therapy in severe cases of endophthalmitis, particularly those complicated by IOFBs. This aggressive treatment modality is deemed essential for optimizing recovery.[71]

Exploratory research has focused on the utility of vitrectomy in managing fungal endophthalmitis, but the mechanical debridement of pathogen load, inflammatory mediators, and toxic substances through vitrectomy remains equally pertinent for bacterial infections. Novel office-based sutureless vitrectomy systems show promise, although their use in treating endophthalmitis has yet to be substantiated in clinical practice. The current body of experimental research on the efficacy of vitrectomy for bacterial endophthalmitis is limited, underscoring the need for further investigation into the benefits of this surgical intervention in managing infectious vitritis.[72]

Periocular injections or subtenon injections are options if necessary.[38] Results from a recent study demonstrated the most common isolate in cases of endophthalmitis following evisceration was S pneumoniae, followed by Aspergillus and P aeruginosa.[38] Endophthalmitis can convert to panophthalmitis if the infection spreads to the sclera and the Tenon capsule.[73] 

In panophthalmitis, the affected eye requires evisceration or enucleation; studies report an evisceration rate ranging from 14.3% to 23.2%.[73] All isolates were susceptible to ceftazidime and levofloxacin, and the minimum inhibitory concentration values for isolates in the current period were identical to those from 1987 to 2001. Despite early and appropriate treatment, outcomes for panophthalmitis were generally poor, with a high enucleation rate.[74] Patients with intravenous drug use are given aminoglycosides and clindamycin to cover the most likely causative organism, B cereus.

Differential Diagnosis

Bacterial endophthalmitis is an ocular emergency characterized by inflammation and infection within the eye. Differentiating it from other conditions with similar presentations is vital for effective treatment (see Table 11). The differential diagnosis includes:

• Sterile endophthalmitis 
  • Similar to infectious endophthalmitis, but occurs as a sterile inflammatory response to intraocular agents or surgery and lacks the growth of organisms on culture [75]
• Fungal endophthalmitis 
  • May present similarly, but has a more indolent course
  • Risk factors include systemic immunosuppression, chronic antibiotic use, and IV drug use
  • Investigation includes fungal cultures and consideration of intravitreal antifungal therapy [76]
• Viral retinitis  
  • Commonly due to cytomegalovirus or herpes simplex virus 
  • Presents with retinal necrosis and hemorrhages
  • May have less prominent pain than bacterial endophthalmitis
  • Requires polymerase chain reaction testing of ocular fluids for definitive diagnosis [77]
• Noninfectious uveitis 
  • Inflammatory condition without infection
  • May be associated with systemic autoimmune conditions [78]
• Acute retinal necrosis 
  • Syndrome characterized by peripheral necrotizing retinitis, usually due to viral etiology
  • Typically progresses to retinal detachment [79]
• Toxic anterior segment syndrome 
  • Acute sterile postoperative inflammation following cataract surgery due to a noninfectious substance entering the anterior segment
  • Distinguished from endophthalmitis by rapid onset and lack of vitreous involvement [76]
• Panuveitis 
  • Involves inflammation of all uveal tracts
  • May mimic the appearance of endophthalmitis [80]
• Retained intraocular foreign body 
  • Must differentiate post-traumatic bacterial endophthalmitis from the simple presence of an intraocular foreign body without infection
  • Imaging studies, such as computed tomography or B-scan ultrasonography, aid in diagnosis [81]
• Masquerade syndromes (eg, intraocular lymphoma) 
  • May present with symptoms similar to endophthalmitis, but the underlying mechanism is neoplastic, rather than infectious [82]
• Ocular ischemic syndrome 
  • Presents with pain and vision loss, but it is due to vascular insufficiency rather than infection [83]
• Retinochoroidal infection 
  • Infection involves the retina and choroid, mimicking the vitreous haze and retinal lesions in endophthalmitis
  • Causative organisms include herpes simplex virus, cytomegalovirus, especially in immunocompromised patients, or toxoplasmosis
  • Diagnosis based on serological tests, ocular fluid analysis, and clinical picture [84]
• Noninfectious posterior or intermediate uveitis 
  • Inflammatory conditions that affect the posterior segment and can resemble the vitritis seen in endophthalmitis
  • May be associated with systemic autoimmune diseases or idiopathic causes
  • Clinical diagnosis, supported by imaging (eg, optical coherence tomography and fluorescein angiography) and excluded from infectious causes.[85]
• Neoplastic conditions 
  • Retinoblastoma, uveal melanoma, ocular surface squamous neoplasia, lymphoma, choroidal hemangioma, optic nerve glioma, ciliary body, and iris tumors, among others
• Large cell lymphoma 
  • May present with vitreous cells and haze, similar to endophthalmitis
  • Typically older population
  • Vitreous biopsy for cytology is often required for diagnosis
• Retinoblastoma 
  • Usually occurs in children
  • May present with leukocoria and vitreous seeding that may resemble endophthalmitis
  • Imaging with ultrasound and MRI, along with clinical examination, is required for diagnosis [86]

Table 11. Differential Diagnosis of Bacterial Endophthalmitis

A thorough history, detailed ocular examination, imaging, and laboratory investigations, including cultures and polymerase chain reaction testing, are essential in diagnosing bacterial endophthalmitis. The correct diagnosis guides targeted therapy, from antibiotics or antivirals to immunosuppressive treatments, depending on the underlying cause (see Table 12).

Table 12. Clinical Differentiation of Bacterial Endophthalmitis, Toxic Anterior Segment Syndrome, and Fungal Endophthalmitis

Red Flags Suggesting Infectious Endophthalmitis

• Rapid visual deterioration
• Hypopyon with vitritis
• Recent intraocular procedure
• Severe ocular pain
• Poor red reflex
• Dense vitreous echoes on B-scan

Pertinent Studies and Ongoing Trials

The management of bacterial endophthalmitis is grounded in pivotal randomized controlled trials (RCTs), prospective cohort studies, and guideline-driven consensus statements. The strongest evidence supporting current recommendations, particularly intravitreal antibiotics and selective PPV, comes from the Endophthalmitis Vitrectomy Study (EVS) and subsequent epidemiologic and interventional studies.[2]

Landmark Randomized Controlled Trial: Endophthalmitis Vitrectomy Study

The EVS remains the most influential RCT guiding treatment of acute postoperative endophthalmitis (see Table 13).

• Population: There were 420 patients with acute postoperative endophthalmitis following cataract surgery or secondary intraocular lens implantation
• Design: Randomized to:
  • Immediate pars plana vitrectomy vs vitreous tap/biopsy
  • Intravenous antibiotics vs no intravenous antibiotics
• Intervention: All patients received intravitreal vancomycin and amikacin.[87]

Impact on recommended treatment

• Immediate intravitreal antibiotics are the standard of care.
• PPV is recommended for patients with light-perception vision.
• Tap-and-inject is acceptable for patients with vision better than light perception.
• Systemic antibiotics are not routinely required in exogenous postoperative cases.

Table 13. Key Findings from the Endophthalmitis Vitrectomy Study

Intracameral Antibiotic Prophylaxis Studies

Multiple large prospective European studies (eg, European Society of Cataract and Refractive Surgeons [ESCRS] trial) demonstrated:

• Significant reduction in postoperative endophthalmitis with intracameral cefuroxime
• Reduction in infection rates from ~0.3% to less than 0.1%

Clinical implication

These studies support the guideline recommendations for intracameral antibiotic prophylaxis in cataract surgery.[88][89] Additional evidence suggests that procedural factors, including surgical technique and intraocular lens selection, as well as perioperative antimicrobial strategies, influence infection risk, although findings across studies are variable.[90] Prevention remains challenging to study due to the low incidence of endophthalmitis; however, adherence to aseptic technique, appropriate wound construction, and antimicrobial prophylaxis is essential in minimizing risk.[91]

Post-Injection Endophthalmitis Studies

Post-injection endophthalmitis is an uncommon but important complication of intravitreal anti-vascular endothelial growth factor therapy. Evidence from large registries and observational studies has clarified incidence rates, organism profiles, and factors influencing infection risk. These data support best practices in aseptic technique and procedural precautions (see Table 14).

Table 14. Bacterial Endophthalmitis Post-Injection Studies

Early Vitrectomy Studies Beyond EVS

Recent retrospective analyses and smaller prospective series suggest:

• Early PPV may improve outcomes in severe cases beyond the EVS light-perception-only criteria.
• Small-gauge vitrectomy techniques allow earlier intervention.
• Possible benefit in highly virulent organisms (eg, Streptococcus, Bacillus).

However, no large modern RCT has definitively replaced EVS recommendations.[92]

Endogenous Endophthalmitis Evidence

Large RCTs for the treatment of endogenous bacterial endophthalmitis do not yet exist. Management is instead based on the following data sources (see Table 15):

• Retrospective case series
• Systemic infection control studies
• Regional organism data (eg, Klebsiella liver abscess studies in Asia)

Evidence supports:

• Combined intravitreal + systemic intravenous antibiotics
• Source control (abscess drainage, catheter removal)
• Early vitrectomy in severe bilateral cases [93]

Table 15. Evidence Supporting Recommended Treatment

EVS, Endophthalmitis Vitrectomy Study; ESCRS, European Society of Cataract and Refractive Surgeons; PPV, pars plana vitrectomy; RCT, randomized controlled trial

Ongoing and Emerging Research Areas

Although no major contemporary RCT equivalent to EVS is currently redefining standard management for bacterial endophthalmitis, ongoing areas of investigation include studies in the following domains (see Table 16).

Table 16. Active Research Areas for Bacterial Endophthalmitis

Current Evidence Gaps

• Limited modern RCT data incorporating the anti-vascular endothelial growth factor era surgical volumes
• Limited randomized data in endogenous endophthalmitis
• Limited pediatric-specific RCT evidence
• No large trial comparing immediate PPV for all patients vs a selective approach

Summary

The management of bacterial endophthalmitis is primarily supported by high-quality evidence from the EVS, which established intravitreal antibiotics as the cornerstone of therapy and defined surgical indications based on presenting visual acuity. Subsequent epidemiologic and prophylactic studies further refined prevention and management strategies. While newer surgical techniques and diagnostic tools continue to evolve, current recommendations remain strongly rooted in EVS-derived evidence and reinforced by international ophthalmic guidelines.

Treatment Planning

Bacterial endophthalmitis is a true ophthalmic emergency, and treatment must be initiated immediately upon clinical suspicion. Therapy should not be delayed for laboratory confirmation. Management is guided by clinical presentation, visual acuity at diagnosis, etiology (exogenous vs endogenous), organism virulence, and presence of complications such as retinal detachment or panophthalmitis (see Image. Treatment Algorithm for Bacterial Endophthalmitis).[58]

Immediate Treatment Principles

• Prompt vitreous sampling (if feasible)
• Immediate intravitreal broad-spectrum antibiotics
• Consideration of PPV based on visual acuity
• Adjunctive topical therapy
• Systemic antibiotics in endogenous cases
• Close monitoring and repeat intervention if needed [29]

The following intravitreal antibiotic doses are supported by AAO and EVS guidelines (see Table 17).

Table 17. Standard Intravitreal Antibiotic Regimen for Bacterial Endophthalmitis

Decision-Making Based on Visual Acuity

The EVS remains the cornerstone for surgical planning (see Table 18).

Table 18. Surgical Planning in Bacterial Endophthalmitis

IOFB, intraocular foreign body; PPV, pars plana vitrectomy

Pars Plana Vitrectomy

Indications:

• Presenting visual acuity = light perception
• Dense vitreous opacification
• Retinal detachment
• Poor response to initial therapy
• Highly virulent organisms

Goals of PPV:

• Remove infective and inflammatory debris.
• Reduce bacterial load.
• Improve antibiotic penetration.
• Improve visualization for retinal assessment.

Modern small-gauge (23G–27G) vitrectomy systems enable earlier and safer intervention than EVS-era techniques.[54]

Adjunctive Therapies

Intravitreal corticosteroids

• Dexamethasone 0.4 mg/0.1 mL (controversial)
• May reduce inflammatory damage
• Use cautiously; evidence is mixed.

Topical therapy

Topical therapy serves as an adjunct to intravitreal antibiotics in the management of bacterial endophthalmitis, primarily targeting anterior-segment inflammation and improving patient comfort (see Table 19).

Table 19. Topical Therapy for Bacterial Endophthalmitis

Systemic antibiotics

Indications:

• Endogenous endophthalmitis
• Orbital involvement
• Panophthalmitis
• Immunocompromised patients

Common systemic regimens:

• Intravenous vancomycin + intravenous ceftriaxone
• Tailored based on culture results

Systemic antibiotics are not routinely required in exogenous postoperative cases, according to EVS findings.[12]

Monitoring and Re-Treatment

Patients require close daily monitoring initially (see Table 20).

Signs of improvement:

• Reduced hypopyon
• Decreased vitritis
• Improved visual acuity
• Reduced ocular pain

Indications for repeat intravitreal injection:

• Persistent inflammation
• Worsening vision
• Positive culture with a resistant organism

Repeat injections are typically administered 48 to 72 hours after initial treatment if needed.[94]

Table 20. Follow-Up Schedule for Bacterial Endophthalmitis

Management of bacterial endophthalmitis varies by underlying etiology, with differences in microbial virulence, route of infection, and risk of complications influencing treatment planning. Recognizing these distinctions helps guide appropriate procedural and antimicrobial interventions (see Table 21).

Table 21. Management of Bacterial Endophthalmitis by Etiologic Category

Complications of bacterial endophthalmitis can significantly impact visual outcomes and often require targeted interventions beyond initial infection control. Early recognition and appropriate management are essential to minimize long-term morbidity (see Table 22).[6]

Table 22. Complication Management for Bacterial Endophthalmitis

Key Principles

• Treatment must not be delayed.
• Intravitreal antibiotics are the cornerstone.
• PPV improves outcomes in light perception vision.
• Systemic antibiotics are reserved for endogenous cases.
• Early aggressive management improves prognosis.

Toxicity and Adverse Effect Management

Management of bacterial endophthalmitis requires aggressive antimicrobial therapy and, in some cases, surgical intervention. However, both the infection itself and the therapeutic interventions may result in ocular and systemic adverse effects. Prompt recognition and appropriate management of treatment-related toxicity are critical to preserving visual function and minimizing complications (see Image. Adverse Effect Monitoring Pathway for Bacterial Endophthalmitis).

Adverse effects may arise from:

• Intravitreal antibiotics
• Systemic antibiotics
• Corticosteroids
• Pars plana vitrectomy
• Inflammatory sequelae of infection [2]

Intravitreal Antibiotic Toxicity

Intravitreal antibiotics are administered in high intraocular concentrations and may cause dose-dependent retinal toxicity if improperly prepared or overdosed (see Table 23). Strict adherence to recommended intravitreal dosing is essential to prevent retinal toxicity.

Table 23. Intravitreal Antibiotic Toxicity in Bacterial Endophthalmitis

Hemorrhagic Occlusive Retinal Vasculitis

Hemorrhagic occlusive retinal vasculitis is a rare but severe complication associated with intracameral or intravitreal vancomycin.

Clinical features:

• Delayed onset (1–2 weeks after surgery)
• Retinal hemorrhages
• Vascular occlusion
• Severe visual loss

Management:

• High-dose systemic and intravitreal corticosteroids
• Avoid future vancomycin exposure
• Aggressive retinal ischemia management (anti-vascular endothelial growth factor, panretinal photocoagulation if needed) [5]

Steroid-Related Adverse Effects

Corticosteroids may be used adjunctively but carry risks (see Table 24). Steroids should only be initiated after adequate antimicrobial coverage.[6]

Table 24. Corticosteroid Toxicity in Bacterial Endophthalmitis

Systemic Antibiotic Toxicity (Endogenous Cases)

When systemic antibiotics are required for endogenous bacterial ophthalmitis, monitor for systemic side effects (see Table 25).

Table 25. Adverse Effects of Systemic Antibiotics in Endogenous Bacterial Endophthalmitis

Surgical Complications (Pars Plana Vitrectomy)

PPV is a key surgical intervention in selected cases of bacterial endophthalmitis but carries inherent procedural risks. Awareness of potential complications and their management is essential for optimizing surgical outcomes (see Table 26).

Table 26. Adverse Effects of Surgery for Bacterial Endophthalmitis

Inflammation-Related Complications

A severe inflammatory response itself may cause:

• Macular edema
• Epiretinal membrane
• Optic nerve damage
• Phthisis bulbi

Management includes:

• Controlled steroid therapy
• Secondary vitreoretinal procedures
• Visual rehabilitation [5]

Table 27 summarizes key toxicity risks associated with treatment modalities for bacterial endophthalmitis, including intravitreal, systemic, surgical, and corticosteroid therapies. Risks range from retinal toxicity and systemic or renal adverse effects to structural surgical complications and intraocular pressure elevation with steroid use, underscoring the need for careful risk-benefit assessment.

Table 27. Bacterial Endophthalmitis Toxicity Risk Stratification

Prevention of Toxicity

• Strict adherence to recommended dosing
• Accurate drug dilution protocols
• Avoidance of aminoglycosides when safer alternatives exist
• Renal function monitoring in systemic therapy
• Early recognition of hemorrhagic occlusive retinal vasculitis
• Close postoperative follow-up [26]

Key Clinical Pearls

• Most cases of retinal toxicity result from dosing errors.
• Ceftazidime is safer than amikacin for gram-negative coverage.
• Steroids should never precede antibiotic administration.
• Sudden worsening after initial improvement warrants urgent reassessment.
• Early intervention prevents permanent structural damage.

Summary

While aggressive antimicrobial therapy is essential in bacterial endophthalmitis, treatment-related toxicity and inflammatory sequelae must be carefully monitored. Intravitreal antibiotics are generally safe when administered correctly, but retinal toxicity, steroid-induced intraocular pressure elevation, systemic antibiotic complications, and surgical risks must be anticipated. A structured monitoring protocol ensures early detection and optimal visual outcomes.[9]

Staging

Unlike malignancies and chronic inflammatory conditions, bacterial endophthalmitis lacks a universally standardized staging system. However, clinical severity–based staging is highly relevant for treatment decisions, prognostication, and surgical planning (see Image. Staging-Based Management of Bacterial Endophthalmitis). Staging is primarily based on:

• Visual acuity at presentation
• Extent of anterior and posterior segment inflammation
• Presence of complications (retinal detachment, panophthalmitis)
• Systemic involvement (endogenous cases)

The Endophthalmitis Vitrectomy Study (EVS) indirectly established a severity-based classification using presenting visual acuity to guide management (see Image. Clinical Severity Staging of Bacterial Endophthalmitis).[3]

Clinical Staging System for Bacterial Endophthalmitis

This severity-based framework synthesizes clinical findings and visual acuity to support risk stratification and procedural decision-making (see Table 28).

Table 28. Severity-Based Clinical Staging for Bacterial Endophthalmitis

EVS-Based Functional Staging

The EVS simplified staging into two major functional categories (see Table 29). This staging remains widely used in modern clinical decision-making.

Table 29. Endophthalmitis Vitrectomy Study–Based Functional Staging

Anatomic Staging 

Anatomic classification complements severity-based staging by defining the extent of intraocular and orbital involvement, which has important implications for disease progression and urgency of intervention (see Table 30).

Table 30. Anatomic Spread–Based Staging for Bacterial Endophthalmitis

Microbiological Severity Correlation

Certain organisms are associated with more aggressive stages at presentation (see Table 31).

Table 31. Microbiologic Correlates of Disease Severity in Bacterial Endophthalmitis

Early-stage detection significantly improves outcomes (see Table 32). Visual acuity at presentation remains the strongest prognostic indicator.

Table 32. Bacterial Endophthalmitis Prognostic Implications by Stage

This simplified grading system translates staging concepts into a practical framework for rapid bedside decision-making and initial management (see Table 33).

Table 33. Proposed Practical Clinical Staging

Key Clinical Points

• A universally standardized staging system does not yet exist, but severity-based classification is clinically useful.
• Visual acuity–based staging guides surgical decisions.
• More virulent organisms correlate with higher stages at presentation.
• Early intervention in Stage I–II dramatically improves prognosis.
• Stage V represents panophthalmitis and may require globe-sacrificing procedures.[2]

Prognosis

The prognosis of bacterial endophthalmitis is variable and hinges on several critical factors. Prompt diagnosis and treatment are paramount for improving outcomes, as delayed therapy can result in rapid deterioration of vision and irreversible ocular damage.

• Pathogen virulence: Infections caused by highly virulent organisms, such as Bacillus species and Pseudomonas aeruginosa, tend to have a poorer prognosis due to rapid progression and extensive ocular damage. Infections caused by Streptococcus pneumoniae are also associated with poor visual outcomes and higher rates of globe loss. Conversely, infections with less aggressive bacteria, such as coagulase-negative staphylococci, may have better visual outcomes with timely and appropriate treatment.[38][95]
• Initiation of therapy: The timing of intervention is crucial; early administration of appropriate intravitreal antibiotics is associated with more favorable visual outcomes.[96]
• Surgical intervention: The need for and timing of vitrectomy both play a role in prognosis. The EVS indicated that immediate vitrectomy benefits cases presenting with a loss of visual acuity to light perception only.[97]
• Host factors: The patient's immune status can significantly influence the prognosis. Immunocompromised individuals or those with diabetes may experience more severe infections and complications, leading to a worse prognosis. Older age has also been associated with poorer outcomes.
• Complications: The development of complications such as retinal detachment, persistent intraocular inflammation, or phthisis bulbi can lead to a poor visual prognosis. Certain clinical scenarios, including endogenous endophthalmitis and concurrent corneal ulceration, are associated with higher rates of evisceration or enucleation.[73]
• Visual acuity at presentation: Patients presenting with better initial visual acuity typically have a more favorable prognosis. Poor presenting visual acuity is one of the strongest predictors of severe outcomes, including the need for globe-sacrificing procedures.
• Rehabilitation potential: Access to and the effectiveness of rehabilitation services, including low-vision aids and occupational therapy, can maximize vision and improve quality of life post-infection.[98]

Despite advances in diagnosis and management, bacterial endophthalmitis remains a condition with a guarded prognosis. Multidisciplinary care involving ophthalmologists, infectious disease specialists, and rehabilitation services is essential for optimizing patient outcomes. Early recognition and aggressive management remain the most important modifiable factors influencing visual outcomes. Continuous research into novel therapeutic strategies and diagnostic tools is also critical to improve the prognostic outlook for this severe ocular infection.

Complications

The following complications pose a significant challenge in the management of bacterial endophthalmitis and may require additional interventions, including surgery. Early recognition and aggressive treatment are critical to minimize the risks.

• Permanent visual impairment: The most feared complication, from partial vision loss to complete blindness.[99]
• Retinal detachment: This complication occurs due to inflammation and traction on the retina, potentially requiring surgical repair.[100]
• Vitreous hemorrhage: Bleeding into the vitreous cavity can obscure vision and complicate infection management.[101]
• Corneal edema and opacification: Inflammation can lead to damage which may become permanent and require corneal transplantation.[102]
• Cystoid macular edema: Fluid accumulation in the macula can lead to distorted central vision.[103]
• Glaucoma: Increased intraocular pressure may develop acutely due to inflammatory debris or chronic trabecular meshwork damage.[104]
• Phthisis bulbi: Severe injury or disease may result in a shrunken, non-functional eye.[105]
• Choroidal effusion: Fluid accumulation in the choroidal space can lead to retinal detachment and decreased vision.[106]
• Endophthalmitis-related uveitis: An inflammatory response in the uveal tract can cause persistent discomfort and photophobia.[107]
• Ocular hypotony: Low intraocular pressure can occur due to ciliary body dysfunction or detachment.[108]
• Epiretinal membrane formation: Scar tissue over the retina can cause visual distortion.[109]
• Optic atrophy: Damage to the optic nerve from severe and prolonged inflammation leads to irreversible vision loss.[110]
• Proliferative vitreoretinopathy: Scar tissue formation can lead to retinal detachment and is challenging to treat.[111]
• Subretinal abscess formation: This complication can occur if the infection extends beyond the vitreous into the retinal tissue.[112]
• Sympathetic ophthalmia: A rare but severe immune-mediated condition affecting the non-infected eye.[113]
• Panophthalmitis: This complication is an extreme form of endophthalmitis that involves all layers and structures of the eye, leading to total loss of vision and a painful, non-functional eye that may necessitate enucleation.[114]
• Corneal ulcer: The infection may progress to involve the cornea, leading to ulceration. Corneal ulcers can be aggressive, leading to perforation and further spread of infection, and may require corneal grafting if structural integrity is compromised.[115]
• Orbital cellulitis: This infection spreads beyond the confines of the eye into the orbital tissues. Orbital cellulitis is a severe condition that can cause pain and swelling and lead to abscess formation, vision loss, and life-threatening complications if the infection spreads to the central nervous system.[102]