Post-cataract surgery endophthalmitis is an infectious inflammation caused by the invasion and proliferation of pathogenic microorganisms into the eye after cataract surgery. It is the most serious complication of cataract surgery, and if appropriate treatment is delayed, it can lead to irreversible vision loss.
The incidence has changed over time and with surgical techniques. In the 1970s, during the era of extracapsular cataract extraction (ECCE), the incidence was 0.327%, but it decreased to 0.087% after standardization of ECCE. Subsequently, with the widespread adoption of clear corneal incision cataract surgery (current phacoemulsification), the incidence rose again to 0.265% 8). In Japan, the incidence is reported to be 0.025–0.052%. Across Asia, it varies widely from 0.01% to 0.22% 7), while in Europe it ranges from 0.04% to 0.7%, and in the United States from 0% to 0.29% 7). The estimated medical cost per case of endophthalmitis is approximately 6,442 USD for the patient’s share, and the societal cost reaches about 15,834 USD 7).
Based on the time of onset, it is classified into acute and delayed (chronic) types, with different causative organisms.
The characteristics of each type are shown below.
| Type | Onset time | Main causative organisms |
|---|---|---|
| Acute | Within 6 weeks after surgery | CNS, Staphylococcus aureus, Streptococcus |
| Delayed | 6 weeks or more after surgery | C. acnes, Fungi |
Approximately 75% of acute cases occur within 1 week after surgery. Delayed cases account for 7.2% of all cases.
In Japan, the incidence is reported to be 0.025–0.052% 11), occurring in approximately 1 in 2,000 to 4,000 cases. Across Asia, the incidence ranges from 0.01% to 0.22%, with regional differences 7). The rate has been decreasing due to improvements in surgical techniques and thorough preventive measures, but it remains a serious complication.
In the acute type, the following symptoms appear suddenly.
In the delayed-onset type (C. acnes endophthalmitis), symptoms are insidious and are often noticed months to years after surgery as mild vision loss or recurrent intraocular inflammation.
Ocular findings differ between acute and delayed-onset types.
Acute Type
Hypopyon: White purulent material accumulates at the bottom of the anterior chamber. This is a very important diagnostic finding.
Inflammatory cells in the anterior chamber: 4+ cell floatation and fibrin deposition are observed 1). Hypopyon exceeding 1 mm indicates severity 1).
Vitreous opacity: Inflammation spreads to the posterior vitreous, making fundus visualization difficult.
Redness and eyelid swelling: Accompanied by strong inflammatory findings on the ocular surface.
Delayed-onset (C. acnes)
IOL/capsular white plaque: Forms a white abscess-like deposit between the intraocular lens (IOL) and the posterior capsule. This is a characteristic finding of C. acnes 4)5).
Recurrent low-grade inflammation: Presents as repeated mild anterior chamber inflammation and is easily misdiagnosed as chronic iridocyclitis.
Culture-negative: The causative organism is often not detected by routine bacterial culture 4)5).
TASS (toxic anterior segment syndrome) typically occurs within 1–2 days postoperatively, often with minimal eye pain. It is characterized mainly by corneal edema and corneal endothelial damage, with little inflammatory spread to the posterior vitreous. Endophthalmitis usually develops 2 or more days after surgery, with prominent eye pain, hypopyon, and vitreous opacity. Differentiation between the two directly affects treatment decisions; when in doubt, collect culture specimens and start antibiotic therapy.
The main route of infection is the intraoperative entry of ocular surface commensal bacteria into the eye. Bacteria normally present on the eyelid margin and conjunctival sac account for 60–80% of causative organisms 6).
The frequency of causative organisms is as follows:
Non-fermenting gram-negative bacteria such as Achromobacter xylosoxidans can also cause postoperative endophthalmitis. They have high biofilm-forming ability and may be difficult to eradicate with antibiotics alone 1).
The combination of sudden vision loss, eye pain, hypopyon, and vitreous opacity during the postoperative course is fundamental for diagnosis. Close observation with high suspicion is necessary, especially in cases with intraoperative complications such as posterior capsule rupture.
Differentiation from TASS (see Clinical Findings) is important; check for the presence of posterior segment inflammation, degree of eye pain, and timing of onset.
Definitive diagnosis requires collection and culture of intraocular fluid (aqueous humor and vitreous fluid).
Even in culture-negative cases, PCR can identify the causative organism. It is particularly useful in C. acnes endophthalmitis.
In the case reported by Wu et al. (2025), both aqueous humor and vitreous fluid were culture-negative, but PCR testing confirmed C. acnes 4). The sensitivity of PCR is 82% for aqueous humor and 78% for vitreous fluid, with specificity reaching 100% and 93%, respectively 4).
Even if the causative organism is not detected by culture, PCR testing improves detection rates. The sensitivity of aqueous humor PCR is reported as 82% and vitreous fluid PCR as 78% 4), and it is particularly effective for identifying slow-growing anaerobic bacteria such as C. acnes. If endophthalmitis is clinically suspected despite negative culture, antibiotic treatment should be initiated while monitoring the patient.
In Japan, the standard treatment for acute postoperative endophthalmitis combines intravitreal antibiotic injection (IOAB) and early pars plana vitrectomy (PPV).
The doses and routes of administration for first-line drugs are shown below.
| Route of administration | Drug and dose |
|---|---|
| Intravitreal injection | Vancomycin (VCM) 1.0 mg/0.1 mL |
| Intravitreal injection | Ceftazidime (CAZ) 2.0 mg/0.1 mL |
| Vitreous perfusate | VCM 20 μg/mL + CAZ 40 μg/mL |
VCM is the first-line drug against gram-positive bacteria (including CNS and MRSE)5). CAZ covers gram-negative bacteria. When administering both agents simultaneously, do not mix them (risk of precipitation).
Based on the findings of the Endophthalmitis Vitrectomy Study (EVS), in cases with severe visual loss to light perception or worse, the vitrectomy group showed better visual prognosis compared to the IOAB-alone group10). Surgical outcomes for postoperative infectious endophthalmitis after cataract surgery have also been reported from Japan12).
When performing vitrectomy, add VCM 20 μg/mL + CAZ 40 μg/mL to the perfusate. Collect vitreous fluid during surgery for culture and PCR.
In delayed-onset C. acnes endophthalmitis, the recurrence rate varies greatly depending on the treatment choice.
IOAB alone
Recurrence rate 100%: With IOAB alone, all cases recur4)5). C. acnes forms a biofilm and is sequestered between the posterior capsule and IOL, making it difficult for antibiotics to reach.
No indication: Monotherapy for C. acnes endophthalmitis is not recommended.
Vitrectomy + capsulectomy + IOAB
Recurrence rate 14–50%: Adding capsulectomy to vitrectomy significantly reduces the recurrence rate4)5). The wider the capsulectomy, the lower the recurrence rate.
IOL preservation possible: A strategy of preserving the IOL while partially or completely removing the capsule. There is a report of achieving corrected visual acuity of 0.7 at 6 months postoperatively4).
Vitrectomy + IOL removal
100% cure rate: Complete removal of the IOL and capsule yields the highest cure rate5). Reported in a review of 120 cases by Fowler et al. (2021)5).
Last resort: Selected when recurrence occurs repeatedly with other methods. Results in aphakia and requires optical rehabilitation.
Fowler et al. (2021) analyzed 6 of their own cases and 120 cases from the literature, reporting a mean time to postoperative diagnosis of C. acnes endophthalmitis of 7.4 ± 5.2 months5). Cure rates were 18% with IOAB alone, 77% with vitrectomy + capsulectomy + IOAB, and 100% with IOL removal5).
According to a systematic review of 21 international prevention guidelines, the following preventive measures are recommended7).
| Preventive measure | Number of guidelines recommending |
|---|---|
| Povidone-iodine conjunctival sac disinfection | 17/21 (81%) |
| Intracameral cefuroxime administration | 16/21 (76%) |
| Preoperative antibiotic eye drops | Only a few |
In C. acnes endophthalmitis, a combination of vitrectomy + capsulectomy (partial or total) + intravitreal antibiotics has been reported to achieve a cure rate of 77% while preserving the IOL 5). However, if capsulectomy is incomplete, 50% recur, so adequate capsulectomy is important 4). In cases of repeated recurrence, IOL removal may eventually be necessary.
A systematic review of international guidelines shows high agreement in recommending povidone-iodine conjunctival sac disinfection and intracameral cefuroxime administration 7). Intracameral cefuroxime is an intracameral antibiotic whose efficacy was proven in the ESCRS RCT 9). Pre- and postoperative antibiotic eye drops are an adjunctive measure to reduce ocular surface bacterial load, but there is insufficient evidence that they alone lower the incidence of endophthalmitis 15).
The main route of infection is the intraoperative entry of normal flora from the conjunctival sac and eyelid margin into the eye through the surgical incision. Once inside the eye, bacteria rapidly proliferate using the nutrient-rich vitreous and aqueous humor as a culture medium.
Bacterial toxins directly damage choroidal vessels and disrupt the blood-ocular barrier. This promotes infiltration of inflammatory cells into the eye, leading to further tissue damage3).
Otsuka et al. (2025) measured choroidal and retinal blood flow over time using laser speckle flowgraphy (LSFG) in two cases of postoperative endophthalmitis3). Before treatment, choroidal blood flow was markedly reduced, and it progressively improved after PPV. In case 1, corneal thickness (CCT) normalized from 396 μm to 187 μm3).
C. acnes (formerly Propionibacterium acnes) is an obligate anaerobic gram-positive rod and a major causative organism of chronic delayed-onset endophthalmitis after cataract surgery. Bacteria that enter the eye during surgery proliferate in the anaerobic environment between the IOL and the posterior capsule, forming a biofilm.
Bacteria within the biofilm have the following characteristics:
The sequestration of C. acnes between the posterior capsule and the IOL is the main factor leading to delayed diagnosis and treatment difficulty4)5).
Laser speckle flowgraphy (LSFG) is a non-invasive technique for monitoring choroidal and retinal blood flow changes in endophthalmitis.
Otsuka et al. (2025) used LSFG in two cases of postoperative endophthalmitis and showed progressive improvement in choroidal blood flow over the course of treatment 3). Case 1 (MRSE infection) achieved corrected visual acuity of 20/25 at 3 months postoperatively, and Case 2 (chronic C. acnes infection 7 years after sutured IOL) achieved 20/33 at 3 months postoperatively 3). This suggests that LSFG may be applicable as a tool for evaluating treatment efficacy and predicting prognosis in endophthalmitis.
As a response to culture-negative cases, improvements in the sensitivity and specificity of causative organism identification using PCR have been reported.
Wu et al. (2025) reported that anterior chamber PCR achieved 82% sensitivity and 100% specificity, while vitreous PCR achieved 78% sensitivity and 93% specificity 4). C. acnes that was not detected by culture was definitively diagnosed by PCR, leading to appropriate surgical selection (vitrectomy + partial capsulectomy + intracapsular VCM/CAZ injection).
Surawatsatien et al. (2025) systematically reviewed 21 guidelines from 2008 to 2023 and evaluated the international consistency of prevention recommendations 7). Povidone-iodine and intracameral cefuroxime showed high agreement, while opinions on preoperative antibiotic eye drops varied among guidelines 7).
Analysis of outbreak cases has identified contaminated surgical instruments, viscoelastic substances, and BSS solutions as causes of simultaneous multiple cases 2). Outbreaks caused by Gram-negative bacteria and fungi suggest different contamination sources than sporadic cases, highlighting the importance of strengthening infection control 2).
