Signs and Symptoms
Due to its numerous potential routes of inoculation, endophthalmitis has no typical age, gender or racial predilection. Patients often manifest pain and significant vision loss upon presentation; visual deterioration may be rapid from the onset of the condition. There is also rapidly progressing diffuse bulbar hyperemia and chemosis of the affected eye. Common associated signs include hypopyon, hypotony, a shallow or flat anterior chamber (suggesting ocular perforation or surgical wound leak), anterior chamber cells and flare, fibrin, pupillary fibrin membrane formation, corneal infiltration, corneal edema, vitritis, retinitis, periphlebitis, retinal detachment and loss of the ophthalmoscopic red reflex.1-3 Often, funduscopic evaluation cannot be accomplished due to media opacification from pupillary fibrin membrane formation or vitritis.
Endophthalmitis can occur either endogenously or exogenously. Patients developing endogenous endophthalmitis typically have a predisposing systemic condition that allows the spread of infection to the eye from a distant site. The most common conditions associated with endogenous endophthalmitis are diabetes, cardiac disease, endocarditis, cancer, HIV/AIDS, hepatitis C, iatrogenic immunosuppression following cancer chemotherapy or organ transplantation, recent hospitalization, recent non-ocular surgery and indwelling catheters.4-8
Infection in virtually any distant body part and microbial sepsis are also strong causative factors for endogenous endophthalmitis.9 Additionally, intravenous drug use can serve as a portal of entry into the bloodstream for microbial pathogens, which can then reach the eye.10 Rarely are patients with endogenous endophthalmitis systemically healthy.
In contrast, patients with exogenous endophthalmitis have a pathogenic inoculation directly into the eye. The portal of entry in these cases is either a traumatic penetrating injury or other open-globe injury—often with a retained intraocular foreign body—or through ocular surgery.11-15 The most common surgical procedure resulting in exogenous endophthalmitis is cataract surgery, though any penetrating ocular procedure, including intravitreal injections, can result in endophthalmitis.16,17 Late-onset trabeculectomy bleb leaks are also a cause of exogenous endophthalmitis.18
Endophthalmitis represents significant inflammation of the vitreous and anterior chamber. Rarely, endophthalmitis may be sterile, resulting from a non-infectious toxin or retained antigenic lens fragments after surgery. Typically, however, endophthalmitis begins when a pathogenic inoculum reaches the eye. Numerous bacteria and fungi have been identified in endophthalmitis. Either a blood-borne pathogen in endogenous endophthalmitis or an organism introduced through the external eye in penetrating trauma or surgical incision reaches the vitreous or anterior chamber, replicates, and establishes a colony. This initiates an antigen-antibody response with subsequent breakdown of the blood/ocular barrier, releasing inflammatory cells with resultant anterior chamber reaction, fibrin, hypopyon and vitritis.
As the organism overcomes host defenses, toxins are released. Depending upon the infective organism, these may include cytolysin, gelatinase, serine protease, pneumolysin, autolysin, alpha-toxin or beta-toxin. This causes further tissue destruction, especially in the retina, and results in significant morbidity.2
Prognosis varies greatly, depending upon the virulence of the infective organism, time of first diagnosis and route of inoculation. Bacterial endophthalmitis typically presents acutely, though chronic inflammation and mild symptoms may occur if a bacterium of low virulence is involved. Cases involving fungal pathogens tend to run a more indolent course, and are commonly encountered in immunocompromised patients. Patients with ocular postoperative endophthalmitis often are infected with their own normal skin flora, typically coagulase-negative Staphylococci.4 Most cases of post-op endophthalmitis are identified within six days of surgery.2,4 Endophthalmitis can also present long after a surgical procedure; this is termed delayed endophthalmitis.
Features associated with better visual acuity outcomes include a better presenting visual acuity, infection with a low-virulence organism, and the absence of retinal detachment.12 In penetrating globe injuries, the most common organisms identified are coagulase-negative Staphylococci and Streptococcus species as well as Bacillus species. In these cases, duration until wound closure is a significant factor; the quicker the globe is repaired, the greater the likelihood of better visual outcome.19
However, exogenous endophthalmitis caused by open-globe injury and retained foreign body tends to have the poorest prognosis.11-13,19 Clinical diagnosis of exogenous endophthalmitis arising from penetrating injury is often delayed due to its initial similarities with traumatic acute inflammatory reactions, which further postpones antibiotic treatment.3
For patients undergoing ocular surgery, endophthalmitis prophylaxis is crucial to a good postoperative outcome.20 This is best accomplished through presurgical and perisurgical antibiosis. For in-office procedures such as intravitreal injection, povidone-iodine irrigation reduces the risk of endophthalmitis.17 The European Society of Cataract and Refractive Surgeons has reported that intracameral injection of 1mg cefuroxime (10mg/mL) at the end of cataract surgery reduced the incidence of postoperative endophthalmitis fivefold.21,22
In any case of endophthalmitis, it is imperative to swiftly begin antimicrobial therapy, identify the causative organism, and then adjust the therapy if warranted by the microbiologic results. The Endophthalmitis Vitrectomy Study (EVS) was designed to determine the roles of immediate pars plana vitrectomy vs. vitreous tap biopsy and systemic antibiotic treatment in the management of postoperative endophthalmitis. The study found no difference in final visual acuity or media clarity with or without the use of systemic antibiotics. In patients whose initial visual acuity was hand motion or better, there was no difference in visual outcome whether or not an immediate vitrectomy was performed. However, in the subgroup of patients with initial light perception-only vision, vitrectomy produced a significantly better visual outcome than vitreous tap biopsy. Thus, it has long been advocated that early vitrectomy is beneficial for those who present with light perception-only vision.23
Vitrectomy confers many benefits, including the provision of microbiologic samples for culturing and the removal of intraocular foreign bodies, infective organisms and retinotoxic endotoxins.3 Additionally, vitreous tap biopsy may not adequately sample a localized infection, yielding a false-negative culture result.
Intravitreal injection, either following a vitrectomy procedure or vitreous tap biopsy, is the mainstay of treatment. Antibiotics include vancomycin, ceftazadime, cefazolin, amikacin, cefuroxime or gentamicin.
Should cultures identify the presence of fungal infection, oral fluconazole or voriconazole or intravitreal amphotericin B are often used.
• When evaluating post-op patients, the mnemonic “RSVP” can help identify patients developing early endophthalmitis: Redness, Sensitivity to light, Vision loss and Pain.
• In the early postoperative period, endophthalmitis must be distinguished from toxic anterior segment syndrome, which is characterized by corneal edema, mild vitreous inflammation and a positive response to steroids.
• The development of hypopyon, vitritis, retinitis, periphlebitis, corneal infiltration, increasing redness and pain with progressive vision loss should raise suspicion for endophthalmitis.
• Prognosis for endophthalmitis of any type is guarded. It is universally agreed that virulence of the infecting organism is the greatest predictor of final visual outcome.
• If endophthalmitis is suspected, referral to a retina specialist is most appropriate.
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14. Asencio MA, Huertas M, Carranza R, et al. A case-control study of post-operative endophthalmitis diagnosed at a Spanish hospital over a 13-year-period. Epidemiol Infect. 2014 Mar 11:1-6. [Epub ahead of print].
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18. Song A, Scott IU, Flynn HW Jr, Budenz DL. Delayed-onset bleb-associated endophthalmitis: clinical features and visual acuity outcomes. Ophthalmology. 2002;109(5):985-91.
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20. Asencio MA, Huertas M, Carranza R, et al. Impact of changes in antibiotic prophylaxis on postoperative endophthalmitis in a Spanish hospital. Ophthalmic Epidemiol. 2014;21(1):45-50.
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23. Endophthalmitis Vitrectomy Study Group. Results of the Endophthalmitis Vitrectomy Study. A randomized trial of immediate vitrectomy and of intravenous antibiotics for the treatment of postoperative bacterial endophthalmitis. Endophthalmitis Vitrectomy Study Group. Arch Ophthalmol. 1995;113(12):1479-96.