Postoperative endophthalmitis is classified based on the time of onset in the eye; acute onset occurs within 6 weeks following surgery, and delayed onset occurs more than 6 weeks following surgery. A specific subtype of endophthalmitis that occurs following filtering bleb surgery has a markedly different spectrum of causative organisms.
Acute-onset postoperative endophthalmitis
Clinical features of acute-onset postoperative endophthalmitis include the following signs: intraocular inflammation, often with hypopyon, conjunctival vascular congestion, and corneal and eyelid edema; symptoms include pain and loss of vision. Common causative organisms are coagulase-negative Staphylococcus species, Staphylococcus aureus, Streptococcus species, and gram-negative organisms. Monitoring includes obtaining intraocular cultures. An anterior chamber specimen is typically obtained by using a 30-gauge needle on a tuberculin syringe. A vitreous specimen can be obtained either by needle tap or by using a vitrectomy instrument. A needle tap of the vitreous is typically accomplished using a 25-gauge, 1-inch needle on a 3-mL syringe (to provide greater vacuum) introduced through the pars plana and directed toward the midvitreous cavity. Vitreous specimens are more likely to yield a positive culture result than are simultaneously obtained aqueous specimens. Management includes administering intravitreal antibiotics; the antibiotics commonly used include ceftazidime and vancomycin. Ceftazidime has largely replaced amikacin or gentamicin in clinical practice because of concerns of potential aminoglycoside toxicity. Intravitreal dexamethasone may reduce posttreatment inflammation, but its role in endophthalmitis management remains controversial.
The use of vitrectomy for acute-onset postoperative endophthalmitis is guided by the results of the Endophthalmitis Vitrectomy Study (EVS; Clinical Trial 20-1). In the EVS, patients were randomly assigned to undergo either vitrectomy or vitreous tap/biopsy. Both groups received intravitreal and subconjunctival antibiotics (vancomycin and amikacin). The EVS concluded that vitrectomy surgery was indicated in patients with acute-onset (within 6 weeks of cataract extraction) postoperative endophthalmitis with light perception vision (Fig 20-7). Patients with hand motions visual acuity or better had equivalent outcomes in both treatment groups.
Figure 20-7 Acute-onset endophthalmitis. A, Patient with marked epibulbar hyperemia, iritis, hypopyon, and endophthalmitis 5 days after cataract surgery. B, After a needle tap of vitreous and injection of intravitreal antibiotics, the inflammation resolved and visual acuity improved to 20/30.
(Courtesy of Harry W. Flynn, Jr, MD.)
Chronic (delayed-onset) endophthalmitis
Chronic endophthalmitis has a progressive or indolent course over months or years. Common causative organisms are Propionibacterium acnes, coagulase-negative Staphylococcus spp, and fungi. Endophthalmitis caused by P acnes characteristically induces a peripheral white plaque within the capsular bag and an associated chronic granulomatous inflammation. An injection of antibiotics into the capsular bag or vitreous cavity does not usually eliminate the infection; instead, the preferred treatment is pars plana vitrectomy, partial capsulectomy with selective removal of intracapsular white plaque, and injection of 1 mg intravitreal vancomycin, adjacent to or inside the capsular bag. If the condition recurs after vitrectomy, removal of the entire capsular bag, with removal or exchange of the intraocular lens (IOL), should be considered (Fig 20-8).
Clark WL, Kaiser PK, Flynn HW Jr, Belfort A, Miller D, Meisler DM. Treatment strategies and visual acuity outcomes in chronic postoperative Propionibacterium acnes endophthalmitis. Ophthalmology. 1999;106(9):1665–1670.
Endophthalmitis associated with conjunctival filtering blebs
Except for the additional sign of a purulent bleb, the clinical features of conjunctival filtering bleb-associated endophthalmitis are similar to those of acute-onset postoperative endophthalmitis. These features include conjunctival vascular congestion and noticeable intraocular inflammation, often with hypopyon (occurring months or years after glaucoma filtering surgery). The initial infection may involve the bleb only (blebitis), without anterior chamber or vitreous involvement. Blebitis without endophthalmitis can be treated with frequent applications of topical and subconjunctival antibiotics and close follow-up. However, if blebitis progresses to bleb-associated endophthalmitis, patients are treated with intravitreal antibiotics with or without vitrectomy. Bleb-associated endophthalmitis typically occurs months to years after surgery, and causative organisms include Streptococcus spp, Haemophilus species, and other gram-positive organisms. The recommended intravitreal antibiotics are similar to those used in acute-onset postoperative endophthalmitis. However, the most common causative organisms in bleb-associated endophthalmitis (ie, Streptococcus or Haemophilus spp) are more virulent than the most frequently encountered organisms in endophthalmitis that occurs after other intraocular surgeries (such as cataract surgery). Even with prompt treatment, the visual outcomes in bleb-associated endophthalmitis are generally worse than for acute-onset endophthalmitis after cataract surgery (Fig 20-9). Management of filtering bleb-associated endophthalmitis is similar to acute-onset post-operative endophthalmitis; however, vitrectomy may be more commonly considered.
Figure 20-8 Chronic (delayed-onset) postoperative endophthalmitis. A, Endophthalmitis in a patient with progressive intraocular inflammation 3 months after cataract surgery. B, Same patient after pars plana vitrectomy, capsulectomy, and injection of intravitreal antibiotics. Culture results confirmed a diagnosis of Propionibacterium acnes endophthalmitis.
(Courtesy of Harry W. Flynn, Jr, MD.)
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.