**7. Treatment modalities**

The most effective treatment for BRI consists of a combination of fortified aminoglycoside or ceftazidime with vancomycin, i.e., a broad-spectrum antibiotic combination. Moxifloxacin tends to be the most popular fluoroquinolone of choice due to its higher intraocular penetration and activity against gram-negative bacteria, gram-positive cocci, and atypical pathogens [65–67]. Topical aminoglycosides may be efficacious in BRI caused by fluoroquinolone-resistant Staphylococcus species [68].

Pre-operative 5% povidone iodine instillation in the conjunctival sac is recommended in the prophylaxis of endophthalmitis for cataract surgery, and the author recommends the same for glaucoma drainage surgery. It has also been used in the treatment regimen for BRI. Povidone iodine is an antiseptic agent which is clinically effective against a broad range of bacteria and fungi. In a British survey, 28% of glaucoma surgeons used povidone iodine in the conjunctival sac to treat BRI [64]. Just one drop of 5% povidone iodine acts rapidly within 2 minutes to reduce the positive swab rate of the ocular surface from 75% to 28% in eyes without active infection [69].

For BRE, a broad-spectrum combination of intravitreal antibiotics that cover gram-positive and gram-negative bacteria can be started empirically before culture results are available [70], e.g., vancomycin and ceftazidime. The author recommends amikacin instead of ceftazidime for beta lactam sensitive patients with cephalosporin cross reactivity.

Practice point: before performing vitreous tap and intravitreal injections in BRI cases, a retinal examination must be performed to exclude retinal detachment or choroidal detachment (which can be associated with bleb leaks and hypotony). If the view is not clear, ultrasound biomicroscopy must be performed to exclude the same.

Vitreous sampling and intravitreal injection in the presence of choroidal detachment could lead to catastrophic choroidal haemorrhage.

The short duration of action of intravitreal antibiotics does limit their efficacy, but generally If there is no improvement after 36–48 h, another intravitreal antibiotic injection can be given in line with culture and sensitivity results, or pars plana vitrectomy (PPV) can be performed [71]. The author's advice is to have a low threshold for PPV in BRE since the infecting organisms tend to be more virulent and the disease course more fulminant than in post-cataract surgery endophthalmitis.

Other modes of administration of antibiotics include the subconjunctival and oral routes. However, subconjunctival antibiotics do not achieve therapeutic levels in the vitreous [72]. A combination of topical and oral antibiotics achieves higher levels in the vitreous than topical therapy alone, but there is no consensus on the use of oral therapy.

Although, antibiotics are the mainstay of treatment for BRI, consideration should also be given to treating concurrent intraocular inflammation. Therefore, topical

## *Post-Operative Infections Following Glaucoma Drainage Surgery DOI: http://dx.doi.org/10.5772/intechopen.105726*

cycloplegics should be used to prevent and release posterior synechiae. Topical steroids should be considered once it is confirmed that the antibiotic treatment is being administered according to sensitivities of cultured organisms and that the treatment is working.

In one study, most of the glaucoma surgeons started topical corticosteroids 24–72 h after the initiation of topical antibiotics [64]. The role of intravitreal steroid therapy lacks evidence but can be considered depending on the response to antimicrobials and the amount of ocular inflammation. Subconjunctival dexamethasone is a reasonable alternative to intravitreal corticosteroids. Steroids are effective in treating inflammation associated with bacterial exotoxins [73] but are contraindicated in fungal disease.

For fungal infections, e.g., severe candida endophthalmitis, a combination of oral amphotericin-B and flucytosine is advised. Fluconazole and oral voriconazole are alternatives that cover a range of fungal species [74, 75]. Usually, a period of 4–6 weeks of treatment is required.

The role of vitrectomy in the setting of endophthalmitis after glaucoma surgery is a matter of debate. The Endophthalmitis Vitrectomy Study (EVS) [60] did not include BRI cases, therefore, strictly speaking, its recommendations cannot be extrapolated to this population. Typically, BRE for example occurs a lot later than the acute setting of post-cataract surgery endophthalmitis. Furthermore, the more virulent organisms found in BRE, would warrant earlier consideration of vitrectomy compared to patients with endophthalmitis following cataract surgery, but evidence-based data to drive this clinical decision are lacking [48, 56]. In cases of fungal BRE, PPV can be sight saving in severe cases [76]. Intravitreal antifungal agents are commonly used in cases of fungal BRE, but evidence for their value is lacking [75]. Intravitreal amphotericin B, voriconazole, and caspofungin are examples of antifungal agents used in BRE [77].
