Medical Care
The EVS evaluated the role of immediate pars plana vitrectomy (VIT) versus intraocular antibiotic injection (TAP) and systemic antibiotics in the treatment of acute postoperative endophthalmitis. Patients were included in the study if they presented within 6 weeks of cataract extraction or secondary IOL implantation, had an initial visual acuity between 20/50 and light perception, and had a view sufficient to perform a VIT. Exclusion criteria included prior treatment of endophthalmitis, previous intraocular surgery, or preexisting eye disease limiting visual acuity to 20/100 or worse. Once enrolled, the 420 patients were assigned to immediate initial TAP or VIT, and then subsequently assigned to receive intravenous antibiotics. The main treatment outcomes evaluated included final visual acuity and media clarity. [12]
The results demonstrated no difference in final visual outcomes in patients who underwent initial TAP or VIT if presenting visual acuity was better than light perception. However, in patients presenting with light perception vision, those who underwent initial VIT were 3 times more likely to achieve 20/40 vision or better, twice as likely to maintain 20/100 vision or better, and had a nearly 50% reduction in the risk of severe visual loss (< 5/200), compared to patients who underwent TAP. No long-term difference occurred in media clarity between the treatment groups. Intravenous antibiotics had no effect on either treatment outcome. [12, 24]
Subsequent reports by the EVS demonstrated that visual outcome in the trial was based largely on the presenting signs and offending organisms. [1, 20, 23] Cases due to coagulase-negative staphylococci or if no organism was isolated demonstrated the best final visual outcome. Endophthalmitis caused by other gram-positive or gram-negative infections had significantly worse final visual acuity. The most common cause for moderate and severe visual loss was macular abnormalities (eg, epiretinal membrane, macular edema, pigmentary degeneration, macular ischemia) and media opacities.
The EVS demonstrated that in many cases of acute postoperative endophthalmitis, patients can be treated with initial TAP without intravenous antibiotic and have a favorable outcome. However, in patients who present early after surgery with overwhelming inflammation and rapidly declining vision, early vitrectomy may be warranted since patients in the EVS who were infected with virulent organisms appeared to have a better visual outcome with vitrectomy than tap and inject. In addition, although no benefit was demonstrated with the use of intravenous antibiotics, the choice of amikacin for gram-positive coverage in the EVS has been questioned because of its poor penetration into the vitreous cavity in animal models. Therefore, in cases of rapid deterioration of vision, the use of appropriate systemic antibiotics can be considered.
Since the EVS specifically excluded patients with postoperative endophthalmitis who underwent any procedure other than cataract surgery, therapy for these cases must be individualized. In patients with conjunctival filtering bleb-associated endophthalmitis, earlier vitrectomy may be preferred in selected cases because of more profound inflammation and the increased probability of more virulent organisms. [13, 21] In chronic postoperative endophthalmitis, initial surgical treatment also may offer advantages over intraocular antibiotics alone. [15, 16]
Vitreous cultures typically grow more often from undiluted samples. Therefore, samples should be obtained by an automated vitrectomy instrument before instillation of balanced salt solution through the posterior infusion cannula.
In chronic postoperative endophthalmitis due to P acnes, intraocular vancomycin alone has been associated with high rates of persistent inflammation. In contrast, vitrectomy with special attention to either partial or total capsular bag excision without IOL removal has been reported effective in eradicating inflammation without removal of the IOL. [15, 16] Some advocate a stepwise approach with vitrectomy, partial or total capsulectomy, and intravitreal vancomycin, and, if inflammation/infection persists, to proceed with vitrectomy, total capsulectomy, and IOL removal.
Drug therapy
The drugs recommended for use in acute postoperative endophthalmitis are discussed in Medication.
Vancomycin has been shown effective against greater than 99% of gram-positive endophthalmitis isolates.
The aminoglycoside amikacin (0.4 mg in 0.1 mL) is useful for gram-negative coverage. Approximately 90% of gram-negative isolates are susceptible to this agent.
Ceftazidime demonstrates similar gram-negative sensitivity profiles as the aminoglycosides and is not associated with retinal toxicity. Therefore, ceftazidime is a reasonable alternative for gram-negative coverage. [13]
The use of intravitreal dexamethasone in the treatment of acute postoperative endophthalmitis remains controversial. [13, 25] Clinicians have used this short-acting corticosteroid to inhibit the inflammatory effects of bacterial endotoxins, host factors, and antibiotics. In a rabbit model of virulent infectious endophthalmitis, dexamethasone was shown to decrease elimination of intraocular vancomycin through the trabecular meshwork, suggesting a new potential benefit to steroid administration. [25]
Surgical Care
The EVS recommended rapid intervention with vitrectomy for patients with severe vision loss (light perception) on presentation. It is important to note again that the EVS only evaluated acute endophthalmitis following cataract extraction or secondary IOL implantation. As noted above, cases following other surgical procedures, such as glaucoma filtering procedure and penetrating keratoplasty, should be individually managed because of the lack of prospective randomized studies, with some advocating vitrectomy at the onset. [13, 21, 26]
Further Outpatient Care
Initially, administer topical therapy hourly and taper only after clinical improvement is seen.
Examine patients on a daily basis during the initial treatment period to ensure adequate sterilization of the vitreous cavity, to control intraocular inflammation, and to identify the need for additional intervention.
In the EVS, a total of 44 patients (10.5%) underwent an additional procedure during the first week after initial treatment, with 6 undergoing a procedure due to a complication of the disease or treatment and 38 due to worsening inflammation. [23] Of the patients in the TAP group that underwent repeat intraocular cultures, 71% had persistent positive cultures, compared to 13% in the VIT group, suggesting that vitrectomy may be more effective in sterilization of the ocular contents.
The EVS also evaluated the need for additional procedures between 1 week and 1 year, the endpoint for follow-up care. A total of 26.9% of patients underwent a late additional procedure. The most common reasons for intervention included opacified posterior capsule (9.0%), retinal detachment (4.3%), recurrent endophthalmitis (3.3%), and glaucoma (2.6%).
