APR 30, 2008
These two articles review the intent and findings of the Endophthalmitis Vitrectomy Study (EVS), which in effect saved Medicare millions of dollars annually by changing the standard of care for the treatment of postcataract and secondary intraocular lens implant surgery endophthalmitis diagnosed within six weeks of surgery.
As described in the article summarizing the study's results, all patients included were treated with intravitreal, subconjunctival, and topical antibiotics, subconjunctival and oral steroids, and cycloplegic drugs. They were randomized to undergo vitreous tap or pars plana vitrectomy (PPV) and to receive either intravenous ceftaxzidime and amikacin sulfate or no intravenous treatment. The endpoints were media clarity and visual acuity after three months and at between nine and 12 months.
The study results showed that intravenous medication did not provide any additional benefits. Of great importance, as well, was that the only patients for which PPV was helpful were those who presented with light perception vision. Their chance of achieving a visual outcome of 20/40 or better tripled with PPV to 33 percent compared with vitreous tap. Those with hand motion vision or better ultimately did just as well with a tap, with 66 percent achieving 20/40 or better with PPV versus 62 percent with a tap. A less known outcome was that PPV was beneficial for diabetic patients, even if they presented with hand motion vision or better. Fifty-seven percent of diabetic patients who underwent PPV achieved visual acuity of 20/40 or better compared with 40 percent who underwent a vitreous tap.
The related commentary points out some weaknesses of the EVS findings. The study preceded the use of antibiotics, such as fluoroquinolones, which effectively cross the blood retinal barrier, achieving high vitreous concentrations with systemic administration. Their use may alter the results of endophthalmitis treatment. The study did not address the treatment of endogenous, bleb-related, or traumatic endophthalmitis. Patients with no light perception were excluded from the study, and this may have skewed the results by eliminating patients infected with the most virulent organisms. We now no longer add subconjunctival injections as a matter of course. Cataract surgery has evolved to involve predominantly clear corneal incision phacoemulsification, and organisms have evolved in their sensitivity patterns. The EVS also did not address the issue of prophylaxis.
The authors of the commentary point out the huge impact that the study, with all of its imperfections, has made on today's standard of care for endophthalmitis, with most treatment now conducted as an outpatient office procedure. The latest European Society of Cataract & Refractive Surgeons study group research, which showed an alarming rate of endophthalmitis of 0.34 percent reduced to 0.07 percent through the use of an intracameral antibiotic during cataract surgery, does not send as clear a message as the EVS regarding best practices but gives food for thought for future paradigms for endophthalmitis prophylaxis.
Dr. Arbisser has received honoraria and research grants from Alcon Laboratories Inc. and Advanced Medical Optics Inc.