Role of the posterior capsule in the prevention of postoperative bacterial endophthalmitis: experimental primate studies and clinical implications.

The posterior capsule has an important effect on the risk of postoperative bacterial endophthalmitis. In order to investigate whether the posterior capsule inhibited the spread of infection into the vitreous we performed extracapsular cataract extraction in both eyes of 10 primates. In one eye of each primate the posterior capsule was left intact and in the other eye a large posterior capsulectomy was performed. When the anterior chambers were challenged with equivalent inocula of Staphylococcus aureus, one of 10 eyes with an intact posterior capsule developed culture-positive vitreous infection. In contrast, nine of 10 eyes with a large posterior capsulectomy developed culture-positive vitreous infection. In a second experiment we investigated the effect of an intraocular lens on the barrier effect. Ten primates received extracapsular cataract extraction in both eyes and pseudophakic implantation. In one eye of each primate the posterior capsule was left intact and a J-loop monoplanar lens was implanted in the ciliary sulcus. In the other eye of each primate a large posterior capsulectomy was followed by implantation of a monoplanar, non-vaulted pseudophakos into the anterior chamber. None of the 10 eyes with a posterior capsule intact and a posterior chamber lens in place developed positive vitreous cultures or histopathological evidence of vitreous infection. Thus the presence of a posterior chamber lens did not appreciably compromise the barrier effect of the intact posterior capsule. 40% of the eyes with a large posterior capsulectomy and a non-vaulted pseudophakos in the anterior chamber developed culture-positive vitreous infection, and 60% of the eyes showed histopathological evidence of vitreous infection.