Posterior Delivery in Disease States

Intravitreal injections of antibiotics (which do not easily penetrate the eye by any other route) are the cornerstone of the management of endophthalmitis although adjunctive treatments, such as IV antibiotics and early vitrectomy have often been employed. A recent multicenter study on postoperative endophthalmitis found that IV antibiotics had no significant effect on clinical outcomes while early vitrectomy was beneficial only in eyes with light perception or worse. In eyes with better vision, early vitrectomy offered no significant benefit (see Chapter 6). The role of IV antibiotics in other causes of endophthalmitis such as trauma was not established in this study (108). An ideal antibiotic for intravitreal use would have a long half-life in the 

Proliferative vitreoretinopathy (PVR) is characterized by the proliferation of cells, thought to be mainly retinal pigment epithelial cells, macrophages, and fibroblasts 

Optimal steroid therapy for PVR would maintain therapeutic levels in the vitreous for a prolonged period at present this can only be achieved by prohibitively high systemic dosing or intravitreal injections (which do not maintain constant drug levels). A sustained release device that maintains constant therapeutic intravitreal levels with minimal systemic exposure may prove useful in the clinical management of PVR, although the potential for ocular effects such as elevation of intraocular pressure and cataract cannot be ignored. 

The local use of cytotoxic chemothetic agents has also been investigated as a means to treat or prevent PVR. Intravitreal injections of daunorubicin have been 

Degradable microspheres of PLA have been investigated as a means to sustain the release of antimetabolites for the treatment of intraocular proliferative disease. Moritera et al. (70) showed that in vitro PLA microspheres containing 1% adria-mycin (doxorubicin) can give sustained, first-order release for approximately two weeks. This sustained release reduced the toxicity of adriamycin compared to injections of a free solution as measured by electroretinogram (ERG). 

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