laser irradiation. Postoperative function was demonstrated with microperimetry, which showed stable fixation and maintained retinal sensitivity over the transplant.

Overall, a mean decline of visual loss is reported if postoperative complications are included. If these cases are excluded from visual analysis, the mean gain in visual acuity is 2–3 lines.2 Van Meurs’ group underscored the latter correlation in a prospective statistical analysis of 48 cases.20 As long as the complication rates remain high, the possible gain of vision limits this surgical technique to cases otherwise not treatable with pharmacologic treatments.24 It is therefore encouraging that mere mechanical ablation, analogous to Holz’s technique, by Ma and associates was able to demonstrate low PVR rates (14.3%) at 1-year follow-up and good functional outcomes in hemorrhagic AMD patients.25

TISSUE ENGINEERING AND RPE REPLACEMENT STRATEGIES

PROSTHESIS OR TISSUE ENGINEERING OF BRUCH’S MEMBRANE

Cellular replacement strategies of the RPE could be beneficial to patients with AMD or related diseases, but may not be effective if BM has been damaged by disease, age, and/or surgery. Delivery and long-term survival of these transplants may require a biocompatible substrate that patches or entirely replaces diseased BM.

In contrast to animal experiments,26 in vitro data suggested that freshly harvested or cultured RPE cell suspensions may fail to survive or function on a damaged BM.27 While histopathologic studies have demonstrated integration of cultured cell suspensions in the subretinal space in animals, formation of multilayered clumps that damaged the overlying neural retina has been reported. Moreover, delivery of cell suspensions to epithelially denuded BM using the bleb techni­ que often showed uneven distribution, with most of the cells settling in the periphery of the RPE lesion. Thus restoration of a continous monolayer using a cell suspension in the subretinal space appears challenging.

Many groups have tried to develop a RPE carrier substrate, which at the same time would serve as either a temporary or a permanent BM prosthesis. Having such an arrangement enables delivery of an intact epithelial patch that is simultaneously protected from hostile influences of aged BM.

Various biologic and artificial substrates have been proposed to date (Table 50.1 and Figure 50.3). Details of particular approaches are beyond the scope of this article and the interested reader is referred to Binder et al.3 Nevertheless, some unifying technical considerations are given. Perhaps the foremost criterion for a carrier material is maintenance of a clinically relevant epithelial phenotype, both in vitro and subsequently

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