Confocal and Histological Features After Poly(Ethylene Glycol) Diacrylate Corneal Inlay Implantation

To evaluate the in vivo biocompatibility of photopolymerized poly(ethylene glycol) diacrylate (PEGDA) intrastromal inlays in rabbit corneas.

Sixty-three eyes of 42 New Zealand rabbits were included. Manual intrastromal pockets were dissected in 42 eyes. PEGDA inlays were obtained using a specifically designed photomask and were inserted in the intrastromal pocket of 21 eyes (inlay group); the remaining 21 right eyes did not receive any implant (pocket-only group). Twenty-one eyes with no intervention were used as controls. In vivo confocal microscopy (IVCM) was performed at every visit. After 2 months, rabbits were sacrificed and corneas removed for histological analysis.

Corneas remained clear in all but two animals, and five cases of corneal neovascularization were seen (P = 0.2). Inlays remained stable without evidence of lateral or anterior migration, and no other complications were observed. No changes in anterior and posterior keratocyte density (P = 0.3 and P = 0.1, respectively) or endothelial cell density (P = 0.23) were observed between groups during the study time by IVCM. On pathology samples, thinning of the epithelium over the inlay area and epithelial hyperplasia over the edges were observed. A polygonal empty space with no evidence of PEGDA hydrogel within the midstroma was seen in the inlay group. Keratocytes were normal in shape and number in the vicinity of the PEGDA implant area.

Photopolymerized PEGDA intrastromal inlays have shown relatively good safety and stability in rabbit corneas. Inlays were biostable in the corneal environment and remained transparent during follow up.

The investigated PEGDA is promising for the development of biocompatible intrastromal implants.