Objective  To detect the biocompatibility of anterior surface PEG-grafted IOLs (via APGD treatment) in rabbit eyes, including complications related to anterior chamber inflammatory reaction and capsule opacification.

Methods  Anterior surfaces of hydrophobic acrylic IOLs were grafted with PEG by APGD treatment. The hydrophilicity of IOL surface was characterized by contact angle test. Thirty-six rabbit eyes were operated on with phacoemulsification and randomly implantation of one from the three types of foldable IOLs: anterior surface PEG-grafted acrylic IOL (PEG-grafted IOL) (n=12), original acrylic IOL (Acrylic IOL) (n=12) and hydrophilic IOL (Akreos IOL) (n=12). Postoperative follow-up was done on the 1^st, 3^rd, 7^th, 14^th, 30^th, 60^th and 90^th days after surgery. On each visit, all rabbits were observed by slitlamp examination to evaluate aqueous flare, aqueous cell, posterior synechia and IOL dislocation. Standardized digital retroilluminated slitlamp images of posterior capsule opacification (PCO) were taken and the evaluation of PCO was done by EPCO 2000 software. The rabbits were killed three months postoperatively, the Miyake-Apple posterior photographic technique was used to evaluate the PCO formation. The IOLs were extracted from the rabbits eyes, and the cells attached on IOLs surface were observed by inverted phase contrast microscopy with hematoxylin and eosin (HE) staining; the samples were also prepared and observed by SEM. Histological sections of rabbits globe were prepared and stained with HE staining, periodic acid-schiff (PAS) and Masson’s trichrome staining to document proliferation of LECs and extracellular matrix (ECM) in capsular bag.
Results  The water contact angle of PEG IOL showed a stable significantly improved hydrophilicity of anterior surface, with a hydrophobic original posterior surface. The follow up observation with slitlamp examination showed that the anterior chamber inflammation was severer in Acrylic IOL group than in other two groups, two eyes in Acrylic IOL group and one eye in Akreos IOL group presented posterior synechia and IOL dislocation, no obvious inflammation was found in eyes with PEG IOLs. On the 7^th and 14^th day postoperatively, the aqueous flare results were statistically higher in Acrylic IOL group than in other two groups (p<0.05), the aqueous cell results showed that no statistically difference among the three groups was observed in the measured time point (p>0.05). The EPCO analysis and Miyake-Apple evaluation revealed that the eyes of Akreos IOLs had higher incidence of PCO compared to those of PEG IOLs and Acrylic IOLs (p<0.05), but there were no statistically significant difference between PEG IOLs and Acrylic IOL groups (p>0.05). The inverted phase contrast microscope observation showed that there were more cells adhered on Acrylic IOLs than PEG IOLs and Akreos IOLs (p<0.05). Histopathological analysis demonstrated the remnant LECs had some growth, and Soemmering’s ring was observed in all groups. However, LECs were stopped at the optic periphery of the Acrylic IOLs and PEG IOLs, which keeping hydrophobic posterior surface. The central posterior capsule area of IOLs were clear in above both groups. In contrast, in Akreos IOL group, the LECs and ECM were observed apparently grew into the central field of the optic, thus leading to the PCO in visual axis area.

Conclusion  The PEG IOLs via APGD treatment had stable hydrophilic anterior surface and original hydrophobic posterior surface. The PEG IOLs have both excellent uveal biocompatibility, characterized by minimal postoperative anterior chamber inflammation, and good capsular biocompatibility, characterized by low incidence of PCO.