[What is a granuloma?]

Foreign body reaction after CyPass® Micro-Stent implantation: a case series

PURPOSE

To retrospectively assess the histopathological particularities of explanted CyPass® Micro-Stent of patients with significant loss of endothelial cell density.

METHODS

This is a case series of fourteen eyes from eleven patients who underwent CyPass® Micro-Stent implantation due to mild to moderate glaucoma and who subsequently suffered from loss of endothelial cell density. Therefore, the explantation of the device was necessary. In addition to the retrospective evaluation of the intraocular pressure and the endothelial cell density at the time of implantation and explantation, every surgically removed implant was histologically examined and evaluated.

RESULTS

Fourteen eyes of eleven patients were in total analysed. The patients-seven males and four females-had a mean age of 62.9 years. The average time between CyPass implantation and explantation was 3.7 years. Eight patients suffered from primary-open-angle glaucoma (POAG), while two patients had a pseudoexfoliation glaucoma (PXG) and one patient had low-pressure glaucoma. Ten of the patients were already pseudophakic before the CyPass implantation and four patients underwent previously glaucoma interventions. There was a significant reduction in the intraocular pressure from 18.57 ± 5.27 mmHg at the time of implantation to 14.78 ± 3.32 mmHg at the time of explantation (p = 0.037). The average endothelial cell density decreased from 1843.67 ± 421.81 to 932.92 ± 412.86/mm² at the time of explantation (p < 0.01). The histological findings showed a fibrous obliteration of the CyPass accompanied by a chronic granulomatous inflammation with giant cell macrophages. Histologically, these findings were consistent with a foreign body granuloma.

CONCLUSIONS

Implants made of polyimides such as the CyPass® Micro-Stent are considered to be biocompatible, but there is no guarantee not to be obliterated or encapsulated. This is the first case series that has detected a foreign body granuloma in multiple eyes after CyPass implantation. However, there is no connection with the type of glaucoma, the extent of previous operations or with the presence of a prolonged postoperative inflammatory reaction.

Distribution of M1 and M2 macrophages in cerebral granulomas caused by Encephalitozoon cuniculi

Encephalitozoon cuniculi spores cause severe granulomatous inflammation in the brain where mononuclear cells and macrophages infiltrate. Here, we orally infected New Zealand white rabbits with 1 × 10⁶E. cuniculi viable spores to study the recruitment and localization of macrophages in brain granulomas. At day 30 post-infection, the positive phenotype markers iNOS (M1) and Arg-1 (M2) were located in the periphery and center of granulomas, respectively. Live intracytoplasmic spores were found only in positive Arg-1 cells. This is the first work to describe the recruitment and distribution of M1 and M2 macrophages in the brain granulomas of rabbits infected with E. cuniculi.

Chronic Granulomatous Inflammation after CyPass® Implantation

A 65-year-old patient suffering from pseudoexfoliation glaucoma and multiple previous surgeries at the right eye underwent CyPass® explantation 19 months after CyPass® Micro-Stent implantation due to chronic inflammation in the an-terior chamber. Histologically, a foreign body granuloma around and in the CyPass® implant was found. We conclude that patients with previous multiple glaucoma surgeries should not undergo CyPass® Micro-Stent implantation.