G. Renard

Formation of intercellular spaces and junctions in regenerating rabbit corneal endothelium

Abstract Rabbit corneal endothelium was destroyed over a diameter of 10 mm using liquid nitrogen applied for 15 sec to the anterior surface. The corneas were afterwards removed at different periods, from 1 day to 2 months and studied by light microscopy after silver impregnation, by transmission electron microscopy, and by scanning electron microscopy in order to study the formation of new intercellular spaces and junctions in the regenerating endothelium. The intercellular spaces and junctions are all reconstituted at the end of the fifth day, when the whole of Descemets membrane is entirely covered by cells. This period also corresponds to the recovery of the endothelial function. The dynamics of the formation of intercellular spaces are described, and the rapid appearance of two types of junctions as soon as contact between cells is completed. Junctions of the first type, always at the apex of the cells, are single or multiple with adjacent intra-cytoplasmic opacities and correspond to the junctional elements of the “terminal bar”. Junctions of the second type, on the lateral plasma membranes of the cells, are not constantly observed; they are straight, or curved. or circular; their length is variable, and they possess a periodicity in their structure, and correspond to gap junctions.

Silicone punctal plug extrusion resulting from spontaneous dissection of canalicular mucosa: A clinical and histopathologic report.

PURPOSEnTo report on an uncommon, previously unidentified, progressive silicone punctal plug extrusion.nnnDESIGNnSmall, retrospective case series.nnnPARTICIPANTSnFive cases of punctal plug extrusion were identified among a series of 424 consecutive implantations. Histopathologic analysis was obtained in one case. One additional referred case was included in this report.nnnRESULTSnThe plugs were completely extruded from the punctal lumen 6 to 14 months after insertion after an otherwise uncomplicated postoperative course. All plugs were retained at the punctal margin by an encircling band of vascularized mucosal tissue originating from the canalicular lumen. The band consisted of connective tissue of canalicular mucosal origin, attached just below the junction of the punctal and canalicular epithelium. Mild mononuclear infiltration was present in the connective tissue component of the punctal region. There was no cytologic or architectural evidence of abnormal epithelium or connective tissue or of pyogenic granuloma.nnnCONCLUSIONSnThese observations suggest that progressive lacrimal punctal plug extrusion may relate to mucosal dissection by the plug edges. We speculate that mechanical stress induced by eyelid closure on an improperly sized or placed implant may result in plug tilt. Subsequent epithelial hyperplasia further enhances the tilt, and the sharper edge of the conical bulb promotes separation of the canalicular mucosa from its distal luminal aspect. At the completion of the extrusion, the mucosal surface is separated from its connective tissue base, at a proximal subpunctal level, causing formation of an encircling tissue band.

Histopathology of lacrimal canalicular mucosa following punctum plug implantation

PURPOSE We present the first report on a histopathological evaluation of the tolerance of human lacrimal canalicular mucosa to the implantation of a silicone punctal plug.METHODS A silicone punctum plug was implanted 10 to 15 days prior to planned surgical resection of the lacrimal canaliculus and adjacent inferior eyelid in 5 patients. The indication for canalicular resection was related to a basal cell carcinoma in 4 cases and to a squamous cell carcinoma in I case. Average duration of implantation was 15 days, with a 15-day punctum-free period in one case.RESULTS Histopathological analysis of specimens revealed a tight conformation of the mucosa to the plug wall. Mild atrophic and hypertrophic changes in mucosal epithelium as well as a moderate inflammatory reaction, consisting of macrophages and polymorphonuclear cells, was observed at the level of the epithelium but not in the adjacent connective tissue.CONCLUSION These results confirm the overall good tolerance of silicone plugs after mid-term impla...