Aqueous dynamic and histological findings after deep sclerectomy with collagen implant in an animal model

Abstract

Aim: The use of an animal model to study the aqueous dynamic and the histological findings after deep sclerectomy with (DSCI) and without collagen implant. Methods: Deep sclerectomy was performed on rabbits' eyes. Eyes were randomly assigned to receive collagen implants. Measurements of intraocular pressure (IOP) and aqueous outflow facility using the constant pressure method through cannulation of the anterior chamber were performed. The system was filled with BSS and cationised ferritin. Histological assessment of the operative site was performed. Sections were stained with haematoxylin and eosin and with Prussian blue. Aqueous drainage vessels were identified by the reaction between ferritin and Prussian blue. All eyes were coded so that the investigator was blind to the type of surgery until the evaluation was completed. Results: A significant decrease in IOP (p,0.05) was observed during the first 6 weeks after DSCI (mean IOP was 13.07 (2.95) mm Hg preoperatively and 9.08 (2.25) mm Hg at 6 weeks); DS without collagen implant revealed a significant decrease in IOP at weeks 4 and 8 after surgery (mean IOP 12.57 (3.52) mm Hg preoperatively, 9.45 (3.38) mm Hg at 4 weeks, and 9.22 (3.39) mm Hg at 8 weeks). Outflow facility was significantly increased throughout the 9 months of follow up in both DSCI and DS groups (p,0.05). The preoperative outflow facility (OF) was 0.15 (0.02) ml/min/mm Hg. At 9 months, OF was 0.52 (0.28) ml/min/mm Hg and 0.46 (0.07) ml/min/mm Hg for DSCI and DS respectively. Light microscopy studies showed the appearance of new aqueous drainage vessels in the sclera adjacent to the dissection site in DSCI and DS and the apparition of spindle cells lining the collagen implant in DSCI after 2 months. Conclusion: A significant IOP decrease was observed during the first weeks after DSCI and DS. DS with or without collagen implant provided a significant increase in outflow facility throughout the 9 months of follow up. This might be partly explained by new drainage vessels in the sclera surrounding the operated site. Microscopic studies revealed the appearance of spindle cells lining the collagen implant in DSCI after 2 months. In an attempt to increase the success rates of nonpenetrating glaucoma surgery, Kozlov et al 1 described using a collagen implant in order to bridge the period of maximal wound healing postoperatively.Although deep sclerectomy with collagen implant (DSCI) is now a recognised procedure, 2-8 performed successfully in several ophthalmic centres, there has been until now no animal model of this surgery.The aim of our study was thus to describe an animal model of deep sclerectomy, and to study the mechanisms of filtration, the aqueous humour dynamics, the evolution of the collagen implant with time, and the scarring response of the different tissues after deep sclerectomy. STUDY DESIGNDeep sclerectomies were performed in both eyes of six groups of three rabbits. The left and right eyes were randomly assigned to undergo either DSCI or deep sclerectomy without collagen implant (DS).T...

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