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Julius T. Oatts, John H. Sinard, Nils A. Loewen; Fibrosis and IOP Differences of Two Suprachoroidal Shunts. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3745.
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To compare the IOP pattern and fibrosis of a suprachoroidal gold shunt to one made of polypropylene.
In order to study material biocompatibility and design differences within a shorter time frame, we chose rabbits that exhibit a more pronounced inflammation and accelerated fibrosis. Ten rabbits underwent implantation of either a suprachoroidal gold shunt (GS, 3.2 x 5.2 x .05 mm3, GMSplus+, Solx) or polypropylene shunt (PS, 4 x 10 x .75 mm3, Aquashunt, OPKO). IOP was monitored with a pneumatonometer and a latest generation tonopen. IOP was measured at several time points preoperatively and then followed postoperatively at peak and trough daily for one week and then weekly. At the conclusion of the experiment, fibrosis was analyzed qualitatively and quantitatively by histology and morphometry.
Rabbits exhibited a circadian IOP rhythm that was lowest at 11 AM (22.8 ± 1 mm Hg) and highest at 8 PM (25.7 ± 2 mm Hg, p=0.77). Compared to preoperative IOP, 11 AM IOP was decreased in both groups through week 6 (GS: 18% p=0.039, PS: 46% p=0.003), with the exception of the GS group at week 1 (p=0.48). 8 PM IOP was significantly decreased at week 6 in both groups (GS: 24% p=0.004, PS: 23% p=0.018). Beginning at week 4, PS showed a more significant IOP decrease from baseline, but only at 11 AM (PS: 39% IOP decrease, GS: 17%, p=0.03). When compared to the other eye, in PS both 11 AM (p=0.008) and 8 PM (p=0.03) IOP was lower through week 6, while in GS only the 8 PM (p=0.049) IOP was lower through week 6. Gold shunts were devoid of foreign body reaction but exhibited fibrosis consisting of a 60 micron layer of collagen on the scleral side and a 30 micron layer on the choroidal side of the shunt. There was partial obstruction of the shunt lumen.
In this rabbit model, both GS and PS decreased IOP through postoperative week 6, while PS was more significant from week 4 onward. GS does not cause notable inflammation, but fibrosis can be observed.
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