Purpose: To design and test the Miami-InnFocus Drainage Implant (MiDi) as a glaucoma shunt that is biocompatible,
flexible, and significantly smaller than existing commercial implants in order to prevent postoperative hypotony, inflammation, scarring, erosion, and extrusion.
Methods: A new biomaterial composed of styrene-b-isobutylene-b-styrene (SIBS) was used in a novel design for a glaucoma drainage implant. The implant consists of a tube 11mm long with an inner diameter of 70, 100, and 150 μm
and outer diameter of 250 μm with a 1mm2 tab located 4.5mm from the proximal tip to prevent migration. The device
was implanted in 15 New Zealand White rabbits for biocompatibility and efficacy testing. A similarly designed implant
made of polydimethylsiloxane was implanted in 6 other animals as a pseudo-control. Typical GDI implantation
technique was modified for this device. The proximal end of the new SIBS implant was inserted 2mm into the anterior
chamber and the distal end placed in a subconjunctival space created by the surgeon. Biocompatibility of the device was
studied by slit-lamp follow-up and intraocular pressure (IOP) measurements recorded periodically. Results:
Biocompatibility of the MiDi was excellent. A low and diffuse bleb was observed with these devices. All SIBS tubes
were patent 9 months after insertion. Immunostaining demonstrated non-continuous deposition of collagen with virtually
no encapsulation. No macrophages or myofibroblast were visible around the SIBS polymer which was found more
bioinert than the control PDMS.
Conclusion: This newly designed glaucoma implant is clinically biocompatible in the rabbit model and maintained
100% patency at 9 months.
Purpose: To demonstrate the biocompatibility of SIBS implants as compared to PDMS implants in the treatment of retinal detachment in New Zealand White (NZW) rabbit model.1,2Introduction: Scleral encircling bands, fixation rings and buckles are utilized for closure of retinal breaks and retina reattachment. The FDA approved PDMS-implant is associated with several post-operative complications, involving thick-fibrotic encapsulations. SIBS, an elastomeric triblock copolymer, was recently FDA approved for use in a cardiovascular drug eluting stent (TAXUSTM, Boston Scientific Corp., MA) and showed excellent biocompatibility and slow drug release capability. Materials and Methods: SIBS (9-mol%-styrene) implants were fabricated (InnFocus LLC, USA) to match PDMS implants (Labtician, Inc, Canada) dimensions. 5 NZW rabbits received SIBS and 4, PDMS-implants. Post-operative exam sequence: day 1 and 2, week 1, 2, 3, 4 and 6, and monthly thereafter for up to 1 year. Anatomohistopathology exams sequence: one SIBS animal at 6 weeks and one animal of each treatment group at 3 and 6-months, and two at 12-months. Results: SIBS compared to PDMS animals exhibited less inflammation and a better buckling effect during the first 6 weeks. At POD 9 months, the conjunctival injection in the SIBS rabbit was none as opposed to the PDMS value and the buckling effect for both groups were equal. There were no visible signs of encapsulation with SIBS. There were no infections in the 9 animals and none of the implants extruded thus far (<10 months). Conclusion: SIBS encircling bands, sleeves, and buckle implants are well tolerated in the rabbit model.
Purpose: To evaluate the feasibility to induce lens epithelial cell death with intraoperative hyperthermia for prevention of secondary cataract. Methods: A prototype miniature resistive hyperthermia probe was designed. The probe contained a thermocouple for temperature feed-back. A timer allowed monitoring of the electrical driving of the hyperthermia probe and the temperature induced as a function of time. To model the heating response, a simple model of the lens capsule was constructed using a thin acrylic plastic shell embedded in a sponge immersed in a water bath at 37°C. The shell was filled with sodium hyaluronate. The probe was positioned at the center of the shell with the thermocouple next to the wall. An experimental protocol was developed to assess the feasibility of increasing the temperature of the human lens to hyperthermia levels in fresh cadaver eyes: An annular metal ring was bonded just below the limbus, the cornea and iris were sectioned, the lens material was removed through a central 5mm diameter capsulorhexis, the capsule was filled with SHA and the globe was set on a temperature-controlled cylindrical vial. Preliminary Results: At 3.3W (2.2V, 1.5A) the shell's content increases from 37°C to 51°C in 30s. At that temperature, LEC death is expected to occur within 1sec. Conclusion: This preliminary study demonstrates the feasibility of increasing the temperature of the capsular bag to kill LECs by hyperthermia.