ABSTRACT
Purpose: To evaluate incisional or excisional tissue-level effects of ab interno goniotomy techniques on human trabecular meshwork (TM). Methods: The TM from human cadaveric corneal rim tissue was treated using three devices: (1) Kahook Dual Blade (KDB) GLIDE, (2) iAccess, and (3) SION. Two human corneal rims were used for each of the iAccess and SION devices and one with the KDB GLIDE, with 360 degrees of TM treated in each case. Sections were then prepared for analysis and comparison between devices. Tissue samples underwent standard histologic processing with H&E stain, followed by comparative analyses. Results: Areas treated with the KDB GLIDE device resulted in nearly complete excision of TM overlying the canal of Schlemm without injury to surrounding tissues. The iAccess device can be used as a focal trephine to create holes or dragged for TM disruption. When used to create holes, iAccess punched through the full thickness of the TM and also disrupted the anterior scleral tissue. It caused some incisional openings through the TM but with significant leaflets remaining and minimal true "hole-punch" effect. When the device tip was dragged, iAccess incised the TM and left debris behind with little, if any, excision of tissue. SION led to both incision and excision of TM with incision predominating over excision. Conclusion: The various methods evaluated to perform ab interno goniotomy resulted in varying degrees of TM incision or excision. Only the KDB GLIDE device resulted in reliable excision of TM, while the other devices produced incision or minimal excision of tissue with residual leaflets and debris. Use of iAccess resulted in focal disruption of the anterior scleral wall. Because incisional approaches that leave longer residual leaflets may be more prone to fibrosis and closure compared to excisional treatments, clinical correlation will be necessary to better understand the significance of these findings with respect to relative effectiveness of intraocular pressure lowering in eyes with glaucoma.
ABSTRACT
PURPOSE: To quantify the effects of modified Ahmed glaucoma valves® (AGV) with anti-fibrotic plate coatings or a plate surface micro-pattern on outflow resistance and tissue response. METHODS: Twelve New Zealand rabbits were divided into four groups: commercially available AGV implants (n = 3), AGV with hydrophilic coating (n = 3), AGV with heparin coating (n = 3), and AGV with a plate surface micro-pattern (n = 3). After 6 weeks, the anterior chamber silicone tube was cannulated in situ and perfused with 2.5 µL/min of saline. The pressures were recorded with a perfusion system to measure outflow resistance. The rabbits were then euthanized followed by enucleation of all eyes for bleb histological analyses. RESULTS: Hydrostatic pressures were significantly lower in AGVs with the hydrophilic plate coating (mean difference -9.6 mm Hg; p < 0.001), heparin-coated plates (mean difference -4.4 mm Hg; p < 0.001), and micro-patterned plates (mean difference -18.6 mm Hg, p < 0.001), indicating lower outflow resistance compared to control AGV models. Fibrotic encapsulation was lower in hydrophilic plate coating (84.2 µm; mean difference -6.2 µm, p = 0.425), micro-patterned surface (63.7 µm; mean difference -26.7 µm, p = 0.003), and heparin plate coating (49.3 µm; mean difference -41.1 µm, p = 0.006) when compared to control AGV models. CONCLUSIONS: Modified AGVs with plate coatings and AGVs with micro-patterned plates both appear to reduce postoperative fibrotic encapsulation and aqueous outflow resistance by altering the tissue response to implanted materials. Further studies are needed to characterize the safety and role of plate surface modifications on glaucoma drainage devices.
