Priyal Shah

Intraocular pressure elevation precedes a phagocytosis decline in a model of pigmentary glaucoma

Background: Outflow regulation and phagocytosis are key functions of the trabecular meshwork (TM), but it is not clear how the two are related in secondary open angle glaucomas characterized by an increased particle load. We hypothesized that diminished TM phagocytosis is not the primary cause of early ocular hypertension and recreated pigment dispersion in a porcine ex vivo model. Methods: Sixteen porcine anterior chamber cultures received a continuous infusion of pigment granules (Pg), while 16 additional anterior chambers served as controls (C). Pressure transducers recorded the intraocular pressure (IOP). The phagocytic capacity of the trabecular meshwork was determined by fluorescent microspheres. Results: The baseline IOPs in Pg and C were similar ( P=0.82). A significant IOP elevation occurred in Pg at 48, 120, and 180 hours (all P<0.01, compared to baseline). The pigment did not cause a reduction in TM phagocytosis at 48 hours, when the earliest IOP elevation occurred, but at 120 hours onward ( P=0.001 compared to C). This reduction did not result in an additional IOP increase at 120 or 180 hours compared to the first IOP elevation at 48 hours ( P>0.05). Conclusions: In this porcine model of pigmentary glaucoma, an IOP elevation occurs much earlier than when phagocytosis fails, suggesting that two separate mechanisms might be at work.

Outflow enhancement by three different ab interno trabeculectomy procedures in a porcine anterior segment model

PurposeTo evaluate three different microincisional ab interno trabeculectomy procedures in a porcine eye perfusion model.MethodsIn perfused porcine anterior segments, 90° of trabecular meshwork (TM) was ablated using the Trabectome (T; nu2009=u20098), Goniotome (G; nu2009=u20098), or Kahook device (K; nu2009=u20098). After 24xa0h, additional 90° of TM was removed. Intraocular pressure (IOP) and outflow facility were measured at 5 and 10xa0μl/min perfusion to simulate an elevated IOP. Structure and function were assessed with canalograms and histology.ResultsAt 5xa0μl/min infusion rate, T resulted in a greater IOP reduction than G or K from baseline (76.12% decrease versus 48.19% and 47.96%, Pu2009=u20090.013). IOP reduction between G and K was similar (Pu2009=u20090.420). Removing another 90° of TM caused an additional IOP reduction only in T and G but not in K. Similarly, T resulted in the largest increase in outflow facility at 5xa0μl/min compared with G and K (first ablation, 3.41 times increase versus 1.95 and 1.87; second ablation, 4.60 versus 2.50 and 1.74) with similar results at 10xa0μl/min (first ablation, 3.28 versus 2.29 and 1.90 (Pu2009=u20090.001); second ablation, 4.10 versus 3.01 and 2.01 (Pu2009=u20090.001)). Canalograms indicated circumferential flow beyond the ablation endpoints.ConclusionsT, G, and K significantly increased the outflow facility. In this model, T had a larger effect than G and K.

Structure–Function Changes of the Porcine Distal Outflow Tract in Response to Nitric Oxide

Purpose To correlate outflow function and outflow tract vessel diameter changes induced by nitric oxide (NO). Methods In a porcine anterior segment perfusion model, the effects of a nitric oxide donor (100 μM DETA-NO) on outflow facility were compared with controls (n = 8 per group) with trabecular meshwork (TM) and after circumferential ab interno trabeculectomy (AIT). Outflow structures were assessed with spectral-domain optical coherence tomography (SD-OCT) before and after NO, or an NO synthase inhibitor (100 μM L-NAME) and the vasoconstrictor, endothelin-1 (100 pg/mL ET-1). Scans were processed with a custom macroscript and aligned for automated reslicing and quantification of cross-sectional outflow tract areas (CSA). Results The facility increased after DETA-NO (Δ of 0.189 ± 0.081 μL/min·mm Hg, P = 0.034) and AIT (Δ of 0.251 ± 0.094 μL/min·mm Hg, P = 0.009), respectively. Even after AIT, DETA-NO increased the facility by 61.5% (Δ of 0.190 ± 0.074 μL/min·mm Hg, P = 0.023) and CSA by 13.9% (P < 0.001). L-NAME + ET-1 decreased CSA by −8.6% (P < 0.001). NO increased the diameter of focal constrictions 5.0 ± 3.8-fold. Conclusions NO can dilate vessels of the distal outflow tract and increase outflow facility in a TM-independent fashion. There are short, focally constricting vessel sections that display large diameter changes and may have a substantial impact on outflow.

Impact of same-session trabectome surgery on Ahmed glaucoma valve outcomes

PurposeTo evaluate the efficacy and survival rates of same session ab interno trabeculectomy with the trabectome and Ahmed glaucoma valve implant (AT) in comparison to the Ahmed glaucoma valve alone (A).MethodA total of 107 eyes undergoing primary glaucoma surgery were enrolled in this retrospective comparative case series, including 48 eyes which underwent AT and 59 eyes which received A alone. Participants were identified using the procedural terminology codes, and their medical records were reviewed. The primary outcome measure was success defined as IOPu2009>u20095xa0mmHg, ≤u200921xa0mmHg and ≥u200920% reduction of IOP from baseline at two consecutive visits after 3xa0months, and no need for glaucoma reoperation. Secondary outcome measures were IOP, the number of glaucoma medications, incidence of a hypertensive phase, and best corrected visual acuity (BCVA).ResultsThe cumulative probability of success at 1xa0year was 70% in AT, and 65% in A (pu2009=u20090.85). IOP decreased significantly from 26.6u2009±u200910.1xa0mmHg at baseline to 14.7u2009±u20093.3xa0mmHg at the final follow-up in AT (pu2009=u20090.001). The corresponding numbers for A were 27.8u2009±u200910.2 and 16.7u2009±u20094.9, respectively (pu2009=u20090.001). The final IOP was significantly lower in AT (pu2009=u20090.022). The number of medications at baseline was comparable in both groups (2.6u2009±u20091.2 in AT and 2.5u2009±u20091.3 in A, pu2009=u20090.851). Corresponding number at 1xa0year visit was 1.2u2009±u20092 in AT and 2.8u2009±u20091.8 in A (pu2009=u20090.001). The incidence of a hypertensive phase was 18.7% in AT and 35.5% in A (pu2009=u20090.05). HP resolved in only 30% of eyes. The criteria for HP resolution were fulfilled in 9 eyes (30%). There was no difference in the rate of resolution of the hypertensive phase between AT and A (33.3 and 28.5%, respectively, pu2009=u20090.67).ConclusionAhmed glaucoma valve implant with same session trabectome surgery significantly decreased the rate of the hypertensive phase and postoperative IOP as well as the number of glaucoma medications.