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Purpose: To analyse the morphological evolution of filtering blebs with anterior-segment OCT (AS-OCT) and its correlation with intraocular pressure after ab externo SIBS microshunt implantation with mitomycin C (MMC) during a 3month follow-up period. Methods: Twenty-eight filtering blebs of 28 patients with open-angle glaucoma were measured horizontally and vertically in the sub-Tenon space with AS-OCT after ab externo SIBS microshunt implantation with MMC. The intraocular pressure (IOP) was monitored simultaneously at each visit. Maturation of and morphological changes in the blebs and correlations with the IOP were recorded. Results: The average median preoperative IOP of 20.7 (range, 12-30) mmHg decreased to 8.5 (range, 4-17), 8.9 (range, 5-17), 10.4 (range, 8-16) and 10.9 (range, 9-15) mmHg at 24 hr, 1 week, 1 month and 3 months, respectively (p < 0.001). A multiform morphology on AS-OCT prevailed at all time points, with a 3.5% rate of a uniform bleb morphology at the first week. The horizontal and vertical diameters of the blebs increased from baseline to the third month. The horizontal expansion (406 AE 127 lm on day 7, p = 0.04, 712 AE 211 lm on day 30, p = 0.02 and 952 AE 218 lm on day 90, p < 0.001) was greater than the vertical expansion (16 AE 18 lm, p = 0.3 on day 1, 63 AE 27 lm, p = 0.02 on day 30 and 137 AE 34 lm, p < 0.001 on day 90) without correlation with the IOP (r = À0.3, p = 0.2). Conclusion: Anterior-segment OCT (AS-OCT) of the filtering blebs formed after ab externo SIBS microshunt implantation showed progressive horizontal and vertical expansion of the blebs in the sub-Tenon space, with a significant peak at the first month not significantly correlated with the decrease in the IOP.

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Introduction:To analyze the effects of PRE-SERFLO on corneal endothelial cell density (ECD). Methods: Forty-six eyes that underwent PRE-SERFLO implantation were followed up for 12 months. Specular microscopy was performed preoperatively and at 1, 3, 6, and 12 months postoperatively to measure central ECD and mean monthly reduction (MMR). Anterior segment optical coherence tomography (AS-OCT) was applied to measure the tube-endothelium (TE \ 200 lm, 201-500 lm, [ 500 lm) distance. The relationship between TE distance and ECD was analyzed with a linear mixed-effects model. Results: Central ECD decreased significantly at 1 year (7.4%, p = 0.04), with an MMR of -15 ± 25 cells/mm 2 . Regarding TE distance groups, there was an 18% ECD reduction in the \ 200 lm group vs. 1% in the [ 500 lm group (p = 0.08). Endothelial cell loss was related to TE distance (mean 482.9 ± 238 lm), with a higher rate at 1 month in comparison to 12 months for the same tube position in the anterior chamber (-174.8 ± 65.2 cells/mm 2 at 1 month vs. 30.2 ± 11.3 cells/mm 2 at 12 months, p \ 0.01). From month 6, tubes located [ 600 lm from the endothelium showed EC loss close to zero. Conclusions: The PRESERFLO implant is associated with a loss of EC from the immediate postoperative period that continues over time at lower rates. A shorter TE distance appears to cause more severe ECD loss.

Purpose To measure the in vitro flow properties of the PRESERFLO implant for comparison with the theoretical resistance to flow. Methods The PRESERFLO was designed to control the flow of aqueous humor according to the Hagen-Poiseuille (HP) equation. Scanning electron microscopy (SEM) was performed to analyze the ultrastructure, and flow measurements were carried out using a gravity-flow setup. Results SEM images of the PRESERFLO showed luminal diameters of 67.73 × 65.95 µm and 63.66 × 70.54 µm. The total diameter was 337.2 µm, and the wall was 154 µm wide. The theoretical calculation of the resistance to flow (R) for an aqueous humor (AH) viscosity of 0.7185 centipoises (cP) was 1.3 mm Hg/(µL/min). Hence, assuming a constant AH flow of 2 µL/min, the pressure differential across the device (ΔP) was estimated to be 2.6 mm Hg. The gravity-flow experiment allowed us to measure the experimental resistance to flow, which was R E = 1.301 mm Hg/(µL/min), in agreement with the theoretical resistance to flow R given by the HP equation. Conclusions The experimental and theoretical flow testing showed that the pressure drop across this device would not be large enough to avoid hypotony unless the resistance to outflow of the sub-Tenon space was sufficient to control the intraocular pressure in the early postoperative period. Translational Relevance The fluid properties of glaucoma subconjunctival drainage devices determine their specific bleb-forming capacity and ability to avoid hypotony and therefore their safety and efficacy profile.