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.

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.

Précis: The Preserflo Microshunt (PSM) is a safe and effective glaucoma microfiltering implant that significantly reduces the intraocular pressure (IOP), either alone or in combination with phacoemulsification, during the first year after surgery. Purpose:The purpose of this study was to assess the safety and efficacy of the PSM for the treatment of open angle glaucoma with 0.2 mg/mL mitomycin C, either alone or in combination with cataract surgery. Methods:A retrospective, open-label study of 64 eyes with primary open angle glaucoma that underwent PSM implantation and were followed up for at least 9 months. Success was defined as IOP 6-17 mm Hg and a reduction of at least 20%, complete without hypotensive medication, and qualified with medication. Safety was assessed by the incidence of adverse events. Secondary endpoints included mean hypotensive medications, visual acuity, and incidence of needling and surgical revision.Results: A total of 51 eyes underwent PSM alone and 13 underwent PSM+phacoemulsification. In the overall population of the study, the mean IOP was significantly reduced from 22.03 ± 0.7 mm Hg at baseline to 12.7 ± 0.4 mm Hg at the final visit, P < 0.0001 (mean follow-up: 11 ± 1.4 mo). The IOP was significantly reduced in both groups (P < 0.0001). Ocular hypotensive medication was reduced significantly from 2.7 ± 0.7 to 0.2 ± 0.5 (P < 0.0001). No significant differences were found in IOP-lowering medication between groups (PSM alone, 0.2 ± 0.08; PSM+phacoemulsification, 0.1 ± 0.1; P = 0.2). At the final visit, 70.3% were considered as complete success and 12.5% as qualified success. The most common adverse event was clinical hypotony (7.8%) followed by hyphema (4.7%), and anterior chamber reformation (1.6%). Overall, 1.6% required needling and 15.6% surgical revision to restore the flow. Conclusion:Glaucoma surgery with the PSM and mitomycin C was efficacious and safe in the short term, either alone or in combination with cataract surgery, and may be considered a surgical option for lowering IOP in primary open angle glaucoma.

Precis: Glaucoma surgery with PRESERFLO Microshunt shows mild and transient changes in the corneal astigmatism, corneal elevation and biometrics in the early postoperative period. Posterior corneal elevation (PCE) tends to be higher in primary open angle glaucoma (POAG). Purpose:The aim was to determine the changes in the corneal keratometry, astigmatism and elevation, refraction, axial length (AL) and anterior chamber depth and volume after the implantation of the PRESERFLO Microshunt in patients with POAG in the early postoperative period.Patients and Methods: Patients diagnosed with POAG who underwent an ab externo (polystyrene-block-isobutylene-block-styrene) microshunt implantation were recruited. The central corneal thickness, the intraocular pressure (IOP), best-corrected visual acuity, refraction, biometrics, and corneal topography with a Scheimpflug topographer were analyzed preoperatively and 24 hours, 1 week, 1 month, and 3 months after surgery.Results: A total of 30 eyes of 29 patients were included. In 24 eyes the device was implanted as a stand-alone procedure and in 6 eyes it was combined with cataract surgery. The results were analyzed separately. The IOP decreased from 21.8 ± 5.2 and 16.5 ± 1.5 mm Hg at baseline to 10.9 ± 1.8 and 10.1 ± 1.1 mm Hg at 3 months in the noncombined and combined groups (P < 0.01). The anterior surface astigmatism, posterior surface astigmatism, and total corneal astigmatism increased in each group 0.4 ± 0.3/0.2 ± 1.0 D, 0.08 ± 0.1/ 0.03 ± 0.1 D and 0.4 ± 0.3/0.2 ± 0.9 D, respectively, at 3 months. The anterior corneal elevation and PCE (ACE max, ACE min, PCE max) increased in the first week (P = 0.01) with no significant changes at 3 months in the noncombined group. The changes observed in the combined group were not significant. The AL decreased to 0.13 ± 0.23 and 0.2 ± 0.07 mm in each group (P = 0.01). There was a significant correlation between the IOP and the maximum elevation of the posterior surface of the cornea at the preoperative examination (r = 0.93, P = 0.02). Conclusions:The PRESERFLO Microshunt implant for glaucoma surgery induces mild and transient changes in corneal astigmatism, AL and anterior chamber depth in the early postoperative period.

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 ( P) 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.