Cellular crosstalk regulates the aqueous humor outflow pathway and provides new targets for glaucoma therapies.

Primary congenital glaucoma (PCG) is a severe disease characterized by developmental defects in the trabecular meshwork (TM) and Schlemm's canal (SC), comprising the conventional aqueous humor outflow pathway of the eye. Recently, heterozygous loss of function variants in TEK and ANGPT1 or compound variants in TEK/SVEP1 were identified in children with PCG. Moreover, common variants in ANGPT1and SVEP1 have been identified as risk alleles for primary open angle glaucoma (POAG) in GWAS studies. Here, we show tissue-specific deletion of Angpt1 or Svep1 from the TM causes PCG in mice with severe defects in the adjacent SC. Single-cell transcriptomic analysis of normal and glaucomatous Angpt1 deficient eyes allowed us to identify distinct TM and SC cell populations and discover additional TM-SC signaling pathways. Furthermore, confirming the importance of angiopoietin signaling in SC, delivery of a recombinant ANGPT1-mimetic promotes developmental SC expansion in healthy and Angpt1 deficient eyes, blunts intraocular pressure (IOP) elevation and RGC loss in a mouse model of PCG and lowers IOP in healthy adult mice. Our data highlight the central role of ANGPT1-TEK signaling and TM-SC crosstalk in IOP homeostasis and provide new candidates for SC-targeted glaucoma therapy.

Effect of oral administration of robenacoxib on inhibition of paracentesis-induced blood-aqueous barrier breakdown in healthy cats.

OBJECTIVE To determine the effect of oral administration of robenacoxib on inhibition of anterior chamber paracentesis (ACP)-induced breakdown of the blood-aqueous barrier (BAB) and assess whether robenacoxib can cross an intact BAB in healthy cats. ANIMALS 12 healthy adult domestic shorthair cats. PROCEDURES Cats received robenacoxib (6-mg tablet in a treat, PO; n = 6) or a control treatment (treat without any drug, PO; 6) once daily for 3 days, beginning 1 day before ACP. One eye of each cat served as an untreated control, whereas the other underwent ACP, during which a 30-gauge needle was used to aspirate 100 µL of aqueous humor for determination of robenacoxib concentration. Both eyes of each cat underwent anterior chamber fluorophotometry at 0 (immediately before), 6, 24, and 48 hours after ACP. Fluorescein concentration and percentage fluorescein increase were used to assess extent of ACP-induced BAB breakdown and compared between cats that did and did not receive robenacoxib. RESULTS Extent of BAB breakdown induced by ACP did not differ significantly between cats that did and did not receive robenacoxib. Low concentrations of robenacoxib were detected in the aqueous humor (mean, 5.32 ng/mL; range, 0.9 to 16 ng/mL) for 5 of the 6 cats that received the drug. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that oral administration of robenacoxib did not significantly decrease extent of BAB breakdown in healthy cats. Detection of low robenacoxib concentrations in the aqueous humor for most treated cats indicated that the drug can cross an intact BAB.

Radiation induced violations of blood circulation in the ciliary body and changes of the anterior chamber angle in the pathogenesis of glaucoma in clean up workers of the Chornobyl NPP accident and residents of contaminated areas. / RADITsIY̆NO INDUKOVANI PORUShENNIa KROVOOBIGU V TsILIARNOMU TILI TA ZMINY KUTA PEREDN'OI KAMERY OKA V PATOGENEZI GLAUKOMY V UChASNYKIV AVARIY̆NYKh ROBIT NA ChORNOBYL'S'KIY̆ AES I MEShKANTsIV ZABRUDNENYKh TERYTORIY̆.

OBJECTIVE: Estimate changes blood filling of the ciliary body and changes of the anterior chamber angle; study their influence to glaucoma pathogenesis in irradiated persons. MATERIALS AND METHODS: Used the results of a randomly selected group survey of 41 clean up workers of the Chornobyl NPP accident (clean up workers), and 18 inhabitants of the zone of guaranteed voluntary resettlement; age at the time of the survey was 45-50 years. The control group consisted of 41 persons of the same age had not radiation exposure. State of the anterior chamber angle studied by gonioscopy, which was conducted 35 clean up workers and 35 persons of the control group. Changes of the blood circulation in the ciliary body examine by the ophtalmoreog raphy, what was done on 12 eyes of 6 clean up workers, control was 12 eyes of 6 persons had not radiation exposure. RESULTS: Detection revealed of the blood circulation in the ciliary body in all clean up workers, reography coefficient was probably lower (p < 0.05), than in the control group. The research of the state of the anterior chamber angle revealed a higher relative risk of appearance of involution changes of the anterior chamber angle in clean up work ers of ChNPP accident, in comparison with the control group was 3.5 (1.27; 9.5) χ2 = 7.48, p = 0.031. The same changes are characteristic for inhabitants of radiation polluted territories. CONCLUSIONS: Influence ionizing radiation causes a blood circulation decrease in the ciliary body and development changes of the angle of the anterior chamber. Presence of these changes can explain the features of the pathogene sis of glaucoma in irradiated late manifestation and, at the same time, severe course.

Platelet activation by ADP is increased in selected patients with anterior ischemic optic neuropathy or retinal vein occlusion.

To investigate whether adenosine diphosphate (ADP)-induced platelet hyperaggregability is associated with nonarteritic anterior ischemic optic neuropathy (NAION) or retinal vein occlusion (RVO). We retrospectively reviewed thrombophilia screening data of patients with NAION or RVO without a history of arterial hypertension, diabetes mellitus, hyperlipidemia, obesity, and cigarette abuse. Patients with a positive family history for thromboembolism were not excluded. Platelet aggregation (area under the curve, AUC) after induction of 0.5, 1.0, and 2.0 µmol of ADP was estimated in 25 NAION and RVO patients and compared with 25 healthy controls. We observed significantly greater platelet aggregation post 0.5 (P = 0.002) and 1.0 (P = 0.008) µmol of ADP among NAION and RVO patients compared with healthy controls. Platelet hyperaggregability was significantly more prevalent in patients than in controls (56% vs. 8%; P = 0.0006). Our results suggest that in NAION and RVO patients without a history of arterial hypertension, diabetes mellitus, hyperlipidemia, obesity, and cigarette abuse, platelets are significantly hyperreactive after induction of very low concentrations of ADP when compared with healthy individuals. This hyperreactivity is particularly evident in patients with a family history of thromboembolism.

Efficacy and safety of intravitreal bevacizumab in eyes with neovascular glaucoma undergoing Ahmed glaucoma valve implantation: 2-year follow-up.

PURPOSE: To evaluate the efficacy and safety of intravitreal bevacizumab (IVB) in eyes with neovascular glaucoma (NVG) undergoing Ahmed glaucoma valve (AGV) implantation. METHODS: This was a multicentre, prospective, randomized clinical trial that enrolled 40 patients with uncontrolled neovascular glaucoma that had undergone panretinal photocoagulation and required glaucoma drainage device implantation. Patients were randomized to receive IVB (1.25 mg) or not during Ahmed valve implant surgery. Injections were administered intra-operatively, and 4 and 8 weeks after surgery. RESULTS: After a mean follow-up of 2.25 ± 0.67 years (range 1.5-3 years), both groups showed a significant decrease in IOP (p < 0.05). There was no difference in IOP between groups except at the 18-month interval, when IOP in IVB group was significantly lower (14.57 ± 1.72 mmHg vs. 18.37 ± 1.06 mmHg - p = 0.0002). There was no difference in survival success rates between groups. At 24 months, there was a trend to patients treated with IVB using less antiglaucoma medications than the control group (p = 0.0648). Complete regression of rubeosis iridis was significantly more frequent in the IVB group (80%) than in the control group (25%) (p = 0.0015). CONCLUSIONS: Intravitreal bevacizumab may lead to regression of new vessels both in the iris and in the anterior chamber angle in patients with neovascular glaucoma undergoing Ahmed glaucoma valve implantation. There is a trend to slightly lower IOPs and number of medications with IVB use during AGV implantation for neovascular glaucoma.

Visualization of the ocular pulse in the anterior chamber of the mouse eye in vivo using phase-sensitive optical coherence tomography.

We report on a phase-based method for accurately measuring the ocular pulse in the anterior chamber in vivo. Using phase-sensitive optical coherence tomography with optimized scanning protocols and equations for compensating bulk motion and environmental vibrations, a high sensitivity of 0.9 µm/s minimal velocity is demonstrated at a wide detection band of 0 to 380 Hz. The pulsatile relative motion between cornea and crystalline lens in rodents is visualized and quantified. The relative motion is most likely caused by respiration (1.6 Hz) and heartbeat (6.6 Hz). The velocity amplitude of the relative motion is 10.3 ± 2.4 µm/s. The displacement amplitudes at the respiratory and cardiac frequencies are 202.5 ± 64.9 and 179.9 ± 49.4 nm, respectively. The potential applications the measurement technique can be found in the evaluation of intraocular pressure and the measurement of biomechanical properties of the ocular tissue, which are important in several ocular diseases.

Sildenafil stimulates aqueous humor turnover in rabbits.

Sildenafil citrate increases ocular blood flow and accelerates the rate of anterior chamber refilling after paracentesis. The latter effect could have resulted from a reduction in outflow facility or from an increase in aqueous humor (AH) production. In this study, we used scanning ocular fluorophotometry to examine the effects of sildenafil on AH turnover, and thus, AH production in eyes of live normal rabbits. For this, the rate of aqueous humor flow (AHF) was quantified with a commercially available fluorophotometer that measured the rate of fluorescein clearance from the anterior segment, which predominantly occurs via the trabecular meshwork. After ≈2 h of control scans to determine the baseline rate of AHF, the rabbits were fed 33 mg of sildenafil and allowed ≈45 min for the drug to enter the systemic circulation. Thereafter, fluorescence scans were retaken for an additional 90-120 min. Sildenafil ingestion increased AHF by about 36%, from 2.31 µL/min to 3.14 µL/min (P < 0.001, as two-tailed paired data, n = 20 eyes). This observation indicates that sildenafil citrate, which is a phosphodiesterase type-5 inhibitor currently marketed as a vasodilator (e.g., Viagra, Revatio), stimulates AHF in rabbits. Our results seem consistent with reports indicating that the drug dilates intraocular arteries and augments intraocular vascular flow. These physiological responses to the agent apparently led to increased fluid entry into the anterior chamber. As such, the drug might have utility in patients with ocular hypotony resulting from insufficient AH formation.

Morphometric analysis of aqueous humor outflow structures with spectral-domain optical coherence tomography.

PURPOSE: To describe morphometric details of the human aqueous humor (AH) outflow microvasculature visualized with 360-degree virtual castings during active AH outflow in cadaver eyes and to compare these structures with corrosion casting studies. METHODS: The conventional AH outflow pathways of donor eyes (n = 7) and eyes in vivo (n = 3) were imaged with spectral-domain optical coherence tomography (SD-OCT) and wide-bandwidth superluminescent diode array during active AH outflow. Digital image contrast was adjusted to isolate AH microvasculature, and images were viewed in a 3D viewer. Additional eyes (n = 3) were perfused with mock AH containing fluorescent tracer microspheres to compare microvasculature patterns. RESULTS: Observations revealed components of the conventional outflow pathway from Schlemm's canal (SC) to the superficial intrascleral venous plexus (ISVP). The superficial ISVP in both our study and corrosion casts were composed of interconnected venules (10-50 µm) forming a hexagonal meshwork. Larger radial arcades (50-100 µm) drained the region nearest SC and converged with larger tortuous vessels (>100 µm). A 360-degree virtual casting closely approximated corrosion casting studies. Tracer studies corroborated our findings. Tracer decorated several larger vessels (50-100 µm) extending posteriorly from the limbus in both raw and contrast-enhanced fluorescence images. Smaller tracer-labeled vessels (30-40 µm) were seen branching between larger vessels and exhibited a similar hexagonal network pattern. CONCLUSIONS: SD-OCT is capable of detailed morphometric analysis of the conventional outflow pathway in vivo or ex vivo with details comparable to corrosion casting techniques.

Noninvasive polarimetric-based glucose monitoring: an in vivo study.

BACKGROUND: Since 1990, there has been significant research devoted toward development of a noninvasive physiological glucose sensor. In this article, we report on the use of optical polarimetry for the noninvasive measurement of physiological glucose concentration in the anterior chamber of the eye of New Zealand white (NZW) rabbits. METHOD: Measurements were acquired using a custom-designed laser-based optical polarimetry system in a total of seven NZW rabbits anesthetized using an isoflurane-only anesthesia protocol. Aqueous humor-based polarimetric measurements were obtained by coupling light through the anterior chamber of the eye. Blood glucose levels were first stabilized and then altered with intravenous dextrose and insulin administration and measured every 3-5 min with a standard glucometer and intermittently with a YSI 2300 glucose analyzer. Acquired polarimetric glucose signals are calibrated to measured blood glucose concentration. RESULTS: Based on a total of 41 data points, Clarke error grid analysis indicated 93% in zone A, 7% in zone B, and 0% in zones C and D, with reference concentrations between 93 and 521 mg/dl. Errors in prediction are shown to be related to gross movement of the rabbit during the procedures, incurring time-varying corneal birefringence effects that directly affect the measured polarimetric signal. These effects can be compensated for with appropriate design modifications. CONCLUSIONS: An optical polarimetry technique was used for in vivo physiological glucose monitoring. The technique demonstrated provides a basis for the development of a noninvasive polarimetric glucose monitor for home, personal, or hospital use.

Relationship between sleep-disordered breathing and iris and/or angle neovascularization in proliferative diabetic retinopathy cases.

PURPOSE: To investigate whether sleep-disordered breathing is a risk factor for iris and/or angle neovascularization in patients with proliferative diabetic retinopathy (PDR). DESIGN: Cross-sectional comparative case series. SUBJECTS AND METHODS: One hundred fifty-one consecutive patients with PDR who underwent surgery in our hospital were divided based on the presence of iris and/or angle neovascularization (NV group, 37 patients) or absence of NV (non-NV group, 114 patients). Pulse oximetry was conducted during the night and the mean SpO(2), 4% oxygen desaturation index (4% ODI times/hour), the lowest SpO(2)% during sleep (lowest SpO(2)), and the cumulative percentage of time at SpO(2) <90% in analysis times (CT90%) were calculated. When the 4% ODI exceeded 5 times/hour, sleep-disordered breathing was diagnosed. The results were compared between the 2 groups. Preoperative systemic parameters also were analyzed by logistic regression to clarify risk factors for the NV group. RESULTS: A mean total of 50% (62% of the NV group and 46% of the non-NV group) was diagnosed with sleep-disordered breathing. The mean SpO(2) and lowest SpO(2) did not differ significantly between the 2 groups; the 4% ODI (12.3 vs 6.6) and CT90% (3.8 vs 1.7) were significantly higher in the NV group (P=.02, for both comparisons). Logistic regression analysis identified insulin therapy (odds ratio [OR], 3.01; 95% confidence interval [CI], 1.26∼7.20; P=.01); and 4% ODI (OR, 1.09; CI, 1.01∼1.16; P=.02) as risk factors for the NV group. CONCLUSIONS: In patients with PDR, nocturnal intermittent hypoxia/reoxygenation resulting from sleep-disordered breathing may be a risk factor for iris and/or angle neovascularization.