Increased Risk of Ocular Hypertension in Patients With Cushing's Disease.

PRCIS: An increased risk of ocular hypertension was seen in Cushing's disease. INTRODUCTION: Systemic steroid use is a significant risk factor for increased intraocular pressure (IOP). The incidence of ocular hypertension may rise to 30%-40% of the general population due to topical or systemic glucocorticoid usage. However, the incidence of ocular hypertension in endogenous hypercortisolemia, as well as the ophthalmological outcomes after endocrine remission due to surgical resection, remain unknown. MATERIALS AND METHODS: The IOP, visual field, and peripapillary retinal nerve fiber layer thickness were documented in all patients with Cushing's disease (CD) admitted to a tertiary pituitary center for surgery from January to July 2019. Patients with acromegaly and patients with nonfunctioning pituitary adenoma (NFPA) during the same study period served as controls. We calculated the odds ratio (OR), identified the risk factors of developing ocular hypertension, and presented postoperative trends of the IOP. RESULTS: A total of 52 patients (38.4±12.4 y old) with CD were included. The IOP was higher in patients with CD (left 19.4±5.4 mm Hg and right 20.0±7.1 mm Hg) than in patients with acromegaly (left 17.5±2.3 mm Hg and right 18.6±7.0 mm Hg, P =0.033) and patients with NFPA (left 17.8±2.6 mm Hg and right 17.4±2.4 mm Hg, P =0.005). A total of 21 eyes (20.2%) in patients with CD were diagnosed with ocular hypertension compared with 4 eyes (4.7%) in the acromegaly group and 4 eyes (4.5%) in the NFPA group. The OR of developing ocular hypertension in patients with CD was 5.1 [95% confidence interval (CI), 1.3-25.1, P =0.029] and 6.6 (95% CI, 1.8-30.3, P =0.007) when compared with the 2 control groups. Among patients with CD, those with a higher urine-free cortisol were more likely to develop ocular hypertension (OR=19.4, 95% CI, 1.7-72.6). The IOP decreased at 1 month after surgery in patients with CD, and the change was sustained for 3 months after surgery. CONCLUSIONS: An increased risk of ocular hypertension was seen in CD and suggests that endogenous hypercortisolemia should be considered as part of the glaucoma assessment. This result warrants the discretion of both ophthalmologists and neuroendocrinologists.

TGF-ß1 Induces Interlukin-11 Expression and Pro-Fibrotic Effect by DNA Demethylation in Subconjunctival Fibroblasts.

Objective: To assess Interlukin-11 (IL11) expression in the tears of patients after filtration surgery and to find out its pro-transdifferentiational and pro-fibrotic functions and mechanisms on subconjunctival human Tenon's capsule fibroblasts (HTFs) induced by transforming growth factor beta1 (TGF-ß1). Methods: Tears were collected from glaucoma patients with or without filtration surgery. The expression of IL11 in tears was examined by enzyme-linked immunosorbent assay. Primary HTFs were prepared as an expansion culture of human Tenon's explants from patients undergoing cataract surgery. TGF-ß1 and IL11 were used to stimulate the cultured HTFs. Quantitative RT-PCR and western blot analyzed the roles of TGF-ß1 in IL11 and DNA methyltransferase (DNMT) expression and the effects of IL11 on collagen-1A1 and α-smooth muscle actin expression. The effects of IL11 on human HTFs' migration were tested via the scratch-wound assay. MassARRAY platform of Sequenom was applied for analyzing the quantitative methylation of the IL11 promoter region. Result: Our data presented significantly high levels of IL11 in the tears of patients who underwent filtration surgery with uncontrolled intraocular pressure (IOP) compared with those who underwent filtration surgery with controlled IOP. The up-regulation of IL11 was related to TGF-ß1. We also found that TGF-ß induced IL11 up-regulation in the HTFs, which activates the HTFs and enhanced the translation of the pro-fibrotic protein expression. This is correlated with inhibiting the activity and expression of DNMTs and demethylating the IL11 promoter. Therefore, IL11 may be an ideal target to be regulated to control the filtering pathway scar formation.

Machine Learning Prediction of Visual Outcome after Surgical Decompression of Sellar Region Tumors.

INTRODUCTION: This study aims to develop a machine learning-based model integrating clinical and ophthalmic features to predict visual outcomes after transsphenoidal resection of sellar region tumors. METHODS: Adult patients with optic chiasm compression by a sellar region tumor were examined to develop a model, and an independent retrospective cohort and a prospective cohort were used to validate our model. Predictors included demographic information, and ophthalmic and laboratory test results. We defined "recovery" as more than 5% for a p-value in mean deviation compared with the general population in the follow-up. Seven machine learning classifiers were employed, and the best-performing algorithm was selected. A decision curve analysis was used to assess the clinical usefulness of our model by estimating net benefit. We developed a nomogram based on essential features ranked by the SHAP score. RESULTS: We included 159 patients (57.2% male), and the mean age was 42.3 years old. Among them, 96 patients were craniopharyngiomas and 63 patients were pituitary adenomas. Larger tumors (3.3 cm vs. 2.8 cm in tumor height) and craniopharyngiomas (73.6%) were associated with a worse prognosis (p < 0.001). Eyes with better outcomes were those with better visual field and thicker ganglion cell layer before operation. The ensemble model yielded the highest AUC of 0.911 [95% CI, 0.885-0.938], and the corresponding accuracy was 84.3%, with 0.863 in sensitivity and 0.820 in specificity. The model yielded AUCs of 0.861 and 0.843 in the two validation cohorts. Our model provided greater net benefit than the competing extremes of intervening in all or no patients in the decision curve analysis. A model explanation using SHAP score demonstrated that visual field, ganglion cell layer, tumor height, total thyroxine, and diagnosis were the most important features in predicting visual outcome. CONCLUSION: SHAP score can be a valuable resource for healthcare professionals in identifying patients with a higher risk of persistent visual deficit. The large-scale and prospective application of the proposed model would strengthen its clinical utility and universal applicability in practice.

Decreased Retinal Vascular Density in Alzheimer's Disease (AD) and Mild Cognitive Impairment (MCI): An Optical Coherence Tomography Angiography (OCTA) Study.

BACKGROUND: To explore the retinal vascular density changes in Alzheimer's disease (AD) and mild cognitive impairment (MCI) patients using optical coherence tomography angiography (OCTA). METHODS: We recruit 62 AD patients, 47 MCI patients, and 49 cognitively healthy controls (HC) in this study. All participants in the study received a comprehensive ophthalmological and neurological evaluation, including global cognitive screening, as well as the Mini-Mental State Examination (MMSE), and completed the following eye examinations: visual acuity (VA), intraocular pressure (IOP), examination with slit-lamp, fundus photography (Version 1.5.0.0, NIDEK CO, LTD) and Optical coherence tomography imaging (software ReVue version 2017.1.0.155, Optovue Inc., Fremont, CA, United States). The visual rating scales for atrophy and white matter lesion in MRI was evaluated for all the patients with AD and MCI. RESULTS: In the AD patient group, the superficial vascular density in the superior, inferior and whole retina was 44.64 ± 3.34, 44.65 ± 3.55, and 44.66 ± 3.36, respectively. These values were 44.24 ± 3.15, 43.72 ± 3.16, and 44 ± 3.07, respectively, in the MCI patient group. After multivariate analysis of the generalized linear model, adjustments for the confounding factors of sex, age, hypertension, diabetes and the quality index of OCTA image, the superficial vascular density in the AD and MCI patient groups was significantly lower than that in the HC group (P < 0.05): 46.94 ± 2.04, 46.67 ± 2.26, and 46.82 ± 2.08, respectively. No difference in the area of the FAZ among the three groups was observed (AD group: 0.34 ± 0.11 mm2; MCI group: 0.36 ± 0.12 mm2; control group: 0.33 ± 0.12 mm2, p > 0.05). The ganglion cell complex (GCC) thickness, inner parafovea thickness, and peripapillary retinal nerve fiber layer (p-RNFL) thickness were associated with the superficial vascular density. We found no significant correlation between the global cognition (MMSE scores) or between the Fazekas score and retinal OCT angiogram flow density. CONCLUSION: The superficial vascular density in the AD and MCI patient groups was significantly lower than that in the HC group. Our findings suggest the retinal microvascular dysfunction occurred in MCI and AD.

Perifovea retinal thickness as an ophthalmic biomarker for mild cognitive impairment and early Alzheimer's disease.

INTRODUCTION: The aim of this study was to investigate retinal thickness as a biomarker for identifying patients with mild cognitive impairment (MCI) and Alzheimer's disease (AD). METHODS: The retinal thickness, utilizing the spectral domain optical coherence tomography, was compared among 73 patients with AD, 51 patients with MCI, 67 cognitive normal control (NC) subjects. RESULTS: The retinal thickness of ganglion cell complex and peripapillary retinal nerve fiber layer decreased in both AD and MCI patients, in comparison with NC subjects (AD vs. NC, P < .01; MCI vs. NC, P < .01). The inner retinal layers in macular area in MCI exhibited significant thinning compared with NC (P < .001). Remarkable association was found between the retinal thickness and brain volume (P < .05). Better correlation was seen between the inner perifovea retinal thickness and the hippocampal and entorhinal cortex volume (r: 0.427-0.644, P < .01). DISCUSSION: The retinal thickness, especially the inner retinal layer thickness, is a potentially early AD marker indicating neurodegeneration.

Endogenous Endophthalmitis Caused by Carbapenem-Resistant Hypervirulent Klebsiella Pneumoniae: A Case Report and Literature Review.

Purpose: To report a rare case of endogenous endophthalmitis caused by carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKP). Methods: A retrospective chart review was conducted. The isolates were characterized by hypermucoviscosity, resistance genes, virulence genes, and multilocus sequence typing. Results: A 47-year-old diabetic woman acquired carbapenem-resistant K. pneumoniae (CRKP) nosocomial pneumonia. Metastatic endophthalmitis occurred in the right eye a week after the occurrence of CRKP bloodstream infection (BSI). Visual acuity decreased to light perception within 3 days. Although vitrectomy relieved ocular pain, endophthalmitis deteriorated due to uncontrollable BSI, and developed to corneal perforation. The strains isolated from bronchoalveolar lavage fluid, blood, and intraocular pus originated from the same clone. The pathogen was hypermucoviscous, belonged to sequence type 11, harbored resistance genes blaKPC-2, blaTEM, blaSHV, rmtB, and virulence genes rmpA2, iucABCD, iroBCD. Conclusions: Endogenous endophthalmitis caused by CR-hvKP has emerged, which is a treatment challenge for both ophthalmologists and physicians.

Outflow facility efficacy of five drugs in enucleated porcine eyes by a method of constant-pressure perfusion.

This study aimed to characterize a technique that assesses the outflow facility (C) efficacy of five kinds of IOP-lowering drugs commonly used clinically in enucleated porcine Eyes. Eyes were perfused at 15 mmHg with GPBS first to establish the baseline outflow facility (C0). Then the anterior chamber contents were exchanged for GPBS with corresponding concentration eye drops (4.9×10(3) nM Brimonidine, 41.1 nM Latanoprost, 3.4×10(3) nM Levobunolol, 3.0×10(3) nM Brinzolamide, 8.3×10(3) nM Pilocarpine) in five groups (n = 6 each), while 6 eyes received GPBS alone as control. The mean stable facility obtained after drug administration (C1) was continuously recorded. The changes between C0 and C1 (ΔC = C1-C0) were analyzed. Finally, for drugs among the five experiment groups with statistical significance, the concentration was reduced 3 times, otherwise the drugs' concentration was increased to 10 times to confirm its effectiveness further using the same methods (n = 6 each). We found that the average baseline outflow facility was 0.24±0.01 µl·min(-1)·mmHg(-1). C increased significantly in Brimonidine and Latanoprost groups, even the concentration of Brimonidine and Latanoprost was decreased 3 times (P < 0.05). However, there was no significantly increase in Levobunolol, Brinzolamide, Pilocarpine and control group (P > 0.05), but when drugs' concentration was increased to 10 times, the C value of Pilocarpine decreased significantly (P = 0.04). No significant washout effects in porcine eyes were observed. To conclude, outflow facility efficacy of five drugs in enucleated porcine eyes may provide a reference for clinical medicine. A constant-pressure perfusion technique should be useful to evaluate effect of pharmacologic agents or surgical manipulations on aqueous humor dynamics.

Angiotensin II as a morphogenic cytokine stimulating fibrogenesis of human tenon's capsule fibroblasts.

PURPOSE: To examine the expression of Angiotensin II (Ang II) and its type I, and type II receptors (AT1R, AT2R) in rabbit Tenon's capsule fibroblasts after trabeculectomy, and to investigate the effects of Ang II on cultured human Tenon's capsule fibroblasts (HTFs) proliferation, migration, phenotype transition, and extracellular matrix (ECM) synthesis. METHODS: In the rabbit, expression of Ang II, AT1R, and AT2R in Tenon's capsule fibroblasts of eyes after trabeculectomy was evaluated by immunohistochemistry. Ang II levels in aqueous humor and plasma were assessed by ELISA. Cultured HTFs, obtained from patients undergoing cataract surgery, were treated with Ang II, TGF-ß1, or vehicle control. Cell proliferation and migration were evaluated by Cell Counting Kit-8 and Transwell assay, and wound scratch assay, respectively. Protein expressions of α-smooth muscle actin (α-SMA) and fibronectin (FN) were measured by Western blot and immunofluorescence. Messenger RNA expressions of α-SMA and FN were measured by real-time PCR. RESULTS: In the rabbit, the expression of Ang II and AT1R increased from 1 day after surgery while AT2R increased from 7 days. In cultured HTFs, Ang II promoted cell proliferation and migration significantly (P < 0.05). Interestingly, the effect of 10(-7) M Ang II was more prominent than higher concentrations (10(-5) M; P < 0.05). Ang II also markedly induced the expression of α-SMA and FN, suggesting a phenotypic transition to myofibroblasts. CONCLUSIONS: Our results show that trabeculectomy alter the levels of Ang II and its receptors in Tenon's capsule fibroblasts, and that Ang II increase HTFs proliferation, migration, and phenotype transition, suggesting that Ang II may play a role in wound healing after trabeculectomy.

Moisture chamber versus lubrication for corneal protection in critically ill patients: a meta-analysis.

PURPOSE: Critically ill patients in the intensive care unit are at increased risk of exposure keratopathy. There is limited evidence available to make the best choice of eye care modality. This meta-analysis aimed to evaluate the effect of moisture chamber compared with lubrication for corneal protection in critically ill patients. METHODS: Studies were identified through PubMed, Embase, The Cochrane Library, and complementary manual searches, up to May 31, 2014. Randomized controlled trials of critically ill patients in the intensive care unit comparing moisture chamber with lubrication and evaluating risk of corneal damage were included. RESULTS: Seven trials were included. The pooled analysis showed that the use of moisture chambers resulted in a reduction of the incidence of corneal damage [risk ratio (RR), 0.27; 95% confidence interval (CI): 0.11-0.67; P = 0.005]. In 1 subgroup analysis, there was a significant difference between the use of moisture chambers and lubricating drops, and the moisture chamber group had a decreased incidence of corneal damage (RR, 0.13; 95% CI: 0.05-0.35; P < 0.0001). In the other subgroup analysis, no statistically significant difference was observed between the use of moisture chambers and lubricating ointments (RR, 0.81; 95% CI: 0.51-1.29; P = 0.38). The overall quality of evidence was low. CONCLUSIONS: The use of moisture chambers is associated with more effective corneal protection compared with lubrication. The analytic result is limited by serious risk of bias and imprecision.

Effects of Y27632 on aqueous humor outflow facility with changes in hydrodynamic pattern and morphology in human eyes.

PURPOSE: To determine the effect of Y27632, a Rho-kinase inhibitor on aqueous outflow facility, flow pattern, and juxtacanalicular tissue (JCT)/trabecular meshwork (TM) morphology in human eyes. METHODS: Sixteen enucleated human eyes were perfused with PBS plus glucose (GPBS) at 15 mm Hg to establish the baseline outflow facility. Six eyes were perfused for short-duration (30 minute) with either 50 µM Y27632 or GPBS (n = 3 per group). Ten eyes were perfused for long duration (3 hours) with either 50 µM Y27632 or GPBS (n = 5 per group). Outflow pattern was labeled using fluorescent microspheres, and effective filtration length (EFL) was measured. Morphologic changes and their relationship to EFL and facility were analyzed. RESULTS: Outflow facility significantly increased after short-duration perfusion with Y27632 compared with its own baseline (P = 0.03), but did not reach statistical significance compared with its controls (P = 0.07). Outflow facility (P = 0.01) and EFL (P < 0.05) were significantly increased after long-duration perfusion with Y27632 compared with its controls. Increases in outflow facility and EFL demonstrated a positive correlation. Morphologically, the TM and JCT of high-tracer regions were more expanded compared with low-tracer regions. A significant increase in JCT thickness was found in the long-duration Y27632 group compared with its control group (10.0 vs. 8.0 µm, P < 0.01). CONCLUSIONS: Y27632 increases outflow facility in human eyes. This increase correlates positively with an increase in EFL, which is associated with an increased expansion in the JCT. Our data suggest that EFL could serve as a novel parameter to correlate with outflow facility.

Clinical and pathological features of acute optic neuritis in Chinese patients.

BACKGROUND: The incentives and the factors that affect the onset and outcome of optic neuritis (ON) are not very clear. The aim of this study is to define and get a comprehensive understanding of the clinical profile of ON, and to identify the factors that were related to the prognosis of the patients. METHODS: Medical records of patients with diagnosis of ON at Huashan Hospital, Fudan University between March 2008 and June 2011 were reviewed. Clinical features, ophthalmologic and neurologic assessments, neuroimaging studies, laboratory examinations, visual recovery, and final outcome of the patients were evaluated by the authors. RESULTS: Records of 50 patients (32 females and 18 males), aged 15 - 56 years, were reviewed, in which 22% patients had a previous onset of ON. Maximal visual deficit was severe in 72.5% (< 20/200). Abnormal rates of hormone levels and rheumatoid indicators were found in 54.2% and 25.0%. ANA test returned positive in 40%, oligoclonal banding (OCB) was identified in 31.3%, and Serum neuromyelitis optica (NMO)-IgG studies were abnormal in 25% of the patients. Neuroimaging abnormalities associated with ON were documented in six patients. Three of the 50 patients have been diagnosed with multiple sclerosis, and two with NMO. Visual acuity was 20/20 or better in 26.1% and 20/100 or worse in 39.1% affected eyes at the last visit. Poor visual acuity at onset is the main factor that would affect the final outcome of vision (P < 0.05). CONCLUSIONS: Vision defects of this group of patients were severe. Females had a higher incidence of ON than males. Hormone levels, rheumatoid indicators and immune parameters may be related to the onset of ON. The severe reduction of visual acuity at onset may be related to the poor outcome of vision in ON patients.

Similar hydrodynamic and morphological changes in the aqueous humor outflow pathway after washout and Y27632 treatment in monkey eyes.

Our previous studies in bovine eyes demonstrated that the structural correlate to the increase in outflow facility after either Rho-kinase inhibitor Y-27632 (Y27) treatment or washout appeared to be separation between the juxtacanalicular tissue (JCT) and inner wall (IW) of the aqueous plexus, the bovine equivalent of Schlemm's canal (SC). While these findings suggest that Y27 and washout may increase outflow facility through a similar mechanism, the anatomy of bovine outflow pathway differs considerably from both the human and monkey outflow pathway; however, only the human eye does not exhibit washout. In light of this, we compared the effects of Y27 and washout on outflow facility, hydrodynamic patterns of outflow, and the morphology of the IW and JCT in monkey eyes, given that their anatomy is closer to human eyes. Twelve freshly enucleated monkey eyes were used in this study. Eyes were perfused with Dulbecco's PBS containing 5.5 mM glucose (GPBS) to establish a baseline facility at 15 mmHg. Four eyes were perfused for a short-duration (30 min) as a control, 4 eyes for a long-duration (180 min) to induce washout, and 4 eyes with GPBS+50 µM Y27 for 30 min. All eyes were then perfused with fluorescent microspheres (0.5 µm; 0.002%) to label the hydrodynamic patterns of outflow and then perfusion-fixed. Confocal images of frontal sections were taken along the IW of SC. The total length (TL) and the tracer-decorated length (FL) of the IW were measured to calculate the average percent effective filtration length (PEFL = FL/TL). Sections with SC were examined by light and electron microscopy. The TL of the IW and the length exhibiting separation (SL) in the JCT were measured to calculate the average percent separation length (PSL = SL/TL). Outflow facility increased 149.2% (p < 0.01) from baseline after washout during long-duration perfusion, and 114.9% (p = 0.004) after Y27 treatment, but did not change significantly after short-duration perfusion in control eyes (p = 0.46). Distribution of the tracer labeling appeared punctate along the IW of control eyes, while a more uniform pattern was observed after washout and Y27 treatment. PEFL in washout (83.4 ± 2.1%) and Y27 treated eyes (82.5 ± 1.6%) was 3.4-fold larger compared to controls (24.2 ± 4.2%, P < 0.001). The JCT appeared distended with loss of connections between JCT cells and between JCT cells and their extracelluar matrix in eyes with washout or after Y-27 treatment. PSL in the JCT was 2.3-fold larger in washout eyes (77.4 ± 3.3%) and 2.2-fold larger in Y27 treated eyes (75.2 ± 5.3%) versus controls (33.5 ± 5.3%, p = 0.001). Significant positive correlations were found between outflow facility and PEFL, facility and PSL and between PEFL and PSL. Our data demonstrated that similar hydrodynamic and morphological changes occurred in the aqueous humor outflow pathway of monkey eyes after induction of washout and Y27 treatment. Both Y27 and washout increase outflow facility by redistributing aqueous outflow through a larger area in the JCT. These hydrodynamic changes are likely driven by morphologic changes associated with a decrease in cell-cell and cell-matrix connections in the JCT.

Relationships between increased aqueous outflow facility during washout with the changes in hydrodynamic pattern and morphology in bovine aqueous outflow pathways.

Previous studies suggest that the structural correlate for the increased outflow facility (C) during washout in the bovine eye is separation between the inner wall (IW) and underlying juxtacanalicular connective tissue (JCT). However, how these structural changes affect hydrodynamic patterns of outflow during washout has not been studied. We hypothesize that an increase in the outflow facility during washout is associated with an increase in the effective filtration area (EFA) of aqueous outflow, which is regulated by a loss of the connectivity between the IW and JCT. To test this hypothesis, the relationship between C and the hydrodynamic patterns of outflow as well as the morphological changes in JCT and IW during the washout were investigated. Ten bovine eyes were perfused at 15 mmHg with Dulbecco's PBS + 5.5 mM glucose (DPBS) for 30 min to establish stable baseline C. After measuring baseline C, five eyes (short-duration group) were perfused with 0.5 mL DPBS containing 0.002% microspheres (0.5 microm) to trace the hydrodynamic pattern of outflow. Five other eyes (long-duration group) were perfused for 3 h to elicit a significant washout effect followed by subsequent perfusion of the same volume (0.5 mL) of microspheres to map out the outflow pattern after washout. All eyes were then perfusion-fixed. Anterior segments were sectioned and prepared for confocal and light microscopy. Total length (TL) and filtration length (FL) of the IW were measured in > or =15 images/eye to calculate percent effective filtration length (PEFL = FL/TL) while TL and length exhibiting JCT/IW separation (SL) were measured in > or =13 images/eye to calculate percent separation length (PSL = SL/TL). In long-duration eyes, C increased 170.5 +/- 21.3% (mean +/- SEM, 1.55 +/- 0.24 vs 4.13 +/- 0.55 microl/min/mmHg, p = 0.001) above baseline. Pre-fixation C (4.13 +/- 0.55 microl/min/mmHg) in long-duration was 1.6-fold greater than that (2.14 +/- 0.61 microl/min/mmHg; p = 0.042) in short-duration. A more uniform tracer labeling was observed in the JCT/IW of long-duration eyes compared to short-duration. PEFL was 2.3-fold larger (52.82 +/- 6.06 vs. 22.2 +/- 6.0%; p = 0.007) and PSL was 2.6-fold larger (54.2 +/- 6.0 vs. 20.5 +/- 1.3%; p = 0.004) in long-duration eyes compared to short-duration. Data from all eyes revealed a positive correlation between PEFL and PSL (p = 0.02). Both PEFL and PSL demonstrated significant positive correlations with the relative increase in C due to washout (p < or = 0.05). An additional experiment was performed in which unequal volumes of tracer (0.5 and 1.0 mL) were perfused in paired eyes for both short- and long-duration (N = 2 for each condition) to examine the affect on PEFL. No significant change in PEFL was found in eyes perfused with 0.5 and 1.0 mL within the same group. These data support our hypothesis that separations between the IW and JCT result in an increase in the EFA that then influences C. Altogether, these data suggest that outflow hydrodynamics and the tissue structure work together to regulate outflow resistance.

Reduction of the available area for aqueous humor outflow and increase in meshwork herniations into collector channels following acute IOP elevation in bovine eyes.

PURPOSE: To understand how hydrodynamic and morphologic changes in the aqueous humor outflow pathway contribute to decreased aqueous humor outflow facility after acute elevation of intraocular pressure (IOP) in bovine eyes. METHODS: Enucleated bovine eyes were perfused at 1 of 4 different pressures (7, 15, 30, 45 mm Hg) while outflow facility was continuously recorded. Dulbecco PBS + 5.5 mM glucose containing fluorescent microspheres (0.5 mum, 0.002% vol/vol) was perfused to outline aqueous outflow patterns, followed by perfusion-fixation. Confocal images were taken along the inner wall (IW) of the aqueous plexus (AP) in radial and frontal sections. Percentage effective filtration length (PEFL; IW length exhibiting tracer labeling/total length of IW) was measured. Herniations of IW into collector channel (CC) ostia were examined and graded for each eye by light microscopy. RESULTS: Increasing IOP from 7 to 45 mm Hg coincided with a twofold decrease in outflow facility (P < 0.0001), a 33% to 57% decrease in PEFL with tracer confined more to the vicinity of CC ostia, progressive collapse of the AP, and increasing percentage of CC ostia exhibiting herniations (from 15.6% +/- 6.5% at 7 mm Hg to 95% +/- 2.3% at 30 mm Hg [P < 10(-4)], reaching 100% at 45 mm Hg). CONCLUSIONS: Decreasing outflow facility during acute IOP elevation coincides with a reduction in available area for aqueous humor outflow and the confinement of outflow to the vicinity of CC ostia. These hydrodynamic changes are likely driven by morphologic changes associated with AP collapse and herniation of IW of AP into CC ostia.

The mechanism of increasing outflow facility by rho-kinase inhibition with Y-27632 in bovine eyes.

Rho-kinase inhibitor Y-27632 (Y-27) affects actomyosin cytoskeletal networks and has been shown to significantly increase outflow facility (C) in enucleated porcine and rabbit eyes, as well as in vivo monkey eyes without obvious toxicity. The mechanisms underlying these responses remain largely unknown. In this study, we investigate how Y-27 affects aqueous humor C, the hydrodynamic patterns of outflow, and the morphology of the inner wall (IW) and juxtacanalicular connective tissue (JCT). 12 bovine eyes were perfused at 15 mmHg with Dulbecco's PBS containing 5.5 mM glucose (DPBS) to establish stable baseline C. The anterior chamber was exchanged and perfused with DPBS containing 50 microM Y-27 in 7 eyes, while 5 eyes received DPBS alone. Eyes were then perfused with DPBS containing fluorescent microspheres (0.5 microm; 0.002% v/v) at a fixed volume to deliver equivalent amounts of tracer to label the hydrodynamic filtration patterns. All eyes were perfusion-fixed with Karnovsky's fixative. Radial and frontal sections were prepared in all quadrants and confocal images were taken along the IW of the aqueous plexus (AP). The total length (TL) and filtration length (FL) of the IW were measured in > or =16 images/eye, and the average percent effective filtration length (PEFL=FL/TL) was calculated. Sections with AP were processed and examined by light and electron microscopy. The TL of the IW and length exhibiting JCT/IW separation (SL) were measured in > or =16 micrographs/eye, and the average percent separation length (PSL=SL/TL) was also calculated. After Y-27 treatment, C increased from 1.54+/-0.34 (+/-SEM) to 2.36+/-0.54 microL/min per mmHg (58.2+/-18.9%) while control eyes changed from 1.67+/-0.41 to 1.71+/-0.39 microl/min per mmHg (6.0+/-9.3%) and the percent changes between the Y-27-treated and control eyes were significant (p=0.03). Control eyes showed segmental distribution of tracer in the trabecular meshwork tending to cluster near collector channel ostia, whereas Y-27-treated eyes showed a more uniform pattern and extensive labeling along the IW. In Y-27-treated eyes, PEFL was 3-fold larger (57.6+/-3.7%) compared to control eyes (18.2+/-4.5%; p<0.001). Light microscopic examination revealed that, with Y-27, the IW and JCT were significantly distended compared to control eyes, with discernible separation between the IW and JCT. PSL was 2.8-fold larger in Y-27-treated eyes (59.3+/-3.6%) than in controls (20.8+/-2.0%; p<0.001). A significant positive correlation was found between PEFL and PSL (p=0.003) suggesting that as connectivity between the JCT and IW decreases the available area for aqueous humor drainage increases along the AP. Our study also demonstrates a significant positive correlation between C and the PSL (p=0.01), a finding identical to what we reported to occur during the "washout" effect in bovine eyes. Our data suggests the structural correlate to the increase in C and PEFL after Y-27-treatment is physical separation between the JCT and IW. The increase in C after Y-27-treatment may share a similar mechanism comparable with the washout effect that occurs in bovine eyes. Overall, these findings support our hypothesis that JCT/IW connectivity influences local outflow hydrodynamics that regulate C, and suggest that strategies targeting JCT/IW connectivity are promising anti-glaucoma therapies to reduce IOP.