Consensus recommendations for trabecular meshwork cell isolation, characterization and culture.

Cultured trabecular meshwork (TM) cells are a valuable model system to study the cellular mechanisms involved in the regulation of conventional outflow resistance and thus intraocular pressure; and their dysfunction resulting in ocular hypertension. In this review, we describe the standard procedures used for the isolation of TM cells from several animal species including humans, and the methods used to validate their identity. Having a set of standard practices for TM cells will increase the scientific rigor when used as a model, and enable other researchers to replicate and build upon previous findings.

Effects of a Schlemm canal scaffold on collector channel ostia in human anterior segments.

This study evaluates the morphologic effect of the implantation of two different sizes of the Hydrus microstent on the outer wall of Schlemm's canal (SC) and collector channel (CC) ostia. Twelve human eyes were dissected at the equator removing the iris, lens, ciliary body and vitreous. The cornea was excised with a corneal trephine exposing a direct view of the angle while leaving the trabecular meshwork (TM) intact. The Hydrus delivery system was used to deliver microstents of 8 mm and 15 mm in length into SC. Following delivery, the tissues were immediately immersed in fixative. After tissue fixation, the microstents were gently lifted out of SC through the TM leaving a small slit opening in the TM. The slit opening was widened by gently dissecting the entire TM. Control eyes underwent dissection before fixation by gently removing the TM exposing the outer wall of SC. The tissues were prepared for scanning electron microscopy (SEM). The external wall of SC was imaged using SEM and were reviewed with particular attention focused on the distribution of irregular particulate matter (IPM), the shape of the CC ostia and the health of the SC endothelium. Three eyes received the 8 mm microstent, two the 15 mm microstent and 6 eyes served as controls. Five of the controls had reported histories of glaucoma while all other eyes were normal. All eyes showed evidence of removal of the trabecular meshwork revealing the external wall of SC. CCs were regularly visible in all eyes and were not obstructed, compressed or their margins disrupted. Nuclear profiles were oriented circumferentially in SC except at regions of CC ostia where they assumed a radial configuration oriented toward the lumen of the CC. The area of microstent contact with SC external wall was examined with SEM and a comparison made between the 8 and 15 mm microstent showing a smaller area of indentation with the 8 mm microstent. The indentations were generally free of particulate debris, were smooth and were devoid of nuclear profiles. In bridged areas adjacent to areas of microstent contact, CCs were identified, appearing patent and intact like those of the control eyes. The eyes receiving 8 mm and 15 mm Hydrus microstents both maintained CC ostia patency but a smaller area of external wall contact was evident from insertion of the 8 mm microstent.

Retrospective review of eyelash number in patients who have undergone full-thickness eyelid resection.

PURPOSE: The purpose of this study was to determine whether a localized full-thickness eyelid excision results in a proportional decrease in the total number of eyelashes or whether a full complement of visible lashes persists, thus suggesting a compensatory increase in the anagen/telogen ratio among the remaining follicles. METHODS: A retrospective chart review was performed on 38 patients who underwent full-thickness eyelid resections repaired with primary eyelid closure for either benign or malignant eyelid lesions. Demographic and surgical data were collected, postoperative eyelid photographs were reviewed, and eyelashes were counted. RESULTS: There were 10 upper eyelids and 28 lower eyelids in 10 men and 28 women, with an average age of 57.9 years (range, 14-86 years). The lesion pathology was benign in 21 cases (55%) and malignant in 17 cases (45%). The full-thickness defect involved <25% of the eyelid in 16 cases (42%) and >25% of the eyelid in 22 cases (58%). The follow-up period ranged from 50 to 319 days, with an average of 94 days. In contralateral controls, upper eyelids had an average of 72.1 lashes and lower eyelids had an average of 38.2 lashes, and there was no statistical significance between men and women. In lower lids that underwent <25% resection, control lids had an average of 37.3 lashes and operative lids had 37.1 lashes. In lower lids that underwent >25% resection, control lids had an average of 38.7 lashes and operative lids had 34.2 lashes. This represents an 11.6% decrease and was statistically significant. In upper eyelids that underwent <25% resection and >25% resection, control eyelids had an average of 74.9 lashes and 69.3 lashes and operative eyelids had 77.6 lashes and 69.1 lashes, respectively. Finally, lash count was compared by benign versus malignant pathologic diagnosis. In upper eyelids with benign lesions and malignant lesions, control eyelids had an average of 73.8 lashes and 65.3 lashes and operative eyelids had 74.6 lashes and 68.3 lashes, respectively. In lower eyelids with benign pathology and malignant lesions, control eyelids had an average of 34.5 lashes and 41.4 lashes and operative eyelids had 33.8 lashes and 36.8 lashes. This represents an 11.1% decrease and was statistically significant. CONCLUSIONS: Full-thickness excision of eyelid margin tissue including lashes does not usually affect postoperative lash numbers. Because the total number of follicles is reduced, the percentage of lashes in the anagen versus the resting or telogen phase apparently increases compared with the preoperative state. This eyelash study contributes to the growing body of literature on the poorly understood topic of hair follicle cycle regulation.

iStent insertion orientation and impact on trabecular meshwork motion resolved by optical coherence tomography imaging.

Significance: The iStent is a popular device designed for glaucoma treatment, functioning by creating an artificial fluid pathway in the trabecular meshwork (TM) to drain aqueous humor. The assessment of iStent implantation surgery is clinically important. However, current tools offer limited information. Aim: We aim to develop innovative assessment strategies for iStent implantation using optical coherence tomography (OCT) to evaluate the position and orientation of the iStent and its biomechanical impact on outflow system dynamics. Approach: We examined four iStents in the two eyes of a glaucoma patient. Three-dimensional (3D) OCT structural imaging was conducted for each iStent, and a semi-automated algorithm was developed for iStent segmentation and visualization, allowing precise measurement of position and orientation. In addition, phase-sensitive OCT (PhS-OCT) imaging was introduced to measure the biomechanical impact of the iStent on the outflow system quantified by cumulative displacement (CDisp) of pulse-dependent trabecular TM motion. Results: The 3D structural image processed by our algorithm definitively resolved the position and orientation of the iStent in the anterior segment, revealing substantial variations in relevant parameters. PhS-OCT imaging demonstrated significantly higher CDisp in the regions between two iStents compared to locations distant from the iStents in both OD ( p = 0.0075 ) and OS ( p = 0.0437 ). Conclusions: Our proposed structural imaging technique improved the characterization of the iStent's placement. The imaging results revealed inherent challenges in achieving precise control of iStent insertion. Furthermore, PhS-OCT imaging unveiled potential biomechanical alterations induced by the iStent. This unique methodology shows potential as a valuable clinical tool for evaluating iStent implantation.

A Novel Technique Identifies Valve-Like Pathways Entering and Exiting Schlemm's Canal in Macaca nemestrina Primates With Similarities to Human Pathways.

Purpose: The aim of the study was 1) to describe a novel combination of techniques that permit immunohistochemistry imaging of Schlemm's canal inlet (SIV) and outlet (SOV) valve-like structures, 2) to identify tissue-level SIV adhesive relationships linking the trabecular meshwork (TM) to hinged collagen leaflets at the Schlemm's canal (SC) external wall, and 3) to determine whether the SIV lumen wall's adhesive vascular markers are similar to those of the SC inner wall endothelium. Materials and Methods: Anterior segments of 16 M. nemestrina primates underwent immunohistochemistry (IHC) labeling. We perfused fluorescent microspheres into 12 of the eyes. Limbal tissues were divided into quadrants, viscoelastic introduced into SC, tissues fixed, immunohistochemistry performed, radial segments cut, tissues clarified, and confocal microscopy performed. Finally, we generated ImageJ 3D projections encompassing the TM, SC, and distal pathways. Results: IHC imaging identified 3D relationships between SIV, collector channel ostia, collector channels (CC), SOV, and intrascleral channels. Imaging depth increased 176.9%, following clarification (p < 0.0001). Imaging demonstrated CD31, collagen type 1 and 4 in the walls of the SIV lumen and more distal pathways. In eight eyes, 384 segments were examined, 447 SIV identified, and 15.4% contained microspheres. Conclusion: Our technique's imaging depth permitted the identification of SIV linkage between the TM and SOV. We found comparable cell-cell adhesion molecules (CD31) and basement membrane components in the SC inner wall and SIV lumen walls. Recent OCT studies have suggested that SIV tensional relationships may control CC entrance dimensions that regulate distal resistance. Cellular adhesive properties sustain SIV tensional relationships. These SIV cell-cell and cell-basement membrane properties warrant further study because abnormalities could be a factor in the IOP elevation of glaucoma.

A novel suprachoroidal microinvasive glaucoma implant: in vivo biocompatibility and biointegration.

BACKGROUND: A major challenge for any glaucoma implant is their ability to provide long-term intraocular pressure lowering efficacy. The formation of a low-permeability fibrous capsule around the device often leads to obstructed drainage channels, which may impair the drainage function of devices. These foreign body-related limitations point to the need to develop biologically inert biomaterials to improve performance in reaching long-term intraocular pressure reduction. The aim of this study was to evaluate in vivo (in rabbits) the ocular biocompatibility and tissue integration of a novel suprachoroidal microinvasive glaucoma implant, MINIject™ (iSTAR Medical, Wavre, Belgium). RESULTS: In two rabbit studies, no biocompatibility issue was induced by the suprachoroidal, ab-externo implantation of the MINIject™ device. Clinical evaluation throughout the 6 post-operative months between the sham and test groups were similar, suggesting most reactions were related to the ab-externo surgical technique used for rabbits, rather than the implant material itself. Histological analysis of ocular tissues at post-operative months 1, 3 and 6 revealed that the implant was well-tolerated and induced only minimal fibroplasia and thus minimal encapsulation around the implant. The microporous structure of the device became rapidly colonized by cells, mostly by macrophages through cell migration, which do not, by their nature, impede the flow of aqueous humor through the device. Time-course analysis showed that once established, pore colonization was stable over time. No fibrosis nor dense connective tissue development were observed within any implant at any time point. The presence of pore colonization may be the process by which encapsulation around the implant is minimized, thus preserving the permeability of the surrounding tissues. No degradation nor structural changes of the implant occurred during the course of both studies. CONCLUSIONS: The novel MINIject™ microinvasive glaucoma implant was well-tolerated in ocular tissues of rabbits, with observance of biointegration, and no biocompatibility issues. Minimal fibrous encapsulation and stable cellular pore colonization provided evidence of preserved drainage properties over time, suggesting that the implant may produce a long-term ability to enhance aqueous outflow.

Reduced Pulsatile Trabecular Meshwork Motion in Eyes With Primary Open Angle Glaucoma Using Phase-Sensitive Optical Coherence Tomography.

Purpose: The purpose of this study was to investigate the difference in pulsatile trabecular meshwork (TM) motion between normal and eyes with POAG using phase-sensitive optical coherence tomography (PhS-OCT). Methods: In this cross-sectional study, eight healthy subjects (16 eyes) and nine patients with POAG (18 eyes) were enrolled. A laboratory-based prototype PhS-OCT system was used to measure pulsatile TM motion. PhS-OCT images were analyzed to obtain parameters of pulsatile TM motion (i.e. maximum velocity [MV] and cumulative displacement [CDisp]). Outflow facility and ocular pulse amplitude were measured using pneumotonography. Detection sensitivity was compared among various parameters by calculating the area under the receiver operating characteristic curves (AUCs). Results: A pulsatile TM motion waveform synchronous with digital pulse was observed using PhS-OCT in both healthy and POAG eyes. The mean MV in eyes with glaucoma was significantly lower than healthy eyes (P < 0.001). The mean CDisp in POAG eyes was also significantly lower than healthy eyes (P < 0.001). CDisp showed a significant correlation (r = 0.46; P = 0.0088) with ocular pulse amplitude in the study. Compared with the outflow facility, both the MV and CDisp were found to have a better discrimination of glaucoma (P < 0.001 and P = 0.0074, respectively). Conclusions: Pulsatile TM motion was reduced in patients with POAG compared to healthy subjects. The underlying mechanism may be due to the altered tissue stiffness or other biomechanical properties of the TM in POAG eyes. Our evidence suggests that the measurement of pulsatile TM motion with PhS-OCT may help in characterizing outflow pathway abnormalities.

Macular microvascular parameters in the ganglion cell-inner plexiform layer derived by optical coherence tomography angiography: Vascular structure-central visual function analysis.

PURPOSE: To investigate the relationships between global and sectoral macular vascular microcirculation parameters in the ganglion cell-inner plexiform layer (GCIPL) assessed by optical coherence tomography angiography (OCTA), and global and sectoral visual field (VF) central mean sensitivity (CMS) assessed by standard automated perimetry. METHODS: Fifty-four eyes with open angle glaucoma were scanned using a swept-source OCTA (Plex Elite 9000, Zeiss, Dublin, CA) and macular vascular microcirculation was measured by calculating the overall flux and vessel area density (VAD) over the entire 6mm x 6mm area, excluding large retinal vessels. Central 10-degree VF CMS was calculated based on 24-2 VF. Pearson correlation was used to investigate the correlation between global and sectoral OCTA parameters and global and sectoral VF CMS. RESULTS: Both global GCIPL flux and VAD were significantly correlated with VF CMS (p<0.001). For the sectoral analysis, sectoral VAD was significantly correlated with sectoral VF CMS in all comparisons except for the inferonasal VF CMS with supero-temporal (ST) GCIPL VAD (p = 0.097). Although highest correlation was observed for both ST VF CMS with inferior GCIPL VAD and infero-temporal VF CMS with superior GCIPL VAD (r = 0.683, p<0.001), there was no significant difference in correlation when compared to the global VAD and other sectors' correlation coefficients (p≥ 0.091), except for the ST GCIPL VAD (p = 0.001). CONCLUSIONS: Global and sectoral macular vascular microcirculation in the GCIPL, as determined by OCTA, was significantly correlated with global and sectoral VF CMS in glaucomatous patients. OCTA can aid in the understanding of the structure-function relationships of the macular region.

Macular Vascular Microcirculation in Eyes With Open-angle Glaucoma Using Different Visual Field Severity Classification Systems.

PRECIS: We found significant differences in macular vascular microcirculation between normal and glaucomatous eyes using optical coherence tomography angiography (OCTA). Macular vascular microcirculation changes also showed significant correlations with visual field (VF) severity classification systems. PURPOSE: To correlate VF severity defined by different classification systems and macular vascular microcirculation in eyes with glaucoma using OCTA. PATIENTS AND METHODS: Twenty normal and 58 open-angle glaucoma (OAG) eyes were scanned using a swept-source OCTA (Plex Elite 9000) and macular vascular microcirculation was measured by calculating the overall blood flux index (BFI) and vessel area density (VAD) over the entire 6×6 mm area excluding the big retinal vessels. Glaucomatous eyes were staged into severity groups based on 4 VF severity classifications: Hodapp-Parrish-Anderson scale, Glaucoma Severity Staging system, ICD-10 glaucoma staging definitions, and VF mean deviation. Central 10-degree VF mean sensitivity (CMS) was calculated based on 24-2 VF. One-way analysis of variance was used to analyze the differences and correlation between macular vascular microcirculation and other clinical parameters. RESULTS: Glaucomatous eyes had significantly lower ganglion cell and inner plexiform layer BFI and VAD (P<0.0001) compared with normal eyes. In OAG patients, BFI and VAD were significantly higher in mild OAG compared with severe OAG with all VF disease severity classification systems (P<0.001). Glaucoma Severity Staging had the highest correlation with changes in macular vascular microcirculation metrics (r=0.734 for BFI; r=0.647 for VAD) and VF CMS had highest correlation with macular vascular microcirculation metrics (r=0.887 for BFI; r=0.903 for VAD). CONCLUSION: Macular vascular microcirculation metrics detected by OCTA correlate with disease severity in glaucomatous eyes. VF CMS, calculated from only 12 tested central 10-degree points, correlated best with macular OCTA.

Peripapillary Retinal Nerve Fiber Layer Vascular Microcirculation in Eyes With Glaucoma and Single-Hemifield Visual Field Loss.

Importance: Understanding the differences in vascular microcirculation of the peripapillary retinal nerve fiber layer (RNFL) between the hemispheres in eyes with glaucoma with single-hemifield visual field (VF) defects may provide insight into the pathophysiology of glaucoma. Objective: To investigate the changes in the microcirculation of the peripapillary RNFL of eyes with glaucoma by using optical microangiography. Design, Setting, and Participants: Eyes with glaucoma and single-hemifield VF defect and normal eyes underwent scanning using an optical microangiography system covering a 6.7 × 6.7-mm2 area centered at the optic nerve head. The RNFL microcirculation was measured within an annulus region centered at the optic nerve head divided into superior and inferior hemispheres. Blood flux index (the mean flow signal intensity in the vessels) and vessel area density (the percentage of the detected vessels in the annulus) were measured. Main Outcomes and Measures: Differences in microcirculation between the hemispheres in eyes with glaucoma and normal eyes and correlations among blood flow metrics, VF thresholds, and clinical optical coherence tomography structural measurements were assessed. Results: Twenty-one eyes from 21 patients with glaucoma (7 men and 14 women; mean [SD] age, 63.7 [9.9] years) and 20 eyes from 20 healthy control individuals (9 men and 11 women; mean [SD] age, 68.3 [10.7] years) were studied. In eyes with glaucoma, the abnormal hemisphere showed a thinner RNFL (mean [SE] difference, 23.5 [4.5] µm; 95% CI, 15.1-32.0 µm; P < .001), lower RNFL blood flux index (mean [SE] difference, 0.04 [0.01]; 95% CI, 0.02-0.05; P < .001), and less vessel area density (mean [SE] difference, 0.08% [0.02%]; 95% CI, 0.05%-0.10%; P < .001) than did the normal hemisphere. Compared with normal eyes, reduced RNFL microcirculation was found in the normal hemisphere of eyes with glaucoma, measured by mean [SE] differences in blood flux index (0.06 [0.01]; 95% CI, 0.04-0.09; P < .001) and vessel area density (0.04% [0.02%]; 95% CI, 0.02%-0.08%; P = .003) but not in RNFL thickness (3.4 [4.7] µm; 95% CI, -6.2 to 12.9 µm; P = .48). Strong correlations were found between the blood flux index and VF mean deviation (Spearman ρ = 0.44; P = .045) and RNFL thickness (Spearman ρ = 0.65; P = .001) in the normal hemisphere of the eye with glaucoma. Conclusions and Relevance: Reduced RNFL microcirculation was detected in the normal hemisphere of eyes with glaucoma, with strong correspondence with VF loss and RNFL thinning. Although the results suggest that vascular dysfunction precedes structural changes seen in glaucoma, longitudinal studies would be needed to confirm this finding.

Estimating Human Trabecular Meshwork Stiffness by Numerical Modeling and Advanced OCT Imaging.

Purpose: The purpose of this study was to estimate human trabecular meshwork (hTM) stiffness, thought to be elevated in glaucoma, using a novel indirect approach, and to compare results with direct en face atomic force microscopy (AFM) measurements. Methods: Postmortem human eyes were perfused to measure outflow facility and identify high- and low-flow regions (HF, LF) by tracer. Optical coherence tomography (OCT) images were obtained as Schlemm's canal luminal pressure was directly manipulated. TM stiffness was deduced by an inverse finite element modeling (FEM) approach. A series of AFM forcemaps was acquired along a line traversing the anterior angle on a radially cut flat-mount corneoscleral wedge with TM facing upward. Results: The elastic modulus of normal hTM estimated by inverse FEM was 70 ± 20 kPa (mean ± SD), whereas glaucomatous hTM was slightly stiffer (98 ± 19 kPa). This trend was consistent with TM stiffnesses measured by AFM: normal hTM stiffness = 1.37 ± 0.56 kPa, which was lower than glaucomatous hTM stiffness (2.75 ± 1.19 kPa). None of these differences were statistically significant. TM in HF wedges was softer than that in LF wedges for both normal and glaucomatous eyes based on the inverse FEM approach but not by AFM. Outflow facility was significantly correlated with TM stiffness estimated by FEM in six human eyes (P = 0.018). Conclusions: TM stiffness is higher, but only modestly so, in glaucomatous patients. Outflow facility in both normal and glaucomatous human eyes appears to associate with TM stiffness. This evidence motivates further studies to investigate factors underlying TM biomechanical property regulation.

Peripapillary Retinal Nerve Fiber Layer Vascular Microcirculation in Glaucoma Using Optical Coherence Tomography-Based Microangiography.

PURPOSE: To investigate the vascular microcirculation changes in the retinal nerve fiber layer (RNFL) in normal, glaucoma suspect, and open-angle glaucoma (OAG) groups using optical coherence tomography-based microangiography (OMAG). METHODS: One eye from each subject was scanned with a Cirrus HD-OCT 5000-based OMAG prototype system montage scanning protocol centered at the optic nerve head (ONH). Blood flow signals were extracted using OMAG algorithm. Retinal nerve fiber layer vascular microcirculation was measured by calculating the blood flux index and vessel area density within a 1.2-mm width annulus centered at the ONH with exclusion of big retinal vessels. One-way ANOVA were performed to analyze the RNFL microcirculation among groups. Linear-regression models were constructed to analyze the correlation between RNFL microcirculation and clinical parameters. Discrimination capabilities of the flow metrics were assessed with the area under the receiver operating characteristic curve (AROC). RESULTS: Twenty normal, 26 glaucoma suspect, and 42 OAG subjects were enrolled. Eyes from OAG subjects and glaucoma suspects showed significantly lower blood flux index compared with normal eyes (P ≤ 0.0015). Retinal nerve fiber layer blood flow metrics showed significant correlations with visual field indices and structural changes in glaucomatous eyes (P ≤ 0.0123). Similar discrimination capability of blood flux index compared with RNFL thickness was found in both disease groups. CONCLUSIONS: Peripapillary RNFL vascular microcirculation measured as blood flux index by OMAG showed significant differences among OAG, glaucoma suspect, and normal controls and was significantly correlated with functional and structural defects. Retinal nerve fiber layer microcirculation measurement using OMAG may help physicians monitor glaucoma.

Repeatability and reproducibility of optic nerve head perfusion measurements using optical coherence tomography angiography.

Optical coherence tomography angiography (OCTA) has increasingly become a clinically useful technique in ophthalmic imaging. We evaluate the repeatability and reproducibility of blood perfusion in the optic nerve head (ONH) measured using optical microangiography (OMAG)-based OCTA. Ten eyes from 10 healthy volunteers are recruited and scanned three times with a 68-kHz Cirrus HD-OCT 5000-based OMAG prototype system (Carl Zeiss Meditec Inc., Dublin, California) centered at the ONH involving two separate visits within six weeks. Vascular images are generated with OMAG processing by detecting the differences in OCT signals between consecutive B-scans acquired at the same retina location. ONH perfusion is quantified as flux, vessel area density, and normalized flux within the ONH for the prelaminar, lamina cribrosa, and the full ONH. Coefficient of variation (CV) and intraclass correlation coefficient (ICC) are used to evaluate intravisit and intervisit repeatability, and interobserver reproducibility. ONH perfusion measurements show high repeatability [CV≤3.7% (intravisit) and ≤5.2% (intervisit)] and interobserver reproducibility (ICC≤0.966) in all three layers by three metrics. OCTA provides a noninvasive method to visualize and quantify ONH perfusion in human eyes with excellent repeatability and reproducibility, which may add additional insight into ONH perfusion in clinical practice.

Optic Disc Perfusion in Primary Open Angle and Normal Tension Glaucoma Eyes Using Optical Coherence Tomography-Based Microangiography.

PURPOSE: To investigate optic disc perfusion differences in normal, primary open-angle glaucoma (POAG), and normal tension glaucoma (NTG) eyes using optical microangiography (OMAG) based optical coherence tomography (OCT) angiography technique. DESIGN: Cross-sectional, observational study. SUBJECTS: Twenty-eight normal, 30 POAG, and 31 NTG subjects. METHODS: One eye from each subject was scanned with a 68 kHz Cirrus HD-OCT 5,000-based OMAG prototype system centered at the optic nerve head (ONH) (Carl Zeiss Meditec Inc, Dublin, CA). Microvascular images were generated from the OMAG dataset by detecting the differences in OCT signal between consecutive B-scans. The pre-laminar layer (preLC) was isolated by a semi-automatic segmentation program. MAIN OUTCOME MEASURES: Optic disc perfusion, quantified as flux, vessel area density, and normalized flux (flux normalized by the vessel area) within the ONH. RESULTS: Glaucomatous eyes had significantly lower optic disc perfusion in preLC in all three perfusion metrics (p<0.0001) compared to normal eyes. The visual field (VF) mean deviation (MD) and pattern standard deviation (PSD) were similar between the POAG and NTG groups, and no differences in optic disc perfusion were observed between POAG and NTG. Univariate analysis revealed significant correlation between optic disc perfusion and VF MD, VF PSD, and rim area in both POAG and NTG groups (p≤0.0288). However, normalized optic disc perfusion was correlated with some structural measures (retinal nerve fiber layer thickness and ONH cup/disc ratio) only in POAG eyes. CONCLUSIONS: Optic disc perfusion detected with OMAG was significantly reduced in POAG and NTG groups compared to normal controls, but no difference was seen between POAG and NTG groups with similar levels of VF damage. Disc perfusion was significantly correlated with VF MD, VF PSD, and rim area in glaucomatous eyes. Vascular changes at the optic disc as measured using OMAG may provide useful information for diagnosis and monitoring of glaucoma.

Optic nerve head perfusion in normal eyes and eyes with glaucoma using optical coherence tomography-based microangiography.

BACKGROUND: To investigate the differences of perfusion in the optic nerve head (ONH) between normal and glaucomatous eyes using optical microangiography (OMAG) based optical coherence tomography (OCT) angiography technique. METHODS: One eye from each subject was scanned with a 68 kHz Cirrus 5000 HD-OCT-based OMAG prototype system centered at the ONH (Carl Zeiss Meditec Inc, Dublin, CA, USA). Microvascular images were generated from the OMAG dataset by detecting the differences in OCT signal between consecutive B-scans. The pre-laminar layer (preLC) was isolated by a semi-automatic segmentation program. En face OMAG images for preLC were generated using signals with highest blood flow signal intensity. ONH perfusion was quantified as flux, vessel area density, and normalized flux within the ONH. Standard t-tests were performed to analyze the ONH perfusion differences between normal and glaucomatous eyes. Linear regression models were constructed to analyze the correlation between ONH perfusion and other clinical measurements. RESULTS: Twenty normal and 21 glaucoma subjects were enrolled. Glaucomatous eyes had significantly lower ONH perfusion in preLC in all three perfusion metrics compared to normal eyes (P≤0.0003). Significant correlations between ONH perfusion and disease severity as well as structural changes were detected in glaucomatous eyes (P≤0.012). CONCLUSIONS: ONH perfusion detected by OMAG showed significant differences between glaucoma and normal controls and was significantly correlated with disease severity and structural defects in glaucomatous eyes. ONH perfusion measurement using OMAG may provide useful information for detection and monitoring of glaucoma.

A Novel Schlemm's Canal Scaffold: Histologic Observations.

PURPOSE: To assess the biocompatibility of a novel implant made of Nitinol (nickel-titanium alloy), designed to improve aqueous humor outflow. MATERIALS AND METHODS: In the first arm of biocompatibility testing, microstents were surgically inserted into Schlemm's canal (SC) of 2 non-human primates (NHPs), and a third NHP served as a surgical sham control. After 13 weeks the animals were killed, and the eyes were examined by light and scanning electron microscopy. Two masked investigators evaluated the histology sections. The second arm utilized 8 New Zealand white rabbits; each rabbit received a microstent inserted into the sclera and subconjunctival space by means of passage across the anterior chamber thus providing contact with several representative ocular tissues. The fellow eye of each rabbit underwent a sham procedure without microstent insertion. The rabbits were killed after 26 weeks, and a trained ocular pathologist examined the specimens using light microscopy. RESULTS: Histologic and scanning electron microscopy analysis of the NHPs demonstrated that the microstents were located in SC. There was no evidence of an acute or chronic inflammatory response, granulation response, or fibrosis in the outflow system or in adjacent tissues. Rabbit eyes showed minimal mononuclear cell infiltration and minimal fibrotic responses at the site of the implants when compared with sham-treated control eyes. CONCLUSIONS: The Hydrus Microstent was associated with minimal inflammation in both NHP and rabbit eyes with extended follow-up. These preclinical studies demonstrate that the Hydrus Microstent appears to have excellent long-term biocompatibility.

Prostaglandin-induced hair growth.

Latanoprost, used clinically in the treatment of glaucoma, induces growth of lashes and ancillary hairs around the eyelids. Manifestations include greater thickness and length of lashes, additional lash rows, conversion of vellus to terminal hairs in canthal areas as well as in regions adjacent to lash rows. In conjunction with increased growth, increased pigmentation occurs. Vellus hairs of the lower eyelids also undergo increased growth and pigmentation. Brief latanoprost therapy for 2-17 days (3-25.5 microg total dosage) induced findings comparable to chronic therapy in five patients. Latanoprost reversed alopecia of the eyelashes in one patient. Laboratory experiments with latanoprost have demonstrated stimulation of hair growth in mice and in the balding scalp of the stumptailed macaque, a primate that demonstrates androgenetic alopecia. The increased number of visible lashes is consistent with the ability of latanoprost to induce anagen (the growth phase) in telogen (resting) follicles while inducing hypertrophic changes in the involved follicles. The increased length of lashes is consistent with the ability of latanoprost to prolong the anagen phase of the hair cycle. Correlation with laboratory studies suggests that initiation and completion of latanoprost hair growth effects occur very early in anagen and the likely target is the dermal papilla.

The aqueous outflow system as a mechanical pump: evidence from examination of tissue and aqueous movement in human and non-human primates.

PURPOSE: To describe a new aqueous outflow model involving a mechanical pump. MATERIALS AND METHODS: Laboratory materials include human and monkey eyes; methods include the dissecting microscope, light microscopy, scanning electron microscopy, transmission electron microscopy, and tracer studies. Clinical methods involve human subject slit lamp, gonioscopy, and operating microscope examination. RESULTS: Laboratory evidence demonstrates that aqueous outflow tissues are responsive to intraocular pressure induced deformation. Deformation occurs in response to small pressure gradients. Laboratory evidence also demonstrates the presence of valves discharging aqueous to Schlemm's canal. The laboratory model predicts pulsatile aqueous discharge in vivo. Clinical in vivo evidence demonstrates pulsatile aqueous flow from the anterior chamber into Schlemm's canal, from Schlemm's canal into collector channels, and from Schlemm's canal into aqueous and episcleral veins, all synchronous with the ocular pulse. CONCLUSIONS: Aqueous outflow tissue deformation caused by normal intraocular pressure transients induces pulsatile one-way discharge of aqueous to the vascular system. The model identifies biomechanical coupling of intraocular pressure with aqueous outflow tissue deformation and also sites of high flow capable of inducing shear stress. These mechanotransduction mechanisms, well characterized as a means of controlling pressure and flow in the vascular system, also provide a means of regulatory feedback to control intraocular pressure and aqueous flow.

Intraocular pressure regulation: findings of pulse-dependent trabecular meshwork motion lead to unifying concepts of intraocular pressure homeostasis.

Intraocular pressure (IOP) is the only treatable risk factor in glaucoma, one of the world's leading causes of blindness. Mechanisms that maintain IOP within a normal range have been poorly understood in contrast to intrinsic mechanisms that regulate systemic blood pressure. Vessel walls experience continuous pulse-induced cyclic pressure and flow. Pressure-dependent wall stress and flow-dependent shear stress provide sensory signals that initiate mechanotransduction responses. The responses optimize vessel wall elasticity, compliance and lumen size, providing a feedback loop to maintain intrinsic pressure homeostasis. Aqueous humor is part of a vascular circulatory loop, being secreted into the anterior chamber of the eye from the vasculature, then returning to the vasculature by passing through the trabecular meshwork (TM), a uniquely modified vessel wall interposed between the anterior chamber and a vascular sinus called Schlemm's canal (SC). Since pressure in circulatory loops elsewhere is modulated by cyclic stresses, one might predict similar pressure modulation in the aqueous outflow system. Recent laboratory evidence in fact demonstrates that cyclic IOP changes alter aqueous outflow while increasing cellularity and contractility of TM cells. Cyclic changes also lead to alterations in gene expression, changes in cytoskeletal networks and modulation of signal transduction. A new technology, phase-based optical coherence tomography, demonstrates in vivo pulse-dependent TM motion like that elsewhere in the vasculature. Recognition of pulse-dependent TM motion provides a linkage to well-characterized mechanisms that provide pressure homeostasis in the systemic vasculature. The linkage may permit unifying concepts of pressure control and provide new insights into IOP homeostatic mechanisms.

Effects of viscoelastic injection into Schlemm's canal in primate and human eyes: potential relevance to viscocanalostomy.

OBJECTIVE: To study possible initial mechanisms of alterations in aqueous outflow that may result from the injection of viscoelastic into Schlemm's canal (SC) during viscocanalostomy. DESIGN: Experimental animal (Macaca nemestrina) and human autopsy study. METHODS: Eyes were dissected into a limbal ring and hemisected or quartered. Uncannulated segments served as controls. In treated segments, SC was cannulated and viscoelastic injected. Segments were fixed and sectioned into continuous 500 to 1000 microm pieces, examined at the dissecting microscope, and photomicrographs were taken. Representative tissue was further prepared for scanning electron microscopy or sectioned at 1 microm. MAIN OUTCOME MEASURES: Tissue sections were examined to determine the extent of dilation and disruption of SC and related structures. SC dimensions were measured in segments from controls, cannulated regions, and regions of viscoelastic injection beyond the cannula insertion. In the hemisected segments, the circumferential extent of SC dilation was determined, and structures within the canal were described and counted. RESULTS: SC was dilated with increased anteroposterior length and height in cannulated and viscoelastic-injected segments in both primate and human eyes relative to untreated controls. The walls of SC were disrupted in both regions of cannulation and of viscoelastic injection, and the collector channels were widely dilated by viscoelastic. With decreasing effectiveness, the injected viscoelastic circumferentially dilated SC as far as 14 mm and 16 mm in primate and human hemisections, respectively. Structures that bridged between the walls of SC were often disrupted. CONCLUSIONS: Cannulation of SC and injection of viscoelastic beyond the cannula resulted in marked dilation of SC and associated collector channels. Lateral walls, inner wall endothelium, and bridging structures of SC were frequently disrupted by cannulation and sometimes by injected viscoelastic. These findings suggest that viscocanalostomy may acutely cause a direct communication between SC and the juxtacanalicular space, and so may initially enhance conventional aqueous outflow. Controlled clinical trials will be necessary to determine the long-term outcomes of this procedure.