PURPOSE: To compare diagnostic performance and structure-function correlations of multifocal electroretinogram (mfERG), full-field flash ERG (ff-ERG) photopic negative response (PhNR) and transient pattern-reversal ERG (PERG) in a non-human primate (NHP) model of experimental glaucoma (EG). METHODS: At baseline and after induction of chronic unilateral IOP elevation, 43 NHP had alternating weekly recordings of retinal nerve fiber layer thickness (RNFLT) by spectral domain OCT (Spectralis) and retinal function by mfERG (7F slow-sequence stimulus, VERIS), ff-ERG (red 0.42 log cd-s/m(2) flashes on blue 30 scotopic cd/m(2) background, LKC UTAS-E3000), and PERG (0.8° checks, 99% contrast, 100 cd/m(2) mean, 5 reversals/s, VERIS). All NHP were followed at least until HRT-confirmed optic nerve head posterior deformation, most to later stages. mfERG responses were filtered into low- and high-frequency components (LFC, HFC, >75 Hz). Peak-to-trough amplitudes of LFC features (N1, P1, N2) and HFC RMS amplitudes were measured and ratios calculated for HFC:P1 and N2:P1. ff-ERG parameters included A-wave (at 10 ms), B-wave (trough-to-peak) and PhNR (baseline-to-trough) amplitudes as well as PhNR:B-wave ratio. PERG parameters included P50 and N95 amplitudes as well as N95:P50 ratio and N95 slope. Diagnostic performance of retinal function parameters was compared using the area under the receiver operating characteristic curve (A-ROC) to discriminate between EG and control eyes. Correlations to RNFLT were compared using Steiger's test. RESULTS: Study duration was 15 ± 8 months. At final follow-up, structural damage in EG eyes measured by RNFLT ranged from 9% above baseline (BL) to 58% below BL; 29/43 EG eyes (67%) and 0/43 of the fellow control eyes exhibited significant (>7%) loss of RNFLT from BL. Using raw parameter values, the largest A-ROC findings for mfERG were: HFC (0.82) and HFC:P1 (0.90); for ff-ERG: PhNR (0.90) and PhNR:B-wave (0.88) and for PERG: P50 (0.64) and N95 (0.61). A-ROC increased when data were expressed as % change from BL, but the pattern of results persisted. At 95% specificity, the diagnostic sensitivity of mfERG HFC:P1 ratio was best, followed by PhNR and PERG. The correlation to RNFLT was stronger for mfERG HFC (R = 0.65) than for PhNR (R = 0.59) or PERG N95 (R = 0.36), (p = 0.20, p = 0.0006, respectively). The PhNR flagged a few EG eyes at the final time point that had not been flagged by mfERG HFC or PERG. CONCLUSIONS: Diagnostic performance and structure-function correlation were strongest for mfERG HFC as compared with ff-ERG PhNR or PERG in NHP EG.
Since its introduction, optical coherence tomography (OCT) has become widely used and accepted as an imaging modality to detect and follow glaucoma, with measurement of the peripapillary retinal nerve fiber layer (pRNFL) being the most utilized parameter. Up until recently, macular thickness parameters have not been commonly used in glaucoma due to results of earlier studies with time-domain OCT (TD-OCT) that revealed macular imaging to be inferior to pRNFL in the diagnosis of glaucoma. The recent advent of spectral-domain OCT (SD-OCT) has renewed interest in the potential uses of macular imaging in glaucoma due to its ability to better segment and measure individual retinal layers. Multiple studies have been performed in the last few years to investigate the diagnostic ability, reproducibility, and limitations of these new SD-OCT macular parameters. The purpose of this paper is to review the findings of those studies to assess the current utility of macular SD-OCT in glaucoma. Overall, SD-OCT has been shown to have higher reproducibility than TD-OCT, and though there have been some conflicting reports, the majority of studies seem to concur that the diagnostic sensitivity of SD-OCT macular parameters is at least comparable to TD-OCT and other SD-OCT parameters.
PurposeTo study the correlation between glaucomatous visual field (VF) defects assessed by standard automated perimetry (SAP) and peripapillary retinal nerve fiber layer (RNFL) thinning measured by spectral domain optical coherence tomography (OCT) using a modified OCT-based peripapillary RNFL structure-function map.Patients and methodsPerimetric glaucoma patients and age-matched normal control subjects were recruited from a university hospital clinic. All eyes underwent testing with the Spectralis spectral domain OCT and SAP on the same day. An OCT-based correspondence map, which correlated VF areas with peripapillary RNFL sectors was created to evaluate the relationship between glaucomatous RNFL thinning and VF loss in six nerve fiber layer bundle areas. Correlations of RNFL thinning with corresponding VF defects were examined using Spearman rank-order correlations. To demonstrate the association between localized VF defects and RNFL thickness, the theoretical curves were made according to an established log-linear model. The measured RNFL thickness values and VF defects were presented in the same scatterplot for each sector.ResultsFifty-six glaucoma patients and 85 normal subjects were included in the study. Significant association between localized VF loss and RNFL thinning was found in corresponding areas. Data from the current study fit well with established log-linear models, which compare RNFL thickness values with VF defects.ConclusionAnalysis of RNFL thinning in eyes with localized glaucomatous VF defects showed good structure-function correlation in a new OCT-based structure-function correspondence map.
PURPOSE: To determine the diagnostic capability of spectral-domain optical coherence tomography in glaucoma patients with visual field defects. DESIGN: Prospective, cross-sectional study. METHODS: SETTINGS: Participants were recruited from a university hospital clinic. STUDY POPULATION: One eye of 85 normal subjects and 61 glaucoma patients with average visual field mean deviation of -9.61 ± 8.76 dB was selected randomly for the study. A subgroup of the glaucoma patients with early visual field defects was calculated separately. OBSERVATION PROCEDURES: Spectralis optical coherence tomography (Heidelberg Engineering, Inc) circular scans were performed to obtain peripapillary retinal nerve fiber layer (RNFL) thicknesses. The RNFL diagnostic parameters based on the normative database were used alone or in combination for identifying glaucomatous RNFL thinning. MAIN OUTCOME MEASURES: To evaluate diagnostic performance, calculations included areas under the receiver operating characteristic curve, sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio, and negative likelihood ratio. RESULTS: Overall RNFL thickness had the highest area under the receiver operating characteristic curve values: 0.952 for all patients and 0.895 for the early glaucoma subgroup. For all patients, the highest sensitivity (98.4%; 95% confidence interval, 96.3% to 100%) was achieved by using 2 criteria: ≥ 1 RNFL sectors being abnormal at the < 5% level and overall classification of borderline or outside normal limits, with specificities of 88.9% (95% confidence interval, 84.0% to 94.0%) and 87.1% (95% confidence interval, 81.6% to 92.5%), respectively, for these 2 criteria. CONCLUSIONS: Statistical parameters for evaluating the diagnostic performance of the Spectralis spectral-domain optical coherence tomography were good for early perimetric glaucoma and were excellent for moderately advanced perimetric glaucoma.
PURPOSE: To review the current published literature on the use of OCT angiography (OCTA) to help detect changes associated with the diagnosis of primary open-angle glaucoma. METHODS: Searches of the peer-reviewed literature were conducted in March 2018, June 2018, April 2019, December 2019, and June 2020 in the PubMed and Cochrane Library databases. Abstracts of 459 articles were examined to exclude reviews and non-English articles. After inclusion and exclusion criteria were applied, 75 articles were selected and the panel methodologist rated them for strength of evidence. Three articles were rated level I and 57 articles were rated level II. The 15 level III articles were excluded. RESULTS: OCT angiography can detect decreased capillary vessel density within the peripapillary nerve fiber layer (level II) and macula (level I and II) in patients with suspected glaucoma, preperimetric glaucoma, and perimetric glaucoma. The degree of vessel density loss correlates significantly with glaucoma severity both overall and topographically (level II) as well as longitudinally (level I). For differentiating glaucomatous from healthy eyes, some studies found that peripapillary and macular vessel density measurements by OCTA show a diagnostic ability (area under the receiver operating characteristic curve) that is comparable with structural OCT retinal nerve fiber and ganglion cell thickness measurements, whereas other studies found that structural OCT measurements perform better. Choroidal or deep-layer microvasculature dropout as measured by OCTA is also associated with glaucoma damage (level I and II). Lower peripapillary and macular vessel density and choroidal microvasculature dropout are associated with faster rates of disease progression (level I and II). CONCLUSIONS: Vessel density loss associated with glaucoma can be detected by OCTA. Peripapillary, macular, and choroidal vessel density parameters may complement visual field and structural OCT measurements in the diagnosis of glaucoma.
PURPOSE: To assess anatomical changes after laser peripheral iridotomy (LPI) and predictors of angle widening based on anterior segment OCT (AS-OCT) and angle opening based on gonioscopy in mainland Chinese primary angle closure suspects (PACS). DESIGN: Prospective observational study. PARTICIPANTS: 454 subjects aged 50 to 70 years with PACS. METHODS: Subjects received clinical examinations including gonioscopy and AS-OCT imaging at baseline and 2 weeks after LPI as part of the Zhongshan Angle Closure Prevention (ZAP) Trial. PACS was defined as inability to visualize pigmented trabecular meshwork in two or more quadrants on static gonioscopy. LPI was performed on one eye per subject in a superior (between 11 to 1 o'clock) or temporal or nasal (at or below 10:30 or 1:30 o'clock) location. Biometric parameters in horizontal and vertical AS-OCT scans were measured and averaged. Multivariable linear and logistic regression modeling were performed to determine predictors of angle widening, defined as change in continuous measurements of mean angle opening distance (AOD750), poor angle widening, defined as the lowest quintile of change in mean AOD750, and poor angle opening, defined as residual PACS after LPI based on gonioscopy. MAIN OUTCOME MEASURES: Anatomical changes and predictors of angle widening and opening after LPI. RESULTS: 454 subjects were included in the analysis. 219 received superior LPIs and 235 received temporal or nasal LPIs. There were significant changes among most biometric parameters (p<0.006) after LPI, including greater AOD750 (p<0.001). 120 eyes (26.4%) had residual PACS after LPI. In multivariable regression analysis, several baseline parameters, including superior LPI location (p=0.004), smaller AOD750 (p<0.001), and greater iris curvature (p<0.001), were predictive of greater angle widening. Temporal or nasal LPI locations (OR=2.60, p<0.0001) and greater baseline AOD750 (OR=2.58, 0.1 mm increment, p<0.001) were most predictive of poor angle widening based on AS-OCT. Smaller mean gonioscopy grade (OR=0.34, 1 grade increment) was most predictive of poor angle opening based on gonioscopy. CONCLUSIONS: Superior LPI location results in significantly greater angle widening based on AS-OCT compared to temporal or nasal locations in a Chinese population with PACS. This supports consideration of superior LPI locations to optimize anatomical changes after LPI.
UNLABELLED: Axon injury is an early event in neurodegenerative diseases that often leads to retrograde neuronal cell death and progressive permanent loss of vital neuronal functions. The connection of these two obviously sequential degenerative events, however, is elusive. Deciphering the upstream signals that trigger the neurodegeneration cascades in both neuronal soma and axon would be a key step toward developing the effective neuroprotectants that are greatly needed in the clinic. We showed previously that optic nerve injury-induced neuronal endoplasmic reticulum (ER) stress plays an important role in retinal ganglion cell (RGC) death. Using two in vivo mouse models of optic neuropathies (traumatic optic nerve injury and glaucoma) and adeno-associated virus-mediated RGC-specific gene targeting, we now show that differential manipulation of unfolded protein response pathways in opposite directions-inhibition of eukaryotic translation initiation factor 2α-C/EBP homologous protein and activation of X-box binding protein 1-promotes both RGC axons and somata survival and preserves visual function. Our results indicate that axon injury-induced neuronal ER stress plays an important role in both axon degeneration and neuron soma death. Neuronal ER stress is therefore a promising therapeutic target for glaucoma and potentially other types of neurodegeneration. SIGNIFICANCE STATEMENT: Neuron soma and axon degeneration have distinct molecular mechanisms although they are clearly connected after axon injury. We previously demonstrated that axon injury induces neuronal endoplasmic reticulum (ER) stress and that manipulation of ER stress molecules synergistically promotes neuron cell body survival. Here we investigated the possibility that ER stress also plays a role in axon degeneration and whether ER stress modulation preserves neuronal function in neurodegenerative diseases. Our results suggest that neuronal ER stress is a general mechanism of degeneration for both neuronal cell body and axon, and that therapeutic targeting of ER stress produces significant functional recovery.
OBJECTIVE: Understanding trends and patterns in the use of minimally invasive glaucoma surgery (MIGS) and patient profiles undergoing each procedure is important given their relative expense and unknown long-term safety and effectiveness. DESIGN: Retrospective analysis SUBJECTS: MIGS and standard glaucoma surgeries recorded in the American Academy of Ophthalmology (AAO) Intelligent Research in Sight (IRIS®) Registry. METHODS: We used the data from IRIS® Registry between 2013-2018 (inclusive) to measure annual number of MIGS and standard surgical techniques (trabeculectomy or glaucoma drainage device (GDD)) performed in the US, stratified by demographic characteristics. Secondary analyses of concurrent surgeries and of subsequent surgeries for MIGS and standard surgical technique were also conducted. MAIN OUTCOME MEASURES: Trends and sociodemographic characteristics of MIGS usage in the US. RESULTS: 203,332 eyes and 232,537 unique procedures had associated, documented International Statistical Classification of Diseases and Related Health Problems (ICD) 9/10 codes for glaucoma and were included in final analyses. Among eyes with documented glaucoma diagnoses, there was a substantial increase in annual MIGS procedures over the study period (from 7,586 in 2013 to 39,677), and a smaller decrease in standard glaucoma procedures (from 16,215 to 13,701). The proportion of iStent procedures almost tripled during the study period (from 14% to 40%), and by 2017 accounted for almost half (43.7%) of all glaucoma surgeries in the US. 21,025 (10.3%) of all eyes received multiple procedures; 7,638 (36.3%) on the same day and 13,387 (63.7%) on subsequent days. ECP and iStent were the most common concurrent procedures (55.4% of all concurrent procedures). Trabeculectomy and GDD were most commonly followed by another standard glaucoma surgery, but when followed by sequential MIGS, ECP and goniotomy were the most common procedures performed (33.0%, 21.9%, respectively). CONCLUSIONS: There was a significant increase in MIGS use over the recent six-year period despite limited evidence of their long-term safety or effectiveness, highlighting the need for trials comparing safety and outcomes of novel MIGS vs traditional surgical treatments for glaucoma.
Glaucoma is marked by a progressive degeneration of the optic nerve and delayed loss of retinal ganglion cells (RGCs), the projection neurons of the eye. Because RGCs are not replaced and because surviving RGCs cannot regenerate their axons, the visual loss in glaucoma is largely irreversible. Here, we describe methods to evaluate treatments that may be beneficial for treating glaucoma using in vitro cell culture models (immunopanning to isolate neonatal RGCs, dissociated mature retinal neurons, retinal explants) and in vivo models that test potential treatments or investigate underlying molecular mechanisms in an intact system. Potentially, use of these models can help investigators continue to improve treatments to preserve RGCs and restore visual function in patients with glaucoma.
PURPOSE: To develop an artificial intelligence (AI) dashboard for monitoring glaucomatous functional loss. DESIGN: Retrospective, cross-sectional, longitudinal cohort study. PARTICIPANTS: Of 31 591 visual fields (VFs) on 8077 subjects, 13 231 VFs from the most recent visit of each patient were included to develop the AI dashboard. Longitudinal VFs from 287 eyes with glaucoma were used to validate the models. METHOD: We entered VF data from the most recent visit of glaucomatous and nonglaucomatous patients into a "pipeline" that included principal component analysis (PCA), manifold learning, and unsupervised clustering to identify eyes with similar global, hemifield, and local patterns of VF loss. We visualized the results on a map, which we refer to as an "AI-enabled glaucoma dashboard." We used density-based clustering and the VF decomposition method called "archetypal analysis" to annotate the dashboard. Finally, we used 2 separate benchmark datasets-one representing "likely nonprogression" and the other representing "likely progression"-to validate the dashboard and assess its ability to portray functional change over time in glaucoma. MAIN OUTCOME MEASURES: The severity and extent of functional loss and characteristic patterns of VF loss in patients with glaucoma. RESULTS: After building the dashboard, we identified 32 nonoverlapping clusters. Each cluster on the dashboard corresponded to a particular global functional severity, an extent of VF loss into different hemifields, and characteristic local patterns of VF loss. By using 2 independent benchmark datasets and a definition of stability as trajectories not passing through over 2 clusters in a left or downward direction, the specificity for detecting "likely nonprogression" was 94% and the sensitivity for detecting "likely progression" was 77%. CONCLUSIONS: The AI-enabled glaucoma dashboard, developed using a large VF dataset containing a broad spectrum of visual deficit types, has the potential to provide clinicians with a user-friendly tool for determination of the severity of glaucomatous vision deficit, the spatial extent of the damage, and a means for monitoring the disease progression.
OBJECTIVE: MYOC (myocilin) mutations account for 3-5% of primary open angle glaucoma (POAG). We aimed to understand the true population-wide penetrance and characteristics of glaucoma among individuals with the most common MYOC variant (p.Gln368Ter) and the impact of a POAG polygenic risk score (PRS) in this population. DESIGN: Cross-sectional population-based METHODS: Individuals with the p.Gln368Ter variant were identified among 77,959 UK Biobank participants with fundus photographs (FPs). A genome-wide POAG PRS was computed and two masked graders reviewed FPs for disc-defined glaucoma (DDG). MAIN OUTCOME MEASURES: Penetrance of glaucoma RESULTS: 200 individuals carried the p.Gln368Ter heterozygous genotype, and 177 had gradable FPs. 132 had no evidence of glaucoma, 45 (25.4%) had probable/definite glaucoma in at least one eye and 19 (10.7%) had bilateral glaucoma. There were no differences in age, race/ethnicity, or gender among groups (p>0.05). Of those with DDG, 31% self-reported or had ICD 9/10 code for glaucoma, while 69% were undiagnosed. Subjects with DDG had higher medication-adjusted cornea-corrected intraocular pressure (IOPcc) (p<0.001) vs. those without glaucoma. This difference in IOPcc was larger in DDG with prior glaucoma diagnosis vs. those not diagnosed (p<0.001). Majority of p.Gln368Ter carriers had IOP in the normal range (<=21 mmHg), though this proportion was lower in those with DDG (p<0.02) and those with prior glaucoma diagnosis (p<0.03). Prevalence of DDG increased with each decile of the POAG PRS. Subjects with DDG had significantly higher PRS compared to those without glaucoma (0.37 ± 0.97 vs 0.01 ± 0.90, p=0.03). Of those with DDG, individuals with prior diagnosis of glaucoma had higher PRS compared to undiagnosed individuals (1.31 ± 0.64 vs 0.00 ± 0.81, p<0.001) and had 27.5 times (95%CI 2.5-306.6) adjusted odds of being in the top decile of PRS for POAG. CONCLUSION: 1 in 4 individuals with MYOC p.Gln368Ter mutation had evidence of glaucoma, a substantially higher penetrance than previously estimated, with 69% of cases undetected. A large portion of p.Gln368Ter carriers have IOP in the normal range, despite similar age, including those with DDG. PRS increases disease penetrance and severity of disease, supporting the utility of PRS in optimizing risk stratification among MYOC p.Gln368Ter carriers.
Posner-Schlossman syndrome (PSS) shares some clinical features with uveitis and open angle glaucoma. Cytokines and autoantibodies have been associated with uveitis and open angle glaucoma. However, the role of serum cytokines and autoantibodies in the pathogenesis of PSS remains unknown. This study aimed to evaluate the associations of type 1 T helper (Th1) and Th17 related cytokines and autoantibodies with PSS. Peripheral blood serum samples were collected from 81 patients with PSS and 97 gender- and age-matched healthy blood donors. Th1 and Th17 related cytokines, including interleukin-1β (IL-1β), IL-12, tumor necrosis factor-α (TNF-α), interferon- γ (IFN-γ), IL-6 and IL-17, and glucose-6-phosphate isomerase (GPI) were determined by double antibody sandwich ELISA. Anti-nuclear antibody (ANA), anti-keratin antibody (AKA) and anti-neutrophil cytoplasmic antibody (ANCA) were detected by indirect immunofluorescence assay. Anti-cardiolipin antibody (ACA)-IgG, ACA-IgM, ACA-IgA, anti-double stranded DNA (anti-dsDNA) and anti-cyclic citrullinated peptide antibody (anti-CCP) were detected by indirect ELISA. Serum levels of IL-1β, IL-12 and IL-6 in PSS patients were significantly lower than those in controls (P < 0.003), and these associations survived the Bonferroni correction (Pc < 0.018). There was no significant difference in serum levels of TNF-α, IFN-γ and IL-17 between the PSS and control groups (Pc > 0.12). Positive rate of serum anti-dsDNA in PSS patients was significantly higher than that in the control group (P = 0.002, Pc = 0.018), while positive rates of serum ANA, AKA, ANCA, ACA-IgG, ACA-IgM, ACA-IgA, GPI and anti-CCP in the PSS group were not significantly different from those in the control group (Pc > 0.09). These results suggest that anti-dsDNA may contribute to the pathogenesis of PSS, while Th1 and Th17 related cytokines and other autoantibodies may not be major contributors to PSS.
The etiology of Posner-Schlossman syndrome (PSS) remains unknown. The association of human leukocyte antigens (HLA) allelic diversity with PSS has been poorly investigated. To evaluate the association of allelic polymorphisms of class I HLA-A, -B and -C and class II HLA-DRB1 and -DQB1 with PSS, 100 unrelated patients with PSS and 128 age- and ethnically matched control subjects were recruited from a southern Chinese Han population. Polymorphisms in exons 2-4 for HLA-A, -B, -C loci, exon 2 for HLA-DRB1 and exons 2,3 for HLA-DQB1 were analyzed for association with PSS at allele and haplotype levels. The allele frequency of HLA-C*1402 in PSS patients was significantly higher than that in controls (P = 0.002, OR = 4.12). This association survived the Bonferroni correction (Pc = 0.04). The allele frequency of HLA-B*1301 in PSS patients was lower than that in the control group (P = 0.003, OR = 0.21), although this association did not survive the Bonferroni correction (Pc = 0.16). In PSS patients, the haplotype frequencies of HLA-A*1101~C*1402 and B*5101~C*1402 were higher than that in controls (P = 0.03, OR = 4.44; P = 0.02, OR = 3.20; respectively), while the HLA-B*1301~C*0304 was lower than that in controls (P = 0.007, OR = 0.23), although these associations did not survive the Bonferroni correction (Pc > 0.16). This study for the first time demonstrated that polymorphisms at the HLA-B and HLA-C loci were nominally associated with PSS in the southern Chinese Han population. Our results suggest that HLA-C*1402, A*1101~C*1402 and B*5101~C*1402 might be risk factors for PSS, whereas HLA-B*1301 plus B*1301~C*0304 might be protective factors against PSS, but even larger datasets are required to confirm these findings. Findings from this study provide valuable new clues for investigating the mechanisms and development of new diagnosis and treatment for PSS.
AIM: To characterize whether a glaucoma model with chronic elevation of the intraocular pressure (IOP) was able to be induced by anterior chamber injection of microbeads in rabbits. METHODS: In order to screen the optimal dose of microbead injection, IOP was measured every 3d for 4wk using handheld applanation tonometer after a single intracameral injection of 10 µL, 25 µL, 50 µL or 100 µL microbeads (5×10(6) beads/mL; n=6/group) in New Zealand White rabbits. To prolong IOP elevation, two intracameral injections of 50 µL microbeads or phosphate buffer saline (PBS) were made respectively at days 0 and 21 (n=24/group). The fellow eye was not treated. At 5wk after the second injection of microbeads or PBS, bright-field microscopy and transmission electron microscopy (TEM) were used to assess the changes in the retina. The expression of glial fibrillary acidic protein (GFAP) in the retina was evaluated by immunofluorescence, quantitative real-time polymerase chain reaction and Western blot at 5wk after the second injection of microbeads. RESULTS: Following a single intracameral injection of 10 µL, 25 µL, 50 µL or 100 µL microbead, IOP levels showed a gradual increase and a later decrease over a 4wk period after a single injection of microbead into the anterior chamber of rabbits. A peak IOP was observed at day 15 after injection. No significant difference in peak value of IOP was found between 10 µL and 25 µL groups (17.13±1.25 mm Hg vs 17.63±0.74 mm Hg; P=0.346). The peak value of IOP from 50 µL group (23.25±1.16 mm Hg) was significantly higher than 10 µL and 25 µL groups (all P<0.05). Administration of 100 µL microbead solution (23.00±0.93 mm Hg) did not lead to a significant increase in IOP compared to the 50 µL group (P=0.64). A prolonged elevated IOP duration up to 8wk was achieved by administering two injections of 50 µL microbeads (20.48±1.21 mm Hg vs 13.60±0.90 mm Hg in PBS-injected group; P<0.05). The bright-field and TEM were used to assess the changes of retinal ganglion cells (RGCs). Compared with PBS-injected group, the extended IOP elevation was associated with the degeneration of optic nerve, the reduction of RGC axons (47.16%, P<0.05) and the increased GFAP expression in the retina (4.74±1.10 vs 1.00±0.46, P<0.05). CONCLUSION: Two injections of microbeads into the ocular anterior chamber of rabbits lead to a prolonged IOP elevation which results in structural abnormality as well as loss in RGCs and their axons without observable ocular structural damage or inflammatory response. We have therefore established a novel and practical model of experimental glaucoma in rabbits.
Purpose: To discover novel therapies that lower IOP by increasing aqueous humor outflow facility, ex vivo ocular perfusion systems provide a valuable tool. However, currently available designs are limited by their throughput. Here we report the development of a compact, scalable perfusion system with improved throughput and its validation using bovine and porcine eyes. Methods: At a fixed IOP of 6 mm Hg, flow rate was measured by flow sensors. We validated the system by measuring the outflow responses to Y-39983 (a Rho kinase inhibitor), endothelin-1 (ET-1), ambrisentan (an antagonist for endothelin receptor A [ETA]), sphigosine-1-phosphate (S1P), JTE-013 (antagonist for S1P receptor 2 [S1P2]), S-nitroso-N-acetylpenicillamine (SNAP, a nitric oxide [NO] donor), and 3-Morpholino-sydnonimine (SIN-1, another NO donor). Results: The instrument design enabled simultaneous measurements of 20 eyes with a footprint of 1 m2. Relative to vehicle control, Y-39983 increased outflow by up to 31% in calf eyes. On the contrary, ET-1 decreased outflow by up to 79%, a response that could be blocked by pretreatment with ambrisentan, indicating a role for ETA receptors. Interestingly, the effect of ET-1 was also inhibited by up to 70% to 80% by pretreatment with NO donors, SNAP and SIN-1. In addition to testing in calf eyes, similar effects of ET-1 and ambrisentan were observed in adult bovine and porcine eyes. Conclusions: The compact eye perfusion platform provides an opportunity to efficiently identify compounds that influence outflow facility and may lead to the discovery of new glaucoma therapies.
Purpose: To study age- and intraocular pressure-induced changes in the glial lamina of the murine optic nerve on the ultrastructural level. Methods: Naïve C57bl/6 mice at various ages spanning the time between early adulthood (3 months) and senescence (30 months) were used in this study. In addition, the intraocular pressure (IOP) was increased in a group of young mice by injection of microbeads into the anterior chamber. The unmyelinated segments of the optic nerve containing the glial lamina were prepared for transmission electron microscopy and imaged at high resolution. Results: Axon packing density decreased slightly with age. Aging nerves contained higher numbers of enlarged and degenerating axons. Mean axonal diameter and in particular the variance of axonal diameter correlated well with age. Axonal mitochondria also showed age-dependent signs of pathology. The mean diameter of axonal mitochondria increased, and aged axons often contained profiles of mitochondria with very few or no cristae. Astrocytic mitochondria remained normal even in very old nerves. Changes to axons and axonal mitochondria in young glaucomatous nerves were comparable with those of 18- to 30-month-old naïve mice. In addition to axons and mitochondria, aged and glaucomatous nerves showed thickening of the blood vessel basement membranes and increased deposition of basement membrane collagen. Conclusions: On the ultrastructural level, the effects of age and elevated IOP are quite similar. One month of elevated IOP seems to have as strongly detrimental effects on the nerve as at least 18 months of normal aging.
Increased intraocular pressure (IOP) represents a major risk factor for glaucoma, a prevalent eye disease characterized by death of retinal ganglion cells; lowering IOP is the only proven treatment strategy to delay disease progression. The main determinant of IOP is the equilibrium between production and drainage of aqueous humor, with compromised drainage generally viewed as the primary contributor to dangerous IOP elevations. Drainage occurs through two pathways in the anterior segment of the eye called conventional and uveoscleral. To gain insights into the cell types that comprise these pathways, we used high-throughput single-cell RNA sequencing (scRNAseq). From ∼24,000 single-cell transcriptomes, we identified 19 cell types with molecular markers for each and used histological methods to localize each type. We then performed similar analyses on four organisms used for experimental studies of IOP dynamics and glaucoma: cynomolgus macaque (), rhesus macaque (), pig (), and mouse (). Many human cell types had counterparts in these models, but differences in cell types and gene expression were evident. Finally, we identified the cell types that express genes implicated in glaucoma in all five species. Together, our results provide foundations for investigating the pathogenesis of glaucoma and for using model systems to assess mechanisms and potential interventions.