Glaucoma

Anand N, Klug E, Nirappel A, Solá-Del Valle D. A Review of Cyclodestructive Procedures for the Treatment of Glaucoma. Semin Ophthalmol 2020;:1-15.Abstract
Cyclodestruction aims to reduce aqueous humor production through the coagulation or destruction of the ciliary body and has been an important treatment choice for glaucoma since the 1930s. The purpose of the current review is to highlight the evidence regarding the safety and efficacy of various cyclodestructive modalities, emphasizing peer-reviewed articles from the last 20 years and the most common variants of these procedures. The review focuses primarily on the two most common variants of transscleral cyclophotocoagulation (TS-CPC), continuous-wave diode cyclophotocoagulation (CW-TSCPC) and MicroPulse diode cyclophotocoagulation (MP-TSCPC) as well as endoscopic cyclophotocoagulation (ECP) and high-intensity focused ultrasound cyclodestruction (HIFU). We believe that the role of cyclodestruction in glaucoma treatment will only continue to expand given the advances in the field, particular with regards to targeted ciliary body destruction and improvement in the safety profile.
Liu WW, McClurkin M, Tsikata E, Hui P-C, Elze T, Celebi ARC, Khoueir Z, Lee R, Shieh E, Simavli H, Que C, Guo R, de Boer J, Chen TC. Three-dimensional Neuroretinal Rim Thickness and Visual Fields in Glaucoma: A Broken-stick Model. J Glaucoma 2020;29(10):952-963.Abstract
PRECIS: In open-angle glaucoma, when neuroretinal rim tissue measured by volumetric optical coherence tomography (OCT) scans is below a third of the normal value, visual field (VF) damage becomes detectable. PURPOSE: To determine the amount of neuroretinal rim tissue thickness below which VF damage becomes detectable. METHODS: In a retrospective cross-sectional study, 1 eye per subject (of 57 healthy and 100 open-angle glaucoma patients) at an academic institution had eye examinations, VF testing, spectral-domain OCT retinal nerve fiber layer (RNFL) thickness measurements, and optic nerve volumetric scans. Using custom algorithms, the minimum distance band (MDB) neuroretinal rim thickness was calculated from optic nerve scans. "Broken-stick" regression was performed for estimating both the MDB and RNFL thickness tipping-point thresholds, below which were associated with initial VF defects in the decibel scale. The slopes for the structure-function relationship above and below the thresholds were computed. Smoothing curves of the MDB and RNFL thickness covariates were evaluated to examine the consistency of the independently identified tipping-point pairs. RESULTS: Plots of VF total deviation against MDB thickness revealed plateaus of VF total deviation unrelated to MDB thickness. Below the thresholds, VF total deviation decreased with MDB thickness, with the associated slopes significantly greater than those above the thresholds (P<0.014). Below 31% of global MDB thickness, and 36.8% and 43.6% of superior and inferior MDB thickness, VF damage becomes detectable. The MDB and RNFL tipping points were in good accordance with the correlation of the MDB and RNFL thickness covariates. CONCLUSIONS: When neuroretinal rim tissue, characterized by MDB thickness in OCT, is below a third of the normal value, VF damage in the decibel scale becomes detectable.
Yousefi S, Elze T, Pasquale LR, Saeedi O, Wang M, Shen LQ, Wellik SR, De Moraes CG, Myers JS, Boland MV. Monitoring Glaucomatous Functional Loss Using an Artificial Intelligence-Enabled Dashboard. Ophthalmology 2020;127(9):1170-1178.Abstract
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.
Gagrani M, Garg I, Ghate D. Surgical interventions for primary congenital glaucoma. Cochrane Database Syst Rev 2020;8:CD008213.Abstract
BACKGROUND: Primary congenital glaucoma (PCG) is an optic neuropathy with high intraocular pressure (IOP) that manifests within the first few years of a child's life and is not associated with other systemic or ocular abnormalities. PCG results in considerable morbidity even in high-income countries. OBJECTIVES: To compare the effectiveness and safety of different surgical techniques for PCG. SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (2020, Issue 4); Ovid MEDLINE; Embase.com; PubMed; metaRegister of Controlled Trials (mRCT) (last searched 23 June 2014); ClinicalTrials.gov; and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). We did not use any date or language restrictions in the electronic search. We last searched the electronic databases on 27 April 2020. SELECTION CRITERIA: We included randomized controlled trials (RCTs) and quasi-RCTs comparing different surgical interventions in children under five years of age with PCG. DATA COLLECTION AND ANALYSIS: We used standard Cochrane methodology. MAIN RESULTS: We included 16 trials (13 RCTs and three quasi-RCTs) with 587 eyes in 446 children. Eleven (69%) trials were conducted in Egypt and the Middle East, three in India, and two in the USA. All included trials involved children younger than five years of age, with follow-up ranging from six to 80 months. The interventions compared varied across trials. Three trials (on 68 children) compared combined trabeculotomy and trabeculectomy (CTT) with trabeculotomy. Meta-analysis of these trials suggests there may be little to no evidence of a difference between groups in mean IOP (mean difference (MD) 0.27 mmHg, 95% confidence interval (CI) -0.74 to 1.29; 88 eyes; 2 studies) and surgical success (risk ratio (RR) 1.01, 95% CI 0.90 to 1.14; 102 eyes; 3 studies) at one year postoperatively. We assessed the certainty of evidence as very low for these outcomes, downgrading for risk of bias (-1) and imprecision (-2). Hyphema was the most common adverse outcome in both groups (no meta-analysis due to considerable heterogeneity; I = 83%). Two trials (on 39 children) compared viscotrabeculotomy to conventional trabeculotomy. Meta-analysis of 42 eyes suggests there is no evidence of between groups difference in mean IOP (MD -1.64, 95% CI -5.94 to 2.66) and surgical success (RR 1.11, 95% CI 0.70 to 1.78) at six months postoperatively. We assessed the certainty of evidence as very low, downgrading for risk of bias and imprecision due to small sample size. Hyphema was the most common adverse outcome (38% in viscotrabeculotomy and 28% in conventional trabeculotomy), with no evidence of difference difference (RR 1.33, 95% CI 0.63 to 2.83). Two trials (on 95 children) compared microcatheter-assisted 360-degree circumferential trabeculotomy to conventional trabeculotomy. Meta-analysis of two trials suggests that mean IOP may be lower in the microcatheter group at six months (MD -2.44, 95% CI -3.69 to -1.19; 100 eyes) and at 12 months (MD -1.77, 95% CI -2.92 to -0.63; 99 eyes); and surgical success was more likely to be achieved in the microcatheter group compared to the conventional trabeculotomy group (RR 1.59, 95% CI 1.14 to 2.21; 60 eyes; 1 trial at 6 months; RR 1.54, 95% CI 1.20 to 1.97; 99 eyes; 2 trials at 12 months). We assessed the certainty of evidence for these outcomes as moderate due to small sample size. Hyphema was the most common adverse outcome (40% in the microcatheter group and 17% in the conventional trabeculotomy group), with greater likelihood of occurring in the microcatheter group (RR 2.25, 95% CI 1.25 to 4.04); the evidence was of moderate certainty due to small sample size (-1). Of the nine remaining trials, no two trials compared the same two surgical interventions: one trial compared CTT versus CTT with sclerectomy; three trials compared various suturing techniques and adjuvant use including mitomycin C, collagen implant in CTT; one trial compared CTT versus Ahmed valve implant in previously failed surgeries; one trial compared CTT with trabeculectomy; one trial compared trabeculotomy to goniotomy; and two trials compared different types of goniotomy. No trials reported quality of life or economic data. Many of the included trials had limitations in study design, implementation, and reporting, therefore the reliability and applicability of the evidence remains unclear. AUTHORS' CONCLUSIONS: The evidence suggests that there may be little to no evidence of difference between CTT and routine conventional trabeculotomy, or between viscotrabeculotomy and routine conventional trabeculotomy. A 360-degree circumferential trabeculotomy may show greater surgical success than conventional trabeculotomy. Considering the rarity of the disease, future research would benefit from a multicenter, possibly international trial, involving parents of children with PCG and with a follow-up of at least one year.
Chen X, Lei F, Zhou C, Chodosh J, Wang L, Huang Y, Dohlman CH, Paschalis EI. Glaucoma after Ocular Surgery or Trauma: The Role of Infiltrating Monocytes and Their Response to Cytokine Inhibitors. Am J Pathol 2020;190(10):2056-2066.Abstract
Glaucoma is a frequent and devastating long-term complication following ocular trauma, including corneal surgery, open globe injury, chemical burn, and infection. Postevent inflammation and neuroglial remodeling play a key role in subsequent ganglion cell apoptosis and glaucoma. To this end, this study was designed to investigate the amplifying role of monocyte infiltration into the retina. By using three different ocular injury mouse models (corneal suture, penetrating keratoplasty, and globe injury) and monocyte fate mapping techniques, we show that ocular trauma or surgery can cause robust infiltration of bone marrow-derived monocytes into the retina and subsequent neuroinflammation by up-regulation of Tnf, Il1b, and Il6 mRNA within 24 hours. This is accompanied by ganglion cell apoptosis and neurodegeneration. Prompt inhibition of tumor necrosis factor-α or IL-1β markedly suppresses monocyte infiltration and ganglion cell loss. Thus, acute ocular injury (surgical or trauma) can lead to rapid neuroretinal inflammation and subsequent ganglion cell loss, the hallmark of glaucoma. Infiltrating monocytes play a central role in this process, likely amplifying the inflammatory cascade, aiding in the activation of retinal microglia. Prompt administration of cytokine inhibitors after ocular injury prevents this infiltration and ameliorates the damage to the retina-suggesting that it may be used prophylactically for neuroprotection against post-traumatic glaucoma.
Mihailovic A, Varadaraj V, Ramulu PY, Friedman DS. Evaluating Goldmann Applanation Tonometry Intraocular Pressure Measurement Agreement Between Ophthalmic Technicians and Physicians. Am J Ophthalmol 2020;219:170-176.Abstract
PURPOSE: To examine IOP measurement disagreement between technicians and physicians and the impact of an educational intervention on the short and long-term disagreement in IOP measurement using Goldmann applanation tonometry. DESIGN: Prospective study designed to enhance measurement reliability. SETTING: A glaucoma clinic at a university hospital. StudyPopulation: 6 technicians and 2 physicians. INTERVENTION: An educational intervention was implemented for the technicians to improve IOP measurement agreement with physicians. MainOutcomeMeasures: Frequency of IOP measurement disagreement between physicians and technicians, defined as a difference in IOP of >2 or >3 mm Hg and assessed at baseline and immediately and 6 months postintervention. RESULTS: IOP was evaluated for a total of 529 eyes (physician measured mean IOP = 16.4 mm Hg [SD = 5.9]), 30 per technician-physician pair for each data collection period: baseline, immediately postintervention and 6 months postintervention. At baseline, physicians disagreed 17% and 7% of the time when measuring IOP using >2 and >3 mm Hg to define disagreement, respectively, whereas the average disagreement between technicians and physicians was 25% and 13%. Disagreement was greater at IOPs greater than 20 mm Hg. No significant changes were noted in the frequency of disagreement between technicians and physicians immediately or 6 months postintervention. CONCLUSIONS: Two physicians measuring the same patient in the same room disagreed by >2 mm Hg in 17% of patients' eyes, and this amount of disagreement was even higher when comparing physicians to certified technicians. An educational intervention did not improve agreement in IOP measurements between technicians and physicians. This highlights an important limitation of Goldmann tonometry.
Kempen JH, Van Natta ML, Friedman DS, Altaweel MM, Ansari H, Dunn JP, Elner SG, Holbrook JT, Lim LL, Sugar EA, Jabs DA, and Group MUST (MUST) TF-up SR. Incidence and Outcome of Uveitic Glaucoma in Eyes With Intermediate, Posterior, or Panuveitis Followed up to 10 Years After Randomization to Fluocinolone Acetonide Implant or Systemic Therapy. Am J Ophthalmol 2020;219:303-316.Abstract
PURPOSE: To evaluate long-term risk and outcomes of glaucoma in eyes with intermediate, posterior, and panuveitis managed with systemic or fluocinolone acetonide (0.59 mg, "implant") therapy. DESIGN: Prospective Follow-up of the Multicenter Uveitis Steroid Treatment (MUST) Clinical Trial Cohort. METHODS: Patients with intermediate, posterior, or panuveitis randomized to implant or systemic therapy (corticosteroid plus immunosuppression in >90%) were followed prospectively for glaucoma incidence and outcome. RESULTS: Among 405 uveitic at-risk eyes of 232 patients (median follow-up = 6.9 years), 40% (79/196) of eyes assigned and treated with implant and 8% (17/209) of eyes assigned and treated with systemic therapy (censoring eyes receiving an implant on implantation) developed glaucoma (hazard ratio [HR] = 5.9, 95% confidence interval [CI] 3.2, 10.8; P < .001). Adjustment for intraocular pressure (IOP) elevation during follow-up only partially mitigated the association of implant treatment with glaucoma incidence: HR = 3.1 (95% CI 1.6, 6.0); P = .001. Among 112 eyes of 83 patients developing glaucoma, the 5-year cumulative incidence following diagnosis of sustained (2 or more consecutive visits) worsening of mean deviation by ≥6 dB was 20% (95% CI 12%, 33%); 5-year cumulative incidence of sustained worsening of cup-to-disc ratio by ≥0.2 was 26% (95% CI 17%, 39%). CONCLUSIONS: The implant has substantially higher risk of glaucoma than systemic therapy, a difference not entirely explained by posttreatment IOP elevation. Management of IOP elevation was effective in preventing worsening of glaucoma for the large majority of cases, but even under expert clinical management, some glaucoma worsened. Uveitis cases should be monitored carefully for IOP elevation and glaucoma indefinitely.
Elhusseiny AM, VanderVeen DK. Outcomes of Glaucoma Drainage Devices in Childhood Glaucoma. Semin Ophthalmol 2020;:1-11.Abstract
PURPOSE: Angle surgery is the gold standard for the management of many types of childhood glaucoma, yet glaucoma drainage devices (GDD) are effective tools for refractory advanced cases or secondary childhood glaucomas. The purpose of this article is to review recently published literature focused on the use of GDDs for pediatric glaucoma, including GDD general principles and surgical outcomes. METHODS: Literature review of various electronic databases was performed. RESULTS: 71 papers were reviewed for outcomes of GDD in childhood glaucomas. Success rates were usually defined by intraocular pressure (IOP) of 5-22 mmHg, with or without medications. Success rates were typically higher for non-valved GDDs but varied by length of follow-up. Non-valved GDDs afford lower and longer-lasting IOP control in pediatric eyes than valved GDD, however, no randomized controlled trials exist in childhood glaucoma. CONCLUSION: Various designs of GDDs are available for management of childhood glaucoma with good short-term success rates; individual patient factors should be taken into consideration when selecting a specific device.
Elhusseiny AM, Jamerson EC, Menshawey R, Tam EK, El Sayed YM. Collector Channels: Role and Evaluation in Schlemm's Canal Surgery. Curr Eye Res 2020;45(10):1181-1187.Abstract
OBJECTIVES: 1) To elucidate the role of collector channels in the aqueous humor outflow pathway 2) To suggest anatomic and functional methods of imaging collector channels in-vitro and in-vivo and 3) To discuss the role of such imaging modalities in the surgical management of glaucoma. METHODS: A thorough literature search was conducted on databases for studies published in English regarding the available methods to determine the role of collecting channels in normal and glaucomatous patients and to assess their patency. RESULTS: Intraocular pressure (IOP) exists as a balance between aqueous humor production and aqueous humor outflow. Collector channels are an essential anatomical constituent of the distal portion of the conventional aqueous humor outflow pathway. There are different surgical options for glaucoma management and with the recent advances in Schlemm's canal-based surgeries, collector channel's patency became a key factor in determining the optimum management for the glaucomatous eye. The advent of anatomic imaging methods has improved the ability to visualize collector channel morphology in-vitro, including swept-source optical coherence tomography (SS-OCT), spectral domain optical coherence tomography (SD-OCT), micro-computed tomography (micro CT), new immunohistochemistry techniques and scanning electron microscopy. The recent advent of real-time assessment of collector channel patency (including evaluation of episcleral venous outflow, observation of episcleral venous fluid wave, and tracer studies utilizing fluorescein, indocyanine green, and trypan blue) has been validated by the aforementioned anatomic imaging modalities. CONCLUSIONS: New modalities of in-vitro and in-vivo studies of collector channels provide promise to aid in the assessment of collector channel patency and individualization of surgical management for glaucoma patients.
Kang JH, VoPham T, Laden F, Rosner BA, Wirostko B, Ritch R, Wiggs JL, Qureshi A, Nan H, Pasquale LR. Cohort Study of Nonmelanoma Skin Cancer and the Risk of Exfoliation Glaucoma. J Glaucoma 2020;29(6):448-455.Abstract
PRECIS: In a cohort study of 120,307 participants with 25+ years of follow-up, a history of nonmelanoma skin cancer (NMSC) was associated with a 40% higher exfoliation glaucoma (XFG) risk. PURPOSE: The purpose of this study was to evaluate the relationship between NMSC (a marker of ultraviolet radiation exposure) and XFG. METHODS: We performed a cohort study of US women (n=79,102; 1980-2014) and men (n=41,205; 1986-2014), aged 40+ years and at risk for glaucoma who reported eye examinations. From 1984 (women)/1988 (men), we asked about basal cell carcinoma or squamous cell carcinoma history separately; in prior years, we asked about any NMSC history in a single question. Squamous cell carcinoma was confirmed with histopathology reports while basal cell carcinoma and any early (<1984/<1988) NMSC history was self-reported. Incident XFG cases (362 women and 83 men) were confirmed with medical records. Using pooled data, we estimated multivariable-adjusted relative risks [MVRRs; 95% confidence intervals (CIs)] with Cox proportional hazards models that were stratified by age (in mo), 2-year time period at risk and average lifetime residential latitude. RESULTS: In multivariable-adjusted analyses, we observed a 40% higher XFG risk with any NMSC history (MVRR=1.40; 95% CI=1.08-1.82); the association was observed even with 4 and 8-year lags in NMSC history. Also, the NMSC association was stronger in younger (below 65 y; MVRR=2.56; 95% CI=1.62-4.05) versus older participants (65 y and above; MVRR=1.25; 95% CI=0.94-1.66; P for interaction=0.01) and those living in the northern latitudes (≥42°N; MVRR=1.92; 95% CI=1.28-2.88) versus more southern latitudes (<42°N; MVRR=1.19; 95% CI=0.86-1.66; P for interaction=0.04). CONCLUSION: NMSC was associated with higher XFG risk, particularly among younger participants and those living in the Northern US.
Junk AK, Chang TC, Vanner E, Chen T. Current Trends in Tonometry and Tonometer Tip Disinfection. J Glaucoma 2020;29(7):507-512.Abstract
PRECIS: A survey among members of the American Glaucoma Society (AGS) and the American Optometry Association (AOA) on tonometer preference and tonometer disinfection indicates a shift to disposable tonometer tips compared with 1987. PURPOSE: This survey's purpose was to determine how eye care providers responded to the 2008 Centers of Disease Control (CDC) tonometer disinfection guidelines, which recommend 10% hypochlorite (dilute bleach) for reusable tonometers. Tonometers measure the eye pressure when they touch the cornea, an essential part of the eye examination. METHODS: AGS and AOA members were surveyed on tonometer preference, tonometer use, disinfection process, disinfectants, disinfection timing, and tonometer damage. RESULTS: Survey responses from 79 AOA members and 197 AGS members are included. The Goldmann tonometer is considered most accurate (70, 89% AOA and 161, 82% AGS). It is preferred by 54 (70%) AOA and 193 (98%) AGS members. Many providers (165) use reusable Goldmann tonometer tips (77, 79% AOA, 88, 45% AGS), and most clean with 70% isopropyl alcohol wipes 59 (77%) AOA and 54 (61%) AGS. In summary, 126 of 276 participants (8, 10% AOA and 118, 60% AGS) follow CDC guidelines by using disposable tips (2 AOA and 109 AGS) or disinfecting reusable tips with 10% hypochlorite (6 AOA and 9 AGS). CONCLUSIONS: The majority of AGS providers follow current CDC tonometer disinfection guidelines by shifting to disposable Goldmann tonometer tips. Only a minority of providers who use reusable tonometer tips disinfect with dilute bleach. Continued education on proper tonometer disinfection is critical to prevent eye-care related infection due to improper disinfection.
E J-Y, Mihailovic A, Kuo P-L, West SK, Friedman DS, Gitlin LN, Li T, Schrack JA, Ramulu PY. Characterizing the Impact of Fear of Falling on Activity and Falls in Older Adults with Glaucoma. J Am Geriatr Soc 2020;68(8):1847-1851.Abstract
OBJECTIVE: Fear of falling (FoF) may alter mobility in older adults, especially among those with visual impairment. Using a longitudinal prospective cohort of older glaucoma patients, we investigated whether and how FoF is associated with future falls and physical activity. DESIGN: Prospective observational cohort study. SETTING: Hospital-based single-center recruitment. PARTICIPANTS: Individuals with glaucoma or suspected glaucoma. MEASUREMENTS: FoF was measured annually over a 3-year period using the University of Illinois at Chicago FoF Questionnaire, with lower Rasch-analyzed FoF scores (in logit units) indicating less fear. Participants recorded falls prospectively over the 3-year period using monthly mail-in calendars. Daily steps were collected annually over 7 days using an accelerometer. Visual field (VF) sensitivity was derived by combining sensitivities from monocular VF results. Participants completed questionnaires to determine other demographic/health characteristics. Multivariate random effects models evaluated within-participant changes in fall rates and physical activity across study years. RESULTS: At lower FoF levels (FoF≤0), each one-unit worsening in FoF score across study years was associated with 2.73 times higher odds of reporting at least one fall in the next year (95% confidence interval [CI] = 1.55-4.81) but was not associated with average daily steps (P = .44). Similar results were seen when fall rates were normalized by number of steps taken (P = .97). At higher FoF levels (FoF > 0), inter-year changes in FoF scores were not significantly associated with reporting a fall in the following year (P = .78) but were associated with 407 fewer average daily steps per one-unit change in FoF (95% CI = -743 to -71). CONCLUSION: FoF is an important psychological factor associated with mobility in glaucoma patients, although specific aspects of mobility (fall rates vs activity levels) affected vary by the degree of FoF. Our findings suggest that customizing behavioral interventions for older adults based on their levels of FoF may be an important strategy for fall prevention and activity promotion. J Am Geriatr Soc 68:1847-1851, 2020.
Liu WW, Werner A, Chen TC. Repair of Tube Erosion by Modifying the Tube Extender. J Glaucoma 2020;29(7):604-606.Abstract
We describe here a case report of a novel technique for tube erosion repair, which modifies and utilizes the commercially available tube extender (Model TE). The modification of the tube extender makes the commercially available tube extender more compact and is useful in cases where conjunctival mobility and space are limited. This debulking of the tube extender may reduce the risk of future tube exposure and dellen formation.
van Zyl T, Yan W, McAdams A, Peng Y-R, Shekhar K, Regev A, Juric D, Sanes JR. Cell atlas of aqueous humor outflow pathways in eyes of humans and four model species provides insight into glaucoma pathogenesis. Proc Natl Acad Sci U S A 2020;117(19):10339-10349.Abstract
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.

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