Glaucoma

Pasquale LR, Loomis SJ, Kang JH, Yaspan BL, Abdrabou W, Budenz DL, Chen TC, Delbono E, Friedman DS, Gaasterland D, Gaasterland T, Grosskreutz CL, Lee RK, Lichter PR, Liu Y, McCarty CA, Moroi SE, Olson LM, Realini T, Rhee DJ, Schuman JS, Singh K, Vollrath D, Wollstein G, Zack DJ, Allingham RR, Pericak-Vance MA, Weinreb RN, Zhang K, Hauser MA, Richards JE, Haines JL, Wiggs JL. CDKN2B-AS1 genotype-glaucoma feature correlations in primary open-angle glaucoma patients from the United States. Am J Ophthalmol 2013;155(2):342-353.e5.Abstract
PURPOSE: To assess the association between single nucleotide polymorphisms (SNPs) of the gene region containing cyclin-dependent kinase inhibitor 2B antisense noncoding RNA (CDKN2B-AS1) and glaucoma features among primary open-angle glaucoma (POAG) patients. DESIGN: Retrospective observational case series. METHODS: We studied associations between 10 CDKN2B-AS1 SNPs and glaucoma features among 976 POAG cases from the Glaucoma Genes and Environment (GLAUGEN) study and 1971 cases from the National Eye Institute Glaucoma Human Genetics Collaboration (NEIGHBOR) consortium. For each patient, we chose the feature from the eye with the higher value. We created cohort-specific multivariable models for glaucoma features and then meta-analyzed the results. RESULTS: For 9 of the 10 protective CDKN2B-AS1 SNPs with minor alleles associated with reduced disease risk (eg, the G allele at rs2157719), POAG patients carrying these minor alleles had smaller cup-to-disc ratio (0.05 units smaller per G allele at diagnosis; 95% CI: -0.08, -0.03; P = 6.23E-05) despite having higher intraocular pressure (IOP) (0.70 mm Hg higher per G allele at DNA collection; 95% CI: 0.40, 1.00; P = 5.45E-06). For the 1 adverse rs3217992 SNP with minor allele A associated with increased disease risk, POAG patients with A alleles had larger cup-to-disc ratio (0.05 units larger per A allele at diagnosis; 95% CI: 0.02, 0.07; P = 4.74E-04) despite having lower IOP (-0.57 mm Hg per A allele at DNA collection; 95% CI: -0.84, -0.29; P = 6.55E-05). CONCLUSION: Alleles of CDKN2B-AS1 SNPs, which influence risk of developing POAG, also modulate optic nerve degeneration among POAG patients, underscoring the role of CDKN2B-AS1 in POAG.
Kang MH, Oh D-J, Kang J-heon, Rhee DJ. Regulation of SPARC by transforming growth factor β2 in human trabecular meshwork. Invest Ophthalmol Vis Sci 2013;54(4):2523-32.Abstract
PURPOSE: An increased aqueous level of TGF-β2 has been found in many primary open-angle glaucoma patients. Secreted Protein, Acidic, and Rich in Cysteine (SPARC)-null mice have a lower intraocular pressure. The mechanistic relationship between SPARC and TGF-β2 in trabecular meshwork (TM) is unknown. We hypothesized that TGF-β2 upregulates SPARC expression in TM. METHODS: Cultured TM cells were incubated with selective inhibitors for p38 MAP kinase (p38), Smad3, p42, JNK, RhoA, PI3K, or TGF-β2 receptor for 2 hours, and then TGF-β2 was added for 24 hours in serum-free media. Quantitative polymerase chain reaction (qPCR) and immunoblot analysis were performed. Immunofluorescent microscopy was used to determine nuclear translocation of signaling proteins. Ad5.hSPARC and Lentiviral shRNA for p38 and Smad3 were constructed, and infected human TM cells. RESULTS: SPARC was upregulated by TGF-β2 in the human TM cells (3.8 ± 1.7-fold, n = 6, P = 0.01 for protein and 7.1 ± 3.7-fold, n = 6, P = 0.01 for mRNA), while upregulation of SPARC had no effect on TGF-β2. TGF-β2-induced SPARC expression was suppressed by inhibitors against p38 (-40.3 ± 20.9%, n = 10, P = 0.0001), Smad3 (-56.2 ± 18.9%, n = 10, P = 0.0001), JNK (-49.1 ± 24.6%, n = 10, P = 0.0001), and TGF-β2 receptor (-83.6 ± 14.4%, n = 6, P = 0.003). Phosphorylation and translocation of Smad3, p38, and MAPKAPK2 were detected at 30 minutes and 1 hour, respectively, following TGF-β2 treatment. Phosphorylation of JNK and c-jun was detected before TGF-β2 treatment. SPARC was suppressed 31 ± 13% (n = 5, P < 0.0001) by shRNA-p38 and 41 ± 3% (n = 5, P < 0.0001) by shRNA-Smad3. CONCLUSIONS: TGF-β2 upregulates SPARC expression in human TM through Smad-dependent (Smad2/3) or -independent (p38) signaling pathways. SPARC may be a downstream regulatory node of TGF-β2-mediated IOP elevation.
Lye-Barthel M, Sun D, Jakobs TC. Morphology of astrocytes in a glaucomatous optic nerve. Invest Ophthalmol Vis Sci 2013;54(2):909-17.Abstract
PURPOSE: To establish the morphologic changes of astrocytes in the glial lamina of glaucomatous mice. METHODS: A strain of mice that expresses GFP in individual astrocytes (hGFAPpr-GFP) was crossed into the DBA/2J strain that develops glaucoma. In the resulting strain (D2.hGFAPpr-GFP) we assessed the severity of glaucoma by staining the retina for neurofilaments and counting the neurons of the retinal ganglion cell layer. We observed the morphology of astrocytes in the glial lamina of the optic nerves. RESULTS: D2.hGFAPpr-GFP mice developed glaucoma in an age-dependent manner. Astrocytes in the glial lamina showed morphologic changes that correlated with the severity of glaucoma. The cells showed thickening of processes from 1.3 ± 0.28 μm in nondiseased animals to 1.71 ± 0.46 μm in eyes with moderate glaucoma and 2.1 ± 0.42 μm in those with severe glaucoma. Their spatial coverage, as determined by their convex polygon area, was reduced in eyes with severe glaucoma. The astrocytes in severely glaucomatous optic nerves also showed simplification of their processes. In 6-month-old mice with no obvious signs of degeneration in the retina, we found astrocytes with appendages growing out of primary astrocyte processes into the axon bundles. This localized hypertrophy of processes was never observed in the hGFAPpr-GFP strain. CONCLUSIONS: Confirming results after optic nerve crush, astrocytes in glaucomatous optic nerves had thickened and simplified processes, and reduced spatial coverage. We also found evidence of localized sprouting of new processes in early stages of the disease, before detectable changes in ganglion cell number.
Haddadin RI, Oh D-J, Kang MH, Villarreal G, Kang J-heon, Jin R, Gong H, Rhee DJ. Thrombospondin-1 (TSP1)-null and TSP2-null mice exhibit lower intraocular pressures. Invest Ophthalmol Vis Sci 2012;53(10):6708-17.Abstract
PURPOSE: Thrombospondin-1 (TSP1) and TSP2 are matricellular proteins that have been shown to regulate cytoskeleton, cell adhesion, and extracellular matrix remodeling. Both TSP1 and TSP2 are found in the trabecular meshwork (TM). In cadaver eyes with primary open-angle glaucoma (POAG), TSP1 is increased in one third of patients. We hypothesized that TSP1 and TSP2 participate in the regulation of intraocular pressure (IOP). Methods. IOPs of TSP1-null, TSP2-null mice, and their corresponding wild-type (WT) mice were measured using a commercial rebound tonometer. Fluorophotometric measurements assessed aqueous turnover. Central corneal thickness (CCT) was measured by optical coherence tomography. Iridocorneal angles were examined using light microscopy (LM), immunofluorescence (IF), and transmission electron microscopy (TEM). RESULTS: Average IOPs of TSP1-null and TSP2-null mice were 10% and 7% less than that of the corresponding WT mice, respectively. CCTs were 6.5% less in TSP1-null mice (P < 0.05) and 1.1% less in TSP2-null mice (P > 0.05). Fluorophotometric measurements suggest that aqueous turnover rates in TSP1-null and TSP2-null mice are greater than those of WT mice. LM of the TSP1-null and TSP2-null iridocorneal angles reveals morphology, which is indistinguishable from that of their corresponding WTs. IF revealed possible concurrent underexpression of TSP2 in TSP1-null mice and of TSP1 in TSP2-null mice. TEM revealed larger collagen fibril diameters in TSP1-null and TSP2-null mice compared with WTs. CONCLUSIONS: TSP1-null and TSP2-null mice have lower IOPs than their WT counterparts. The rate of aqueous turnover suggests that the mechanism is enhanced outflow facility. An alteration in the extracellular matrix may contribute to this finding.
Wu H, de Boer JF, Chen TC. Diagnostic capability of spectral-domain optical coherence tomography for glaucoma. Am J Ophthalmol 2012;153(5):815-826.e2.Abstract
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.
Vu KTH, Jager MJ, Chen DF. The Immunology of Glaucoma. Asia Pac J Ophthalmol (Phila) 2012;1(5):303-11.Abstract
The presence of specific antibodies and T cells that are specific in patients with glaucoma supports the idea that the immune system may play an important role in the initiation and/or sustainment of glaucomatous optic neuropathy, at least in some patients. At present, our understanding regarding immunological mechanisms associated with glaucomatous optic neuropathy is far from satisfactory. In this review, we examined evidence suggesting involvement of autoimmune responses in the pathogenesis of glaucoma. These include detection of autoantibodies and T cells and expression of cytokines and stress proteins in patients with glaucoma. Although immune responses are thought to be detrimental, some responses may exert a protective effect against neurodegenerative damage. Likely, the balance between positive and negative regulators determines the survival or demise of cells. It is vital that research continues to elucidate the roles of the immune system in glaucomatous neurodegeneration and the possibility of alternative modalities of treatment. These studies may also provide valuable molecular biomarkers for the diagnosis and identification of a specific cohort of patients with glaucoma, that is, those with normal-tension glaucoma.
Wiggs JL, Hewitt AW, Fan BJ, Wang DY, Figueiredo Sena DR, O'Brien C, Realini A, Craig JE, Dimasi DP, Mackey DA, Haines JL, Pasquale LR. The p53 codon 72 PRO/PRO genotype may be associated with initial central visual field defects in caucasians with primary open angle glaucoma. PLoS One 2012;7(9):e45613.Abstract
BACKGROUND: Loss of vision in glaucoma is due to apoptotic retinal ganglion cell loss. While p53 modulates apoptosis, gene association studies between p53 variants and glaucoma have been inconsistent. In this study we evaluate the association between a p53 variant functionally known to influence apoptosis (codon 72 Pro/Arg) and the subset of primary open angle glaucoma (POAG) patients with early loss of central visual field. METHODS: Genotypes for the p53 codon 72 polymorphism (Pro/Arg) were obtained for 264 POAG patients and 400 controls from the U.S. and in replication studies for 308 POAG patients and 178 controls from Australia (GIST). The glaucoma patients were divided into two groups according to location of initial visual field defect (either paracentral or peripheral). All cases and controls were Caucasian with European ancestry. RESULTS: The p53-PRO/PRO genotype was more frequent in the U.S. POAG patients with early visual field defects in the paracentral regions compared with those in the peripheral regions or control group (p=2.7 × 10(-5)). We replicated this finding in the GIST cohort (p  =7.3 × 10(-3), and in the pooled sample (p=6.6 × 10(-7)) and in a meta-analysis of both the US and GIST datasets (1.3 × 10(-6), OR 2.17 (1.58-2.98 for the PRO allele). CONCLUSIONS: These results suggest that the p53 codon 72 PRO/PRO genotype is potentially associated with early paracentral visual field defects in primary open-angle glaucoma patients.
Wong JJ, Chen TC, Shen LQ, Pasquale LR. Macular imaging for glaucoma using spectral-domain optical coherence tomography: a review. Semin Ophthalmol 2012;27(5-6):160-6.Abstract
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.
Shazly TA, Latina MA, Dagianis JJ, Chitturi S. Effect of central corneal thickness on the long-term outcome of selective laser trabeculoplasty as primary treatment for ocular hypertension and primary open-angle glaucoma. Cornea 2012;31(8):883-6.Abstract
PURPOSE: To determine if central corneal thickness (CCT) impacts the intraocular pressure (IOP)-lowering effect of selective laser trabeculoplasty (SLT) in patients with ocular hypertension (OHT) and primary open-angle glaucoma (POAG). METHODS: A retrospective chart review of consecutive patients, who underwent SLT as primary treatment for OHT and POAG, between 2002 and 2005, was performed. Partial correlation analysis was performed to correlate the CCT to the percentage of IOP reduction at 3 to 30 months after SLT. Independent samples t test was performed to compare mean percentage of IOP reduction in eyes with CCT less than 555 μm versus CCT 555 μm or greater. RESULTS: Eighty eyes of 47 patients were identified. The partial correlation coefficient value between the CCT and percentage of IOP reduction after SLT at 3 months was -0.253 (P = 0.025), at 12 months it was -0.22 (P = 0.049), and at 30 months it was 0.301 (P = 0.007). Independent samples t test showed that the mean percentage of IOP reduction in eyes with thinner corneas (CCT < 555 μm) was greater than that in thicker corneas (CCT ≥ 555 μm) at 3-, 6-, 9-, 12-, and 30-month post-SLT (P < 0.05). CONCLUSIONS: In patients with POAG and OHT, percentage of IOP reduction after SLT was significantly greater in eyes with thinner corneas (CCT < 555 μm). These findings indicate that patients treated with SLT as primary therapy who had thinner corneas demonstrated better IOP control for at least 30 months after SLT.
Wiggs JL, Yaspan BL, Hauser MA, Kang JH, Allingham RR, Olson LM, Abdrabou W, Fan BJ, Wang DY, Brodeur W, Budenz DL, Caprioli J, Crenshaw A, Crooks K, Delbono E, Doheny KF, Friedman DS, Gaasterland D, Gaasterland T, Laurie C, Lee RK, Lichter PR, Loomis S, Liu Y, Medeiros FA, McCarty C, Mirel D, Moroi SE, Musch DC, Realini A, Rozsa FW, Schuman JS, Scott K, Singh K, Stein JD, Trager EH, Vanveldhuisen P, Vollrath D, Wollstein G, Yoneyama S, Zhang K, Weinreb RN, Ernst J, Kellis M, Masuda T, Zack D, Richards JE, Pericak-Vance M, Pasquale LR, Haines JL. Common variants at 9p21 and 8q22 are associated with increased susceptibility to optic nerve degeneration in glaucoma. PLoS Genet 2012;8(4):e1002654.Abstract
Optic nerve degeneration caused by glaucoma is a leading cause of blindness worldwide. Patients affected by the normal-pressure form of glaucoma are more likely to harbor risk alleles for glaucoma-related optic nerve disease. We have performed a meta-analysis of two independent genome-wide association studies for primary open angle glaucoma (POAG) followed by a normal-pressure glaucoma (NPG, defined by intraocular pressure (IOP) less than 22 mmHg) subgroup analysis. The single-nucleotide polymorphisms that showed the most significant associations were tested for association with a second form of glaucoma, exfoliation-syndrome glaucoma. The overall meta-analysis of the GLAUGEN and NEIGHBOR dataset results (3,146 cases and 3,487 controls) identified significant associations between two loci and POAG: the CDKN2BAS region on 9p21 (rs2157719 [G], OR = 0.69 [95%CI 0.63-0.75], p = 1.86×10⁻¹⁸), and the SIX1/SIX6 region on chromosome 14q23 (rs10483727 [A], OR = 1.32 [95%CI 1.21-1.43], p = 3.87×10⁻¹¹). In sub-group analysis two loci were significantly associated with NPG: 9p21 containing the CDKN2BAS gene (rs2157719 [G], OR = 0.58 [95% CI 0.50-0.67], p = 1.17×10⁻¹²) and a probable regulatory region on 8q22 (rs284489 [G], OR = 0.62 [95% CI 0.53-0.72], p = 8.88×10⁻¹⁰). Both NPG loci were also nominally associated with a second type of glaucoma, exfoliation syndrome glaucoma (rs2157719 [G], OR = 0.59 [95% CI 0.41-0.87], p = 0.004 and rs284489 [G], OR = 0.76 [95% CI 0.54-1.06], p = 0.021), suggesting that these loci might contribute more generally to optic nerve degeneration in glaucoma. Because both loci influence transforming growth factor beta (TGF-beta) signaling, we performed a genomic pathway analysis that showed an association between the TGF-beta pathway and NPG (permuted p = 0.009). These results suggest that neuro-protective therapies targeting TGF-beta signaling could be effective for multiple forms of glaucoma.
Shazly TA, Latina MA. Use of processed pericardium graft to plug patulous old sclerostomy track during glaucoma shunt revision for exposure. Ophthalmic Surg Lasers Imaging 2012;43(1):72-5.Abstract
The authors demonstrate a reproducible technique using processed pericardium to seal sclerostomy track during glaucoma shunt revision. The suggested method involves placement of a wedge-shaped processed pericardial graft into the old sclerostomy tract following tube explantation. The graft is trimmed and sutured to the sclera. The tube is reinserted into a new sclerostomy and then sutured in place and covered in the usual fashion. This method allowed relatively easy treatment of three patients with patulous sclerostomy with necrotic edges. A successful tube revision and repositioning of the tube using this technique was performed on three patients with exposed tubes. The intraocular pressure was between 8 and 12 mm Hg from postoperative day 1. The authors suggest the use of pericardium plug to adequately seal the old sclerostomy track during glaucoma shunt revision. The plug allows tube repositioning at a new site without the need to suture the friable sclerostomy edges.
Roh M, Zhang Y, Murakami Y, Thanos A, Lee SC, Vavvas DG, Benowitz LI, Miller JW. Etanercept, a widely used inhibitor of tumor necrosis factor-α (TNF-α), prevents retinal ganglion cell loss in a rat model of glaucoma. PLoS One 2012;7(7):e40065.Abstract
BACKGROUND: Visual loss in glaucoma is associated with pathological changes in retinal ganglion cell (RGC) axons and a slow decline in the RGC population. Age and elevated intraocular pressure (IOP) are the main risk factors for glaucomatous loss of vision. Several studies have implicated the proinflammatory cytokine tumor necrosis factor-α (TNF-α) as a link between elevated IOP and RGC death, but the cellular source of TNF-α and its causative role in RGC death remain uncertain. Here, using a rat model of glaucoma, we investigated the source of elevated TNF-α and examined whether Etanercept, a TNF-α blocker that is in common clinical use for other indications, is protective against RGC death. METHODOLOGY/PRINCIPAL FINDINGS: Episcleral vein cauterization (EVC) caused intraocular pressure (IOP) to be elevated for at least 28 days. IOP elevation resulted in a dramatic increase in TNF-α levels within a few days, axonal degeneration, and a 38% loss of RGCs by 4 weeks. Immunostaining coupled with confocal microscopy showed that OHT induced robust induction of TNF-α in Iba-1-positive microglia around the optic nerve head (ONH). Despite persistent elevation of IOP, Etanercept reduced microglial activation, TNF-α levels, axon degeneration in the optic nerve, and the loss of RGCs. CONCLUSIONS/SIGNIFICANCE: Ocular hypertension (OHT) triggers an inflammatory response characterized by the appearance of activated microglia around the ONH that express TNF-α. Blocking TNF-α activity with a clinically approved agent inhibits this microglial response and prevents axonal degeneration and loss of RGCs. These findings suggest a new treatment strategy for glaucoma using TNF-α antagonists or suppressors of inflammation.

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