Glaucoma

Leidl MC, Choi CJ, Syed ZA, Melki SA. Intraocular pressure fluctuation and glaucoma progression: what do we know?. Br J Ophthalmol 2014;98(10):1315-1319.Abstract

While mean intraocular pressure (IOP) has long been known to correlate with glaucomatous damage, the role of IOP fluctuation is less clearly defined. There is extensive evidence in the literature for and against the value of short-term and long-term IOP fluctuation in the evaluation and prognosis of patients with glaucoma. We present here the arguments made by both sides, as well as a discussion of the pitfalls of prior research and potential directions for future studies. Until a reliable method is developed that allows for constant IOP monitoring, many variables will continue to hinder us from drawing adequate conclusions regarding the significance of IOP variation.

Wiggs JL, Pasquale LR. Expression and Regulation of LOXL1 and Elastin-related Genes in Eyes With Exfoliation Syndrome. J Glaucoma 2014;:S62-3.Abstract

Variants in LOXL1 are significantly associated with exfoliation syndrome (XFS), however the impact of the associated variants on disease development is not yet understood. Initially the associated missense changes, R141L and G153D, were considered to be pathogenic alleles. Flipping of the risk allele in certain populations for both missense variants provided strong evidence that these missense changes are not biologically significant and suggest that other LOXL1 variant(s), in linkage disequilibrium with these missense variants, predispose to exfoliation syndrome by affecting gene expression or protein function. Several lines of evidence support dysregulation of LOXL1 gene expression as a contributing factor to disease development. First, in the German population the R141L (rs1048661) risk allele reduced LOXL1 expression by 20%. Second, haplotype analysis identified a risk haplotype that includes including R141L, G153D, as well as a LOXL1 promoter region variant previously shown to reduce gene expression (rs16958477). Third, the LOXL1 risk haplotype influences gene expression induced by disease-associated factors TGF-B1, oxidative stress, UV light and hypoxia. Finally, a LOXL1 null mouse has some features of XFS suggesting that decreased enzyme activity contributes to predisposition to the disease. Collectively, these results suggest that dysregulation of LOXL1 expression is a contributing factor to exfoliation disease development.

Gharahkhani P, Burdon KP, Fogarty R, Sharma S, Hewitt AW, Martin S, Law MH, Cremin K, Bailey JCN, Loomis SJ, Pasquale LR, Haines JL, Hauser MA, Viswanathan AC, McGuffin P, Topouzis F, Foster PJ, Graham SL, Casson RJ, Chehade M, White AJ, Zhou T, Souzeau E, Landers J, Fitzgerald JT, Klebe S, Ruddle JB, Goldberg I, Healey PR, Healey PR, Healey PR, Mills RA, Wang JJ, Montgomery GW, Martin NG, Radford-Smith G, Whiteman DC, Brown MA, Wiggs JL, Mackey DA, Mitchell P, Macgregor S, Craig JE. Common variants near ABCA1, AFAP1 and GMDS confer risk of primary open-angle glaucoma. Nat Genet 2014;46(10):1120-5.Abstract

Primary open-angle glaucoma (POAG) is a major cause of irreversible blindness worldwide. We performed a genome-wide association study in an Australian discovery cohort comprising 1,155 cases with advanced POAG and 1,992 controls. We investigated the association of the top SNPs from the discovery stage in two Australian replication cohorts (932 cases and 6,862 controls total) and two US replication cohorts (2,616 cases and 2,634 controls total). Meta-analysis of all cohorts identified three loci newly associated with development of POAG. These loci are located upstream of ABCA1 (rs2472493[G], odds ratio (OR) = 1.31, P = 2.1 × 10(-19)), within AFAP1 (rs4619890[G], OR = 1.20, P = 7.0 × 10(-10)) and within GMDS (rs11969985[G], OR = 1.31, P = 7.7 × 10(-10)). Using RT-PCR and immunolabeling, we show that these genes are expressed within human retina, optic nerve and trabecular meshwork and that ABCA1 and AFAP1 are also expressed in retinal ganglion cells.

Springelkamp H, Höhn R, Mishra A, Hysi PG, Khor C-C, Loomis SJ, Bailey JCN, Gibson J, Thorleifsson G, Janssen SF, Luo X, Ramdas WD, Vithana E, Nongpiur ME, Montgomery GW, Xu L, Mountain JE, Gharahkhani P, Lu Y, Amin N, Karssen LC, Sim K-S, van Leeuwen EM, Iglesias AI, Verhoeven VJM, Hauser MA, Loon S-C, Despriet DDG, Nag A, Venturini C, Sanfilippo PG, Schillert A, Kang JH, Landers J, Jonasson F, Cree AJ, van Koolwijk LME, Rivadeneira F, Souzeau E, Jonsson V, Menon G, Menon G, Weinreb RN, de Jong PTVM, Oostra BA, Uitterlinden AG, Hofman A, Ennis S, Thorsteinsdottir U, Burdon KP, Burdon KP, Burdon KP, Spector TD, Mirshahi A, Saw S-M, Vingerling JR, Teo Y-Y, Haines JL, Wolfs RCW, Lemij HG, Tai E-S, Jansonius NM, Jonas JB, Cheng C-Y, Aung T, Viswanathan AC, Klaver CCW, Craig JE, Macgregor S, Mackey DA, Lotery AJ, Stefansson K, Bergen AAB, Young TL, Wiggs JL, Pfeiffer N, Wong T-Y, Pasquale LR, Hewitt AW, van Duijn CM, Hammond CJ, Hammond CJ, Hammond CJ, Hammond CJ. Meta-analysis of genome-wide association studies identifies novel loci that influence cupping and the glaucomatous process. Nat Commun 2014;5:4883.Abstract

Glaucoma is characterized by irreversible optic nerve degeneration and is the most frequent cause of irreversible blindness worldwide. Here, the International Glaucoma Genetics Consortium conducts a meta-analysis of genome-wide association studies of vertical cup-disc ratio (VCDR), an important disease-related optic nerve parameter. In 21,094 individuals of European ancestry and 6,784 individuals of Asian ancestry, we identify 10 new loci associated with variation in VCDR. In a separate risk-score analysis of five case-control studies, Caucasians in the highest quintile have a 2.5-fold increased risk of primary open-angle glaucoma as compared with those in the lowest quintile. This study has more than doubled the known loci associated with optic disc cupping and will allow greater understanding of mechanisms involved in this common blinding condition.

Pasquale LR, Jiwani AZ, Zehavi-Dorin T, Majd A, Rhee DJ, Chen T, Turalba A, Shen L, Brauner S, Grosskreutz C, Gardiner M, Chen S, Borboli-Gerogiannis S, Greenstein SH, Chang K, Ritch R, Loomis S, Kang JH, Wiggs JL, Levkovitch-Verbin H. Solar exposure and residential geographic history in relation to exfoliation syndrome in the United States and Israel. JAMA Ophthalmol 2014;132(12):1439-45.Abstract
IMPORTANCE: Residential (geographic) history and extent of solar exposure may be important risk factors for exfoliation syndrome (XFS) but, to our knowledge, detailed lifetime solar exposure has not been previously evaluated in XFS. OBJECTIVE: To assess the relation between residential history, solar exposure, and XFS. DESIGN, SETTING, AND PARTICIPANTS: This clinic-based case-control study was conducted in the United States and Israel. It involved XFS cases and control individuals (all ≥60-year-old white individuals) enrolled from 2010 to 2012 (United States: 118 cases and 106 control participants; Israel: 67 cases and 72 control participants). MAIN OUTCOMES AND MEASURES: Weighted lifetime average latitude of residence and average number of hours per week spent outdoors as determined by validated questionnaires. RESULTS: In multivariable analyses, each degree of weighted lifetime average residential latitude away from the equator was associated with 11% increased odds of XFS (pooled odds ratio [OR], 1.11; 95% CI, 1.05-1.17; P < .001). Furthermore, every hour per week spent outdoors during the summer, averaged over a lifetime, was associated with 4% increased odds of XFS (pooled OR, 1.04; 95% CI, 1.00-1.07; P = .03). For every 1% of average lifetime summer time between 10 am and 4 pm that sunglasses were worn, the odds of XFS decreased by 2% (OR, 0.98; 95% CI, 0.97-0.99; P < .001) in the United States but not in Israel (OR, 1.00; 95% CI, 0.99-1.01; P = .92; P for heterogeneity = .005). In the United States, after controlling for important environmental covariates, history of work over water or snow was associated with increased odds of XFS (OR, 3.86; 95% CI, 1.36-10.9); in Israel, there were too few people with such history for analysis. We did not identify an association between brimmed hat wear and XFS (P > .57). CONCLUSIONS AND RELEVANCE: Lifetime outdoor activities may contribute to XFS. The association with work over snow or water and the lack of association with brimmed hat wear suggests that ocular exposure to light from reflective surfaces may be an important type of exposure in XFS etiology.
Wang R, Wiggs JL. Common and Rare Genetic Risk Factors for Glaucoma. Cold Spring Harb Perspect Med 2014;Abstract

The characterization of genes responsible for glaucoma is the critical first step toward the development of gene-based diagnostic and screening tests, which could identify individuals at risk for disease before irreversible optic nerve damage occurs. Early-onset forms of glaucoma affecting children and young adults are typically inherited as Mendelian autosomal dominant or recessive traits whereas glaucoma affecting older adults has complex inheritance. In this report, we present a comprehensive overview of the genes and genomic regions contributing to inherited glaucoma.

Feke GT, Rhee DJ, Turalba AV, Pasquale LR. Effects of dorzolamide-timolol and brimonidine-timolol on retinal vascular autoregulation and ocular perfusion pressure in primary open angle glaucoma. J Ocul Pharmacol Ther 2013;29(7):639-45.Abstract
PURPOSE: To assess whether dorzolamide 2%-timolol 0.5% (D/T) and/or brimonidine 0.2%-timolol 0.5% (B/T) alters retinal vascular autoregulation (RVA) and seated ocular perfusion pressure (sOPP) in primary open angle glaucoma (POAG) patients who demonstrate retinal vascular dysregulation (RVD) on timolol 0.5% alone. METHODS: In this prospective, observer-masked, crossover study, 21 POAG patients with untreated intraocular pressure (IOP) >21 mmHg were treated for 6 weeks with timolol 0.5%. Subsequently, we measured inferior temporal retinal artery blood flow in the left eye with subjects seated and then while reclined for 30 min using the Canon Laser Blood Flowmeter. Subjects with a change in retinal blood flow in response to posture change outside of the range previously found in healthy subjects were designated as having RVD and randomized to either D/T or B/T for 6 weeks and re-tested. This was followed by treatment with the opposite medication. RESULTS: Seven of the 21 subjects demonstrated RVD in response to posture change following timolol 0.5%. Multiple linear regression analysis indicated that lower sOPP was the main determinant of RVD (P=0.033). After treatment with D/T, all 7 converted from RVD to normal RVA status (P=0.001). Four of 6 subjects showed a similar return to normal RVA following B/T (P=0.066). Mid-morning sOPP was 41.1±5.5 mmHg post-timolol, 46.3±6.5 mmHg post-D/T, and 38.6±6.0 mmHg post-B/T (D/T vs. B/T, P=0.026). CONCLUSIONS: D/T significantly improved RVA in POAG patients exhibiting RVD while on timolol 0.5% alone. D/T also increased sOPP compared to B/T. There was no significant difference (P=0.37) between D/T and B/T in improving RVA.
Walton DS, Nagao K, Yeung HH, Kane SA. Late-recognized primary congenital glaucoma. J Pediatr Ophthalmol Strabismus 2013;50(4):234-8.Abstract
PURPOSE: To describe a cohort of children with late-recognized primary congenital glaucoma (LRPCG), including age of presentation, age-related diagnostic signs, clinical abnormalities, and results of glaucoma surgery. METHODS: The medical records of 31 patients (49 eyes) with PCG recognized after 1 year of age were reviewed retrospectively. Patients were confirmed to have PCG based on their increased intraocular pressure (IOP), anterior segment abnormalities including findings on gonioscopy, and the absence of other causes of childhood glaucoma. The outcome of glaucoma surgery was reviewed and success measured by assessment of the relative control of IOP, occurrence of significant complications, and need for additional glaucoma surgery. RESULTS: Average age at diagnosis of glaucoma was 4.7 years (36% diagnosed at > 4 years of age). The most common initial diagnostic signs were corneal enlargement (46%, average age of 2.0 years), photophobia (20%, average age of 3.3 years), and suspected poor visual acuity (32%, average age of 9.9 years). Corneal cloudiness was not an initial sign for any patient. Haab's striae were present in 60% of the affected 49 eyes. Gonioscopy findings were abnormal in 82%, but the ciliary body band was seen in 81% and the scleral spur was visible in 47%. Sixty-one goniotomy procedures were performed for 39 eyes with overall success in 95% (37 eyes) and complete success in 65% (27 eyes). The final visual acuity was 20/200 or worse in 31% (15 eyes) and 20/40 or better in 60% (29 eyes). CONCLUSIONS: An awareness of and familiarity with the subtle diagnostic signs of LRPCG can enable its differentiation from primary juvenile glaucoma and contribute to earlier recognition and treatment. Glaucoma surgery is often required for LRPCG and goniosurgery is the recommended initial procedure.
Wiggs JL, Howell GR, Linkroum K, Abdrabou W, Hodges E, Braine CE, Pasquale LR, Hannon GJ, Haines JL, John SWM. Variations in COL15A1 and COL18A1 influence age of onset of primary open angle glaucoma. Clin Genet 2013;84(2):167-74.Abstract
Primary open angle glaucoma (POAG) is a genetically and phenotypically complex disease that is a leading cause of blindness worldwide. Previously we completed a genome-wide scan for early-onset POAG that identified a locus on 9q22 (GLC1J). To identify potential causative variants underlying GLC1J, we used targeted DNA capture followed by high throughput sequencing of individuals from four GLC1J pedigrees, followed by Sanger sequencing to screen candidate variants in additional pedigrees. A mutation likely to cause early-onset glaucoma was not identified, however COL15A1 variants were found in the youngest affected members of 7 of 15 pedigrees with variable disease onset. In addition, the most common COL15A1 variant, R163H, influenced the age of onset in adult POAG cases. RNA in situ hybridization of mouse eyes shows that Col15a1 is expressed in the multiple ocular structures including ciliary body, astrocytes of the optic nerve and cells in the ganglion cell layer. Sanger sequencing of COL18A1, a related multiplexin collagen, identified a rare variant, A1381T, in members of three additional pedigrees with early-onset disease. These results suggest genetic variation in COL15A1 and COL18A1 can modify the age of onset of both early and late onset POAG.
Swaminathan SS, Oh D-J, Kang MH, Ren R, Jin R, Gong H, Rhee DJ. Secreted protein acidic and rich in cysteine (SPARC)-null mice exhibit more uniform outflow. Invest Ophthalmol Vis Sci 2013;54(3):2035-47.Abstract
PURPOSE: Secreted protein acidic and rich in cysteine (SPARC) is a matricellular protein known to regulate extracellular matrix (ECM) in many tissues and is highly expressed in trabecular meshwork (TM). SPARC-null mice have a 15% to 20% decrease in intraocular pressure (IOP) compared to wild-type (WT) mice. We hypothesized that mouse aqueous outflow is segmental, and that transgenic deletion of SPARC causes a more uniform pattern that correlates with IOP and TM morphology. METHODS: Eyes of C57BL6-SV129 WT and SPARC-null mice were injected with fluorescent microbeads, which were also passively exposed to freshly enucleated eyes. Confocal and electron microscopy were performed. Percentage effective filtration length (PEFL) was calculated as PEFL = FL/TL × 100%, where TL = total length and FL = filtration length. IOP was measured by rebound tonometry. RESULTS: Passive microbead affinity for WT and SPARC-null ECM did not differ. Segmental flow was observed in the mouse eye. SPARC-null mice had a 23% decrease in IOP. PEFL increased in SPARC-null (70.61 ± 11.36%) versus WT mice (54.68 ± 9.95%, P < 0.005; n = 11 pairs), and PEFL and IOP were negatively correlated (R(2) = 0.72, n = 10 pairs). Morphologically, TM of high-tracer regions had increased separation between beams compared to low-tracer regions. Collagen fibril diameter decreased in SPARC-null (28.272 nm) versus WT tissue (34.961 nm, P < 0.0005; n = 3 pairs). CONCLUSIONS: Aqueous outflow in mice is segmental. SPARC-null mice demonstrated a more uniform outflow pattern and decreased collagen fibril diameter. Areas of high flow had less compact juxtacanalicular connective tissue ECM, and IOP was inversely correlated with PEFL. Our data show a correlation between morphology, aqueous outflow, and IOP, indicating a modulatory role of SPARC in IOP regulation.
Wiggs JL, Hauser MA, Abdrabou W, Allingham RR, Budenz DL, Delbono E, Friedman DS, Kang JH, Gaasterland D, Gaasterland T, Lee RK, Lichter PR, Loomis S, Liu Y, McCarty C, Medeiros FA, Moroi SE, Olson LM, Realini A, Richards JE, Rozsa FW, Schuman JS, Singh K, Stein JD, Vollrath D, Weinreb RN, Wollstein G, Yaspan BL, Yoneyama S, Zack D, Zhang K, Pericak-Vance M, Pasquale LR, Haines JL. The NEIGHBOR consortium primary open-angle glaucoma genome-wide association study: rationale, study design, and clinical variables. J Glaucoma 2013;22(7):517-25.Abstract
Primary open-angle glaucoma (POAG) is a common disease with complex inheritance. The identification of genes predisposing to POAG is an important step toward the development of novel gene-based methods of diagnosis and treatment. Genome-wide association studies (GWAS) have successfully identified genes contributing to complex traits such as POAG however, such studies frequently require very large sample sizes, and thus, collaborations and consortia have been of critical importance for the GWAS approach. In this report we describe the formation of the NEIGHBOR consortium, the harmonized case control definitions used for a POAG GWAS, the clinical features of the cases and controls, and the rationale for the GWAS study design.
Oh D-J, Kang MH, Ooi YH, Choi KR, Sage HE, Rhee DJ. Overexpression of SPARC in human trabecular meshwork increases intraocular pressure and alters extracellular matrix. Invest Ophthalmol Vis Sci 2013;54(5):3309-19.Abstract
PURPOSE: Intraocular pressure (IOP) regulation is largely unknown. SPARC-null mice demonstrate a lower IOP resulting from increased outflow. SPARC is a matricellular protein often associated with fibrosis. We hypothesized that SPARC overexpression would alter IOP by affecting extracellular matrix (ECM) synthesis and/or turnover in the trabecular meshwork (TM). METHODS: An adenoviral vector containing human SPARC was used to increase SPARC expression in human TM endothelial cells and perfused human anterior segments using multiplicities of infection (MOIs) 25 or 50. Total RNA from TM was used for quantitative PCR, while protein from cell lysates and conditioned media were used for immunoblot analyses and zymography. After completion of perfusion, the anterior segments were fixed, sectioned, and examined by light and confocal microscopy. RESULTS: SPARC overexpression increased the IOP of perfused human anterior segments. Fibronectin and collagens IV and I protein levels were elevated in both TM cell cultures and within the juxtacanalicular (JCT) region of perfused anterior segments. Collagen VI and laminin protein levels were increased in TM cell cultures but not in perfused anterior segments. The protein levels of pro-MMP-9 decreased while the kinetic inhibitors of metalloproteinases, TIMP-1 and PAI-1 protein levels, increased at MOI 25. At MOI 50, the protein levels of pro-MMP-1, -3, and -9 also decreased while PAI-1 and TIMP-1 and -3 increased. Only MMP-9 activity was decreased on zymography. mRNA levels of the collagens, fibronectin, and laminin were not affected by SPARC overexpression. CONCLUSIONS: SPARC overexpression increases IOP in perfused cadaveric human anterior segments resulting from a qualitative change the JCT ECM. Selective decrease of MMP-9 activity is likely part of the mechanism. SPARC is a regulatory node for IOP.
Pasquale LR, Brusie S. The blue arc entoptic phenomenon in glaucoma (an American ophthalmological thesis). Trans Am Ophthalmol Soc 2013;111:46-55.Abstract
PURPOSE: To determine whether the blue arc entoptic phenomenon, a positive visual response originating from the retina with a shape that conforms to the topology of the nerve fiber layer, is depressed in glaucoma. METHODS: We recruited a cross-sectional, nonconsecutive sample of 202 patients from a single institution in a prospective manner. Subjects underwent full ophthalmic examination, including standard automated perimetry (Humphrey Visual Field 24-2) or frequency doubling technology (Screening C 20-5) perimetry. Eligible patients viewed computer-generated stimuli under conditions chosen to optimize perception of the blue arcs. Unmasked testers instructed patients to report whether they were able to perceive blue arcs but did not reveal what response was expected. We created multivariable logistic regression models to ascertain the demographic and clinical parameters associated with perceiving the blue arcs. RESULTS: In multivariable analyses, each 0.1 unit increase in cup-disc ratio was associated with 36% reduced likelihood of perceiving the blue arcs (odds ratio [OR] = 0.66 [95% confidence interval (CI): 0.53-0.83], P<.001). A smaller mean defect was associated with an increased likelihood of perceiving the blue arcs (OR=1.79 [95% CI: 1.40-2.28]); P<.001), while larger pattern standard deviation (OR=0.72 [95% CI: 0.57-0.91]; P=.005) and abnormal glaucoma hemifield test (OR=0.25 [0.10-0.65]; P=.006) were associated with a reduced likelihood of perceiving them. Older age and media opacity were also associated with an inability to perceive the blue arcs. CONCLUSION: In this study, the inability to perceive the blue arcs correlated with structural and functional features associated with glaucoma, although older age and media opacity were also predictors of this entoptic response.
Pasquale LR, Loomis SJ, Weinreb RN, Kang JH, Yaspan BL, Bailey JC, Gaasterland D, Gaasterland T, Lee RK, Scott WK, Lichter PR, Budenz DL, Liu Y, Realini T, Friedman DS, McCarty CA, Moroi SE, Olson L, Schuman JS, Singh K, Vollrath D, Wollstein G, Zack DJ, Brilliant M, Sit AJ, Christen WG, Fingert J, Kraft P, Zhang K, Allingham RR, Pericak-Vance MA, Richards JE, Hauser MA, Haines JL, Wiggs JL. Estrogen pathway polymorphisms in relation to primary open angle glaucoma: an analysis accounting for gender from the United States. Mol Vis 2013;19:1471-81.Abstract
PURPOSE: Circulating estrogen levels are relevant in glaucoma phenotypic traits. We assessed the association between an estrogen metabolism single nucleotide polymorphism (SNP) panel in relation to primary open angle glaucoma (POAG), accounting for gender. METHODS: We included 3,108 POAG cases and 3,430 controls of both genders from the Glaucoma Genes and Environment (GLAUGEN) study and the National Eye Institute Glaucoma Human Genetics Collaboration (NEIGHBOR) consortium genotyped on the Illumina 660W-Quad platform. We assessed the relation between the SNP panels representative of estrogen metabolism and POAG using pathway- and gene-based approaches with the Pathway Analysis by Randomization Incorporating Structure (PARIS) software. PARIS executes a permutation algorithm to assess statistical significance relative to the pathways and genes of comparable genetic architecture. These analyses were performed using the meta-analyzed results from the GLAUGEN and NEIGHBOR data sets. We evaluated POAG overall as well as two subtypes of POAG defined as intraocular pressure (IOP) ≥22 mmHg (high-pressure glaucoma [HPG]) or IOP <22 mmHg (normal pressure glaucoma [NPG]) at diagnosis. We conducted these analyses for each gender separately and then jointly in men and women. RESULTS: Among women, the estrogen SNP pathway was associated with POAG overall (permuted p=0.006) and HPG (permuted p<0.001) but not NPG (permuted p=0.09). Interestingly, there was no relation between the estrogen SNP pathway and POAG when men were considered alone (permuted p>0.99). Among women, gene-based analyses revealed that the catechol-O-methyltransferase gene showed strong associations with HTG (permuted gene p≤0.001) and NPG (permuted gene p=0.01). CONCLUSIONS: The estrogen SNP pathway was associated with POAG among women.

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