Investigation of the Rho-kinase Gene Polymorphism in Primary Open-angle Glaucoma

Purpose: Genetic factors are shown to have a role in the development of primary open-angle glaucoma (POAG). The aim of this study was to determine the effects of genetic polymorphisms of Rho-kinase (ROCK) genes on the risk of POAG in a Turkish population.

Methods: Genomic DNA was extracted from leukocytes of the peripheral blood, and 8 single nucleotide polymorphisms in the ROCK1 and ROCK2 genes were analysed in 179 patients with POAG and in 182 healthy controls of similar age by using BioMark HD dynamic array system.

Results: Neither genotype distributions nor the allele frequencies for the ROCK1 (rs35996865) and ROCK2 [rs2290156, rs965665, rs10178332, rs2230774 (Thr431Asn), rs2230774 (Thr431Ser), rs6755196, and rs726843] gene polymorphisms showed a significant difference between the groups. There were also no marked associations between the haplotype frequencies and POAG.

Conclusions: This is the first study to examine the involvement of ROCK1 and ROCK2 gene variations in the risk of POAG development. This study demonstrated that the polymorphisms studied are not associated with the increased risk of development of POAG in the Turkish population.     

Analysis of toll-like receptor rs4986790 polymorphism in Saudi patients with primary open angle glaucoma

Background: To investigate whether SNP rs4986790 in toll-like receptors (TLRs) is a risk factor for primary open angle glaucoma (POAG) in a Saudi population.

Materials and methods: A cohort of 85 unrelated POAG patients and 95 unrelated control subjects from Saudi Arabia were genotyped utilizing Taq-Man® assay. The association between mutant genotypes and various clinical indices important for POAG was investigated.

Results: Among cases, the normal pattern (A/A) was detected in 70 (82.4%) of the subjects, A/G in 14 (16.5%) and G/G in one subject only (1.2%). Among controls, prevalence of the genotype (A/A) was detected in 86 (90.5%), the (A/G) genotype in 8 (8.4%) and homozygous mutated genotype (G/G) in 1 (1.1%) subjects. Comparing cases to controls, the odds ratio of having heterozygous mutation (A/G) was 2.15 [95% CI: 0.853–5.417], which was not significant (p = 0.114). The odds ratio of having homozygous mutation (G/G) was 1.22 [95% CI: 0.075–19.99], which was statistically non-significant (p = 0.568). Likewise, the presence of the mutated allele (G) was non-significantly different between cases and controls (p = 0.154). Comparing cases to controls as regards co-morbidity with other systemic diseases, there were no statistically significant differences between groups in all assessed diseases except for a family history of glaucoma (p = 0.014)

Conclusions: In conclusion, we could not detect any direct link between genotypes or allele frequencies of SNP rs4986790 in the TLR4 gene and POAG. In contrast, genotype (A/A) may be protective against POAG especially among individuals with no family history of glaucoma.     

MYOC Mutations in Black South African Patients with Primary Open-angle Glaucoma: Genetic Testing and Cascade Screening

Background: Primary Open Angle Glaucoma (POAG) is an important cause of irreversible blindness in South Africa. Mutations in the MYOC gene are important in monogenic POAG. This study aimed to characterize potentially pathogenic MYOC mutations in this population.

Materials and Methods: Self-identified black South African POAG patients (215) and unaffected control participants (214) had ophthalmological examinations and DNA extraction. Potentially pathogenic MYOC variants were genotyped in the study population. Family members of participants with the mutations were screened for glaucoma clinically and for the mutations using Sanger sequencing.

Results: The following mutations were genotyped: Gly374Val (2 POAG patients), Lys500Arg (3 POAG patients) and Tyr453del (5 POAG patients). None of the relatives screened for Gly374Val had the mutation or POAG. The Lys500Arg mutation did not co-segregate with the disease in an affected family. The Tyr453del mutation co-segregated with the disease, but demonstrated incomplete penetrance. POAG patients with the Tyr453del mutation had adult-onset POAG with high intraocular pressures and advanced cupping.

Conclusions: Overall, 3.3% of black South Africans with POAG have a Gly374Val or Tyr453del MYOC mutation. The Tyr453del mutation is incompletely penetrant. That the mutation is necessary but insufficient introduces a counseling dilemma. Mutation screening can, however, identify high-risk individuals who can be monitored to detect early signs of the disease. The Gly374Val mutation is predicted to be damaging to MYOC. The Lys500Arg mutation is predicted to be benign and tolerated. This study has important implications for the management and counseling of black South African patients with POAG and their families.     

Clinical and genetic characterization of a large primary open angle glaucoma pedigree

Purpose: To both characterize the clinical features of large primary open angle glaucoma (POAG) pedigree from a village in southern India and to investigate the genetic basis of their disease.

Materials and methods: Eighty-four members of a large pedigree received complete eye examinations including slit lamp examination, tonometry, gonioscopy, and ophthalmoscopy. Some were further studied with perimetry. Those diagnosed with POAG were tested for disease-causing mutations in the myocilin and optineurin genes with Sanger sequencing.

Results: Fourteen of 84 family members were diagnosed with POAG, while eight were clinically judged to be POAG-suspects. The family structure and the pattern of glaucoma in the pedigree are complex. Features of glaucoma in this pedigree include relatively early age at diagnosis (mean 50 ± 14 years) and maximum intraocular pressures ranging from 14 to 36 mm Hg with a mean of 23 mm Hg ± 6.5 mm Hg. Patients had an average central corneal thickness (mean 529 ± 37.8 microns) and moderate cup-to-disc ratios (0.74 ± 0.14). No mutations were detected in myocilin, optineurin, or TANK binding kinase 1 (TBK1).

Conclusions: We report a five-generation pedigree with a complex pattern of POAG inheritance that includes 22 POAG patients and glaucoma suspects. Although the familial clustering of POAG in this pedigree is consistent with dominant inheritance of a glaucoma-causing gene, mutations were not detected in genes previously associated with autosomal dominant glaucoma, suggesting the involvement of a novel disease-causing gene in this pedigree.     

Lack of Association Between LOXL1 Gene Polymorphisms and Primary Open Angle Glaucoma in the Saudi Arabian Population

Purpose: To investigate whether major single nucleotide polymorphisms (SNPs) in the LOXL1 gene associated with pseudoexfoliation glaucoma are associated with primary open angle glaucoma (POAG) in the Saudi Arabian population.

Methods: The regions of the LOXL1 gene associated with pseudoexfoliation glaucoma, encompassing the three common SNPs, (rs1048661, rs3825942 and rs2165241), were sequenced in a Saudi Arabian dataset consisting of 96 POAG cases and 101 healthy controls.

Results: The allele frequency of the G exfoliation risk allele for SNP rs1048661 in POAG cases and controls was 0.75 and 0.76 (p?=?0.886), respectively and the allele frequency difference was not statistically significant (p?=?0.866). There was no statistically significant difference in the genotypes between patients and controls (p?=?0.261 and 0.156 for genotypes G/G and G/T respectively). As for SNP rs3825942, the frequency of the “G” allele in the POAG patients was comparable to that in the controls (p?=?0.477) and there was no statistically significant difference in genotype G/G and A/G frequency in the study groups. As for SNP rs2165241, the “T” allele frequency in the POAG patients (0.46) was slightly higher than the frequency in controls (0.39), but this difference was not statistically significant (p?=?0.176).

Conclusion: The Saudi Arabian POAG population, similar to all other populations studied to date, demonstrates no association with SNPs associated with pseudoexfoliation glaucoma.     

Identification and genotype phenotype correlation of novel mutations in SIX6 gene in primary open angle glaucoma

Background: Recently SIX1 and SIX6 genes have been associated with primary open angle glaucoma (POAG). This study was planned to do mutation screening in SIX1 and SIX6 genes in North Indian POAG patients and correlate with clinical phenotypes.

Materials and Methods: SIX1 and SIX6 genes were amplified by PCR and sequenced in 115 POAG cases and 105 controls. Four pathogenecity prediction tools (MutationTaster, PolyPhen-2 HumDiv, PolyPhen-2 HumVar and SIFT) were used to predict the pathogenicity of the missense mutations. Protein modeling studies were done to predict the effect of the missense mutations on the protein structure and function.

Results: Two novel mutations p.R116G and p.R116E were observed in the SIX6 gene of patients with POAG. The mutations p.R116G and p.R116E were predicted to be pathogenic and replacement of R116 by G or E might lead to loss of interaction between DNA and R116 of wild type SIX6 protein. The patients with the mutation p.R116E had significantly more visual field damage (MD) and early age of onset of the disease. No sequence variations were observed in the SIX1 gene.

Conclusion: These results expand the mutation spectrum of SIX6 gene and suggest that SIX6 gene plays an important role in POAG pathogenesis.     

Genetic factors influencing the reduction of central corneal thickness in disorders affecting the eye

Background: The aim was to summarize and discuss the current knowledge about genetic factors influencing the reduction of central corneal thickness (CCT) in disorders affecting the eye, such as primary open-angle glaucoma (POAG), brittle cornea syndrome (BCS), keratoconus (KTCN), Ehlers–Danlos syndrome (EDS; types I, II, and VI), osteogenesis imperfecta (OI), and myopia.

Materials and methods: A review of the published literature by use of key databases such as PubMed was undertaken in accordance with PRISMA guidelines and experience based on own research findings was applied.

Results: The differences in CCT measurements among those affected with diverse disorders and healthy individuals were evaluated. Then we considered the influence of genetic factors on CCT reduction. Disorders were compared based on phenotypes and sequence variants found in patients.

Conclusions: Specific sequence variants in COL8A2, PRDM5 and ZNF469, COL5A1 and ZNF469, and COL5A1 and COL5A2 could probably contribute to a CCT reduction in POAG, BCS, KTCN, and EDS, respectively. Similar sequence variants and phenotypes were identified and assessed in more than one disease.     

Characteristics of Undiagnosed Primary Open-Angle Glaucoma: The Tajimi Study

Purpose: To evaluate the characteristics of patients with previously undiagnosed primary open-angle glaucoma (POAG) in the Tajimi Study.

Methods: Background and ophthalmic examination data from 111 patients previously undiagnosed with POAG from the Tajimi Study, a population-based survey of glaucoma, were analyzed and compared with those of eight patients with previously diagnosed glaucoma.

Results: The mean deviation (MD) and vertical cup-to-disc ratio (vC/D) of the worse eye of each patient averaged ?5.5 decibels (dB) and 0.72 and ?10.4?dB and 0.83, respectively, in undiagnosed and diagnosed POAG. In undiagnosed POAG, arcuate and partial arcuate patterns accounted for 50% of the pattern of the visual field (VF) damage, and 95% of patients presented with intraocular pressure of 21?mmHg or less (normal tension glaucoma). The undiagnosed group had better MD and smaller vC/D values in the worse eye and less involvement of bilateral VFs than the diagnosed group (p?=?0.004–0.050 with Bonferroni correction), while other factors, including mean sensitivity of the binocular VF, showed no intergroup difference.

Conclusion: The characteristics of Japanese patients with previously undiagnosed POAG indicated that bilateral evaluation of the optic disc and VF are important for identifying individuals with glaucoma.     

Association of single-nucleotide polymorphisms in non-coding regions of the TLR4 gene with primary open angle glaucoma in a Mexican population

Background: Toll-like receptor 4 (TLR4) non-coding polymorphisms are associated to primary open angle glaucoma (POAG), normal tension glaucoma, and pseudoexfoliation glaucoma. This study was performed to determine whether non-coding single nucleotide polymorphisms (SNPs) in the TLR4 gene contribute to POAG in a Mexican population.

Material and methods: A total of 187 unrelated Mexican patients with POAG and 109 control subjects were included. Allelic, genotypic, and haplotypic diversity was assessed for the non-coding polymorphisms rs11536889, rs1927911, rs12377632, and rs2149356 of the TLR4 gene. Genotyping of target SNPs was performed by 5′ exonuclease allelic discrimination assays.

Results: Strong linkage disequilibrium was observed among the SNPs (D’ > 0.818), which were located in one haplotype block. The rs11536889 polymorphism was not associated to POAG in any case. The frequency of the minor allele of rs2149356 was significantly higher in the glaucoma group, conferring an increased risk of POAG (p = 0.0018, OR = 1.803, 95% CI 1.2556–2.5890) whereas minor allele of rs12377632 was significantly lower, attributing a protective effect (p = 0.0001, OR = 0.6662, 95% CI 0.4753–0.9339). Subjects with genotypes carrying the minor allele of rs1927911 and rs2149356 shown an increased risk for POAG (p = 0.03, OR = 1.78, 95% CI 1.10–2.87, and p < 0.0004, OR =2.62, 95%CI 1.61–4.27 respectively). Finally, we found significant risk haplotypes. The GTT haplotype (constituted by rs1927911, rs12377632, and rs2149356) reached the higher OR (p = 0.0026, OR = 4.70, 95% CI 1.73–12.77).

Conclusions: We have identified intronic TLR4 SNPs as genetic susceptibility alleles for POAG in a Mexican population. Our findings support the association of the TLR4 gene with POAG.     

Optic disc morphology in “age-related atrophic glaucoma”

Background: This study was performed in order to evaluate whether, in primary open-angle glaucoma (POAG), patients with a different degree of fundus tessellation vary in optic disc morphology and level of intraocular pressure Methods: Color stereo optic disc photographs of 562 patients with POAG and a myopic refractive error of less than –8 diopters were morphometrically examined. According to the degree of fundus tessellation, the total group was divided into a tessellated subgroup (n = 256) and a nontessellated subgroup (n = 306,) both matched for neuroretinal rim area and refractive error Results: In the tessellated subgroup, as compared to the nontessellated subgroup, the mean maximal intraocular pressure values were significantly lower, the parapapillary atrophy was significantly larger, the optic cup was significantly more shallow, frequency of disc hemorrhages was lower, the mean visual field defect was significantly more marked, and patient age was significantly higher. Within the whole study group, the degree of fundus tessellation increased significantly (P<0.005) with decreasing mean maximal intraocular pressure, decreasing optic cup depth, and increasing degree of parapapillary atrophy. In the subgroups with the highest degree of fundus tessellation, parapapillary atrophy was the greatest and the mean maximal intraocular pressure was the lowest compared to other subgroups Conclusion: At the low-pressure end of POAG, marked fundus tessellation is associated with large parapapillary atrophy, shallow disc cupping, mostly concentric emaciation of the neuroretinal rim, and high patient age. The results suggest a distinct subtype of POAG in older patients with relatively low intraocular pressure leading to a mainly diffuse atrophy of the optic nerve.     

Gene polymorphisms of the MMP1, MMP9, MMP12, IL‐1β and TIMP1 and the risk of primary open‐angle glaucoma

Background: Primary open‐angle glaucoma (POAG) is the main cause of irreversible blindness worldwide. Matrix metalloproteinases (MMPs) and their regulators (TIMPs and ILs) have been extensively studied as POAG risk factors. Recent reports have showed several single‐nucleotide polymorphisms (SNPs) for MMPs, TIMPs and ILs encoding genes in patients with POAG. The aim of this study was to investigate association of the ‐1607 1G/2G MMP1, ‐the 1562 C/T MMP9, the ‐82 A/G MMP12, the ‐511 C/T IL‐1β and the 372 T/C TIMP1 gene polymorphisms with POAG occurrence and to investigate their impact on main clinical features. Material and methods: In the present case–control study, we examined group of 511 unrelated Caucasian subjects consist of 255 patients with POAG (mean age 70 ± 15) and 256 controls (mean age 67 ± 16). Determination of genes polymorphic variants was made using polymerase chain reaction–restriction fragment length polymorphism technique (PCR‐RFLP). The odds ratios (ORs) and 95% confidence intervals (CIs) for each genotype and allele were calculated. Results: Presented study showed statistically significant increase in the POAG development risk of the ‐1607 2G/2G MMP1 genotype (OR 1.75; 95% CI, 1.11–2.75; p = 0.014) and for the ‐1607 2G MMP1 allele (OR 1.35; 95% CI, 1.05–1.73; p = 0.017), as well as for the ‐1562 C/T MMP9 genotype (OR 1.74; 95% CI, 1.17–2.59; p = 0.006) and the ‐1562 T MMP9 allele (OR 1.55; 95% CI, 1.10–2.17; p = 0.012) in patients with POAG in comparison with healthy control group. We also observed positive association of the ‐511 T/T IL‐1β genotype (OR 2.60; 95% CI, 1.41–4.80; p = 0.002) as well as the ‐511 T IL‐1β allele occurrence with an increased POAG development risk (OR 1.47; 95% CI, 1.13–1.90; p = 0.003). Furthermore, we found an association of the ‐1607 1G/2G MMP1, ‐1562 C/T MMP9 (anova , p < 0.001) and the ‐511 C/T IL‐1β gene polymorphism (anova , p < 0.05) with decreased retinal nerve fibre layer (RNFL) thickness in patients with POAG group. Results displayed also an association of the 372 T/C TIMP1 gene polymorphism with normal range RNFL (anova , p < 0.001). We observed an association of decreased RA value (rim area) with the ‐82 A/G MMP12 (anova , p < 0.001). Normal RA value was observed in patients with POAG group connected with the 372 T/C TIMP1 (anova , p < 0.05) and the ‐511 C/T IL‐1β (anova , p < 0.05) genes polymorphisms occurrence. Finally, results showed an association of the ‐1562 C/T MMP9 (anova , p < 0.001) gene polymorphism with decreased cup/disc index in patients with POAG group. Conclusion: In conclusion, we suggest that the ‐1607 1G/2G MMP1, ‐1562 C/T MMP9, ‐511 C/T IL‐1β gene polymorphisms can be considered as an important risk factors associated with POAG.     

Undiagnosed Primary Open-Angle Glaucoma in Korea: The Korean National Health and Nutrition Examination Survey 2008–2009

Purpose: To evaluate the characteristics of patients with previously undiagnosed primary open-angle glaucoma (POAG) in Korea.

Methods: This study examined data from 391 subjects obtained from the 2008–2009 Korean National Health and Nutrition Examination Survey (KNHANES). The KNHANES is a population-based, cross-sectional epidemiological survey. Participants aged 19 years or older completed standardized interviews and dilated ocular examinations, including measurement of intraocular pressure, visual fields with frequency doubling perimetry, and fundus photography. Data from the 361 patients with previously undiagnosed POAG were analyzed and compared with data from the 30 patients with previously diagnosed glaucoma.

Results: A total of 92.3% of POAG cases were undiagnosed before this study. Adjusted for age and sex, the strongest risk factor for undiagnosed glaucoma was longer elapsed time since last eye doctor visit. Glaucoma patients who had not visited an eye specialist in the last 3 years were 22 times (95% confidence interval, CI, 4.49–105.64, p < 0.001) more likely to have undiagnosed disease compared with patients who had visited an eye specialist in the last month. Another significant factor for previously undiagnosed glaucoma was smaller cup-to-disc ratio (odds ratio, OR, 0.60/0.1 units, 95% CI 0.43–0.85/0.1 units, p = 0.004). The higher vertical cup-to-disc ratio of a subject’s two eyes was significantly different between those with previously undiagnosed (0.69) and diagnosed (0.78) POAG (p = 0.001).

Conclusions: The undiagnosed POAG group had a longer interval from last eye doctor visit and smaller vertical cup-to-disc ratio compared to the diagnosed group.     

Investigation of CAV1/CAV2 rs4236601 and CDKN2B-AS1 rs2157719 in primary open-angle glaucoma patients from Brazil

Large-scale genome-wide association studies have identified several susceptibility variants associated with the risk of primary open-angle glaucoma (POAG), among which rs4236601 (CAV1/CAV2) at chromosome 7q31 and rs2157719 at chromosome 9p21 (CDKN2B-AS1). The purpose of this study was to investigate whether these variants contribute to the incidence of POAG in a sample of the Brazilian Southeastern population and to determine the best-fitted genetic model for these single nucleotide polymorphisms (SNPs). A case-control study with 557 individuals, 310 with POAG, and 247 controls was conducted through PCR and direct sequencing. We observed a significant effect of the heterozygous genotype (G/A) of rs2157719 that occurred more frequently in the control group (p = 0.0004; OR: 0.517, CI 95%: 0.357–0.745). Allele frequencies also differed between cases and controls (p = 0.006; OR: 0.694, CI 95%: 0.522–0.922) with the best-fitted genetic model for rs2157719 being the codominant model. No differences were observed for genotype and allele distributions in relation to rs4236601 in the CAV1/CAV2 region. The association of rs2157719 (CDKN2B-AS1) with the POAG phenotype corroborates previously published results, reinforcing the importance of this variant in POAG etiology.     

Efficacy of apraclonidine ophthalmic solution (lopidine) in presumed silicon oil-induced glaucoma and primary open-angle glaucoma

Background: This pilot study evaluated the acute effects of topical ocular apraclonidine 1% (Iopidine) in 10 patients with presumed silicone oil-induced secondary glaucoma (SOIG) and in 10 patients with high-pressure primary open-angle glaucoma (POAG) despite maximum tolerated medical therapy. Methods: Intraocular pressure (TOP) measurements were carried out before and 1, 2 and 3 h after a single drop of apraclonidine. Results: Patients with SIOG presented with a mean IOP of 30.0 ± 2.8 mmHg, which was reduced to 21.7 ± 2.9 mmHg (P<0.001) after 1 h, to 20.4 ± 2.3 mmHg (P<0.001) after 2 h and to 20.0±2.5 mmHg (P<0.001) after 3 h. In the POAG group, TOP was reduced from 25.9±1.9 mmHg before treatment to 18.9±1.4 mmHg after 1 h (P<0.001), 17.7±1.2 mmHg after 2 h (P<0.001) and 16.9±0.9 mmHg after 3 h (P<0.001). There were no significant changes in blood pressure or pulse rate. Conclusion: This study confirmed the activity of apraclonidine as an TOP suppressant.This study was presented in abstract at the 1993 ARVO meeting, Sarasota, Florida (poster 2422)     

Clinical relevance of optineurin sequence alterations in Japanese glaucoma patients

Purpose:To study the clinical relevance of sequence alterations in the optineurin gene (OPTN) among Japanese patients with open-angle glaucoma, including both primary open-angle glaucoma (POAG) and normal tension glaucoma (NTG). Methods:Genomic DNA was isolated from 83 patients with open-angle glaucoma (55 with POAG and 28 with NTG) and 58 control subjects. The 13 exons of OPTN corresponding to the coding region were amplified by polymerase chain reaction and directly sequenced. Clinical factors were compared between glaucoma patients with and without a certain nucleotide change. Results:The reported heterozygous mutations, c.458G > A(Glu50Lys) in exon 4 and c.691_692insAG in exon 6, were not found in any glaucoma patients or control subjects. The reported c.603T > A(Met98Lys) in exon 5 was significantly more prevalent in the POAG (8/55, 14.5%, p = 0.0147) and NTG (4/28, 14.2%, p = 0.0369) patients, and even in both the POAG and NTG patients combined (12/83, 14.4%, p = 0.0149, Fisher exact probability test), than in the control subjects (1/58, 1.7%). The rates of the reported c.1944G > A(Arg545Gln) in exon 16 were not significantly different between open-angle glaucoma patients (3/83, 3.6%) and control subjects (4/58, 6.8%). In addition, a heterozygous change, c.412G > A(Thr34Thr) in exon 4 was found in 18 (21.6%) open-angle glaucoma patients and seven (12.0%) control subjects. Another heterozygous change, c.457C > T(Thr49Thr), in exon 4 was found only in three POAG patients. The 18 open-angle glaucoma patients with c.412G > A showed significantly larger cup-to-disc ratios (p = 0.0178, Mann-Whitney U test), significantly more deteriorated mean deviations of the visual field in the left eye at the final visit (p = 0.0076), and a significantly higher rate of surgery and/or laser history (p = 0.0321, Fisher exact probability test) than the 65 open-angle glaucoma patients without the nucleotide change. Conclusions:Met98Lys is a risk-associated alteration for open-angle glaucoma, including POAG and NTG, in the Japanese population as initially reported. The amino acid-preserving polymorphism, c.412G > A, may be a genetic risk factor for the progression of open-angle glaucoma in this Japanese population.     

Endothelin-like immunoreactivity in aqueous humor of patients with primary open-angle glaucoma and cataract

Background: Experimental evidence suggests a role of endothelin-1 (ET) in the regulation of intraocular pressure (IOP). Method: Therefore, inpatients undergoing cataract surgery, ET-like immunoreactivity (STIR) was measured by radioimmunoassay in pooled samples of aqueous humor of eyes with primary open-angle glaucoma (POAG) and normotensive eyes with cataract only. Results: ETIR was significantly (P < 0.05) higher in patients with cataract and POAG (20.5 ± 1.8 pg/ml,n = 12; preoperative IOP 21.4 ± I.1 mmHg,n = 33) than in patients with cataract only (15.8 ± 1.6 pg/m1,n = 15; preoperative IOP 16.0 ± 0.6 mmHg,n = 77). Conclusion: This finding may indicate a role of ET in POAG or ocular antihypertensive treatment, and its relevance should be further investigated.     

Homocysteine and nitric oxide levels in plasma of patients with pseudoexfoliation syndrome,pseudoexfoliation glaucoma,and primary open-angle glaucoma

Purpose To evaluate plasma total homocysteine (tHcy) and nitric oxide (NO) marker levels in patients with pseudoexfoliation syndrome (PXS), pseudoexfoliation glaucoma (PXG), primary open-angle glaucoma (POAG), and normal controls.Methods This cross-sectional, prospective study involved 19 patients with POAG, 18 with PXS, 22 with PXG, and 20 control subjects. Fasting tHcy levels of all study participants were determined using a fluorescence polarization immunoassay method. Quantitation of total nitrate was based on the Griess reaction, in which a chromophore with a strong absorbance at 545 nm is formed by reaction of nitrite with a mixture of naphthylethylenediamine and sulphanilamide.Results The mean plasma homocysteine level was statistically significantly elevated in the PXS (p=0.033) and the PXG (p=0.023) groups but not in the POAG group (p=0.996) when compared with the control group. Multiple logistic regression analyses comparing the various patient groups with the single control group indicated that elevation in plasma homocysteine concentration was a significant risk factor for PXS (odds ratio per 1 mol/l increase in homocysteine concentration=2.05, 95% CI=1.19–3.52) and PXG (odds ratio per 1 mol/l increase in homocysteine concentration=1.36, 95% CI=1.00–1.85) but was not a significant risk factor for POAG (odds ratio per 1 mol/l increase in homocysteine concentration=0.99, 95% CI=0.78–1.26). NO markers levels were found to be slightly higher in PXS and PXG patients than control and POAG patients but the differences were not statistically significant (p=0.151). Multiple logistic regression analyses comparing the various patient groups with the single control group indicated that elevation in NO marker concentration was not a significant risk factor for PXS (odds ratio per 1 mol/l increase in NO concentration=1.00, 95% CI=0.99–1.01), PXG (odds ratio per 1 mol/l increase in NO concentration=1.00, 95% CI=0.99–1.00) and POAG (odds ratio per 1 mol/l increase in NO concentration=0.99, 95% CI=0.99–1.00). No statistically significant correlations were observed between plasma tHcy and NO markers in study groups (p>0.05).Conclusion Elevated levels of homocysteine in pseudoexfoliation patients with and without glaucoma may partly explain the increased risk of vascular disease among patients with pseudoexfoliation. No significant difference was found in plasma NO markers among the POAG, PXS, PXG, and the control subjects.     

Myocilin mt.1 gene promoter single nucleotide polymorphism (-1000C>G) in Brazilian patients with primary open angle glaucoma

Background: The myocilin (MYOC) gene promoter polymorphism -1000C>G (MYOC mt.1) can be associated with faster progression of primary open angle glaucoma (POAG). The purpose of this study was to investigate the MYOC mt.1 in Brazilian patients with POAG and to evaluate its possible role on the phenotype and the severity of the disease.

Material and methods: One hundred sixty-seven POAG patients and 130 normal controls were enrolled. DNA samples were prepared and the MYOC mt.1 polymorphism was screened by real-time polymerase chain reaction (RT – PCR) in an Single-nucleotide polymorphism (SNP) assay. Frequencies of the MYOC mt.1 promoter polymorphism were determined for both groups and compared by Fisher’s exact test and Chi-square test with Yate’s correction. Intraocular pressure (IOP), cup-to-disc ratio (C/D), number of glaucoma medications, and number of glaucoma surgeries were compared between MYOC mt.1 carriers and non-carriers.

Results: MYOC mt.1 genotype frequencies did not differ between POAG and controls (P = 0.420); 14.6% of controls and 16.4% of POAG patients were MYOC mt.1 carriers (CG or GG). Frequencies of the G allele were similar between glaucomatous patients and controls (7.3% and 9.2%, respectively; P = 0.477). Among POAG patients, there were no differences in mean C/D ratio, IOP, number of glaucoma medications, and surgical procedures for IOP control between carries and non-carriers of the MYOC mt.1 promoter polymorphism (p>0.05).

Conclusion: The G allele of the MYOC mt.1 promoter polymorphism was equally distributed among POAG patients and healthy subjects and it is possibly unrelated to the risk and severity of disease in the Brazilian population.     

Inverse correlation between endothelin-1-induced peripheral microvascular vasoconstriction and blood pressure in glaucoma patients

Background: The potent vasoconstrictor peptide endothelin-I has been shown to participate in the control of peripheral vascular tone and in the regulation of ocular perfusion. In glaucoma patients vasospasms and arterial hypotension have been identified as risk factors for the progression of glaucomatous damage, and the regulation of endothelin-1 release is disturbed in some of these patients. The aim of this study was to assess the relationship between resting blood pressure and cutaneous vascular responsiveness to endothelin-1 and phenylephrine in patients with glaucoma and in matched controls. Methods: In 9 patients with primary open-angle glaucoma (POAG), 7 patient with normal tension glaucoma (NTG), and 16 age- and sex-matched controls, endothelin-1 and phenylephrine responses were assessed in the human forearm microcirculation using laser Doppler flowmetry during intra-arterial drug administration. Blood pressure was measured intra-arterially. Results: In contrast to ₁-adrenergic effects, endothelin-1 responses were inversely correlated to both systolic (r ² = 0.27,P = 0.05) and diastolic (r ² = 0.54,P = 0.001) blood pressure in glaucoma patients, whereas there was no such correlation in controls. Patients with lower blood pressure values were more sensitive to the vasoconstrictor effects of endothelin-1. Cutaneous responsiveness to endothelin-1 and phenylephrine was similar in glaucoma patients and in controls. Conclusion: These results reveal that glaucoma patients appear to have peripheral microvascular abnormalities which are exhibited as altered responsiveness to endothelin-1. Thus, this study supports the hypothesis that endothelin-l-related microvascular dysfunction may be involved in the pathogenesis of glaucomatous damage.     

Risk Factors Associated with Progression to Blindness from Primary Open-Angle Glaucoma in an African-American Population

Purpose: To determine the risk factors associated with progression to blindness from primary open-angle glaucoma (POAG) in an African-American population.

Methods: This study examined 2119 patients enrolled in the Primary Open-Angle African-American Glaucoma Genetics (POAAGG) study. A total of 59 eyes were identified as legally blind as a result of POAG (cases) and were age-and sex-matched to 59 non-blind eyes with glaucoma (controls). Chart reviews were performed to record known and suspected risk factors.

Results: Cases were diagnosed with POAG at an earlier age than controls (p = 0.005). Of the 59 eyes of cases, 16 eyes (27.1%) presented with blindness at diagnosis. Cases had worse visual acuity (VA) at diagnosis (p < 0.0001), with VA worse than 20/40 conferring a 27 times higher risk of progression to blindness (p = 0.0005). Blind eyes also demonstrated more visual field defects (p = 0.01), higher pre-treatment intraocular pressure (IOP; p < 0.0001), and higher cup-to-disc ratio (p = 0.006) at diagnosis. IOP was less controlled in cases, and those with IOP ≥21 mmHg at more than 20% of follow-up visits were 73 times more likely to become blind (p < 0.0001). Cases missed a greater number of appointments per year (p = 0.003) and had non-adherence issues noted in their charts more often than controls (p = 0.03). However, other compliance data did not significantly differ between groups.

Conclusion: Access to care, initial VA worse than 20/40, and poor control of IOP were the major risk factors associated with blindness from POAG. Future studies should examine earlier, more effective approaches to glaucoma screening as well as the role of genetics in these significantly younger patients who progress to blindness.