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Purpose: Recent studies in U.S. populations have indicated that the Y402H variant of the complement factor H (CFH) gene contains a major risk susceptibility allele for age-related macular degeneration (AMD). This study was conducted to ascertain whether this is also true in a non-U.S. population and also whether the at-risk allele is associated with the clinical phenotype of disease and the age at diagnosis., Methods: Two hundred thirty-six unrelated individuals with AMD and 144 unrelated but ethnically matched control subjects were recruited and examined. All subjects completed a standard questionnaire, were given a fundus examination, and provided a blood sample for DNA extraction. Alleles of Y402H in the CFH gene were determined by use of a MALDI-TOF-based approach followed by statistical analysis., Results: Individuals with AMD who had at least one copy of the C allele of Y402H had an increased risk of disease (odds ratio [OR] 2.98; 95% confidence interval [CI] 1.81-4.93) compared with cases with the T allele. On subgroup analysis, this risk was found to be most significant in individuals with neovascular disease (OR 4.34; 95% CI 1.94, 9.71). In addition, individuals with neovascular disease who were homozygous CC presented with a significant 7.0-year earlier age at diagnosis relative to those individuals who were homozygous TT. The population-attributable risk for the C allele ranged between 47% to 69%, depending on the AMD disease subtype., Conclusions: The C allele of Y402H represents a significant risk factor in individuals with AMD, and this effect is most pronounced in individuals with neovascular disease.

It is estimated that 1.6 billion people worldwide have myopia, a refractive error, and this number is expected to increase to approximately 2.5 billion by the year 2020. It is now well established that both the environment and genetics play a role in the development of myopia. However, the exact contribution of each of these components to myopia development has yet to be completely determined. Twin studies (classical twin model) are commonly used to determine the weighting of genetic and environmental components in disease. Over the last century, twin studies have investigated the heritability of refractive errors in different sample populations and have collectively supported a genetic basis to refractive errors. However, different sample populations and methods of data collection have produced a wide range of heritability estimates ranging from .5 to .9. This article will review those twin studies that have investigated refractive error, particularly myopia, as well as biometric measures linked to refractive error, to compare heritability estimates and methodology designs.

Background: Whole blood provides one of the most common sources of both high-quality DNA and high-quantity DNA for molecular biological purposes. Typically, blood storage at 4 degrees C is short term, which ranges from a few days to a few weeks. However, long-term storage usually involves blood being frozen, with a resultant loss in DNA yield. The authors examined the effects of long-term storage at 4 degrees C., Methods: Duplicate blood samples were collected from 301 participants (aged 20-98 years) enrolled as part of ongoing studies. Samples were stored at 4 degrees C for between 11 days and 922 days, and DNA was subsequently extracted using a phenol/chloroform procedure., Results: A negative correlation of the number of storage days existed at 4 degrees C with DNA yield. The main determinant on DNA yield was the age of the participant in the study, with older persons having a lower DNA yield., Conclusions: Long-term storage of blood at 4 degrees C does have a detrimental effect on DNA yield, but this effect seemed less significant than the age of a person. The impact of age of a person or storage time has a minimal impact on DNA quality. Therefore, storage of blood at 4 degrees C offers an acceptable alternative to frozen storage.

Monozygotic twins had mirror-image congenital esotropia and discordant refractive errors. One had right congenital esotropia surgically corrected during childhood, and the other had left congenital esotropia surgically corrected at 3 and 6 years old.

Progression of age-related macular degeneration (AMD), the leading cause of blindness in the elderly, was followed in a cohort of 238 individuals from a single center. Individuals with an epsilon (epsilon)2 genotype (c.526C>T of reference sequence NM_000041.2) of the apolipoprotein (APOE) gene were found to be strongly associated with disease with a significant 4.8-fold increased relative risk compared to individuals with an epsilon4 genotype (c.388T>C of reference sequence NM_000041.2) (odds ratio [OR], 4.8; 95% confidence interval [CI], 1.19-19.09) and a nearly significant three-fold increased relative risk compared to individuals with an epsilon3 genotype (reference sequence NM_000041.2) (OR, 2.8; 95% CI, 0.96-19.09). This finding was present only in females who progressed with AMD, which suggests that there may be a gender-specific role in progression of AMD in individuals with an epsilon2 allele. A gender-related factor is therefore implicated either directly or indirectly in the AMD disease process., ((c) 2006 Wiley-Liss, Inc.)

Purpose: To examine whether genetic factors significantly influence macular thickness in healthy older subjects., Methods: A classic twin study was performed to compare the correlation of macular thickness between monozygotic (MZ) and dizygotic (DZ) twins in a sample of population-based volunteer twins. The study included 109 white twin pairs from 50 to 80 years of age without evidence of manifest eye disease and corrected visual acuity better than 6/7.5. Dilated macular optical coherence tomography (OCT), fundus photography, clinical examination, ocular biometry, a health-dietary questionnaire, and subjective autorefraction were performed on all subjects., Results: Correlation of retinal thickness was significantly greater between MZ twin pairs than DZ pairs in all macular regions. The MZ-to-DZ correlation was 0.88:0.44 for the foveal region, 0.79:0.47 for the inner macular region, and 0.81:0.50 for the outer macular region. With adjustment for significant covariates and model fitting, final heritability estimates of 85%, 81%, and 81%, respectively, were obtained. A significant correlation between foveal thickness and gender was present, with the men having significantly thicker foveae. There was a significant negative correlation between outer macular thickness and axial length., Conclusions: This study confirms that macular thickness in older healthy subjects, as measured by OCT, may be affected by genetic factors. Factors such as axial length, gender and age, warrant further examination in larger population-based studies, as variables that may influence macular thickness. This finding suggests an inherited basis of macular thickness and may help in the understanding of the factors that govern macular structure and function.

Purpose: Myopia is considered to be a complex disease involving both environmental and genetic factors. The Genes in Myopia (GEM) Study aims to recruit probands with myopia and their family members to allow genetic analysis of myopia to be undertaken. The purpose of this paper is to describe the methodology and recruitment of probands and families for the GEM Study., Methods: In a sample-based prospective study, 2,095 probands with myopia of -0.50 DS or worse and a positive family history of myopia were contacted via the Melbourne Excimer Laser Group (MELG) database. Probands and family members recruited into the study undertook a detailed assessment including questionnaire, best-corrected visual acuity, objective and subjective refraction, axial length, anterior chamber depth, keratometry readings, slit-lamp examination, height, weight and head circumference measurements, and blood sample collection for DNA analysis., Results: 280 probands with myopia have been recruited into the GEM Study. Probands had a mean age of 49.33 yrs. (SD +/- 11.64) with the average age of myopia onset being 12.58 years (SD +/- 6.71). The average spherical-component refractive error was: right eye -5.13 DS (SD +/- 3.06) and left eye -5.14 DS (SD +/- 3.16). Probands with extreme myopia (-10 DS or worse) showed the highest study participation rate of 56%, when compared to high (-5 DS < -10 DS) (20%), moderate (-3 DS < - 5 DS) (18%) and low myopia (-0.5 DS < -3 DS) (10%). A total of 279 out of 505 (55%) additional family members recruited were also found to be myopic., Conclusions: The GEM study has used a targeted approach to identify an Australian cohort with a diverse spread of myopia, ranging from low to extreme. Recruitment of probands via the use of an excimer laser practice has proved to be an efficient and economic means of identifying probands with a family history of myopia. In addition, the participation rate in the study appears to vary reflecting a proband's perception of disease severity.

Purpose: To ascertain whether there is a common disease haplotype for the Q368STOP mutation of the myocilin gene in Australian and Canadian families with primary open-angle glaucoma (POAG)., Design: Family pedigree study., Methods: A disease haplotype for the Q368STOP mutation of the myocilin gene has previously been identified in 15 Tasmanian families with POAG. The four microsatellite markers that constitute this 0.14-megabase (Mb) disease haplotype were genotyped in individuals from a large French Canadian family with POAG (family CT) and two unrelated French Canadian individuals with ocular hypertension., Results: The Tasmanian Q368STOP disease haplotype was identified in affected individuals from family CT, and the same alleles were shared at the four microsatellite markers in the two unrelated French Canadian individuals., Conclusion: The same disease haplotype for the Q368STOP mutation of the myocilin gene was found in both the Tasmanian and French Canadian populations, supporting the view that this mutation arose from a common Caucasian founder.

Purpose: The purpose of this study was to identify genetic contributions to primary open-angle glaucoma (POAG) through investigations of two quantitative components of the POAG phenotype., Methods: Genome-wide multipoint variance-components linkage analyses of maximum recorded intraocular pressure (IOP) and maximum vertical cup-to-disc ratio were conducted on data from a single, large Australian POAG pedigree that has been found to segregate the myocilin Q368X mutation in some individuals., Results: Multipoint linkage analysis of maximum recorded IOP produced a peak LOD score of 3.3 (P = 0.00015) near marker D10S537 on 10q22, whereas the maximum cup-to-disc ratio produced a peak LOD score of 2.3 (P = 0.00056) near markers D1S197 to D1S220 on 1p32. Inclusion of the myocilin Q368X mutation as a covariate provided evidence of an interaction between this mutation and the IOP and cup-to-disc ratio loci., Conclusions: Significant linkage has been identified for maximum IOP and suggestive linkage for vertical cup-to-disc ratio. Identification of genes contributing to the variance of these traits will enhance understanding of the pathophysiology of POAG as a whole.

Primary open-angle glaucoma (POAG) is one of the leading causes of blindness in the world. It is a clinically variable group of diseases with the majority of cases presenting as the late onset adult type. Several chromosomal loci have been implicated in disease aetiology, but causal mutations have only been identified in a small proportion of glaucoma. We have previously described a large six-generation Tasmanian family with POAG exhibiting genetic heterogeneity. In this family, approximately one third of affected individuals presented with a glutamine-368-STOP (Q368STOP) mutation in the myocilin gene. We now use a Markov Chain Monte Carlo (MCMC) method to identify a second disease region in this family on the short arm of chromosome 3. This disease locus was initially mapped to the marker D3S1298 and a subsequent minimum disease region of 9 cM between markers D3S1298 and D3S1289 was identified through additional mapping. The region did not overlap with any previously described locus for POAG. Using a multiplicative relative risk model, we identified a positive association between this region and the Q368STOP mutation of myocilin on chromosome 1 in affected individuals. These findings provide evidence of a new autosomal dominant glaucoma locus on the short arm of chromosome 3.

Purpose: To investigate the prevalence of the Q368STOP myocilin mutation in a population-based cohort: the Blue Mountains Eye Study (BMES)., Design: Population-based study., Methods: DNA was extracted from 2,142 individuals collected through the BMES, including 31 individuals with glaucoma. All individuals were screened for the presence of the Q368STOP mutation of myocilin. Genotyping of the microsatellite markers My5, My3, D1S2815, and D1S1619 was also undertaken., Results: None of the 31 open-angle glaucoma-positive individuals presented with the Q368STOP mutation. However, two individuals (aged 56 and 72) with no clinical signs of OAG, were identified with this mutation. Allele sharing at the four microsatellite markers defining the Q368STOP disease haplotype for OAG was found in these two individuals., Conclusions: The Q368STOP myocilin mutation occurs at a low prevalence (0.09%) in a general, older population.

Background: The optineurin (OPTN) gene has been reported to possess both causal as well as risk-associated alleles for open-angle glaucoma. However, these findings have so far only been reported in family and clinic based studies. The aim of this study was to investigate the spectrum of mutations and gene variants in OPTN that might be present in people with glaucoma from a population-based study, the Blue Mountains Eye Study (BMES)., Methods: A total of 108 subjects of Caucasian origin were identified at baseline in the BMES as having open-angle glaucoma. Blood samples were available from 27 of these, of whom 18 had high-tension glaucoma and the remaining nine had normal-tension glaucoma. Ninety-four control subjects were chosen at random from the BMES, who satisfied the criteria of not having glaucoma at baseline and were over age 70 years. The 13 coding exons (exons 4-16 inclusive) and their intron-exon boundaries of OPTN were screened by the use of single-strand conformation polymorphism. Samples exhibiting mobility shifts were di-deoxy nucleotide sequenced. The M98K polymorphism was additionally screened using the restriction enzyme Stu1 in all cases and controls in this study., Results: The M98K risk-associated alteration was identified in 2/18 (11%) subjects with high-tension glaucoma, 0/9 subjects (0%) with normal-tension glaucoma and 3/94 (3.2%) controls. However, association of this variant with disease was not significant (P = 0.2 for each phenotype) for either high-tension glaucoma or normal-tension glaucoma. A novel variant (P556P in exon 16) was found in one subject with open-angle glaucoma and a previously described variant (exon 7) was found in a further subject with open-angle glaucoma and in one control. No other OPTN variants were identified in this study cohort., Conclusions: Cross-sectional analysis from baseline observations of the BMES suggested that the M98K risk-associated allele appeared at a higher prevalence in high-tension glaucoma compared with controls, although this finding was not statistically significant.

Purpose: To investigate the reported association of the two single-nucleotide polymorphisms (SNPs) of the paraoxonase gene (PON1), Met-Leu 55 (M55L) and Gln-Arg 192 (Q192R), in individuals of Anglo-Celtic descent who have age-related macular degeneration (AMD)., Design: Case-control association study., Methods: Sixty-two individuals with late (end-stage) AMD and 115 control subjects (without AMD) were included in this study. The M55L and Q192R SNPs were amplified by polymerase chain reaction and genotyped, and statistical analysis was undertaken., Results: No association of either SNP was detected in persons of Anglo-Celtic descent who had AMD, although there was a significant difference in SNP allele frequency between Anglo-Celtic and Japanese individuals., Conclusion: The M55L and Q192R SNPs of the PON1 gene do not appear to be associated with late AMD in individuals of Anglo-Celtic descent.

Purpose: To date, of all the genes studied in relation to age-related macular degeneration (AMD), the alleles of the apolipoprotein (apoE) gene have been the most consistently associated with disease. However, not all apoE studies have found an association, and among these the associations differ. The current study was conducted to investigate further the association of this gene in AMD., Methods: Three hundred twenty-two unrelated individuals with diagnosed AMD and 123 unrelated but ethnically matched control subjects were analyzed. All subjects completed a standard questionnaire and were given a fundus examination. A blood sample was collected for DNA extraction. The common allelic variants of apoE were screened through the use of polymerase chain reaction (PCR) and restriction enzyme digestion followed by statistical analysis., Results: Individuals with the epsilon3 epsilon4 genotype of apoE had an approximate halving of disease risk for late (end-stage) AMD (odds ratio [OR] 0.58, 95% confidence interval [CI] 0.34-0.98) relative to the epsilon3 epsilon3 genotype at age of ascertainment. Stratification of late AMD into atrophic and neovascular disease revealed that the greatest protective effect for the epsilon3 epsilon4 genotype was in individuals with atrophic disease (OR 0.35, 95% CI 0.13-0.92). Men with the epsilon3 epsilon4 genotype also showed almost a threefold reduction in risk of disease in late AMD (OR 0.36, 95% CI 0.16-0.82). However, individuals with late AMD and the epsilon2 epsilon3 genotype had a significantly earlier mean age of diagnosis of disease (3.4 years, P = 0.015) compared with those with the epsilon3 epsilon3 genotype, and this was most evident in women (3.9 years, P = 0.011) and in individuals with neovascular disease (4.7 years, P = 0.003)., Conclusions: The alleles of apoE appear to have a role in the etiology of AMD, with the epsilon4 allele being protective, or at the very least, delaying the age of diagnosis of disease, whereas the epsilon2 allele appears to have a modifier effect by bringing forward the mean age of disease diagnosis.

Primary open-angle glaucoma (POAG) is a leading cause of blindness in the world. A number of mutations in the myocilin gene have been identified that predispose to glaucoma. The most frequent of these is the Glutamine368STOP (Q368STOP) mutation. It has been postulated that individuals with the Q368STOP mutation are derived from a common founder. To clarify this situation, we studied 15 unrelated POAG families who carried the Q368STOP mutation, from south eastern Australia. In one large family, nine affected and ten unaffected individuals were identified with the Q368STOP mutation. Closely linked polymorphic microsatellite markers were used to establish a disease haplotype in this family. Additional genotyping of markers in another 14 unrelated Q368STOP families revealed the presence of the same disease haplotype. These findings indicate that the Q368STOP mutation in all 15 families shared a common origin prior to the European settlement of Australia in the early 1800s.

Background: A single base change within the EFEMP1 gene has been associated with malattia leventinese and Doyne honeycomb retinal dystrophy, two dominantly inherited macular diseases with early onset drusen. The aim of this study was to determine whether the same disease allele was also associated with other forms of early onset drusen or familial cases of age-related macular degeneration., Methods: Thirteen index cases of early onset drusen together with 15 other family members were examined. In addition, 54 familial cases of age-related macular degeneration were examined. Blood was taken for DNA analysis and screened for the Arg345Trp disease-associated allele of the EFEMP1 gene. Twenty-four cases of malattia leventinese or Doyne honeycomb retinal dystrophy were also screened as positive controls. Another 150 ethnicity- and age-matched individuals acted as controls., Results: The Arg345Trp disease-associated allele in the EFEMP1 gene was confirmed in individuals with malattia leventinese and Doyne honeycomb retinal dystrophy. However, involvement of this allele was not evident in either early onset drusen or familial age-related macular degeneration., Conclusions: The Arg345Trp disease-associated allele of the EFEMP1 gene does not appear to be associated with cases of early onset drusen that fall outside the diagnosis of malattia leventinese or Doyne honeycomb retinal dystrophy, nor does it appear to play a role in familial age-related macular degeneration. These findings do not exclude the involvement of other alleles of the EFEMP1 gene in either phenotype. The genetic mechanisms involved in the heterogeneous group of early onset drusen remain to be elucidated but should lead to insights into the genetic causes of macular diseases.