Genes of the unfolded protein response pathway harbor risk alleles for primary open angle glaucoma.

The statistical power of genome-wide association (GWA) studies to detect risk alleles for human diseases is limited by the unfavorable ratio of SNPs to study subjects. This multiple testing problem can be surmounted with very large population sizes when common alleles of large effects give rise to disease status. However, GWA approaches fall short when many rare alleles may give rise to a common disease, or when the number of subjects that can be recruited is limited. Here, we demonstrate that this multiple testing problem can be overcome by a comparative genomics approach in which an initial genome-wide screen in a genetically amenable model organism is used to identify human orthologues that may harbor risk alleles for adult-onset primary open angle glaucoma (POAG). Glaucoma is a major cause of blindness, which affects over 60 million people worldwide. Several genes have been associated with juvenile onset glaucoma, but genetic factors that predispose to adult onset primary open angle glaucoma (POAG) remain largely unknown. Previous genome-wide analysis in a Drosophila ocular hypertension model identified transcripts with altered regulation and showed induction of the unfolded protein response (UPR) upon overexpression of transgenic human glaucoma-associated myocilin (MYOC). We selected 16 orthologous genes with 62 polymorphic markers and identified in two independent human populations two genes of the UPR that harbor POAG risk alleles, BIRC6 and PDIA5. Thus, effectiveness of the UPR in response to accumulation of misfolded or aggregated proteins may contribute to the pathogenesis of POAG and provide targets for early therapeutic intervention.

Toll-like receptor 3 and geographic atrophy in age-related macular degeneration.

BACKGROUND: Age-related macular degeneration is the most common cause of irreversible visual impairment in the developed world. Advanced age-related macular degeneration consists of geographic atrophy and choroidal neovascularization. The specific genetic variants that predispose patients to geographic atrophy are largely unknown. METHODS: We tested for an association between the functional toll-like receptor 3 gene (TLR3) variant rs3775291 (involving the substitution of phenylalanine for leucine at amino acid 412) and age-related macular degeneration in Americans of European descent. We also tested for the effect of TLR3 Leu and Phe variants on the viability of human retinal pigment epithelial cells in vitro and on apoptosis of retinal pigment epithelial cells from wild-type mice and Tlr3-knockout (Tlr3(-/-)) mice. RESULTS: The Phe variant (encoded by the T allele at rs3775291) was associated with protection against geographic atrophy (P=0.005). This association was replicated in two independent case-control series of geographic atrophy (P=5.43x10(-4) and P=0.002). No association was found between TLR3 variants and choroidal neovascularization. A prototypic TLR3 ligand induced apoptosis in a greater fraction of human retinal pigment epithelial cells with the Leu-Leu genotype than those with the Leu-Phe genotype and in a greater fraction of wild-type mice than Tlr3(-/-) mice. CONCLUSIONS: The TLR3 412Phe variant confers protection against geographic atrophy, probably by suppressing the death of retinal pigment epithelial cells. Since double-stranded RNA (dsRNA) can activate TLR3-mediated apoptosis, our results suggest a role of viral dsRNA in the development of geographic atrophy and point to the potential toxic effects of short-interfering-RNA therapies in the eye.

Promoter polymorphism of the erythropoietin gene in severe diabetic eye and kidney complications.

Significant morbidity and mortality among patients with diabetes mellitus result largely from a greatly increased incidence of microvascular complications. Proliferative diabetic retinopathy (PDR) and end stage renal disease (ESRD) are two of the most common and severe microvascular complications of diabetes. A high concordance exists in the development of PDR and ESRD in diabetic patients, as well as strong familial aggregation of these complications, suggesting a common underlying genetic mechanism. However, the precise gene(s) and genetic variant(s) involved remain largely unknown. Erythropoietin (EPO) is a potent angiogenic factor observed in the diabetic human and mouse eye. By a combination of case-control association and functional studies, we demonstrate that the T allele of SNP rs1617640 in the promoter of the EPO gene is significantly associated with PDR and ESRD in three European-American cohorts [Utah: P = 1.91 x 10(-3); Genetics of Kidneys in Diabetes (GoKinD) Study: P = 2.66 x 10(-8); and Boston: P = 2.1 x 10(-2)]. The EPO concentration in human vitreous body was 7.5-fold higher in normal subjects with the TT risk genotype than in those with the GG genotype. Computational analysis suggests that the risk allele (T) of rs1617640 creates a matrix match with the EVI1/MEL1 or AP1 binding site, accounting for an observed 25-fold enhancement of luciferase reporter expression as compared with the G allele. These results suggest that rs1617640 in the EPO promoter is significantly associated with PDR and ESRD. This study identifies a disease risk-associated gene and potential pathway mediating severe diabetic microvascular complications.

Genetic association of LOXL1 gene variants and exfoliation glaucoma in a Utah cohort.

Exfoliation glaucoma (XFG) is the commonest identifiable cause of secondary open-angle glaucoma worldwide, characterized by the deposition of fibrillar proteins in the anterior segment of the eye. We investigated LOXL1 gene variants previously identified to confer susceptibility to XFG in a Utah Caucasian cohort. After a standard eye examination protocol we genotyped SNPs rs2165241and rs3825942 in 62 XFG or exfoliation syndrome (XFS) patients and 170 normal controls. Genotype frequency distribution, odds ratios (ORs) and population attributable risks were calculated for the risk alleles. The SNP rs2165241 was significantly associated with XFG and XFS (p = 4.13 x 10(-9)) for an additive model, OR(het) = 4.42 (2.30-8.50), OR(hom) = 34.19 (4.48-261.00); T allele: 83.1% in cases versus 52.4% in controls). Significant association was also found for rs3825942: (p = 1.89 x 10(-6)). Our findings confirm genetic association of LOXL1 with XFG and XFS and implicate a potential role of cross linking of elastin in the pathogenesis of XFG. This information will potentially guide glaucoma monitoring efforts by targeting individuals whose genetic profiles put them at higher risk for XFG.

HTRA1 variant confers similar risks to geographic atrophy and neovascular age-related macular degeneration.

Age-related macular degeneration (AMD) is the most common cause of irreversible visual impairment in the developed world. The two forms of advanced AMD, geographic atrophy (GA) and choroidal neovascularization (wet AMD), represent two types of degenerative processes in the macula that lead to loss of central vision. Soft confluent drusen, characterized by deposits in macula without visual loss are considered a precursor of advanced AMD. A single nucleotide polymorphism, rs11200638, in the promoter of HTRA1 has been shown to increases the risk for wet AMD. However, its impact on soft confluent drusen and GA or the relationship between them is unclear. To better understand the role the HTRA1 polymorphism plays in AMD subtypes, we genotyped an expanded Utah population with 658 patients having advanced AMD or soft confluent drusen and 294 normal controls and found that the rs11200638 was significantly associated with GA. This association remains significant conditional on LOC387715 rs10490924. In addition, rs11200638 was significantly associated with soft confluent drusen, which are strongly immunolabeled with HTRA1 antibody in an AMD eye with GA similar to wet AMD. Two-locus analyses were performed for CFH Y402H variant at 1q31 and the HTRA1 polymorphism. Together CFH and HTRA1 risk variants increase the odds of having AMD by more than 40 times. These findings expand the role of HTRA1 in AMD. Understanding the underlying molecular mechanism will provide an important insight in pathogenesis of AMD.

A variant of the HTRA1 gene increases susceptibility to age-related macular degeneration.

Age-related macular degeneration (AMD) is the most common cause of irreversible vision loss in the developed world and has a strong genetic predisposition. A locus at human chromosome 10q26 affects the risk of AMD, but the precise gene(s) have not been identified. We genotyped 581 AMD cases and 309 normal controls in a Caucasian cohort in Utah. We demonstrate that a single-nucleotide polymorphism, rs11200638, in the promoter region of HTRA1 is the most likely causal variant for AMD at 10q26 and is estimated to confer a population attributable risk of 49.3%. The HTRA1 gene encodes a secreted serine protease. Preliminary analysis of lymphocytes and retinal pigment epithelium from four AMD patients revealed that the risk allele was associated with elevated expression levels of HTRA1 mRNA and protein. We also found that drusen in the eyes of AMD patients were strongly immunolabeled with HTRA1 antibody. Together, these findings support a key role for HTRA1 in AMD susceptibility and identify a potential new pathway for AMD pathogenesis.

CFH Y402H confers similar risk of soft drusen and both forms of advanced AMD.

BACKGROUND: Age-related macular degeneration (AMD) is the most common cause of irreversible visual impairment in the developed world. The two forms of advanced AMD, geographic atrophy and neovascular AMD, represent different pathological processes in the macula that lead to loss of central vision. Soft drusen, characterized by deposits in the macula without visual loss, are considered to be a precursor of advanced AMD. Recently, it has been proposed that a common missense variant, Y402H, in the Complement Factor H (CFH) gene increases the risk for advanced AMD. However, its impact on soft drusen, GA, or neovascular AMD--or the relationship between them--is unclear. METHODS AND FINDINGS: We genotyped 581 Icelandic patients with advanced AMD (278 neovascular AMD, 203 GA, and 100 with mixed neovascular AMD/GA), and 435 with early AMD (of whom 220 had soft drusen). A second cohort of 431 US patients from Utah, 322 with advanced AMD (244 neovascular AMD and 78 GA) and 109 early-AMD cases with soft drusen, were analyzed. We confirmed that the CFH Y402H variant shows significant association to advanced AMD, with odds ratio of 2.39 in Icelandic patients (p = 5.9 x 10(-12)) and odds ratio of 2.14 in US patients from Utah (p = 2.0 x 10(-9)) with advanced AMD. Furthermore, we show that the Y402H variant confers similar risk of soft drusen and both forms of advanced AMD (GA or neovascular AMD). CONCLUSION: Soft drusen occur prior to progression to advanced AMD and represent a histological feature shared by neovascular AMD and GA. Our results suggest that CFH is a major risk factor of soft drusen, and additional genetic factors and/or environmental factors may be required for progression to advanced AMD.

A comparison of topical and retrobulbar anesthesia for trabeculectomy.

PURPOSE: To compare the safety and efficacy of topical versus retrobulbar anesthesia for primary trabeculectomy METHODS: A prospective study of 36 consecutive patients undergoing trabeculectomy who were randomized to receive topical (n = 18) or retrobulbar (n = 18) anesthesia. Operating conditions, patient comfort, and surgical outcome were evaluated. SETTINGS: Tertiary-care university hospital ambulatory surgical center. RESULTS: There were no differences in operating conditions (P = 0.14), pain during (P = 0.54) or after (P = 0.76) surgery, or supplemental anesthesia required (P = 0.34) between the two groups. Very few patients in either group were bothered by touch sensation, tissue manipulation, or the microscope light. Chemosis, subconjunctival hemorrhage and eyelid hemorrhage were seen exclusively in the retrobulbar group (P <0.03), and were all attributable to the injection. Inadvertent eye movement was present more frequently in the topical group (P = 0.01), although this did not pose a problem to the surgeon. No surgical complications were encountered in either group. CONCLUSION: Topical anesthesia is a safe and effective alternative to retrobulbar anesthesia for primary trabeculectomy.

Topical versus retrobulbar anesthesia for combined phacotrabeculectomy: prospective randomized study.

PURPOSE: To compare the safety and efficacy of topical and retrobulbar anesthesia for combined phacotrabeculectomy. SETTING: Tertiary-care university hospital ambulatory surgical center. METHODS: In this prospective study, 40 consecutive patients having combined phacotrabeculectomy were randomized to receive topical (n = 20) or retrobulbar (n = 20) anesthesia. Operating conditions, patient comfort, and surgical outcome were evaluated. RESULTS: There was no significant between-group difference in operating conditions (P =.56), pain during (P =.41) or after (P =.23) surgery, or supplemental anesthesia required (P =.49). Few patients in either group were bothered by tissue manipulation or the microscope light, although more patients in the topical group were slightly bothered by touch sensation (P =.05). Chemosis, subconjunctival hemorrhage, and eyelid hematoma were seen almost exclusively in the retrobulbar group (P <.05). Inadvertent eye movement was present more frequently in the topical group (P =.04), although this did not pose a problem to the surgeon. CONCLUSION: Topical anesthesia is a safe and effective alternative to retrobulbar anesthesia for combined phacotrabeculectomy.

Significant postoperative refractive errors in vivo with the Mentor Memorylens intraocular lens.

PURPOSE: To determine the difference between the predicted and postoperative refraction in eyes after implantation of the Mentor MemoryLens intraocular lens (IOL) and compare these results with those of 2 other types of foldable IOLs implanted by the same surgeons. SETTING: Community-based group practice ophthalmology clinic. METHODS: All operated eyes (341) of all patients who had routine phacoemulsification with implantation of a MemoryLens IOL performed by 1 of 2 surgeons were evaluated retrospectively. The predicted refractive error and actual postoperative refractive error were compared in each eye in the MemoryLens group and in 2 smaller control groups with an AcrySof acrylic (Alcon) or SI-40 silicone (Allergan Medical Optics) IOL implanted by the same surgeons using identical technique and IOL calculation parameters. Patients in whom the difference between the predicted and actual postoperative refraction fell significantly outside expected parameters were rechecked with repeat axial length and keratometric readings, and these measurements were used to back-calculate the effective in vivo IOL power. RESULTS: The MemoryLens group had significantly greater variability in postoperative refractive results from those predicted by the Hoffer program than the 2 control groups. The postoperative refractive error in the MemoryLens group differed from +1.50 to -5.50 diopters (D) from that predicted by the IOL calculation formulas. When the outlier groups (ie, greater than +0.50 D or less than -1.00 D from predicted refractive error) were evaluated and compared to the rest of the MemoryLens group and the 2 control groups, no significant difference in axial length, keratometric measurements, operative surgeon, surgical technique, or patient age was found. Repeat axial length and keratometric measurements in the outlier group were not significantly different from those in the same eyes preoperatively. Back-calculation using postoperative axial length and keratometric measurements in the highly myopic outlier group showed that the mean difference between the labeled IOL power and actual in vivo IOL power in the outlier group was -3.08 D (range -1.98 to -7.54 D). The best corrected visual acuity was not affected in patients in the outlier groups despite the refractive variability. CONCLUSION: The variation in postoperative refractive results in the MemoryLens group was significantly greater than in the 2 other foldable IOL groups.