Towards in vivo regulon kinetics: PurR activation by 5-phosphoribosyl-α-1-pyrophosphate during purine depletion in Lactococcus lactis.

Short-term adaptation to changing environments relies on regulatory elements translating shifting metabolite concentrations into a specifically optimized transcriptome. So far the focus of analyses has been divided between regulatory elements identified in vivo and kinetic studies of small molecules interacting with the regulatory elements in vitro. Here we describe how in vivo regulon kinetics can describe a regulon through the effects of the metabolite controlling it, exemplified by temporal purine exhaustion in Lactococcus lactis. We deduced a causal relation between the pathway precursor 5-phosphoribosyl-α-1-pyrophosphate (PRPP) and individual mRNA levels, whereby unambiguous and homogeneous relations could be obtained for PurR regulated genes, thus linking a specific regulon to a specific metabolite. As PurR activates gene expression upon binding of PRPP, the pur mRNA curves reflect the in vivo kinetics of PurR PRPP binding and activation. The method singled out the xpt-pbuX operon as kinetically distinct, which was found to be caused by a guanine riboswitch whose regulation was overlaying the PurR regulation. Importantly, genes could be clustered according to regulatory mechanism and long-term consequences could be distinguished from transient changes--many of which would not be seen in a long-term adaptation to a new environment. The strategy outlined here can be adapted to analyse the individual effects of members from larger metabolomes in virtually any organism, for elucidating regulatory networks in vivo.

Nanosecond-laser application in intermediate AMD: 12-month results of fundus appearance and macular function.

BACKGROUND: A novel, ultra-low energy nanosecond laser (retinal rejuvenation therapy) has been developed with the aim to slow progression of early age-related macular degeneration (AMD). The safety, changes in fundus characteristics and macular function in a cohort of participants with bilateral intermediate AMD are reported. DESIGN: Prospective non-randomised, pilot intervention study. PARTICIPANTS OR SAMPLES: Subjects with bilateral intermediate AMD (n = 50, aged 50-75 years). METHODS: Ultra-low energy laser pulses applied in 12 spots around the macula of one eye (0.15-0.45 mJ), using 400 µm diameter spot, 3 nanosecond pulse length, 532 nm wavelength and energy titrated to each patient. MAIN OUTCOME MEASURES: Best corrected visual acuity, drusen area and macular sensitivity (flicker perimetry) at baseline and at 3, 6 and 12 months post-laser. RESULTS: Treatment was painless with no clinically visible lesions. No participant developed choroidal neovascularization, while two with thin central retinal thickness at baseline developed atrophy at 12-month follow up. Drusen area was reduced in 44% of treated eyes and 22% of untreated fellow eyes, with changes in drusen and function not being coincident. Improvement in flicker threshold within the central 3° was observed in both the treated and untreated fellow eyes at 3 months post-laser. Of the 11 eyes at greatest risk of progression (flicker defect >15 dB), seven improved sufficiently to be taken out of this high-risk category. CONCLUSIONS: A single unilateral application of nanosecond laser to the macula produced bilateral improvements in macula appearance and function. The nanosecond retinal rejuvenation therapy laser warrants ongoing evaluation as an early intervention for AMD.

Younger siblings, C-reactive protein, and risk of age-related macular degeneration.

In this study, we examined the relationship between exposure to siblings and 1) the risk of age-related macular degeneration (AMD) and 2) C-reactive protein levels. We retrospectively analyzed pooled cross-sectional data from 2 studies: the Cardiovascular Health and Age-Related Maculopathy Study (2001-2002) and the Age-Related Maculopathy Statin Study (2004-2006). Associations between number of siblings and AMD were assessed by using multinomial logistic regression. Associations between number of siblings and C-reactive protein levels were examined by using a generalized linear model for γ distribution. A higher number of younger siblings was associated with significantly lower odds of early AMD in those with a family history of AMD (odds ratio = 0.2, 95% confidence interval: 0.1, 0.8) (P = 0.022) but was unrelated to AMD for those who had no family history of the disease (odds ratio = 1.0, 95% confidence interval: 0.9, 1.2) (P = 0.874). A higher number of younger siblings correlated with lower C-reactive protein levels (ß = -0.19, 95% confidence interval: -0.38, -0.01) (P = 0.036). This supports the theory that immune modulation contributes to AMD pathogenesis and suggests that exposure to younger siblings might be protective when there is a family history of AMD.

A comparative analysis of the intestinal metagenomes present in guinea pigs (Cavia porcellus) and humans (Homo sapiens).

BACKGROUND: Guinea pig (Cavia porcellus) is an important model for human intestinal research. We have characterized the faecal microbiota of 60 guinea pigs using Illumina shotgun metagenomics, and used this data to compile a gene catalogue of its prevalent microbiota. Subsequently, we compared the guinea pig microbiome to existing human gut metagenome data from the MetaHIT project. RESULTS: We found that the bacterial richness obtained for human samples was lower than for guinea pig samples. The intestinal microbiotas of both species were dominated by the two phyla Bacteroidetes and Firmicutes, but at genus level, the majority of identified genera (320 of 376) were differently abundant in the two hosts. For example, the guinea pig contained considerably more of the mucin-degrading Akkermansia, as well as of the methanogenic archaea Methanobrevibacter than found in humans. Most microbiome functional categories were less abundant in guinea pigs than in humans. Exceptions included functional categories possibly reflecting dehydration/rehydration stress in the guinea pig intestine. Finally, we showed that microbiological databases have serious anthropocentric biases, which impacts model organism research. CONCLUSIONS: The results lay the foundation for future gastrointestinal research applying guinea pigs as models for humans.

Gene-environment interaction in progression of AMD: the CFH gene, smoking and exposure to chronic infection.

A number of risk factors including the complement factor H (CFH) gene, smoking and Chlamydia pneumoniae have been associated with age-related macular degeneration (AMD). However, the mechanisms underlying how these risk factors might be involved in disease progression and disease aetiology is poorly understood. A cohort series of 233 individuals followed for AMD progression over a mean period of 7 years underwent a full eye examination, blood was taken for DNA and antibody titre and individuals completed a standard medical and general questionnaire. Y402H variants of the CFH gene were assessed with disease progression as well as examination of interaction between Y402H variants and smoking and Y402H variants and the pathogen C. pneumoniae. The CC risk genotype of Y402H was significantly associated with increased AMD progression [odds ratio (OR) 2.43, 95% confidence interval (95% CI) 1.07-5.49] as was smoking (OR 2.28, 95% CI 1.26-4.12). However, the risk of progression was greatly increased to almost 12-fold (OR 11.8, 95% CI 2.1-65.8) when, in addition to having the C risk allele, subjects also presented with the upper tertile of antibodies to the bacterial pathogen C. pneumoniae compared with those with the T allele of Y402H and the lowest antibody tertile. This demonstrates for the first time the existence of a gene environment-interaction between pathogenic load of C. pneumoniae and the CFH gene in the aetiology of AMD.

C-reactive protein levels and complement factor H polymorphism interaction in age-related macular degeneration and its progression.

PURPOSE: To determine the effect of elevated level of C-reactive protein (CRP) and its joint effect with the complement factor H (CFH) polymorphism on prevalent age-related macular degeneration (AMD) and its progression. DESIGN: Two-arm case-control study: (a) Study on prevalent AMD cases and population-based controls; (b) longitudinal study on AMD progression, comparing those in whom AMD progressed with those with no progression. PARTICIPANTS: (a) A cross-sectional sample of 544 participants, of whom 312 had features of early or late AMD and 232 were controls; (b) a sample of 254 early AMD cases, followed for 7 years. METHODS: The study was conducted in Melbourne, Australia. Macular stereo photographs were graded for AMD according to the International Classification and Grading System. High-sensitivity CRP was measured in fresh serum, and genotyping was performed through the Australian Genome Research Facility. The association of CRP with outcomes was tested using multivariate logistic regression analysis adjusted for age, smoking, anti-inflammatory medications, and the CC genotype of the CFH gene. Risk factor interaction was explored using an additive model. MAIN OUTCOME MEASURES: Prevalent early AMD, prevalent late AMD, progressed AMD, and measures of risk factor interaction. RESULTS: Elevated CRP levels were associated with late AMD: odds ratio (OR), 3.12; 95% confidence interval (CI), 1.38-7.07. An association of elevated CRP with AMD progression was weaker: OR, 1.90 (95% CI, 0.88-4.10). A combination of elevated CRP and the CC (Y402H) genotype resulted in a super-additivity of the risks, with odds ratios of 19.3 (95% CI, 2.8-134) for late AMD, and 6.8 (95% CI, 1.2-38.8) for AMD progression, with the attributable proportion of risk owing to CRP-CFH interaction calculated at 26% for prevalent late AMD and 22% for AMD progression. CONCLUSIONS: Synergistic influence of CRP levels and the at risk genotype of the CFH gene resulted in a super-additive risk for prevalent late AMD and AMD progression. Testing for the combination of these 2 risk factors to predict a high risk of AMD and its progression would allow for targeted trials of new intervention strategies.

Gene-environment interactions and aging visual function: a classical twin study.

OBJECTIVE: To elucidate the contribution of environmental versus genetic factors to the significant losses in visual function associated with normal aging. DESIGN: A classical twin study. PARTICIPANTS: Forty-two twin pairs (21 monozygotic and 21 dizygotic; age 57-75 years) with normal visual acuity recruited through the Australian Twin Registry. METHODS: Cone function was evaluated by establishing absolute cone contrast thresholds to flicker (4 and 14 Hz) and isoluminant red and blue colors under steady state adaptation. Adaptation dynamics were determined for both cones and rods. Bootstrap resampling was used to return robust intrapair correlations for each parameter. MAIN OUTCOME MEASURES: Psychophysical thresholds and adaptational time constants. RESULTS: The intrapair correlations for all color and flicker thresholds, as well as cone absolute threshold, were significantly higher in monozygotic compared with dizygotic twin pairs (P<0.05). Rod absolute thresholds (P = 0.28) and rod and cone recovery rate (P = 0.83; P = 0.79, respectively) did not show significant differences between monozygotic and dizygotic twins in their intrapair correlations, indicating that steady-state cone thresholds and flicker thresholds have a marked genetic contribution, in contrast with rod thresholds and adaptive processes, which are influenced more by environmental factors over a lifetime. CONCLUSIONS: Genes and the environment contribute differently to important neuronal processes in the retina and the role they may play in the decline in visual function as we age. Consequently, retinal structures involved in rod thresholds and adaptive processes may be responsive to appropriate environmental manipulation. Because the functions tested are commonly impaired in the early stages of age-related macular degeneration, which is known to have a multifactorial etiology, this study supports the view that pathogenic pathways early in the disease may be altered by appropriate environmental intervention. FINANCIAL DISCLOSURE(S): The authors have no proprietary or commercial interest in any materials discussed in this article.

Measuring rod and cone dynamics in age-related maculopathy.

PURPOSE: A cathode-ray-tube (CRT) monitor-based technique was used to isolate clinically significant components of dark adaptation. The utility of the technique in identifying adaptation abnormalities in eyes with age-related maculopathy (ARM) is described. METHODS: A CRT dark adaptometer was developed to assess cone and rod recovery after photopigment bleach. The following measures were obtained: cone recovery rate (R(c); in decades per minute) and absolute threshold (Tf(c); log candelas per square meter), rod recovery rate (R(r); decades per minute), and rod-cone transition (rod-cone break [RCB], in minutes). These components were isolated by appropriately selecting stimulus size, stimulus location, pigment bleach, and test duration and by coupling the CRT with judiciously selected neutral-density (ND) filters. The protocol was developed by using 5 young observers and was tested on 27 subjects with ARM in the study eye and 22 age-matched control subjects. RESULTS: The parameters necessary for effective isolation of cone and early phase rod dark adaptation were a 2.6 ND filter (for a standard CRT monitor, 0.08-80 cd . m(-2) luminance output); a 4 degrees foveated, 200-ms, achromatic spot; approximately 30% pigment bleaching; and a 30-minute test duration. These settings returned obvious rod and cone recovery curves in control and ARM eyes that were compatible with conventional test methods and identified 93% of participants with ARM as having delayed dynamics in at least one of the parameters. Cone recovery dynamics were significantly slower in the ARM group when compared with age-matched control subjects (R(c), 0.99 +/- 0.35 vs. 2.63 +/- 0.61 decades . min(-1), P < 0.0001). Three of the 27 eyes with ARM did not achieve RCB during the allowed duration (30 minutes). The remaining eyes with ARM (n = 24) exhibited a significant delay in rod recovery (R(r)(,) ARM, 0.16 +/- 0.03 vs. controls, 0.22 +/- 0.02 decades . min(-1), P < 0.0001) and the average time to RCB (+/-SD) in the ARM group was significantly longer than in the control subjects (19.12 +/- 5.17 minutes vs. 10.40 +/- 2.49 minutes, P < 0.0001). CONCLUSIONS: The CRT dark-adaptation technique described in this article is an effective test for identifying abnormalities in cone and rod recovery. Slowed cone and rod recovery and a delayed RCB were evident in the eyes with ARM. The test method is potentially useful for clinical intervention trials in which ARM progression is monitored.

Novel measures of cardiovascular health and its association with prevalence and progression of age-related macular degeneration: the CHARM Study.

BACKGROUND: To determine if novel measures of cardiovascular health are associated with prevalence or progression of age-related macular degeneration (AMD). METHODS: Measures of the cardiovascular system: included intima media thickness (IMT), pulse wave velocity (PWV), systemic arterial compliance (SAC), carotid augmentation index (AI). For the prevalence study, hospital-based AMD cases and population-based age- and gender-matched controls with no signs of AMD in either eye were enrolled. For the progression component, participants with early AMD were recruited from two previous studies; cases were defined as progression in one or both eyes and controls were defined as no progression in either eye. RESULTS: 160 cases and 160 controls were included in the prevalence component. The upper two quartiles of SAC, implying good cardiovascular health, were significantly associated with increased risk of AMD (OR = 2.54, 95% CL = 1.29, 4.99). High PWV was associated with increased prevalent AMD. Progression was observed in 82 (32.3%) of the 254 subjects recruited for the progression component. Higher AI (worse cardiovascular function) was protective for AMD progression (OR = 0.30, 95%CL = 0.13, 0.69). Higher aortic PWV was associated with increased risk of AMD progression; the highest risk was seen with the second lowest velocity (OR = 6.22, 95% CL = 2.35, 16.46). CONCLUSION: The results were unexpected in that better cardiovascular health was associated with increased risk of prevalent AMD and progression. Inconsistent findings between the prevalence and progression components could be due to truly different disease etiologies or to spurious findings, as can occur with inherent biases in case control studies of prevalence. Further investigation of these non-invasive methods of characterizing the cardiovascular system should be undertaken as they may help to further elucidate the role of the cardiovascular system in the etiology of prevalent AMD and progression.

Analytical validation of a next generation sequencing liquid biopsy assay for high sensitivity broad molecular profiling.

Circulating tumor DNA (ctDNA) analysis is being incorporated into cancer care; notably in profiling patients to guide treatment decisions. Responses to targeted therapies have been observed in patients with actionable mutations detected in plasma DNA at variant allele fractions (VAFs) below 0.5%. Highly sensitive methods are therefore required for optimal clinical use. To enable objective assessment of assay performance, detailed analytical validation is required. We developed the InVisionFirst™ assay, an assay based on enhanced tagged amplicon sequencing (eTAm-Seq™) technology to profile 36 genes commonly mutated in non-small cell lung cancer (NSCLC) and other cancer types for actionable genomic alterations in cell-free DNA. The assay has been developed to detect point mutations, indels, amplifications and gene fusions that commonly occur in NSCLC. For analytical validation, two 10mL blood tubes were collected from NSCLC patients and healthy volunteer donors. In addition, contrived samples were used to represent a wide spectrum of genetic aberrations and VAFs. Samples were analyzed by multiple operators, at different times and using different reagent Lots. Results were compared with digital PCR (dPCR). The InVisionFirst assay demonstrated an excellent limit of detection, with 99.48% sensitivity for SNVs present at VAF range 0.25%-0.33%, 92.46% sensitivity for indels at 0.25% VAF and a high rate of detection at lower frequencies while retaining high specificity (99.9997% per base). The assay also detected ALK and ROS1 gene fusions, and DNA amplifications in ERBB2, FGFR1, MET and EGFR with high sensitivity and specificity. Comparison between the InVisionFirst assay and dPCR in a series of cancer patients showed high concordance. This analytical validation demonstrated that the InVisionFirst assay is highly sensitive, specific and robust, and meets analytical requirements for clinical applications.

Development of a highly sensitive liquid biopsy platform to detect clinically-relevant cancer mutations at low allele fractions in cell-free DNA.

INTRODUCTION: Detection and monitoring of circulating tumor DNA (ctDNA) is rapidly becoming a diagnostic, prognostic and predictive tool in cancer patient care. A growing number of gene targets have been identified as diagnostic or actionable, requiring the development of reliable technology that provides analysis of multiple genes in parallel. We have developed the InVision™ liquid biopsy platform which utilizes enhanced TAm-Seq™ (eTAm-Seq™) technology, an amplicon-based next generation sequencing method for the identification of clinically-relevant somatic alterations at low frequency in ctDNA across a panel of 35 cancer-related genes. MATERIALS AND METHODS: We present analytical validation of the eTAm-Seq technology across two laboratories to determine the reproducibility of mutation identification. We assess the quantitative performance of eTAm-Seq technology for analysis of single nucleotide variants in clinically-relevant genes as compared to digital PCR (dPCR), using both established DNA standards and novel full-process control material. RESULTS: The assay detected mutant alleles down to 0.02% AF, with high per-base specificity of 99.9997%. Across two laboratories, analysis of samples with optimal amount of DNA detected 94% mutations at 0.25%-0.33% allele fraction (AF), with 90% of mutations detected for samples with lower amounts of input DNA. CONCLUSIONS: These studies demonstrate that eTAm-Seq technology is a robust and reproducible technology for the identification and quantification of somatic mutations in circulating tumor DNA, and support its use in clinical applications for precision medicine.

Dietary lutein, zeaxanthin, and fats and the progression of age-related macular degeneration.

BACKGROUND: To estimate the effect of dietary intake of lutein and zeaxanthin (L/Z) and fats on the progression of age-related macular degeneration (AMD). METHODS: Two hundred and fifty-four subjects identified with early age-related macular degeneration (AMD) were re-examined to determine 7-year AMD progression. Intakes of L/Z and fatty acids were estimated from food frequency questionnaires. Progression was defined by 3 different definitions, 2 quantitative and 1 qualitative, which varied in the stringency of the change required for the AMD to be deemed to have progressed. Covariates included age, smoking, AMD family history, source study, and follow-up duration. RESULTS: Energy-adjusted L/Z intake as a continuous variable was associated with AMD progression in the worse affected eye when defined by the most stringent criterion (odds ratio [OR] = 2.65, 95% confidence interval [CI] 1.13-6.22, p = 0.02). Similar associations were observed for the 2 other progression definitions (p = 0.18 and p = 0.13). Energy-adjusted omega-3 fatty acid intake modelled as a quintile median was associated with AMD progression only in the side-by-side assessment (OR = 2.56, 95% CI 1.11-5.91, p = 0.03), with borderline significance in the other 2 definitions (p = 0.05 and p = 0.08). No association of AMD progression was observed with the intake of either total fat or other subgroups: saturated, polyunsaturated, or monounsaturated fats; trans fatty acids; or omega-6 fatty acids. INTERPRETATION: The findings of the study are counterintuitive, suggesting that increased intakes of dietary L/Z and omega-3 fatty acids are associated with progression of AMD. These results may indicate that too much of a good thing might be harmful. It is possible that in this study participants adopted a more healthy diet, having been aware of their AMD status at the beginning of the study. This healthy diet was then reflected in the dietary questionnaire completed at the end of study. However, this explanation may not adequately explain why those whose AMD had progressed, on the basis of fundus signs and not symptoms such as visual acuity decline, adopted a healthier lifestyle more aggressively than those without progression.

Apolipoprotein (APOE) gene is associated with progression of age-related macular degeneration (AMD).

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.

Development of cataract and associated risk factors: the Visual Impairment Project.

OBJECTIVE: To evaluate risk factors for the development of cataract in Australian residents. METHODS: A total of 3721 participants from 9 randomly selected urban districts within Victoria were recruited and invited to attend comprehensive standardized interviews and ophthalmic examinations at baseline and then 5-year follow-up. Lens opacities were graded clinically and on photographs according to the Wilmer cataract grading system. The development of cortical, nuclear, and posterior subcapsular cataract were assessed separately for associated risk factors. Risk exposure at baseline was used as the predictor for cataract development, which included various sociodemographic, dietary, familial, medical, and ocular characteristics of the participants. Risk factor analyses were performed by univariate and multivariate logistic regression. RESULTS: Increased age was a risk factor for development of all types of cataract with an increasing risk trend throughout life for nuclear cataract. Female sex, a laborer's occupation, and myopia were independent risk factors for development of cortical cataract. For development of nuclear cataract, the independent risk factors were having a birthplace outside Australia and New Zealand, current cigarette smoking, and having a history of arthritis. Diabetes mellitus and having taken calcium channel blockers for longer than 5 years were independent risk factors for posterior subcapsular cataract. CONCLUSIONS: The trend of increasing incidence of cataract with increased age is a major public health concern with an aging population in Australia and the world. Among the risk factors identified, cigarette smoking is a factor that is readily modifiable and preventable. The other risk factors identified require further support or clarification of underlying mechanisms to find modifiable features.

Multiple comparisons model-based clustering and ternary pattern tree numerical display of gene response to treatment: procedure and application to the preclinical evaluation of chemopreventive agents.

Microarray technology has greatly aided the identification of genes that are expressed differentially. Statistical analysis of such data by multiple comparisons procedures has been slow to develop, in part, because methods to cluster the results of such comparisons in biologically meaningful ways have not been available. We isolated and analyzed, by Northern blot and GeneChip, replicate liver RNA samples (n = 4/group) from rats fed with control diet or diet containing one of three chemopreventive compounds, selected because their pharmacological activities, including RNA expression response, are relatively well understood. We report on a classification tree, based on the results of nonparametric multiple comparisons, which results in the bipolar hierarchical clustering of genes in relation to their response to treatment. In addition to identifying treatment-responsive genes, application of this procedure to our test study identified the known pharmacological relationships among the treatment groups without supervision. Also, small treatment-specific subsets of genes were identified that may be indicative of additional pharmacophores present in the test compounds.

Five-year incidence of bilateral cause-specific visual impairment in the Melbourne Visual Impairment Project.

PURPOSE: To describe the age-, gender-, and cause-specific 5-year incidence of bilateral visual impairment in participants in the Melbourne Visual Impairment Project, Victoria, Australia. METHODS: Participants aged 40 years and older were recruited from Melbourne, Victoria, Australia, by random cluster sampling. The mean age of the 3271 (83% of the eligible) participants was 59 +/- 12 (SD) years. Of the participants, 54% were female. The initial baseline study (1992-1994) was followed by a 5-year incidence study (1997-1999). At both time points of the study, participants underwent a standardized testing procedure. Distance and near vision was tested using logarithm of the minimum angle of resolution (logMAR) charts, followed by refraction if needed. Visual fields were assessed by the 24-2 Humphrey field test (FastPac, Humphrey Field Analyzer; Carl Zeiss Meditec, Dublin, CA). Also, intraocular pressure, ocular motility, dilated ophthalmoscopy, and photography of the lens and the fundus were conducted. Furthermore, an interview included demographic characteristics, history of eye disease, medical history, and medication use. For classification of visual impairment, both visual acuity (VA) and visual fields (VF) examination results were used. Four levels of bilateral presenting visual impairment were defined: mild (VA, <20/40-20/60, and/or VF, homonymous hemianopia), moderate (VA, <20/60-20/200, and/or VF, constriction <20 degrees to 10 degrees from fixation), severe (VA, <20/200-10/200, and/or VF, constriction <10 degrees to 5 degrees from fixation), and profound (VA, <10/200, and/or VF, constriction <5 degrees from fixation). For all participants found to be visually impaired, the major cause was identified. RESULTS: Of the 3040 people eligible to attend follow-up 2594 (85%) participated. Data were available for 2530 (98%) participants. In 105 participants (4.22%; 95% confidence limit 2.58-5.85) some degree of visual impairment developed. The main causes were undercorrected refractive error (59%), age-related macular degeneration, cataract and neuro-ophthalmic disorders (7% each), glaucoma (3%), and diabetic retinopathy (1%). The main cause of severe and profound visual impairment was age-related macular degeneration (37%). CONCLUSIONS: Undercorrected refractive error was the primary cause of new cases of visual impairment in this population. Further research is needed to understand the origin of this and to develop appropriate prevention measures. Age-related macular degeneration is the primary cause of severe or profound vision loss in Australia. This disease requires further investigation for effective cure and preventive strategies.

Incidence and progression of cataract in the Melbourne Visual Impairment Project.

PURPOSE: To determine the 5-year incidence and progression of cataract and cataract surgery in the Melbourne Visual Impairment Project. DESIGN: Prospective cohort study. methods: Demographic information including race, sex, age, and education level was collected at baseline. Cortical cataract was defined as 4/16 or greater opacity; progression was defined as a more than 2/16 increase. Nuclear cataract was defined as Wilmer standard grade 2 or higher; progression was defined as more than 0.5 increase. Posterior subcapsular (PSC) cataract was defined as opacity 1 mm(2) or greater; progression was defined as greater than 1 mm(2) increase. results: Of the 3040 participants eligible to attend follow-up examinations, 2594 (85% of those eligible) participated. The mean age of participants at follow-up was 62.5 years, and 55% were female. The percentage of patients who had at least one lens extracted over 5 years increased from 0.5% of those aged 40 to 49 years at baseline to 35.7% of those aged 80 years or more at baseline. The overall incidence of the three types of cataract was as follows: cortical 7.7% (95% confidence limits [CL] = 5.8-9.8), nuclear 16.4% (95% CL = 12.1-20.8), and PSC 7% (95% CL = 5.3-8.7). The overall progression of cataract was cortical 14.3% (95% CL = 10.2-18.3), nuclear 19.3% (95% CL = 15.9-22.7), and PSC 20% (95% CL = 8.7-31.1). The incidence and progression rates increased significantly by age, but the rates were not significantly different by sex. CONCLUSION: These cataract incidence data confirm the public health importance of cataract in Australia. The data also support the need to plan both primary prevention program and adequate surgical services to meet the anticipated increase in demand with the aging population.

Factors affecting perceptual thresholds in a suprachoroidal retinal prosthesis.

PURPOSE: The suprachoroidal location for a retinal prosthesis provides advantages over other locations in terms of a simplified surgical procedure and a potentially more stable electrode-neural interface. The aim of this study was to assess the factors affecting perceptual thresholds, and to optimize stimulus parameters to achieve the lowest thresholds in patients implanted with a suprachoroidal retinal prosthesis. METHODS: Three patients with profound vision loss from retinitis pigmentosa were implanted with a suprachoroidal array. Perceptual thresholds measured on individual electrodes were analyzed as a function of stimulus (return configuration, pulse polarity, pulse width, interphase gap, and rate), electrode (area and number of ganged electrodes), and clinical (retinal thickness and electrode-retina distance) parameters. RESULTS: A total of 92.8% of 904 measurements made up to 680 days post implantation yielded thresholds (range, 44-436 nanocoulombs [nC]) below the safe charge limit. Thresholds were found to vary between individuals and to depend significantly on electrode-retina distance, negligibly on retinal thickness, and not on electrode area or the number of ganged electrodes. Lowest thresholds were achieved when using a monopolar return, anodic-first polarity, short pulse widths (100 µs) combined with long interphase gaps (500 µs), and high stimulation rates (≥400 pulses per second [pps]). CONCLUSIONS: With suprachoroidal stimulation, anodic-first pulses with a monopolar return are most efficacious. To enable high rates, an appropriate combination of pulse width and interphase gap must be chosen to ensure low thresholds and electrode voltages. Electrode-retina distance needs to be monitored carefully owing to its influence on thresholds. These results inform implantable stimulator specifications for a suprachoroidal retinal prosthesis. (ClinicalTrials.gov number, NCT01603576.).