Optics for Low Vision Enabling

For people with central visual field loss, eccentric vision is all that they have to rely on. Even for those who learn how to correctly utilize their eccentric vision, it will never be as good as the central for two entirely different reasons: the off-axis optics of the eye can result in large refractive errors, and the low function of the peripheral retina. This thesis deals with the first of these factors: how to study and correct the eccentric aberrations in people with low vision by measuring the optics of their eyes, correcting the aberrations, particularly astigmatism, and evaluating improvements in visual functions. The individual variations are large for both astigmatism and higher order aberrations such as coma. The main results of this research show that visual improvements through eccentric corrections are possible in spite of the retina’s poor function outside of the macula. Eccentric optical correction affects both resolution and detection capacities. A person’s visual ability can also be influenced by their awareness and training of eccentric viewing

Eccentric correction in central visual field loss

It is not often that one is instantaneously able to apply the results of basic research. This work is an example of such an exception. A widely held conviction has been that human peripheral vision could not be improved through optical correction. It

Excentrisk korrektion vid centrala scotom

Det är sällan man får vara med om att nya grundforskningsresultat tillämpas i samma ögonblick som de kommer fram. Detta arbete är ett exempel på ett sådant undantag. Fram till nu har det funnits en övertygelse om att människans sidseende inte kan för

Raytracing in the compensation of the peripheral optics of the eye

Abstract Background: Many people with a visual impairment have only peripheral vision. However, there is limited knowledge of the peripheral optics of the eye and only some measurements are available in this field. Methods: We simulated the paths of peripheral rays through the eye by means of raytracing. Five programs were compared. The OSLO raytracing software proved to be not only the best one in these circumstances but we also found it very well suited to our purpose. Remaining uncertainties are entirely due to a lack of input data about the peripheral part of the optical system of the eye. We designed compensatory optics on the basis of the test results. Results: Lenses have been manufactured in accordance with the calculations made by the program for angles of incidence of 20, 40, and 60 degrees. The lenses are high compensation astigmatic lenses. The results of perimeter examinations of changes in peripheral vision using attachment optics were inconclusive, while tests of the lenses as attachments in front of a fundus camera produced successful preliminary results. Conclusion: The next step is to test peripheral vision compensatory optics in traffic situations (driving simulator). At the same time attempts are being made to find methods and instruments for measuring the peripheral optics of the eye. Keywords: astigmatism, central scotoma, raytracing, macula degeneration, peripheral vision

Population genomics of the Viking world.

The maritime expansion of Scandinavian populations during the Viking Age (about AD 750-1050) was a far-flung transformation in world history1,2. Here we sequenced the genomes of 442 humans from archaeological sites across Europe and Greenland (to a median depth of about 1×) to understand the global influence of this expansion. We find the Viking period involved gene flow into Scandinavia from the south and east. We observe genetic structure within Scandinavia, with diversity hotspots in the south and restricted gene flow within Scandinavia. We find evidence for a major influx of Danish ancestry into England; a Swedish influx into the Baltic; and Norwegian influx into Ireland, Iceland and Greenland. Additionally, we see substantial ancestry from elsewhere in Europe entering Scandinavia during the Viking Age. Our ancient DNA analysis also revealed that a Viking expedition included close family members. By comparing with modern populations, we find that pigmentation-associated loci have undergone strong population differentiation during the past millennium, and trace positively selected loci-including the lactase-persistence allele of LCT and alleles of ANKA that are associated with the immune response-in detail. We conclude that the Viking diaspora was characterized by substantial transregional engagement: distinct populations influenced the genomic makeup of different regions of Europe, and Scandinavia experienced increased contact with the rest of the continent

Identification of additional risk loci for stroke and small vessel disease: a meta-analysis of genome-wide association studies

BACKGROUND: Genetic determinants of stroke, the leading neurological cause of death and disability, are poorly understood and have seldom been explored in the general population. Our aim was to identify additional loci for stroke by doing a meta-analysis of genome-wide association studies. METHODS: For the discovery sample, we did a genome-wide analysis of common genetic variants associated with incident stroke risk in 18 population-based cohorts comprising 84 961 participants, of whom 4348 had stroke. Stroke diagnosis was ascertained and validated by the study investigators. Mean age at stroke ranged from 45·8 years to 76·4 years, and data collection in the studies took place between 1948 and 2013. We did validation analyses for variants yielding a significant association (at p<5 × 10(-6)) with all-stroke, ischaemic stroke, cardioembolic ischaemic stroke, or non-cardioembolic ischaemic stroke in the largest available cross-sectional studies (70 804 participants, of whom 19 816 had stroke). Summary-level results of discovery and follow-up stages were combined using inverse-variance weighted fixed-effects meta-analysis, and in-silico lookups were done in stroke subtypes. For genome-wide significant findings (at p<5 × 10(-8)), we explored associations with additional cerebrovascular phenotypes and did functional experiments using conditional (inducible) deletion of the probable causal gene in mice. We also studied the expression of orthologs of this probable causal gene and its effects on cerebral vasculature in zebrafish mutants. FINDINGS: We replicated seven of eight known loci associated with risk for ischaemic stroke, and identified a novel locus at chromosome 6p25 (rs12204590, near FOXF2) associated with risk of all-stroke (odds ratio [OR] 1·08, 95% CI 1·05-1·12, p=1·48 × 10(-8); minor allele frequency 21%). The rs12204590 stroke risk allele was also associated with increased MRI-defined burden of white matter hyperintensity-a marker of cerebral small vessel disease-in stroke-free adults (n=21 079; p=0·0025). Consistently, young patients (aged 2-32 years) with segmental deletions of FOXF2 showed an extensive burden of white matter hyperintensity. Deletion of Foxf2 in adult mice resulted in cerebral infarction, reactive gliosis, and microhaemorrhage. The orthologs of FOXF2 in zebrafish (foxf2b and foxf2a) are expressed in brain pericytes and mutant foxf2b(-/-) cerebral vessels show decreased smooth muscle cell and pericyte coverage. INTERPRETATION: We identified common variants near FOXF2 that are associated with increased stroke susceptibility. Epidemiological and experimental data suggest that FOXF2 mediates this association, potentially via differentiation defects of cerebral vascular mural cells. Further expression studies in appropriate human tissues, and further functional experiments with long follow-up periods are needed to fully understand the underlying mechanisms

New genetic loci link adipose and insulin biology to body fat distribution.

Body fat distribution is a heritable trait and a well-established predictor of adverse metabolic outcomes, independent of overall adiposity. To increase our understanding of the genetic basis of body fat distribution and its molecular links to cardiometabolic traits, here we conduct genome-wide association meta-analyses of traits related to waist and hip circumferences in up to 224,459 individuals. We identify 49 loci (33 new) associated with waist-to-hip ratio adjusted for body mass index (BMI), and an additional 19 loci newly associated with related waist and hip circumference measures (P < 5 × 10(-8)). In total, 20 of the 49 waist-to-hip ratio adjusted for BMI loci show significant sexual dimorphism, 19 of which display a stronger effect in women. The identified loci were enriched for genes expressed in adipose tissue and for putative regulatory elements in adipocytes. Pathway analyses implicated adipogenesis, angiogenesis, transcriptional regulation and insulin resistance as processes affecting fat distribution, providing insight into potential pathophysiological mechanisms

The first successful eccentric correction

This paper presents a new procedure for assessing off-axis refractive errors; in this case, oblique astigmatism. By using photorefraction to objectively measure the off-axis refraction, it is possible to identify and provide eccentric correction that results in better image quality for the preferred retinal location (PRL) or the trained retinal location (TRL). This paper describes the case of a 56-year-old man who has suffered from a large central visual field loss (CFL) for more than 30 years. He is the first case to show an improvement of visual function in the peripheral portion he uses outside the macula when eccentric correction is used. A ring target test from ring perimetry (HRP) was used to assess the residual vision. Contrast sensitivity function was also evaluated. The results correlated with the subjective improvement reported by the low vision person. More cases need to be evaluated and new technology developed in order to improve optical and visual assessment

Widesight - a project aimed at improving peripheral vision

Our group of researchers from a variety of backgrounds has been investigating the possibility of improving vision for patients with central scotoma. So far, these patients have only been offered enlarging devices and training. We hope that new knowledge about the peripheral vision optics of the eye will result in improvements in image quality and that this can be helpful for people with low vision caused by central scotomas. We have used raytracing in eye models and by means of optimization we have obtained optical corrections at oblique angles. We will now proceed with individual laboratory measurements, which we believe will increase the understanding of individual variations and provide more information about which eye aberrations can be corrected and how. Subsequently, we will test whether vision can be improved or not. By collaborating with, research laboratories, optics manufacturers and people with impaired vision and by using our clinical and physical-optical experience we expect to develop the area further