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Myopia
Kinds of Myopia Terms modified by Myopia Selected AbstractsPRODIGALITY AND MYOPIA,TWO RATIONALES FOR SOCIAL SECURITY*THE MANCHESTER SCHOOL, Issue 6 2008PIERRE PESTIEAU Among the rationales for social security, there is the fact that some people have to be forced to save. To explain undersaving, rational prodigality and hyperbolic preferences are often cited but treated separably. In this paper we study those two particular behaviors that lead to forced saving within an optimal income tax second-best setting. [source] The Separation Theorem, Investor "Myopia", and Market Prices: A Discussion of "Do Institutional Investors Prefer Near-Term Earnings over Long-Run Value?",CONTEMPORARY ACCOUNTING RESEARCH, Issue 2 2001William M. Cready First page of article [source] Collective Myopia and Disciplinary Power Behind the Scenes of Unethical Practices: A Diagnostic Theory on Japanese OrganizationJOURNAL OF MANAGEMENT STUDIES, Issue 3 2002Nobuyuki Chikudate This study draws on multiple writings to offer a new conceptualization, one that aids in the assessment of unethical practices. Traditionally, phenomenology and the sociology of knowledge have focused on perception, cognition and common sense. Ethnomethodology has focused on procedural infrastructures of ordinary lives. This article combines concepts and ideas from these methodologies in the general concept of ,collective myopia' with some Habermasian and Foucaultian influences. The conceptualization focuses on normative controls operating behind the scenes of unethical practices in Japanese business. The contributions of national culture to the crimes are omitted as much as possible to establish a position of general theory. The conceptualization is then applied to examine the case of the Dai-ichi Kangyo Bank, which was linked to racketeering in 1997. [source] School grades and myopiaOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 2 2007Seang-Mei Saw Abstract Aim:, To evaluate the association between school performance and myopia in Singapore children. Methods:, Children aged 10,12 years from two schools in the Singapore Cohort study Of the Risk factors for Myopia (SCORM) were included. Results of a Year 4 standard nation-wide examination were obtained. Cycloplegic autorefraction and A-scan ultrasound biometry measurements were performed in the schools. Results:, The odds ratio for myopia (defined as right eye spherical equivalent at least ,0.5 D) was 2.5 (95% confidence interval 1.4,4.5) for children with average school examination scores in the fourth quartile compared with the first, after adjusting for confounders including reading in books per week and IQ test scores. Similar significant associations were found for English language (p = 0.001) and native language school examination scores (p < 0.001), while the associations with mathematics school examination scores were of borderline significance (p = 0.055). Conclusion:, School grades, a possible indicator of either cumulative engagement in near work activity or intelligence, were positively associated with myopia in Singapore children. [source] Relative Axial Myopia Induced by Prolonged Light Exposure in C57BL/6 MicePHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2010Xiangtian Zhou Ambient lighting is essential for ocular development in many species, however, disruption in diurnal lighting cycle can affect the development in refraction and axial growth of the eye. This study investigated the effects of prolonged daily lighting on refraction and various optical components of the eye by raising C57BL/6 mice under three different light/dark cycles (18/6, 12/12 and 6/18). Egr-1 mRNA expression, apoptosis and histology of the retina and size of the scleral fibrils were evaluated in these three lighting cycles. Results showed that there was a trend of myopic development, increasing vitreous chamber depth and thinning of the retina in eyes from 6/18 to 18/6 groups. Retinal Egr-1 mRNA expression and diameter of scleral fibrils were reduced with the prolongation of daily lighting from 6/18 to 18/6. However, retinal apoptosis was not detected in all the groups. These results suggest that prolonged lighting can induce axial myopia in inbred mice. This model, which uses mice with similar genetic backgrounds, provides an alternative to the currently available models and therefore is useful for evaluation of refractive errors caused by changes in environmental illumination. [source] Risk Measurement and Investment Myopia in Hedge Fund Management,ASIA-PACIFIC JOURNAL OF FINANCIAL STUDIES, Issue 1 2009Xun Li Abstract Lo (2001) surveys the literature on risk management for hedge funds, and recommends a dynamic and transparent risk measurement for the evolutionary hedge fund industry by citing Albert Einstein's comments. This study is to explore the feasibility and advantages of adopting a dynamic absolute-deviation risk measurement in hedge fund management. It does not only provide an optimal asset allocation strategy both analytically and numerically in a dynamic mean-absolute deviation (DMAD) setting for hedge fund managers, but also contributes to mitigation of potential investment myopia problems in their risk-taking behaviors. It sheds light on risk management and investor-fund manager agency conflicts in the hedge fund industry and adds to the literature on portfolio selection and optimal asset allocation. [source] A case-control study on risk factors for nuclear, cortical and posterior subcapsular cataract: The Casteldaccia Eye StudyACTA OPHTHALMOLOGICA, Issue 5 2005Giuseppe Giuffrè Abstract. Purpose:,To investigate risk factors for nuclear, cortical and posterior subcapsular age-related cataract. Methods:,A case-control study was carried out on subjects aged 40 years and older, living in Casteldaccia, Sicily. Twenty-seven potential risk factors were investigated. Nuclear, cortical and posterior subcapsular opacities of the lens were classified according to the Lens Opacities Classification System II. Subjects with advanced lens opacities represented the cases, while an identical number of subjects without or with early cataract, matched for sex and age, were recruited as controls from within the same population. Results:,Univariate analysis showed that myopia and iris atrophy were significantly associated with nuclear cataract. Iris atrophy, use of corticosteroids, pseudoexfoliation syndrome and familial occurrence of cataract were positively correlated with cortical cataract. Myopia, iris atrophy, use of corticosteroids and familial occurrence of cataract presented an association with posterior subcapsular cataract. After multivariate analysis, the variables that remained significantly associated were myopia and iris atrophy for nuclear cataract; iris atrophy, pseudoexfoliation syndrome and familial occurrence of cataract for cortical cataract; and myopia, iris atrophy and familial occurrence of cataract for posterior subcapsular cataract. Conclusion:,In addition to well known risk factors such as myopia or use of corticosteroids, the Casteldaccia case-control study shows that iris atrophy represents a previously unrecognized risk factor for each of the three types of cataract. [source] Myopia profile in Copenhagen medical students 1996,98.ACTA OPHTHALMOLOGICA, Issue 5 2000Refractive stability over a century is suggested ABSTRACT. Purpose: To assess the myopia prevalence and profile in today's Danish medical students and to compare the pattern with previous and contemporary investigations. Methods: As part of the tutoring in ophthalmology 1996,98 Copenhagen medical students of five successive terms (in their 10th semester, n=294) were interviewed and spot-checked about their refraction. Myopia from ,0.5 D was recorded and myopia onset age stated. Results: The age range was 22,41 years, median age 26. Myopia ranging from ,0.5 to ,8 D was encountered in 147 students (50% of all; females 53.9%, males 45%). In seven the myopia was unilateral. Median values for myopia degree and onset age were ,2.5 D and 16 years in female myopes (n=89) which differed significantly from the male values (n=58) of ,1.5 D and 18 years. Including the age of 18 as lower cut-off for adult-onset myopia 44.9% of the myopes belonged to this category. Conclusions: The results are in close agreement with recent Norwegian student investigations, and there is no obvious trend of a worsening of the academic myopia issue in our part of the world. This is in marked contrast to student myopia profiles as reported in Taiwan, Singapore, and Hong Kong where myopia is booming, by number and degree. [source] Expanded mutational spectrum in Cohen syndrome, tissue expression, and transcript variants of COH1,HUMAN MUTATION, Issue 2 2009Wenke Seifert Abstract Cohen syndrome is characterised by mental retardation, postnatal microcephaly, facial dysmorphism, pigmentary retinopathy, myopia, and intermittent neutropenia. Mutations in COH1 (VPS13B) have been found in patients with Cohen syndrome from diverse ethnic origins. We have carried out mutation analysis in twelve novel patients with Cohen syndrome from nine families. In this series, we have identified 13 different mutations in COH1, twelve of these are novel including six frameshift mutations, four nonsense mutations, two splice site mutations, and a one-codon deletion. Since different transcripts of COH1 have been reported previously, we have analysed the expression patterns of COH1 splice variants. The transcript variant NM_152564 including exon 28b showed ubiquitous expression in all examined human tissues. In contrast, human brain and retina showed differential splicing of exon 28 (NM_017890). Moreover, analysis of mouse tissues revealed ubiquitous expression of Coh1 homologous to human NM_152564 in all examined tissues but no prevalent alternative splicing. © 2008 Wiley-Liss, Inc. [source] Knobloch syndrome: Novel mutations in COL18A1, evidence for genetic heterogeneity, and a functionally impaired polymorphism in endostatin,HUMAN MUTATION, Issue 1 2004Olivier Menzel Abstract Knobloch syndrome (KNO) is an autosomal recessive disorder characterized by high myopia, vitreoretinal degeneration with retinal detachment, and congenital encephalocele. Pathogenic mutations in the COL18A1 gene on 21q22.3 were recently identified in KNO families. Analysis of two unrelated KNO families from Hungary and New Zealand allowed us to confirm the involvement of COL18A1 in the pathogenesis of KNO and to demonstrate the existence of genetic heterogeneity. Two COL18A1 mutations were identified in the Hungarian family: a 1-bp insertion causing a frameshift and a premature in-frame stop codon and an amino acid substitution. This missense variant is located in a conserved amino acid of endostatin, a cleavage product of the carboxy-terminal domain of collagen alpha 1 XVIII. D1437N (D104N in endostatin) likely represents a pathogenic mutation, as we show that the endostatin N104 mutant is impaired in its affinity towards laminin. Linkage to the COL18A1 locus was excluded in the New Zealand family, providing evidence for the existence of a second KNO locus. We named the second unmapped locus for Knobloch syndrome KNO2. Mutation analysis excluded COL15A1, a member of the multiplexin collagen subfamily similar to COL18A1, as being responsible for KNO2. Hum Mutat 23:77,84, 2004. © 2003 Wiley-Liss, Inc. [source] The Impact of Asia on World Politics: China and India Options for the United States,INTERNATIONAL STUDIES REVIEW, Issue 4 2006RONALD L. TAMMEN The United States, by concentrating its intellectual, diplomatic, and military energy on the Middle East, is neglecting the far more substantial long-range challenges that will arise in Asia by mid-century. This strategic myopia is magnified by the lack of a clear national strategy, one that should be focused on recognizing the full implications of the rise of China and India into the ranks of great powers. Informed by theoretical arguments and offering policy options, this essay examines the coming Asian challenge against the backdrop of a world with three great powers potentially competing for resources, allies, and leadership within Asia and, more broadly, the international system. [source] A novel genetic variant of BMP2K contributes to high myopiaJOURNAL OF CLINICAL LABORATORY ANALYSIS, Issue 6 2009Hsin-Ping Liu Abstract Loss of eye growth regulation may cause myopia, because modulation of optic globe size is essential for the generation of normal optic power. Evidence has implied variations of BMP2 gene expression mediate ocular development and retinal tissue remodeling. Given BMP2 as a potential regulator involved in myopia development, we investigate whether gene BMP2-inducible kinase (BMP2K, BIKe), whose expression is up-regulated during BMP2-induced osteoblast differentiation, contributes to susceptibility of high myopia. Participants grouped into high myopia had a spherical equivalent greater than ,6.00 D, compared with a control group of spherical equivalent less than ,0.5 D. Genotyping of polymorphisms 1379 G/A (rs2288255) and 3171 C/G (rs12507099), corresponding with 405 Gly/Ser and 1002 Thr/Ser variation in the BMP2K gene were determined by PCR-restriction fragment length polymorphism and associative study performed by comparing high myopic subjects and healthy controls. The frequency of A allele in the BMP2K gene 1379 G/A polymorphism showed a significant difference between cases and controls (P<0.001, OR=2.99, 95% CI=1.62,5.54) and subjects with either AA or AG genotype show higher risk than GG genotype (P<0.001, OR=3.07, 95% CI=1.59,5.92), while 3171 C/G polymorphism was not significant from this survey. These data suggest that BMP2K gene 1379 G/A variant is strongly correlated with high myopia and may contribute to a genetic risk factor for high degrees of myopic pathogenesis. J. Clin. Lab. Anal. 23:362,367, 2009. © 2009 Wiley-Liss, Inc. [source] Learning to love the older consumerJOURNAL OF CONSUMER BEHAVIOUR, Issue 1 2001Isabelle Szmigin Abstract This paper examines how and why marketing has largely ignored the older consumer and concentrated on younger targets. It explores some of the myths of the older consumer and through examining recent research in the USA and the UK makes a plea for accepting the older consumer as still very much in the main stream of marketing. It also explores how society constructs age and how older people may wish to see themselves. While age related myopia is unsatisfactory for both consumers and marketing, older consumers may express a wide range of identities, making them a potentially complex target for marketing. The paper suggests that more research is needed to explore the different motives and identities of these important consumers with a view to better meeting their needs in terms of appropriate products, messages and media. Copyright © 2001 Henry Stewart Publications. [source] Competitor identification and competitor analysis: a broad-based managerial approachMANAGERIAL AND DECISION ECONOMICS, Issue 4-5 2002Mark Bergen Managerial myopia in identifying competitive threats is a well-recognized phenomenon (Levitt, 1960; Zajac and Bazerman, 1991). Identifying such threats is particularly problematic, since they may arise from substitutability on the supply side as well as on the demand side. Managers who focus only on the product market arena in scanning their competitive environment may fail to notice threats that are developing due to the resources and latent capabilities of indirect or potential competitors. This paper brings together insights from the fields of strategic management and marketing to develop a simple but powerful set of tools for helping managers overcome this common problem. We present a two-stage framework for competitor identification and analysis that brings into consideration a broad range of competitors, including potential competitors, substitutors, and indirect competitors. Specifically we draw from Peteraf and Bergen's (2001) framework for competitor identification to develop a hierarchy of competitor awareness. That is used, in combination with resource equivalence, to generate hypotheses on competitive analysis. This framework not only extends the ken of managers, but also facilitates an assessment of the strategic opportunities and threats that various competitors represent and allows managers to assess their significance in relative terms. Copyright © 2002 John Wiley & Sons, Ltd. [source] Clinical outcomes of corneal wavefront customized ablation strategies with SCHWIND CAM in LASIK treatmentsOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 5 2009Maria Clara Arbelaez Abstract Purpose:, To evaluate the clinical outcomes of aspheric corneal wavefront (CW) ablation profiles in LASIK treatments. Methods:, Thirty eyes treated with CW ablation profiles were included after a follow-up of 6 months. In all cases, standard examinations including preoperative and postoperative wavefront analysis with a CW topographer (Optikon Keratron Scout) were performed. Custom Ablation Manager (CAM) software was used to plan corneal wavefront customized aspheric treatments, and the ESIRIS flying spot excimer laser system was used to perform the ablations (both SCHWIND eye-tech-solutions, Kleinhostheim, Germany). Clinical outcomes were evaluated in terms of predictability, refractive outcome, safety, and wavefront aberration. Results:, In general, the postoperative uncorrected visual acuity and the best corrected visual acuity improved (p < 0.001). In particular, the trefoil, coma, and spherical aberrations, as well as the total root-mean-square values of higher order aberrations, were significantly reduced (p < 0.05) when the pre-existing aberrations were greater than the repeatability and the biological noise. Conclusions:, The study results indicate that the aspheric corneal wavefront customized CAM approach for planning ablation volumes yields visual, optical, and refractive results comparable to those of other wavefront-guided customized techniques for correction of myopia and myopic astigmatism. The CW customized approach shows its strength in cases where abnormal optical systems are expected. Apart from the risk of additional ablation of corneal tissue, systematic wavefront-customized corneal ablation can be considered as a safe and beneficial method. [source] A critical evaluation of the evidence supporting the practice of behavioural vision therapyOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 1 2009Brendan T. Barrett Abstract In 2000, the UK's College of Optometrists commissioned a report to critically evaluate the theory and practice of behavioural optometry. The report which followed Jennings (2000; Behavioural optometry , a critical review. Optom. Pract. 1: 67) concluded that there was a lack of controlled clinical trials to support behavioural management strategies. The purpose of this report was to evaluate the evidence in support of behavioural approaches as it stands in 2008. The available evidence was reviewed under 10 headings, selected because they represent patient groups/conditions that behavioural optometrists are treating, or because they represent approaches to treatment that have been advocated in the behavioural literature. The headings selected were: (1) vision therapy for accommodation/vergence disorders; (2) the underachieving child; (3) prisms for near binocular disorders and for producing postural change; (4) near point stress and low-plus prescriptions; (5) use of low-plus lenses at near to slow the progression of myopia; (6) therapy to reduce myopia; (7) behavioural approaches to the treatment of strabismus and amblyopia; (8) training central and peripheral awareness and syntonics; (9) sports vision therapy; (10) neurological disorders and neuro-rehabilitation after trauma/stroke. There is a continued paucity of controlled trials in the literature to support behavioural optometry approaches. Although there are areas where the available evidence is consistent with claims made by behavioural optometrists (most notably in relation to the treatment of convergence insufficiency, the use of yoked prisms in neurological patients, and in vision rehabilitation after brain disease/injury), a large majority of behavioural management approaches are not evidence-based, and thus cannot be advocated. [source] Technical Note: Effect of contact lenses on measurement of the accommodation microfluctuationsOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 1 2008Mhairi Day Abstract Aim:, Dynamic measurement of accommodation in subjects with myopia usually involves recording through soft contact lenses (CLs) to correct the refractive error. Conversely, dynamic accommodation measurement in emmetropic control subjects is generally undertaken without any corrective lenses. The aim of this experiment was to determine whether CL correction affects the measurement of accommodation microfluctuations using infrared refractometry, and whether this needs to be considered in studies which attempt to compare accommodation responses between the two groups. Methods:, Ten young emmetropic subjects viewed a high contrast Maltese cross target monocularly using the right eye at a target vergence of 0 D. The subjects viewed the target under two conditions: with CL condition and without CL condition, where the subjects viewed the target with the eye only. Accommodation responses of the right eye were recorded continuously for 2 min at a sampling rate of 52 Hz using the Shin-Nippon SRW-5000 autorefractor. Results:, No significant difference (two-tailed paired t -test, t9 = ,1.499, p = 0.168) was found in mean accommodation response between the with CL (mean ± S.D. = ,0.02 ± 0.24 D) and without CL conditions (mean ± S.D. = +0.01 ± 0.25 D). No significant (two-tailed paired t -test, t9 = 0.151, p = 0.883) difference in the magnitude of the accommodation microfluctuations was found between the with CL (mean ± S.D. = 0.162 ± 0.04 D) and without CL condition (mean ± S.D. = 0.169 ± 0.04 D). Power spectrum analysis revealed no differences in the characteristics of the microfluctuations waveform between the two conditions. A control experiment carried out on a subgroup of five subjects using a negative (,3 D) CL demonstrated that there was no significant effect of the dioptric power of the CL on the magnitude of the accommodation microfluctuations (anova: F3,15 = 0.254, p = 0.782). Conclusion:, Thin soft CLs do not affect the magnitude or frequency characteristics of accommodation microfluctuations when measured using the Shin-Nippon SRW-5000. [source] School grades and myopiaOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 2 2007Seang-Mei Saw Abstract Aim:, To evaluate the association between school performance and myopia in Singapore children. Methods:, Children aged 10,12 years from two schools in the Singapore Cohort study Of the Risk factors for Myopia (SCORM) were included. Results of a Year 4 standard nation-wide examination were obtained. Cycloplegic autorefraction and A-scan ultrasound biometry measurements were performed in the schools. Results:, The odds ratio for myopia (defined as right eye spherical equivalent at least ,0.5 D) was 2.5 (95% confidence interval 1.4,4.5) for children with average school examination scores in the fourth quartile compared with the first, after adjusting for confounders including reading in books per week and IQ test scores. Similar significant associations were found for English language (p = 0.001) and native language school examination scores (p < 0.001), while the associations with mathematics school examination scores were of borderline significance (p = 0.055). Conclusion:, School grades, a possible indicator of either cumulative engagement in near work activity or intelligence, were positively associated with myopia in Singapore children. [source] Changes in the visual field following laser in situ keratomileusis for myopiaOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 2 2007Antonio Lleó-Pérez Abstract Purpose:, To assess the changes of the visual field (VF) caused by transient intraocular pressure (IOP) peaks during laser in situ keratomileusis (LASIK) surgery for myopia using automated perimetry. Methods:, This prospective study involved 94 eyes of 94 patients who underwent a conventional LASIK procedure. A complete eye examination was carried out in which the IOP measurement, and Humphrey 24-2 SITA standard VF were tested prior to LASIK and 6 and 12 months after LASIK. Patients were divided into two subgroups according to their refractive error. VF global indices, Glaucoma Hemifield Test and the number of depressed points deviating at p < 5%, p < 2%, p < 1% and p < 0.5% on the Pattern Deviation probability maps were compared using the analysis of variance. Results:, In the low myopia group, there were no significant differences in the analysed variables, except a slight decrease in mean deviation (MD) when comparing results prior to and 6 months following LASIK (p = 0.036; anova) that returned to baseline values at 12 months after surgery. In the moderate and high myopia group, there were no statistically significant differences in any of the variables analysed. No significant correlation was found between the transitory reduction in MD and any of the variables studied. Conclusions:, In patients with low myopia, the VF undergoes a transitory increase in diffuse defects 6 months after surgery, with spontaneous recovery at 12 months after LASIK procedure. Possible explanations for these findings are discussed. [source] Refractive group differences in accommodation microfluctuations with changing accommodation stimulusOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 1 2006Mhairi Day Abstract Purpose:, Microfluctuations of accommodation are known to increase in magnitude with increasing accommodation stimulus. Reduced sensitivity to blur in myopic subjects could also lead to increases in the magnitude of the microfluctuations. The aim of this study is to examine the effect of variations in accommodation stimulus upon the microfluctuations in different refractive groups. Methods:, Thirty-six subjects were divided into three groups depending upon their refractive error and age of onset of their myopia; 12 emmetropes (EMMs), 12 early onset myopes (EOMs) and 12 late-onset myopes (LOMs). Steady-state accommodation responses were recorded continuously for 2 min using the Shin-Nippon SRW-5000 autorefractor at a sampling rate of 52 Hz while viewing targets at accommodation stimuli levels of 0, 1, 2, 3 and 4 D in a Badal (+5 D) optical system. Results:, The EMMs and EOMs showed systematic increases in the root mean square (r.m.s.) value of the microfluctuations with increasing accommodation stimulus. In contrast, no systematic variation with accommodation stimulus was found for the LOMs. Power spectrum analysis demonstrated that increases in the size of the microfluctuations were mediated by increases in the power of the low frequency components of the accommodation response. Conclusions:, The magnitude of the microfluctuations in the EMMs and EOMs may be influenced primarily by accommodation response-induced zonular relaxation effects or to changes in the physical properties of the accommodation plant with increasing accommodation response. The LOMs may have an increased baseline neural blur threshold, which appears to modulate the magnitude of the accommodative microfluctuations for low accommodation levels. At higher accommodation demands, the changes in the physical properties of the accommodation plant or the zonular relaxation effects appear to exceed the blur threshold, and the known association between microfluctuations and accommodation stimulus level is restored. [source] Analysis of refractive state ratios and the onset of myopiaOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 1 2006J. T. Lin Abstract Purpose:, To develop formulae for the refractive state ratios, axial length growth and the age of onset (A*) of myopia. Calculated results are compared with measurements. Methods:, Using an image equation, the axial length in the ametropic state (L) is related to the length in the emmetropic state (L*) and refractive error (D) by a rate of change M (D mm,1). Three refractive state ratios are defined: C1 = L/r1, C2 = L/L* and C3 = L/H, where r1 and H are the anterior surface radius of the cornea and the transverse dimension of the eye, respectively. The age of onset A* is calculated by the rate of change of refractive error (M) and the axial growth rates N and N* in the ametropic and emmetropic states, respectively. Results:, The three ratios C1, C2 and C3 are increasing function of the myopia power, for example, C1 = 3.4, 3.1, 2.9 for D = ,8, 0, +4 dioptres, respectively. The calculated C1* (for the emmetropic state) varies between 3.08 and 3.14, depending on corneal shape, and C3 = 0.985, 1.0, 1.04 for D = +3, 0, ,3 dioptres: these values are consistent with measured data. For a typical system with effective focal length F = 22.25 mm, L* = 24.2 mm and L = 23.4, 24.9, 25.9 mm for D = +2, ,2, ,5 dioptres, respectively. The calculated rates of change of refractive error M = 2.3,2.9 D mm,1 for F = 22,23 mm are also consistent with measured values 2.4,2.7 D mm,1. The age of onset A* is calculated to be proportional to 1/(M dN), where dN = N,N* is the axial growth rate difference between the ametropic and emmetropic states and may be used as a better predictor for myopia onset than the conventional ratio L/r1. The A* is given by the crossing of L and L* curves, in which myopia onset occurs earlier for larger M dN. Conclusion:, The theory provides formulae to calculate various refractive state ratios, which are consistent with measurements. By defining two rate functions, M and N, the onset of myopia can be predicted. [source] Refractive error and ocular biometry in Jordanian adultsOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 4 2005Edward A. H. Mallen Abstract The aim of this study was to establish the prevalence of refractive errors in Jordanian adults of working age, and to study the ocular biometric correlates of refractive error in this population. Refractive error and ocular biometry were measured in 1093 Jordanian adult subjects aged 17,40 years to determine the prevalence of refractive error, and explore structural correlations of ametropia. Refractive error was measured using a Grand-Seiko GR-3100K closed-view infrared autorefractor. Ocular component measurements were made using A-scan ultrasonography and autokeratometry. The prevalence of myopia [spherical equivalent refraction (SER) less than ,0.50 DS] and hyperopia (SER greater than +0.50 DS) was 53.71 and 5.67% respectively; 40.62% of the sample was emmetropic (refraction between +0.50 D and ,0.50 D inclusive in both principal meridians). The distribution of SER was found to show marked leptokurtosis, exhibiting a peak between plano and 1 D of myopia. Corneal radius, anterior chamber depth, crystalline lens thickness, vitreous chamber depth and axial length (AL) parameters were normally distributed in the population studied. AL to corneal curvature ratio was not normally distributed, and showed marked leptokurtosis. Linear regression analysis showed that AL correlated most closely with spherical equivalent refractive error. This study has established a database of refractive error prevalence and ocular biometric correlates of ametropia in a Middle Eastern population of working age. [source] The autonomic control of accommodation and implications for human myopia development: a reviewOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 5 2003Jennifer C. Chen Abstract Prolonged nearwork has long been associated with myopia development, however, there is no well described linking mechanism. One theory suggests that if accommodation accuracy during nearwork is not maintained, the defocused retinal image leads to myopia development. Here we review the findings of research aimed at determining whether the autonomic inputs to the ciliary smooth muscle are involved in this type of environmental myopia. We examine whether an autonomic imbalance could be a precursor to axial elongation and the resulting myopia. Accommodation responses, such as tonic accommodation and nearwork-induced accommodative adaptation, as a function of refractive error, are described in relation to an autonomic imbalance model. The collective results of this research point to anomalous accommodation responses, possibly as a result of underlying anomalous autonomic input to the ciliary muscle, being involved in myopia development and progression. [source] Vision status of children with oculocutaneous albinismOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 6 2002A. O. Oduntan Purpose:, Black South African children with oculocutaneous (OCA) albinism were examined optometrically to establish the level of vision improvement that could be achieved following optical correction. Methods:, The children (N = 153) (males 50.3%; females 49.7%), aged 7,17 years (mean = 10.76 ± 2.25 years) were examined with a logMAR VA chart, cover tests, retinoscopy (dry), subjective refraction, Vistech contrast sensitivity test, ophthalmoscopy, Randot stereotest, Ishihara and Farnsworth Panel D-15 tests. Results:, Many (34.6%) of the children had strabismus, 2,25 prism dioptres. Uncorrected distance VAs were: OD: Finger counting (FC) to 6/7.5 , 2, OS: 6/7.5 + 2 to 6/7.5 , 3, OU: 6/60 , 1 to 6/7.5. Most (67.6%) of the children had myopia. Others (30.8%) had hyperopia or emmetropia (1.7%). Astigmatism was present in 92.25% of the children. The nearest equivalent spherical powers were: OD: ,12.00 to +2.75 D (mean = ,1.48 ± 2.28 D) and OS: ,8.00 to +5. 75 D (mean = 1.36 ± 2.18 D). Following optical correction, VA improvement ranged from one to three lines in 71.2% of the children. The corrected VAs were, OD FC to 6/6 , 1, OS 6/7.5 + 2 to 6/6 , 1, and OU 6/60 to 6/6. Many (84.3%) of the children had corrected VA worse than 6/18 in the better eye and were therefore classified as partially sighted or blind (VA worse than 3/60). Stereoacuity was poor (500,70 sec arc) in most (89.5%) of the children, whilst others could not perceive the minimum 500 sec arc on the test. Contrast sensitivity was poor, maximum spatial frequency being 18 cpd with peak sensitivity at 3 cpd. Many (83%) of the children, however, had normal colour vision. Conclusion:, These children with OCA had poor VA, which could be improved significantly with optical correction. Their poor contrast sensitivity and depth perception, however, were not improved. Most of the children with OCA had normal colour vision. [source] Referral rates for a functional vision screening among a large cosmopolitan sample of Australian childrenOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 1 2002Barbara Junghans The aim of this study was to investigate the incidence of functional vision problems in a large unselected cosmopolitan population of primary school-age children and to investigate whether constant clinical criteria for functional vision problems would be implemented by the practitioners involved in the screening. Refractive errors, near point of convergence, stereopsis, strabismus, heterophoria and accommodative facility were assessed for 2697 children (3,12 years) of varying racial backgrounds living in Australia. The spherical component of the refractive error ranged from ,7.75 to +9.50 D (mean +0.54 D, ±0.79) with a distribution skewed towards hypermetropia; astigmatism ranged from 0 to 4.25 D (mean ,0.16 D, ±0.35). There was a trend towards less hypermetropia and slightly more astigmatism with age. Mean near point of convergence was 5.4 ± 2.9 cm, heterophoria at far and near was 0.12 ± 1.58, exophoria and 1.05 ± 2.53, exophoria, respectively, 0.55% of children exhibited vertical phoria at near >0.5,, accommodative facility ranged from 0 to 24 cycles per minute (cpm) (mean 11.2 cpm, ±3.7), stereopsis varied from 20 to 800 s (,,) of arc with 50% of children having 40,, or better. The prevalence of strabismus was particularly low (0.3%). Twenty percent of the children were referred for further assessment based on criteria of one or more of: stereopsis >70,,, accommodative facility <8 cpm, near point of convergence (NPC) >9 cm, near exophoria >10, or near esophoria >5,, shift in eso or exophoria , 4, between distance and near, astigmatism , 1 D, myopia more than ,0.75 D, or hyperopia >+1.50 D. Post-hoc analysis of the record cards seeking the reason for further assessment indicates that referrals appear to have been based upon clinical intuition rather than on a set number of borderline or unsatisfactory results. [source] Facility of accommodation in myopiaOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 5 2001Daniel J. O'Leary Summary Purpose: Myopes have been shown to have abnormal accommodative characteristics. This study investigated the characteristics of accommodation facility in myopic and emmetropic students. Methods: Distance and near positive and negative accommodation response time components of facility were measured over a 1 min period using a ,2.00 D/zero lens pair for distance responses and a ±2.00 D lens pair for near responses. 79 students (37 myopes and 42 emmetropes) aged 18,27 years acted as subjects. Subjects were masked, and the results were analysed in a masked fashion. Results: Mean distance facility was significantly lower (9.7 cycles per minute (cpm)) in the myopic group compared with the mean distance facility in the emmetropic group (15.6 cpm; p <0.005). There was no significant difference in the near facilities of the two groups (11.5 cpm in myopes vs 12.9 cpm in emmetropes). Positive accommodation response time for distance vision was greater than 4 s in 45% of myopes and in 9% of emmetropes. Conclusions: Our findings confirm that myopes tend to have abnormal accommodation responses to blur. Distance facility, but not near facility of accommodation is more frequently reduced in myopes than in emmetropes. [source] Relative Axial Myopia Induced by Prolonged Light Exposure in C57BL/6 MicePHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2010Xiangtian Zhou Ambient lighting is essential for ocular development in many species, however, disruption in diurnal lighting cycle can affect the development in refraction and axial growth of the eye. This study investigated the effects of prolonged daily lighting on refraction and various optical components of the eye by raising C57BL/6 mice under three different light/dark cycles (18/6, 12/12 and 6/18). Egr-1 mRNA expression, apoptosis and histology of the retina and size of the scleral fibrils were evaluated in these three lighting cycles. Results showed that there was a trend of myopic development, increasing vitreous chamber depth and thinning of the retina in eyes from 6/18 to 18/6 groups. Retinal Egr-1 mRNA expression and diameter of scleral fibrils were reduced with the prolongation of daily lighting from 6/18 to 18/6. However, retinal apoptosis was not detected in all the groups. These results suggest that prolonged lighting can induce axial myopia in inbred mice. This model, which uses mice with similar genetic backgrounds, provides an alternative to the currently available models and therefore is useful for evaluation of refractive errors caused by changes in environmental illumination. [source] Hedging or Market Timing?THE JOURNAL OF FINANCE, Issue 2 2005Selecting the Interest Rate Exposure of Corporate Debt ABSTRACT This paper examines whether firms are hedging or timing the market when selecting the interest rate exposure of their new debt issuances. I use a more accurate measure of the interest rate exposure chosen by firms by combining the initial exposure of newly issued debt securities with their use of interest rate swaps. The results indicate that the final interest rate exposure is largely driven by the slope of the yield curve at the time the debt is issued. These results suggest that interest rate risk management practices are primarily driven by speculation or myopia, not hedging considerations. [source] Retinal and Optic Nerve DiseasesARTIFICIAL ORGANS, Issue 11 2003Eyal Margalit Abstract:, A variety of disease processes can affect the retina and/or the optic nerve, including vascular or ischemic disease, inflammatory or infectious disease, and degenerative disease. These disease processes may selectively damage certain parts of the retina or optic nerve, and the specific areas that are damaged may have implications for the design of potential therapeutic visual prosthetic devices. Outer retinal diseases include age-related macular degeneration, pathologic myopia, and retinitis pigmentosa. Although the retinal photoreceptors may be lost, the inner retina is relatively well-preserved in these diseases and may be a target for retinal prosthetic devices. Inner retinal diseases include retinal vascular diseases such as diabetic retinopathy, retinal venous occlusive disease, and retinopathy of prematurity. Other retinal diseases such as ocular infections (retinitis, endophthalmitis) may affect all retinal layers. Because the inner retinal cells, including the retinal ganglion cells, may be destroyed in these diseases (inner retinal or whole retinal), prosthetic devices that stimulate the inner retina may not be effective. Common optic nerve diseases include glaucoma, optic neuritis, and ischemic optic neuropathy. Because the ganglion cell nerve fibers themselves are damaged, visual prosthetics for these diseases will need to target more distal portions of the visual pathway, such as the visual cortex. Clearly, a sound understanding of retinal and optic nerve disease pathophysiology is critical for designing and choosing the optimal visual prosthetic device. [source] A review of Donnai-Barrow and facio-oculo-acoustico-renal (DB/FOAR) syndrome: Clinical features and differential diagnosisBIRTH DEFECTS RESEARCH, Issue 1 2009Barbara R. Pober Abstract Mutations in the gene LRP2 have recently been identified as the cause of Donnai-Barrow and Facio-oculo-acoustico-renal (DB/FOAR) syndrome. More than two dozen cases, the first reported more than 30 years ago by Holmes, have been published. Summarizing available information, we highlight the cardinal features of the disorder found in ,90% of published cases. These features include: agenesis of the corpus callosum, developmental delay, enlarged anterior fontanelle, high myopia, hypertelorism, proteinuria, and sensorineural hearing loss. Congenital diaphragmatic hernia and omphalocele are reported in only half of the patients. There is no evidence for genotype-phenotype correlation, though the sample size is too small to preclude this with certainty. Although several conditions to consider in the differential diagnosis are highlighted, the diagnosis of DB/FOAR syndrome should not be difficult to establish as its constellation of findings is strikingly characteristic. Birth Defects Research (Part A), 2009. © 2008 Wiley-Liss, Inc. [source] | ||||||||||||||||