The prevalence and causes of vision loss in Indigenous Australians: the National Indigenous Eye Health Survey

Aim: To determine the prevalence and causes of vision loss in Indigenous Australians. Design, setting and participants: A national, stratified, random cluster sample was drawn from 30 communities across Australia that each included about 300 Indigenous people of all ages. A sample of non-Indigenous adults aged 40 years was also tested at several remote sites for comparison. Participants were examined using a standardised protocol that included a questionnaire (self-administered or completed with the help of field staff), visual acuity (VA) testing on presentation and after correction, visual field testing, trachoma grading, and fundus and lens photography. The data were collected in 2008. Main outcome measures: VA; prevalence of low vision and blindness; causes of vision loss; rates of vision loss in Indigenous compared with non-Indigenous adults. Results: 1694Indigenouschildrenand1189Indigenousadultswereexamined, representing recruitment rates of 84% for children aged 5–15 years and 72% for adults aged 40 years. Rates of low vision (VA \u3c 6/12 to 6/60) were 1.5% (95% CI, 0.9%–2.1%) in children and 9.4% (95% CI, 7.8%–11.1%) in adults. Rates of blindness (VA \u3c 6/60) were 0.2% (95% CI, 0.04%–0.5%) in children and 1.9% (95% CI, 1.1%–2.6%) in adults. The principal cause of low vision in both adults and children was refractive error. The principal causes of blindness in adults were cataract, refractive error and optic atrophy. Relative risks (RRs) of vision loss and blindness in Indigenous adults compared with adults in the mainstream Australian population were 2.8 and 6.2, respectively. By contrast, RRs of vision loss and blindness in Indigenous children compared with mainstream children were 0.2 and 0.6, respectively. Conclusion: Many causes of vision loss in our sample were readily avoidable. Better allocation of services and resources is required to give all Australians equal access to eye health services

Trachomaas one of the leading cause of low vision In Kano State

Trachoma is fast becoming a common cause of low vision in developing countries. In order to ascertain this, a survey of one thousand (1000) subjects with low vision aged between 15-70 years with mean age of 31.30 years was conducted in the northern part of Nigeria. These subjects were seen from 1990-1998 (a period of 9 years) in three leading specialist eye centres in Kano State (ECWA Savana and General hospital). Data on sex, age, cause of low vision, and the visual acuity was obtained and analysed using percentages. The result revealed that, trachoma was the second highest leading cause of blindness after cataract with 243 subjects representing (24.3%) of the sample population.And female subjects were more affected than their male counterpart with 69.1% and 30.9% respectively. The most affected age group was 5-15 years with 50 (20.6%) of the sample population and the least affected age group was 60-70 years with30 representing (12.3%).Also 85.5% of the study population had visual acuity of 20/1000 while 14.5% had acuity of 20/700. And all the subject in this study population had the infection at terminal stage. In conclusion therefore, the study has shown that trachoma is the second highest cause of partial blindness or low vision, with more than 20% of the sample population affected. Thus there is need for urgent enlightenment on preventive measure to save our citizen especially those in Northern Nigeria from themenace of trachoma

Visual impairment amongst adult diabetics attending a tertiary outpatient clinic

Background: To determine the prevalence of diabetic retinopathy maculopathy and cataract amongst diabetics and the prevalence of visual impairment amongst diabetics attending the Komfo  Anokye Teaching Hospital eye unit. There are no current data in the study area on the prevalence of visual impairment and blindness amongst diabetics. This data is required in planning for screening and prevention of blindness due to diabetics.Methods: This was a hospital based cross sectional study. Subjects were diabetic patients attending the diabetic clinic. Simple random sampling was used. Demographic was taken. Visual acuity and refraction was done. Slit lamp examination was used to identify cataract. Maculopathy and retinopathy was determined using a 90D Volk lens and an indirect ophthalmoscope.Results: Non -insulin dependent diabetics constituted 97.1% whilst 2.9% were insulin dependent diabetics. The prevalence of the outcomes measures was: Cataract (23.7%) mild and moderate retinopathy (13.7%) severe proliferative retinopathy (1.8%) maculopathy (6.8%). Prevalence of low vision and blindness was 18.4%. Amongst diabetics 59.1% had no previous eye evaluation. Impaired vision due to cataract was 24.0 % representing a 40% decline in a decade.Conclusion: The prevalence of visual impairment was high at 18.4%. The reduction in impaired vision due to cataract over a decade is suggestive of either an improved cataract surgical rate or improved diabetic care or both. Majority of the diabetic patients 59.1% had not received prior ocular evaluation. There is an urgent need to have a screening program in this areaFunding: NoneKeywords: Diabetics, retinopathy, maculopathy, visual impairment, blindnes

Neural correlates of motion-induced blindness in the human brain

Motion-induced blindness (MIB) is a visual phenomenon in which highly salient visual targets spontaneously disappear from visual awareness (and subsequently reappear) when superimposed on a moving background of distracters. Such fluctuations in awareness of the targets, although they remain physically present, provide an ideal paradigm to study the neural correlates of visual awareness. Existing behavioral data on MIB are consistent both with a role for structures early in visual processing and with involvement of high-level visual processes. To further investigate this issue, we used high field functional MRI to investigate signals in human low-level visual cortex and motion-sensitive area V5/MT while participants reported disappearance and reappearance of an MIB target. Surprisingly, perceptual invisibility of the target was coupled to an increase in activity in low-level visual cortex plus area V5/MT compared with when the target was visible. This increase was largest in retinotopic regions representing the target location. One possibility is that our findings result from an active process of completion of the field of distracters that acts locally in the visual cortex, coupled to a more global process that facilitates invisibility in general visual cortex. Our findings show that the earliest anatomical stages of human visual cortical processing are implicated in MIB, as with other forms of bistable perception

Spatial representation and low vision: two studies on the content, accuracy and utility of mental representations

The paper reports on two studies being conducted with students from Dorton College - Royal London Society for the Blind (RLSB) in Kent. The first experiment will examine the content and accuracy of mental representations of a well-known environment. Students will walk a route around the college campus and learn the position of ten buildings or structures. They will then be asked to make heading judgments, estimate distances, complete a spatial cued model and sequentially visit a series of locations. The second experiment will examine the strategies and coding heuristics used to explore a complex novel environment. Students will be asked to explore a maze and learn the location of different places. Their search patterns will be digitally tracked, coded and analyzed using GIS software.Students will be tested using the same methods as in the first experiment and their performance level will be correlated with their exploratory patterns. Throughout the paper we are reminded that construct validity can only be secured by employing multiple converging techniques in the collection and analysis of cognitive data. Methods should be designed to test content and accuracy as well as the utility of mental representations

Dichromacy: Color Vision Impairment and Consanguinity in Heterogenous Population of Pakistan

Background and Objectives: Dichromacy, an X-linked recessive disorder is identified worldwide, more in males than females. In European Caucasians, its incidence is 8% in males and 0.5% in females. In India, it is 8.73% in males and 1.69% in females, and in Iran, it is 8.18% in males and 0.43% in females. Population based epidemiological data about dichromacy in different ethnic groups in Pakistan is not available. The aim of this study was to find out the population prevalence of inherited red-green dichromacy in a heterogenous population of the district of Chiniot, Punjab, Pakistan, and to determine the impact of consanguinity and ethnicity. Methods: In this cross-sectional study, boys and girls of the higher secondary schools were examined in the three tehsils of district Chiniot. Pseudoisochromatic Ishihara Test has been employed for detection of dichromacy in the study population. The sample size was calculated statistically as 260, which was expanded to 705 and divided by population density of the three tehsils. Results: Screening of 359 males and 346 females revealed 19 (5.29%) dichromat males and only 2 (0.58%) females. The study population belonged to 23 castes / isonym groups. The consanguinity found in the district of Chiniot is 84.82% and in the dichromat families, it is 85.71%, of which 52.37% are first cousin. Interpretation & Conclusion: The study has shown that the incidence of dichromacy could be reduced through genetic counselin

Seeing, Sensing, and Scrutinizing

Large changes in a scene often become difficult to notice if made during an eye movement, image flicker, movie cut, or other such disturbance. It is argued here that this <i>change blindness</i> can serve as a useful tool to explore various aspects of vision. This argument centers around the proposal that focused attention is needed for the explicit perception of change. Given this, the study of change perception can provide a useful way to determine the nature of visual attention, and to cast new light on the way that it is—and is not—involved in visual perception. To illustrate the power of this approach, this paper surveys its use in exploring three different aspects of vision. The first concerns the general nature of <i>seeing</i>. To explain why change blindness can be easily induced in experiments but apparently not in everyday life, it is proposed that perception involves a <i>virtual representation</i>, where object representations do not accumulate, but are formed as needed. An architecture containing both attentional and nonattentional streams is proposed as a way to implement this scheme. The second aspect concerns the ability of observers to detect change even when they have no visual experience of it. This <i>sensing</i> is found to take on at least two forms: detection without visual experience (but still with conscious awareness), and detection without any awareness at all. It is proposed that these are both due to the operation of a nonattentional visual stream. The final aspect considered is the nature of visual attention itself—the mechanisms involved when <i>scrutinizing</i> items. Experiments using controlled stimuli show the existence of various limits on visual search for change. It is shown that these limits provide a powerful means to map out the attentional mechanisms involved

Beyond statistical testing: individual differences and the contentand accuracy of mental representations of space

The article uses data from two experiments on the content and accuracy of mentalrepresentations of space by the blind and visually impaired in order expose some of theshortcomings of typical statistical testing and propose an individual differences approach to theanalysis of data. It begins with a discussion of some of the problems associated with the strictclassification and eventual comparison of individuals between groups. The individual differencesapproach is then presented and the concepts of ability and present competence are explored alongwith the importance of detailed participant description. Examples from the two experiments areused to demonstrate how null hypothesis significance testing can be complemented with effect sizeestimates, box-plots and ranking techniques. Throughout the article we are reminded of the need toadopt mutually supportive techniques to account for the heterogeneity of experience and skillsbetween participants. The article uses data from two experiments on the content and accuracy of mentalrepresentations of space by the blind and visually impaired in order expose some of theshortcomings of typical statistical testing and propose an individual differences approach to theanalysis of data. It begins with a discussion of some of the problems associated with the strictclassification and eventual comparison of individuals between groups. The individual differencesapproach is then presented and the concepts of ability and present competence are explored alongwith the importance of detailed participant description. Examples from the two experiments areused to demonstrate how null hypothesis significance testing can be complemented with effect sizeestimates, box-plots and ranking techniques. Throughout the article we are reminded of the need toadopt mutually supportive techniques to account for the heterogeneity of experience and skillsbetween participants

Does Phenomenal Consciousness Overflow Attention? An Argument from Feature-Integration

In the past two decades a number of arguments have been given in favor of the possibility of phenomenal consciousness without attentional access, otherwise known as phenomenal overflow. This paper will show that the empirical data commonly cited in support of this thesis is, at best, ambiguous between two equally plausible interpretations, one of which does not posit phenomenology beyond attention. Next, after citing evidence for the feature-integration theory of attention, this paper will give an account of the relationship between consciousness and attention that accounts for both the empirical data and our phenomenological intuitions without positing phenomenal consciousness beyond attention. Having undercut the motivations for accepting phenomenal overflow along with having given reasons to think that phenomenal overflow does not occur, I end with the tentative conclusion that attention is a necessary condition for phenomenal consciousness