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PubMed1996

Polarization contrast vision in Octopus.

While the ability to analyze polarized light is widespread among animals, its contribution to form vision has not yet been documented. We tested the hypothesis that polarization vision can be used for object discrimination, by training octopuses to distinguish between targets on the basis of the presence or absence of a pattern produced by a 90 degrees polarization contrast within the target. Octopuses recognized a 90 degrees contrast pattern within a single target, when presented either on a horizontal/vertical axis or on a 45 degrees/135 degrees axis. They were able to transfer their learning to new situations and to detect a polarization contrast when the orientations of the e-vector of light passing through the target center and background differed by as little as 20 degrees. Polarization vision may provide information similar to that available from color vision and thus serve to enhance the detection and recognition of objects.

Animals↗

PubMed2000

The deep fovea, sideways vision and spiral flight paths in raptors.

Raptors - falcons, hawks and eagles in this study - have two regions of the retina in each eye that are specialized for acute vision: the deep fovea and the shallow fovea. The line of sight of the deep fovea points forwards and approximately 45 degrees to the right or left of the head axis, while that of the shallow fovea also points forwards but approximately 15 degrees to the right or left of the head axis. The anatomy of the foveae suggests that the deep fovea has the higher acuity. Several species of raptors in this study repeatedly moved their heads among three positions while looking at an object: straight, with the head axis pointing towards the object; or sideways to the right or left, with the head axis pointing approximately 40 degrees to the side of the object. Since raptors do not rotate their eyes noticeably in the sockets, these movements presumably cause the image of the object to fall on the shallow and deep foveae. The movements occurred approximately every 2 s on average in hawks and falcons, and approximately every 5 s in bald eagles. The proportion of time that the raptors spent looking straight or sideways at an object depended on how far away the object was. At a distances closer than 8 m, they spent more time looking at the object straight, but as the distance increased to 21 m, they spent more time looking at it sideways. At distances of 40 m or more, raptors looked sideways at the object 80 % or more of the time. This dependence of head position on distance suggests that raptors use their more acute sideways vision to look at distant objects and sacrifice acuity for stereoscopic binocular vision to look at close objects. Having their most acute vision towards the side causes a conflict in raptors such as falcons, which dive at prey from great distances at high speeds: at a speed of 70 m s(-)(1), turning their head sideways to view the prey straight ahead with high visual acuity may increase aerodynamic drag by a factor of 2 or more and slow the raptor down. Raptors could resolve this conflict by diving along a logarithmic spiral path with their head straight and one eye looking sideways at the prey, rather than following the straight path to the prey with their head turned sideways. Although the spiral path is longer than the straight path, a mathematical model for an 'ideal falcon' shows that the falcon could reach the prey more quickly along the spiral path because the speed advantage of a straight head more than compensates for the longer path.

Air Movements↗

PubMed1999

Motion sickness in public road transport: the relative importance of motion, vision and individual differences.

The relative importance of vehicle motion, a view of the road ahead and passenger characteristics in the causation of motion sickness in road transport has been investigated using survey data from 3256 coach passengers and measurements of coach motion. Overall, 28% of passengers said they felt unwell during coach travel. Prior experience of sickness, travel regularity and age were the factors most highly correlated with illness. Increased vehicle motion and poorer forward vision also correlated with illness. Little difference in illness was apparent with a good view of the road ahead, regardless of motion exposure, although vision alone was not sufficient to eliminate passenger sickness entirely. The results suggest that travel sickness could be significantly reduced by improved forward external vision and that improved forward vision may be particularly beneficial for individuals new to coach travel and for those who travel less often.

Adolescent↗

PubMed1978

A general zone theory of color and brightness vision. I. Basic formulation.

A general theory of color and brightness vision, developed from basic principles of the Helmholtz and Hering points-of-view on color vision is presented in a general mathematical form suitable for quantitative analysis. Visual sensation is described by a vector expressed in terms of Hering-like elements for color and brightness which underlie in their spatial-temporal variations the perceptions of form and change. The photic stimulus of vision is recognized to act first and only through photoabsorption producing a Helmholtz-like vector of quantum absorptions. The physiological transformation of the Helmholtz photochemical excitations into the Hering sensation responses is represented as a vector of general operators. The result is a mathematical framework encompassing traditional psychophysical and sensory scaling experiments. The theory is utilized to demonstrate that for many traditional (Class A) psychophysical observations, the physiological operator reduces to a linear (matrix) transformation. For static, uniform, focal stimulation, this reduction is seen to be the basis for earlier specific linear models of color vision. We also illustrate that static intensity-level effects (Bezold-Brücke hue shifts, unique hue invariance) can be modeled from the theory by power, but not logarithmic, intensity-level dependence for the sensation elements.

Color↗

PubMed2004

Disturbance of vision by COX-2 inhibitors.

In this review, 35 cases of acute, reversible, sometimes severe, disturbances of vision closely associated with the use of celecoxib or rofecoxib are described. These were identified from three different databases using strict selection criteria. The events included temporary blindness, visual field defect, scotoma, teichopsia, blurred vision, decreased vision and abnormal vision. The reactions had a mean onset time of 9.5 days and recovery occurred within 3 days following withdrawal of the drug. The reactions do not appear to be related to age, gender, dose, or indication for use. The incidence of reported cases is estimated to be not less than 5 per 10,000 patients. Possible mechanisms for this type of reaction are described. The most likely appears to be the result of interference with the retinal blood supply through reduced production of prostanoids. Genetic polymorphisms that affect drug metabolism or uptake could be risk factors and are discussed along with suggestions for research.

Adult↗

PubMed2006

Project Universal Preschool Vision Screening: a demonstration project.

OBJECTIVES: Visual disorders among preschool-aged children are common, yet screening is infrequent. The purpose of this project was to implement the vision screening recommendations proposed by the Maternal and Child Health Bureau and National Eye Institute Vision Screening in the Preschool Child Task Force: monocular visual acuity and stereopsis testing. METHODS: Four sites fully participated in the implementation of the task force recommendations with 3- and 4-year-old children. Two of the sites worked with primary care practices (testing performed by staff); 2 worked with community-based programs (testing performed by lay volunteers). Each site tracked number of children screened by age, as well as proportion testable, referred, and with documented follow-up evaluation. RESULTS: Variations in implementation of the recommendations were observed. Successful screening among 3-year-olds ranged from 70% to 93%; referral rates were 1% to 41%, and follow-up rates were 29% to 100%. Successful screening among 4-year-olds ranged from 88% to 98%; referral rates were 2% to 40%, and follow-up rates were 41% to 100%. The proportion of 3-year-olds who were treated was significantly different between the community-based sites (n = 20) and the primary care sites (n = 2). Similarly, the proportion of 4-year-olds who were treated was significantly different between the community-based sites (n = 36) and the primary care sites (n = 11). CONCLUSION: . The variability across pilot sites in numbers successfully screened and numbers referred suggests that all aspects of preschool vision screening need thorough review before the goal of universal preschool vision screening can be realized.

Child Health Services↗

PubMed1992

Color vision deficits and Rorschach performance in aged persons.

Forty-two community residing older adults (M age = 69.28) (32 color normal, 10 color deficient) were administered the Rorschach and measures of both verbal and nonverbal intelligence in order to explore the effect of color vision deficiencies on affective responsivity. Among the sample of older persons screened for both visual and auditory acuity, when controls for intelligence and numbers of responses were made, greater affective constriction was found in the protocols of color vision deficient persons, relative to color normal individuals. These data suggest that Rorschach indicators of affective constriction may be biased in the case of individuals who have experienced color vision decrements. Consequently, first screening for color vision decrements when assessing older persons' personality dynamics may be desirable.

Aged↗

PubMed2005

Effects of limited peripheral vision on shuttle sprint performance of soccer players.

This study examined the effect of limited peripheral vision on the shuttle sprint performance of soccer players. Participants were 14 male soccer players of a student soccer club (M age = 22.1 yr., SD = 1.3 yr.). They performed a repeated shuttle sprint with full and limited peripheral vision. Mean total sprint time and mean turning time increased significantly with limited peripheral vision. It is concluded that only turning during shuttle sprint performance decreases when sprinting with a restricted peripheral field of view, indicating the use of peripheral vision for the control of directional changes while sprinting.

Adult↗

PubMed2001

Digital vision theory: Boolean logic model.

Guild (1932) stated the general requirements for processing signals in color vision system and a digital format of his paradigm is developed in this paper. The disk structure generates the digital receptor pulse. The input modalities form sets, linked by intersections, joins, and complement junctions. The synapses are elements in these junctions. Complex synapses form junctions to create Boolean logic processing. A computer program using these Boolean logic functions calculates: Light and dark adaptation responses; Color matching and spectral coordinate functions; Chromatic adaptation; Color shift responses; and Dynamic neural responses. These calculations compare favorably with the experimental data. The processing criteria for signals in the vision system are given by Guild (1932). The analysis in this paper uses his criteria to develop a model of the vision system. A computer program simulates the digital processing of signals from the external photon source to the neural output signals from the ganglion cells in the inner-plexiform layer. The responses are compared with the responses of actual vision systems.

Color Perception↗

PubMedDate not supplied

Loneliness in low-vision older women.

The purpose of this analysis was to identify predictors of loneliness in women 75 years of age and older with low vision. The sample of 56 women was derived from a larger study of low-vision adults. Women's loneliness, optimism, social support, living arrangement, vision, and perceived health were examined using the revised University of California, Los Angeles, Loneliness Scale, the Life Orientation Test, the Social Support Questionnaire, and a demographic questionnaire. Data were analyzed using descriptive statistics, Pearson correlations, multiple regressions, and t-tests. Optimism and social support satisfaction were found to predict degree of loneliness in the sample. Women who were less optimistic and less satisfied with their social support system experienced higher levels of loneliness. Duration of visual impairment was associated with duration of loneliness. The findings provide nurses with information for identifying low-vision older women who are at risk for loneliness.

Aged↗

PubMedDate not supplied

A developmental approach to preschool vision screening.

A developmental approach to preschool vision screening is described. The choice of acuity testing material in this test is determined by the child's capabilities, assessed prior to acuity testing. When compared with the Society for Prevention of Blindness test, this approach yields approximately half the number of untestables. Further, the acuity data from the two screening tests are quite similar, and both agree well with data from an additional screening by a pediatric ophthalmologist. Screening of preschool children usually requires a number of compromises in methods felt to be ideal for adults. Sacrifices in cost (i.e., additional personnel to assist the tester), additional effort (i.e., prior training of the children), or precision of acuity measures (i.e., cruder picture type targets for all children and use of isolated targets) are typically made to assure testability. These problems have been minimized by the Experimental method. Because of its low untestability rate and its apparently valid acuity data, this developmental vision screening test can be recommended as a cost effective approach to preschool vision screening. Previous research has shown that ratings of a child's behavior during this developmentally oriented vision screening test predict results of diagnostic cognitive tests as accurately as extensive tests designed exclusively for developmental screening. This test is then extremely cost effective when used for comprehensive preschool screening.

Child, Preschool↗

PubMedDate not supplied

Color vision in diabetic school children.

The color vision of 64 diabetic school children was studied. Acquired color vision defects due to diabetes could not be found in any of the children. Two of the children had a congenital red-green color vision defect. In the examination, three different pseudoisochromatic plate tests (Isihara, Standard Pseudoisochromatic Plates part 2, and Lanthony Tritan Album) were used as well as the Nagel anomaloscope and three different cap arrangement tests (Panel D 15, Lanthony Desaturated Panel, and Farnsworth-Munsell 100 hue). The plate tests and the anomaloscope examination were fast, reliable, and well accepted by the children. The cap arrangement tests took more time, and many of the children neither liked nor properly performed these tests. Twelve color dependent glucose strip tests for diabetes care at home were also studied. A few of the youngest school children made mistakes in interpreting the colors of these strips, although their color vision was normal.

Adolescent↗

PubMedDate not supplied

A sweep VEP test for color vision deficits in infants and young children.

PURPOSE: Color vision testing in young children typically is precluded by the motor and cognitive skills required by standard tests; yet this information can be useful for diagnosis and counseling in many conditions. The purpose of this study is to evaluate a visual evoked potential (VEP) method for assessing red-green color vision anomalies in pediatric patients. METHOD: The relative chromatic luminance (C = R/R + G) of a rapidly reversing red-green checkerboard was varied across a wide range within a short viewing period (10 sec). Swept-parameter VEP methods were used to measure the cortical response to the range of C presented. RESULTS: Individuals with normal color vision exhibit a VEP response that exceeds noise levels across all values of C, often with an amplitude minima near the photopic equiluminant point (C = 0.5). Results from children with established protan and deutan color vision anomalies show loss of VEP amplitude and phase at values of C consistent with the respective color defect. A patient with achromatopsia showed a generalized depression of VEP response across all values of C tested. CONCLUSION: Color sweep VEP techniques appear promising for the clinical assessment of color status in pediatric patients.

Child↗

PubMedDate not supplied

Characteristics of a pediatric low-vision population.

BACKGROUND: Assessment of the causes of childhood blindness is important to develop preventive and therapeutic strategies that can reduce the incidence of visual impairment. METHODS: A retrospective survey of the clinical records of 395 consecutive children younger than 14 years of age who were attended by the Low Vision Service of State University of Campinas (UNICAMP) was conducted. Data on the age distribution, the causes of low vision, the types of low vision aids prescribed, the follow up of their use, and improvement in visual acuity were obtained. RESULTS: Congenital bilateral toxoplasmic macular scars, optic atrophy, and congenital cataracts were the major causes of low vision in this population. The optical aid most frequently prescribed was a telescope. The improvement of visual acuity with the use of aids was highly significant.

Adolescent↗

PubMedDate not supplied

Effect of tear film stability on fluctuation of vision after photorefractive keratectomy.

PURPOSE: To evaluate the difference in tear film break-up between normal eyes and eyes after photorefractive keratectomy (PRK) and its impact on quality of vision in PRK eyes. METHODS: Seventy-seven normal eyes and 76 eyes with no ocular pathology except refractive error that had PRK were enrolled. Tear film break-up time was determined under slit-lamp microscopy with fluorescent staining. Two videokeratographs (TMS-1) were taken before and immediately after tear film break-up. Surface asymmetry index, surface regularity index, and subtractive maps were analyzed to evaluate corneal topographic changes before and after tear film break-up. RESULTS: The distribution of tear film break-up in the central cornea was different in PRK eyes than in normal eyes (P < .0001). Distributions of tear film break-up after PRK were localized more in the upper and lower temporal regions than in normal eyes; incidence of tear film break-up in the central cornea was decreased. There were no significant differences in tear film break-up between normal eyes and eyes after PRK (P = .69). Twelve PRK patients (24 eyes, 32%) experienced fluctuation of vision and fatigue during normal activities after PRK. We divided eyes after PRK into two groups (with and without fluctuation of vision) and found a statistically significant difference in surface asymmetry index before tear film break-up between the two groups (P = .0092). CONCLUSION: The distribution of tear film break-up is changed after PRK. Eyes after PRK experienced more fluctuation of vision than normal eyes.

Adult↗

PubMedDate not supplied

Changes in mesopic vision after photorefractive keratectomy for myopia.

PURPOSE: To evaluate the mesopic functions of excimer laser treated eyes with different treatment diameters and different laser beam delivery systems. METHODS: In Group 1, 38 eyes were treated with the Aesculap Meditec MEL 60 ArF scanning laser beam excimer laser. The treatment diameter was 5.0 mm. In Group 2, 38 eyes were treated with the Aesculap Meditec MEL 70(G-Scan) flying spot excimer laser; the chosen treatment diameter was 6.5 mm. In Group 3, there were 38 eyes with no treatment; vision was corrected only with spectacles (control group). All eyes had 20/20 best spectacle-corrected visual acuity before surgery, as did the control group. Measurements were carried out preoperatively and at 12 months following surgery. All eyes exhibited normal corneal wound healing, and subepithelial haze was <0.5 according to Hanna's scale. Mesopic functions (mesopic vision and glare sensitivity) were tested with the Mesoptometer II. RESULTS: The average preoperative refractive error in Group 1 was -3.40 D; in Group 2, -3.38 D; in Group 3, -3.44 D. In Group 1, 34% of the treated eyes met the night driving requirements (recognition at 1:5 contrast level), whereas in Group 2, 85%, and in Group 3, 95% of the eyes fulfilled this criteria. When contrast vision was tested under glare conditions in Group 1, 31.6%; in Group 2, 80%; and in Group 3, 94.7% of the eyes identified the target orientation (Landolt ring) at contrast level 1:5. CONCLUSIONS: The unoperated spectacle wearers had better results in all tested functions. The larger 6.5-mm treatment diameter with the use of the flying spot laser beam delivery system resulted in better mesopic function and contrast vision under mesopic conditions than the smaller 5.0-mm diameter.

Adult↗

PubMed1995

Functional considerations in evaluation and treatment of the client with low vision.

In evaluating and treating clients who have low vision, the occupational therapist must consider factors in addition to typical measures of the client's visual acuity, field loss, and oculomotor control. It is important to consider the functional implications of the client's ocular pathology, including illumination needs, contrast sensitivity, sensitivity to glare, and need for magnification as well as environmental factors such as the amount of pattern in a visual task, the amount of lighting and contrast available, and the conditions under which the task is performed. These factors are all relevant to occupational therapy low vision rehabilitation because each may influence the way in which a client uses his or her residual vision and achieves successful adaptation. This article provides an overview of these factors and presents a suggested protocol for evaluation of the client with low vision.

Activities of Daily Living↗

PubMed1995

Occupational therapy and the person with diabetes and vision impairment.

Diabetes affects 5.2% of the population; many of those persons experience loss of vision as one complication of the disease. Occupational therapists are treating these persons, often for other resulting complications (such as stroke or amputations), or are being asked to adapt techniques or equipment (such as insulin-drawing devices) needed for diabetes management. Because no guidelines exist for occupational therapy with persons with diabetes or vision loss or both, occupational therapists may be unsure of appropriate treatment approaches. Among the approaches described in the occupational therapy literature, common ones include collaboration with other professionals and incorporation of one or more aspects of the diabetes regimen into the person's life-style. When addressing persons who have both diabetes and vision loss, therapists consider their own knowledge base as well as the persons' needs in managing their diabetes. Treatment ideas include enhancing the visual environment or incorporating tactile and auditory feedback with self-management tasks such as testing blood glucose levels. Collaboration with and referral to diabetes and low-vision professionals are adjuncts to therapy and ensure a comprehensive and ongoing diabetes management program.

Activities of Daily Living↗