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At least 91 records · Page 5Linked to original sources
PubMed1989

Television and vision: reading captions when vision is blurred.

Closed captions for television have become an important means of communication for hearing-impaired people. Yet, previous studies show that hearing-impaired people are very likely to have visual problems that may interfere with caption reading. In this study, the effect of reduced vision on caption reading is examined. Six hearing-impaired and 14 hearing subjects viewed segments of captioned movies on a 19-inch television screen at a distance of three meters. All of the subjects had normal vision. Their vision was blurred with plus lenses of five different strengths. The data show that caption reading is affected by relatively small amounts of blur. If a person has even a slight visual problem, the caption letters under normal television viewing conditions are too small for maximum reading performance.

Adult↗
PubMed2003

Color vision at low light intensity, dark adaptation, Purkinje shift, critical flicker frequency and the deterioration of vision at low illumination. Neurophysiology at the nanometer range of neural structure.

The discovery that color vision extends to low illumination reported in this communication eliminates the duplicity theory as an explanation of vision differing at high and low illumination. Instead, an explanation of the difference was found when analyzing synaptic interaction between retinal neurons, made possible by revealing the synaptic connections between the neurons through three-dimensional reconstruction of the outer plexiform layer and by applying information communicated by published recordings of the potential of retinal neurons. The synaptic connections revealed the existence of a large horizontal cell network and of cone networks. The networks contribute continuous information regarding average light intensity over an area of the retina. The opposite sign of the network input maintains bipolar cell threshold constant when illumination varies. When at low illumination the network potential approaches a minimum the consequent extensive increase of transmitter release at network synapses eliminates fine tuning of synaptic transmission at these synapses. This accounts for the deterioration of vision at low illumination by eliminating spatial brightness contrast enhancement and also accounts for the difference in critical flicker frequency at high and low illumination. Network interference accounts for the two phases of dark adaptation and for the Purkinje shift. The analysis revealed conditions for particularly fast synaptic transmission leading to cascade like transmission at sequences of synapses. The overall design of the neural circuits establishes conditions for fast processing of information. This is the consequence of the neurons responding with graded changes of the membrane potential and conducting potentials electrotonically. Such neurons are therefore particularly suitable for processing of information.

Animals↗
PubMed1989

[Examination of central vision. Visual acuity, contrast sensitivity, color vision].

In the neurophysiological organization of the visual system, form, color, movement, and depth perception are processed separately. Therefore, sensorial examination methods should test each of these basic functions separately, since they may be affected individually or to different extents by pathologic processes. For diagnosis the limit of visual acuity, i.e., the capacity for discrimination must be searched for, using Paliaga's "limits method". Visual acuity can also be tested in infants by the preferential looking method. Contrast sensitivity is tested using sinusoidal grid patterns of varying contrast and spatial frequency. In routine practice, however, this is usually achieved more easily with acuity cards on which contrast is reduced in several stages. The "two-equation method" is a colorimetric test combining two metameric matches, red + green = yellow, and blue + green = cyan, for testing color vision. The test requires an anomaloscope or anomalometer with four light channels. With this method it is possible to test the "red", "green", and "blue" cones and the "red-green" and "blue-yellow" opponents. The test provides a qualitative and quantitative evaluation of color vision disorders. If no colorimeter is available, classic printed test can be used. However, they might never achieve the same qualitative and quantitative precision.

Color Perception Tests↗
PubMed1993

Three-dimensional Hi-vision system for microneurosurgical documentation based on wide-vision telepresence system using one camera and one monitor.

A three-dimensional (3-D) high-definition television (Hi-Vision) system suitable for attachment to a stereoscopic operating microscope allowing 3-D medical documentation using one Hi-Vision camera and one Hi-Vision monitor is described. The system provides 3-D high-definition microneurosurgical recorded images suitable for viewing on a screen or monitor, or for printing.

Documentation↗
PubMedDate not supplied

Hyper-vision in a patient with central and paracentral vision loss reflects cortical reorganization.

SM, a 21-year-old female, presents an extensive central scotoma (30 deg) with dense absolute scotoma (visual acuity = 10/100) in the macular area (10 deg) due to Stargardt's disease. We provide behavioral evidence of cortical plastic reorganization since the patient could perform several visual tasks with her poor-vision eyes better than controls, although high spatial frequency sensitivity and visual acuity are severely impaired. Between 2.5-deg and 12-deg eccentricities, SM presented (1) normal acuity for crowded letters, provided stimulus size is above acuity thresholds for single letters; (2) a two-fold sensitivity increase (d-prime) with respect to controls in a simple search task; and (3) largely above-threshold performance in a lexical decision task carried out randomly by controls. SM's hyper-vision may reflect a long-term sensory gain specific for unimpaired low spatial-frequency mechanisms, which may result from modifications in response properties due to practice-dependent changes in excitatory/inhibitory intracortical connections.

Acoustic Maculae↗
PubMed2006

Field evaluation of the Welch Allyn SureSight vision screener: incorporating the vision in preschoolers study recommendations.

INTRODUCTION: The prospective Vision in Preschoolers (VIP) study evaluated 11 methods of screening and proposed referral criteria for the Welch Allyn SureSight(trade mark) Vision Screener with 90% and 94% specificity. The SureSight had a higher sensitivity than most other screening techniques when these criteria were applied. We evaluated the usefulness of these criteria in a field study of healthy preschool children. METHODS: The SureSight software was altered to recommend referral using the VIP referral criteria with 90% specificity. Lions Club volunteers screened preschool children throughout Tennessee. Referred children underwent comprehensive eye examinations with cycloplegic refraction. Examination failure criteria were based upon published standards. Reanalysis using the 94% specificity criteria was then performed. Outcomes included referral rate and positive predictive value. RESULTS: The SureSight was used to screen 4,733 children, and screening was successful in 99.7% of children. The referral rate using the 90% specificity criteria was 12.2%. Most children (73%) were referred for suspected astigmatism. The positive predictive value was 30%. Using the 94% specificity criteria from the VIP study decreased the referral rate to 7.9% and substantially decreased over referral for suspected astigmatism; however, several anisometropes went undetected. Higher specificity was achieved by raising astigmatism referral criteria to 2.2 diopters while leaving the anisometropia criteria unchanged. CONCLUSIONS: The SureSight can be used successfully for preschool screening in the field provided that criteria with high specificity are incorporated into the instrument's software program. Higher rates of positive predictive value can be achieved without jeopardizing sensitivity by raising astigmatism referral criteria to 2.2 diopters.

Amblyopia↗
PubMed2000

Disturbances of spatial vision and object vision correlate differently with regional cerebral glucose metabolism in Alzheimer's disease.

There is evidence of two neuronal systems for visual cognition which are referred to as spatial vision and object vision. We subjected 49 patients with mild-to-moderate probable Alzheimer's disease (AD) to tasks associated with these two types of visual cognition. Visual counting was employed as a task to assess visuospatial recognition. Identification of overlapping figures and discrimination of visual forms were used as visuoperceptual tasks that require an ability to recognize objects. Regional cerebral glucose metabolism (rCMRglc) of the subjects was also determined by positron emission tomography. Multivariate statistics controlling for the confounding factors assessed the correlation between the task performances and the rCMRglc. The visual counting score significantly correlated with the metabolic rate of the bilateral inferior parietal lobules. On the other hand, the scores of the visuoperceptual tasks significantly correlated with the metabolic rate of the right middle temporal gyrus and the right inferior parietal lobule. The present study showed that visuospatial disturbance was related to bilateral parietal metabolism, and that visuoperceptual disturbance was related to right temporo-parietal metabolism in patients with mild-to-moderate AD.

Aged↗
PubMed2001

Gecko vision--retinal organization, foveae and implications for binocular vision.

Geckos comprise both nocturnal and diurnal genera, and between these categories there are several transitions. As their retinae have definitely to be classified as pure cone retinae, they provide an especially attractive model for comparison of organization and regional specializations adapted to very different photic environments. While the visual cells themselves show clear adaptations to nocturnal or diurnal lifestyles, the overall retinal organization is more related to that of diurnal vertebrates. Nocturnal geckos have lost any foveae of their diurnal ancestors, but they have retained a low convergence ratio and a high visual cell density. To enhance visual sensitivity, they exploit binocular - but not necessarily stereoscopic - vision. Diurnal species have retained binocular vision. Most diurnal species have developed new foveae, which are consequently located not in the central but in the temporal region of the retina.

Animals↗
PubMed2002

[Ginkgo extract in impaired vision--treatment with special extract EGb 761 of impaired vision due to dry senile macular degeneration].

The therapeutic efficacy of Ginkgo special extract Egb 761 was investigated in a controlled, double-blind trial involving 99 patients with impaired vision due to senile, dry macular degeneration. The primary objective target variable was the change in the corrected visual acuity of the more severely impaired eye at baseline, during a six months treatment period with either 240 mg/die (group I = 50 patients) or 60 mg/die (group II = 49 patients) Egb 761. Marked improvement of the study participants' vision was observed in both treatment groups already after four weeks, with more pronounced improvements in group I (acuity increases by 0.13 in group I vs. 0.10 in group II after 24 weeks). The fraction of patients with improvement of visual acuity > or = 0.2 was nearly twice as large in the group treated with 240 mg/die Egb 761 as in patients receiving the lower dosage (p = 0.08). Subjective health impairments, if present, could be improved during treatment as well. The investigator rated a favorable tolerability for both dosages of Egb 761. In conclusion, the results demonstrate the therapeutic efficacy of Egb 761 in patients with senile, dry macular degeneration, with obvious benefits in every-day life.

Aged↗
PubMed1994

Outcome of low vision aid provision: the effectiveness of a low vision clinic.

PURPOSE: Although there is an increasing need for primary low vision (LV) care, few studies have considered the success rates of optometric LV rehabilitation. We considered the objective success and perceived benefit obtained by 57 elderly LV patients. METHOD: Tests of reading speed and questionnaires were administered in the patient's home after initial and follow-up visits to a LV clinic. Additional information was taken from the patient's clinic record. RESULTS: Benefits from attending the clinic were reported by 89.5% of patients and 81% of patients were regularly using low vision aids (LVA's). There was a discrepancy between ability to read 1M print in the clinic (75% of patients) and the reported ability to read regular-sized print at home (35%). Perceived benefit from visiting the clinic was strongly associated with the ability to perform daily living tasks and to read 2M print. There was some association between perceived benefit and frequency of using the LVA's, but not with duration of use. CONCLUSION: The results encourage a change in emphasis during LV assessments from sustained reading to the ability to perform daily living activities.

Activities of Daily Living↗
PubMed1996

Clinical vision characteristics of the congenital achromatopsias. II. Color vision.

Twelve X-linked (XL) achromats and 43 autosomal recessive (AR) achromats were tested using the Farnsworth D-15, Nagel anomaloscope, Sloan achromatopsia test, and Berson test using standard procedures. All of the tests identify achromatopsia, but very few differentially diagnose the various types. AR achromats were subclassified as complete (rods only) or incomplete (residual cone function present) by additional psychophysical testing. Complete and incomplete ARs do not perform differently on any clinical color vision measure, indicating that (1) rods predominantly mediate vision in both groups and (2) these tests are not useful for distinguishing between the groups. Both groups show considerable interindividual variation on all measures. Only one of the measures, the Berson test, designed to distinguish XLs from ARs, does so reliably. XLs and ARs do not differ significantly on the Nagel anomaloscope or most of the Sloan plates. The confusion angles of the D-15 do differ for the two groups, but the variability in each group makes the measure unreliable for classifying individuals. The Berson test is recommended to distinguish the XL from AR achromats.

Adolescent↗
PubMedDate not supplied

Associations between specific measures of vision and vision-related quality of life in patients with bothnia dystrophy, a defined type of retinitis pigmentosa.

PURPOSE: To assess the relationship between objective tests of visual function and vision-related quality of life in patients with Bothnia dystrophy (BD), a retinal dystrophy of retinitis pigmentosa type with progressive maculopathy. METHODS: Forty-nine patients were tested. Weighted distance logMAR visual acuity (WVA), weighted logMAR low contrast VA (WCS), and binocular visual field (VF) areas were calculated. Vision-related quality of life (VRQL) was assessed using the 25-item National Eye Institute-Visual Function Questionnaire (NEI-VFQ-25). Correlation statistics were used and adjusted analyses of the relationship between the composite score and the objective visual function tests were performed with multiple linear regression. RESULTS: VRQL was significantly correlated with age, WVA, WCS, and binocular VF areas (P < 0.001). Calculation of partial correlation coefficients showed age to be significantly correlated only with VF (V-4-e) area (P < 0.0001). Multiple linear regression analyses revealed age and WVA to be significantly associated with the NEI-VFQ-25 composite score (P < 0.02 and P = 0.001, respectively). WVA alone was the strongest predictor of self-reported experience of total visual function in BD patients (r 2= 0.69). CONCLUSIONS: A strong relationship between objective tests of visual function and patient perceived VRQL as assessed by a questionnaire was found. WVA was the strongest predictor and together with age explained almost 70% of the variability of the composite score of the questionnaire.

Adolescent↗
PubMed2005

The Medawar Lecture 2001 knowledge for vision: vision for knowledge.

An evolutionary development of perception is suggested-from passive reception to active perception to explicit conception-earlier stages being largely retained and incorporated in later species. A key is innate and then individually learned knowledge, giving meaning to sensory signals. Inappropriate or misapplied knowledge produces rich cognitive phenomena of illusions, revealing normally hidden processes of vision, tentatively classified here in a 'periodic table'. Phenomena of physiology are distinguished from phenomena of general rules and specific object knowledge. It is concluded that vision uses implicit knowledge, and provides knowledge for intelligent behaviour and for explicit conceptual understanding including science.

Biological Evolution↗
PubMedDate not supplied

The disturbances of object vision and spatial vision in Alzheimer's disease.

Thirty-one patients with mild-to-moderate Alzheimer's disease (AD) underwent a test battery of complex visual tasks. We assessed the scores using a principal-factor analysis to elucidate the underlying deficits. There were three independent factors: The first factor included the tasks of identifying and comparing forms of visual stimuli. The second factor consisted of digit span and digit symbol tasks, and the third factor consisted of a specified visual counting task. We considered these three factors as representing the dysfunctions of object recognition, general attention and spatial recognition, respectively. These results underline the disturbances of the two visual systems, object vision and spatial vision, in early-AD patients.

Aged↗
PubMedDate not supplied

Low vision rehabilitation: vision requirements for driving.

Driving requires several different sets of abilities, the interaction of which is complex. The combination of these factors, rather than any single factor alone, may make it inadvisable to issue a driver's license. Although vision is the predominant source of information for the driver, visual abilities are only one of the factors to be considered when judging the overall driving ability of an applicant. The final determination can only be made through on-the-road evaluation and cannot be based on the evaluation of vision alone. Individual evaluations should include a review of the past driving record and of nonvisual driving-related abilities, as well as observation of on-the-road performance by a qualified driving instructor or driving evaluator.

Adaptation, Psychological↗
PubMed1982

Effects of an anticholinergic drug, benactyzine hyrochloride, on vision and vision performance.

Benactyzine is an anticholinergic agent which has been used in past years in psychiatry, but is little used today. It has central and peripheral anticholinergic effects, and when administered intramuscularly, it has a rapid onset of action. This may make it useful as an antidote for organophosphate poisoning, in spite of side-effects such as deficits of short term memory, concentration, and attention. As an anticholinergic drug it could also be expected to produce vision changes by its action on the intraocular musculature controlling the pupil and lens accommodation. We tested the drug on six volunteer subjects to establish the visual side-effects of intramuscular administration. We found that it reduced static and dynamic visual acuity, increased pupil size, reduced amplitude of accommodation and contrast sensitivity, while having little or no effect on glare recovery, color vision, intraocular pressure, stereoacuity, oculomotor tracking, and distance heterophoria. Benactyzine produced reductions in visual performance for up to 3 h and had the greatest effects on functions which have significant cognitive components. The present results suggest that the drug is unsuitable for treatment for oganophosphate poisoning when continuous performance is required, although a definitive test of ths suggestion would require that performance should be tested when benactyzine and the organophosphate of interest were combined.

Adult↗
PubMed1996

[The effect of rapid alternating eye covering on formation of binocular vision in convergent squint treated with a localization method. I. Binocular vision examined in free space].

The authors have examined 35 children aged between 6 and 13 years. They were children with convergent fixed squint (angle: from +4 degrees to +26 degrees) with convergent fixation. The patients were treated in accordance with the localizing method -stage II/III. Visual acuity of the master eye was equal 1.0, and of the squinting eye-from 0.3 to 0.8 after correction. Children were practising 2 x 7-10 minutes for 5 days on an apparatus modelled on the Starkiewicz alteroobturator, looking straight forward and with eyes alternatively covered. They had the binocular vision at long and short distance checked with the use of a test with coloured filters (TF), classical Bagolini test (Bki). In all patients the subjective test was positive. Among 35 examined cases the tests for binocular vision did not change in 17. In 16 patients the image seen with the squinting eye came close to the one seen with the master eye by the average of 2.6 degrees at long distance and 4.3 degrees at short distance. Improvement took place after first exercise (8 children) or after all five exercises (8 children).

Adolescent↗