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At least 1,369 records · Page 76Linked to original sources
PubMed2003

Restoration of binocular single vision after long-term fusion disruption.

BACKGROUND: One of the most difficult situations faced by orthoptists and pediatric ophthalmologists is attempting to restore binocular single vision to a patient who has experienced a long-term disruption of fusion. Initial poor results with standard treatment modalities, including prisms and strabismus surgery, may lead to a diagnosis of intractable diplopia. METHODS: We examined, treated, and followed up 5 patients with strabismus after an extended period of monocular vision loss. All patients were diplopic after the restoration of visual acuity in the affected eye. RESULTS: All 5 patients experienced a period of uncomfortable intermittent fusion with the initial prismatic correction. After many months of close follow-up with prism and orthoptic therapy, comfortable fusion was restored for 3 patients. Convergence amplitudes improved with the orthoptic exercises, and we were eventually able to eliminate most or all of the horizontal prism in the 3 patients who regained binocular single vision; however vertical fusion was less responsive and most often required permanent prismatic correction. CONCLUSIONS: A combination of prism therapy, orthoptic treatment, and follow-up during a period of many months to years can restore fusion in some patients who have experienced a long-term disruption of fusion.

Adolescent↗
PubMed2001

The task of explaining sight: Helmholtz's writings on vision as a test case for models of science popularization.

Studies of Helmholtz's popular lectures on science have concentrated on reconstructing his vision of the scientific enterprise, of its nature, its benefits, and its "civilizing power." This paper offers a different perspective by focusing on Helmholtz's attempts to expose his own scientific work to a wider public. Drawing on recent discussions about how to study science popularization, it analyzes how he made his work on sensory physiology accessible to various audiences. It is argued that the exposition of the theory of vision comprises a complex, multilayered transformation of epistemic messages, which includes the recasting of arguments, recontextualizations, shifting emphasis, and significant changes in style. The popular writings on vision were directed to several different audiences, and, as such, manifest a delicate balance between conflicting agendas. An analysis of the texts indicates that neither the traditional two-step model of science popularization nor the more recent attempt to regard popularization as an "expository continuum" provides appropriate historiographical frameworks to study the popularization of scientific knowledge.

Germany↗
PubMedDate not supplied

Evaluation of an updated HRR color vision test.

The HRR pseudoisochromatic plate (pip) test was originally designed as a screening and diagnostic test for color vision deficiencies. The original HRR test is now long out of print. We evaluate here the new 4th edition of the HRR test, produced in 2002 by Richmond Products. The 2002 edition was compared to the original 1955 edition for a group of subjects with normal color vision and a group who had been previously diagnosed as having color vision deficiencies. The color deficient subjects spanned the range of severity among people with red-green deficiencies except for one individual who had a mild congenital tritan deficiency. The new test compared favorably with the original and in at least two areas, outperformed it. Among subjects with deutan defects the classification of severity correlated better with the anomaloscope results than the original; all the subjects who were classified as dichromats on the anomaloscope were rated as "severe" on the new HRR, while those diagnosed as anomalous trichromats were rated as mild or medium on the new test. Among those with moderate and severe defects the new test was highly accurate in correctly categorizing subjects as protan or deutan. In addition, a mild tritan subject made a tritan error on the new test whereas he was misdiagnosed as normal on the original.

Adult↗
PubMed2002

Resource allocation to prevent trachomatous low vision among older individuals in rural areas of less developed countries.

Trachomatous low vision can be prevented by treating or preventing infection or through surgery to treat trichiasis. Resource allocation to prevent trachomatous low vision should be directed to those interventions that are the most cost-effective. In order to assess which of many potential interventions are the more cost-effective, data on the epidemiology of the disease, the effectiveness of community- and facility-based interventions, and the cost of the interventions are required. This paper provides a stylized model of the path from risk of infection through disease to trachomatous low vision or blindness that delineates the points at which interventions may occur and for which data are required. The literature reveals a considerable amount of data regarding the epidemiology of the trachoma and its sequelae but little on the effectiveness of community-based interventions and only one study that measured costs directly. More data are needed to assist policy makers and international program partners who seek to make efficient resource allocation decisions in an effort to eliminate trachoma as a cause of incident blindness in the developing countries in which trachomatous blindness remains prevalent.

Anti-Bacterial Agents↗
PubMed1996

Colour vision in diabetic and normal pseudophakes is worse than expected.

Automated colour vision testing in pseudophakes showed unexpected results. Chromatic discrimination sensitivity was measured in 22 diabetic pseudophakes with no retinopathy, 23 diabetic pseudophakes with background retinopathy and 34 non-diabetic pseudophakes. These results were compared with those in age-matched normal and diabetic phakic subjects, all of whom had good vision. The diabetics were also matched for retinopathy grading and duration of diabetes. In all three groups, red-green discrimination sensitivity was worse in the pseudophakes when compared with the corresponding phakic subjects (normals, p < 0.001; no retinopathy, p = 0.467; background retinopathy, p = 0.057). However, tritan vision was marginally worse in the normal pseudophake group but was better in the two diabetic pseudophake groups, when compared with phakic controls. This may be due to a reduction in tritan sensitivity in age-matched phakic controls from the effects of increased lens yellowing with age.

Aged↗
PubMed2003

Vision and eating behavior in obese subjects.

OBJECTIVE: Vision is one of a number of factors influencing the amount of food consumed during a meal. The purpose of this study was to investigate the impact of vision on the microstructure of the eating behavior of obese subjects. RESEARCH METHODS AND PROCEDURES: Eighteen obese subjects with a body mass index (mean +/- SD) of 39.1 +/- 6.3 kg/m(2) twice consumed a standardized test meal in excess, once with and once without a blindfold. The microstructure of the eating behavior was registered by VIKTOR, a computerized eating monitor. Subjective motivation to eat (i.e., desire to eat, hunger, satiety, and prospective consumption) was rated by visual analogue scales (VASs) before, immediately after, and then hourly up to 3 hours after the test meals. RESULTS: The obese subjects ate 24% less food when blindfolded (359 +/- 194 g vs. 472 +/- 179 g; p < 0.01). Despite a smaller amount of food consumed when blindfolded, there were no significant differences with or without the blindfold for any of the VASs measuring subjective motivation to eat after test meals. DISCUSSION: The importance of vision in regulating our eating behavior was demonstrated in this study. The obese subjects ate 24% less food blindfolded without feeling less full. Eating blindfolded could be tested as a didactic tool to make obese subjects aware of what factors affect the termination of eating.

Adult↗
PubMed2006

Restoration of vision in RPE65-deficient Briard dogs using an AAV serotype 4 vector that specifically targets the retinal pigmented epithelium.

Previous studies have tested gene replacement therapy in RPE65-deficient dogs using recombinant adeno-associated virus 2/2 (rAAV2/2), -2/1 or -2/5 mediated delivery of the RPE65 gene. They all documented restoration of dark- and light-adapted electroretinography responses and improved psychophysical outcomes. Use of a specific RPE65 promoter and a rAAV vector that targets transgene expression specifically to the RPE may, however, provide a safer setting for the long-term therapeutic expression of RPE65. Subretinal injection of rAAV2 pseudotyped with serotype 4 (rAAV2/4) specifically targets the RPE. The purpose of our study was to evaluate a rAAV2/4 vector carrying a human RPE65cDNA driven by a human RPE65 promoter, for the ability to restore vision in RPE65-/- purebred Briard dogs and to assess the safety of gene transfer with respect to retinal morphology and function. rAAV2/4 and rAAV2/2 vectors containing similar human RPE65 promoter and cDNA cassettes were generated and administered subretinally in eight affected dogs, ages 8-30 months (n = 6 with rAAV2/4, n = 2 with rAAV2/2). Although fluorescein angiography and optical coherence tomography examinations displayed retinal abnormalities in treated retinas, electrophysiological analysis demonstrated that restoration of rod and cone photoreceptor function started as soon as 15 days post-injection, reaching maximal function at 3 months post-injection, and remaining stable thereafter in all animals treated at 8-11 months of age. As assessed by the ability of these animals to avoid obstacles in both dim and normal light, functional vision was restored in the treated eye, whereas the untreated contralateral eye served as an internal control. The dog treated at a later age (30 months) did not recover retinal function or vision, suggesting that there might be a therapeutic window for the successful treatment of RPE65-/- dogs by gene replacement therapy.

Animals↗
PubMed2000

Aetiology of childhood vision impairment, metropolitan Atlanta, 1991-93.

Data from the population-based Metropolitan Atlanta Developmental Disabilities Surveillance Program (MADDSP) were used to describe the underlying causes of vision impairment (VI; corrected visual acuity in the better eye of 20/70 or worse) in young children (n = 228) in metropolitan Atlanta in 1991-93. Children with VI were identified through record review at multiple educational and medical sources. Children were categorised as having isolated VI or multiple disabilities (i.e. VI plus one or more of four additional developmental disabilities) and as having low vision (visual acuity 20/70-20/400) or blindness (visual acuity worse than 20/400). Medical conditions abstracted from MADDSP sources were reviewed to determine the probable aetiology of a child's VI. Aetiologies were assigned to one of three developmental time periods: prenatal, perinatal, or postnatal. Prenatal aetiologies were identified in 43% of the children; 38% of the prenatal aetiologies were genetic. Perinatal aetiologies were found in 27% of the children. Postnatal aetiologies were rare. Prenatal aetiologies were more common in children with isolated VI; perinatal and postnatal aetiologies were more common in children with multiple disabilities. Children with prenatal aetiologies tended to have less severe vision loss than did children with perinatal or postnatal aetiologies. The distribution varied by birthweight, but did not differ significantly by sex or race.

Abnormalities, Multiple↗
PubMed2000

Scale-invariant superiority of foveal vision in perceptual categorization.

The recognition of objects is exceedingly difficult in indirect view. This complication cannot be explained in terms of retino-cortical magnification, as size scaling fails to establish position invariance both for character recognition [Strasburger, H. & Rentschler, I. (1996) Eur. J. Neurosci., 8 1787-1791] and pattern classification [Jüttner, M. & Rentschler, I. (1996) Vision Res., 36, 1007-1021]. Thus we compared, for two tasks of discrimination learning and category learning with respect to a common set of grey-level patterns, how humans perform in foveal and extrafoveal vision. Observers learnt to discriminate (size-scaled) images equally well in foveal and extrafoveal view, whereas they displayed profound deficiencies in extrafoveal category learning for the same patterns. From the behavioural learning data, internal representations of the learning signals were reconstructed by means of computer simulations. For foveal view, these representations were found to be veridical to their physical counterparts for both learning tasks. For extrafoveal view, they were severely distorted for category learning but not for discrimination learning. A variance reduction of the pattern classes by a factor of 100 reduced the dissociation between extrafoveal categorization and discrimination but did not remove it. These observations suggest a scale-invariant superiority of foveal vision for learning object categories. This implies a high degree of space variance of visual cognition which is vastly underestimated by classical measures of visual performance, e.g. acuity, visual field and contrast sensitivity.

Adult↗
PubMed1999

Evaluating the outcomes of low vision rehabilitation.

The requirement for those providing healthcare to measure outcomes raises the fundamental question of how these should be measured. Both the scale of the low vision population and the different models of care proposed make it a pressing need to determine outcomes using valid and reliable measures. In this study we describe the development and piloting of a questionnaire designed to meet this requirement. The questionnaire was piloted on 56 subjects with age-related macular degeneration (ARMD). Test-retest reliability of the questionnaire was estimated using a further sample of 28 subjects with ARMD. Pilot testing confirmed the feasibility of administering the questionnaire to an elderly population with ARMD. A total of 87% of the sample reported using an LVA (65% on a daily basis), predominantly for a reading task. The number of tasks an LVA was used for, its frequency of use, length of continuous use and ease of use are significantly associated with the rating of an LVA as important/less important (P < 0.0001), but the acuity achieved with the device is not significantly associated with rated importance (P = 0.11), reinforcing doubt about the validity of visual function outcomes. The limitations of this pilot study and earlier case series in describing the outcomes of low vision care are discussed and a randomised controlled trial using a broad range of outcomes is proposed in order to fully describe the effectiveness of low vision rehabilitation and inform the debate about models of care.

Aged↗
PubMed2003

A review of current knowledge on Electronic Vision Enhancement Systems for the visually impaired.

Magnification can be provided to assist those with visual impairment to make the best use of remaining vision. Electronic transverse magnification of an object was first conceived for use in low vision in the late 1950s, but has developed slowly and is not extensively prescribed because of its relatively high cost and lack of portability. Electronic devices providing transverse magnification have been termed closed-circuit television (CCTVs) because of the direct cable link between the camera imaging system and monitor viewing system, but this description generally refers to surveillance devices and does not indicate the provision of features such as magnification and contrast enhancement. Therefore, the term Electronic Vision Enhancement Systems (EVES) is proposed to better distinguish and describe such devices. This paper reviews current knowledge on EVES for the visually impaired in terms of: classification; hardware and software (development of technology, magnification and field-of-view, contrast and image enhancement); user aspects (users and usage, reading speed and duration, and training); and potential future development of EVES.

Persons with Disabilities↗
PubMed2001

Comparative impact of hearing and vision impairment on subsequent functioning.

OBJECTIVES: The purpose of this study was to compare independent impacts of two levels of self-reported hearing and vision impairment on subsequent disability, physical functioning, mental health, and social functioning. DESIGN: A 1-year prospective cohort study. SETTING: San Francisco Bay Area, California. PARTICIPANTS: Two thousand four hundred forty-two community-dwelling men and women age 50 to 102 from the Alameda County Study (California). MEASUREMENTS: Hearing and vision impairment were assessed in 1994. Outcomes, measured in 1995, included physical disability (activities of daily living, instrumental activities of daily living, physical performance, mobility, and lack of participation in activities), mental health (self-assessed, major depressive episode), and social functioning (feeling left out, feeling lonely, hard to feel close to others, inability to pay attention). All 1995 outcomes were adjusted for baseline 1994 values. RESULTS: Both impairments had strong independent impacts on subsequent functioning. Vision impairment exerted a more wide-ranging impact on functional status, ranging from physical disability to social functioning. However, the results also highlighted the importance of hearing impairment, even when mild. CONCLUSIONS: These impairments can be partially ameliorated through prevention, assessment, and treatment strategies. Greater attention to sensory impairments by clinicians, patients, public health advocates, and researchers is needed to enhance functioning in older adults.

Activities of Daily Living↗
PubMed1999

[Impairment of mesopic vision following photorefractive keratectomy of myopia].

PURPOSE: Halos, glare disability and problems during night driving are significant side effects of photorefractive keratectomy, caused by increasing optical aberrations under reduced conditions of luminiscence. In a previously performed retrospective study an impairment of mesopic vision in most of the investigated eyes was found. To prove these results, a prospective study was conducted. METHODS AND PATIENTS: In a prospective, consecutive study mesopic function was investigated in 41 myopic patients, who were interested in PRK. 26 patients underwent surgery (Summit ExciMed UV200LA, optical zone 5 mm), which was performed in 30 eyes. Mesopic function (contrast vision, glare sensitivity) was measured by using the Mesoptometer II test in all 30 eyes preoperatively and 6 to 9 months postoperatively. Additionally, 21 eyes were examined after 12 to 15 months of follow up. RESULTS: There was a statistically significant reduction of contrast vision and increase of glare sensitivity after 6 to 9 and 12 to 15 months. The Mesoptometer II contrast level of 1:5 (with and without glare) can be used as a critical parameter for the decision, whether mesopic function is markedly reduced or not. Before surgery, contrast level of 1:5 without glare was not recognized in 30%, with glare in 40%. After 6 to 9 months, this contrast level was not recognized in 73% of the 30 eyes without glare, with glare in 80%. Out of these 30 eyes, 21 eyes were followed over 12 to 15 months. Whereas 38% of these eyes (with glare 48%) did not recognized the critical contrast level before surgery, this rate increased to 67% (with glare 81%) 12 to 15 months after surgery. CONCLUSIONS: Impairment of mesopic function has to be considered as a possible side effect of PRK (optical zone 5 mm). Although further investigations are needed, the indication for PRK in special professions (pilots, professional drivers) should be very critical discussed.

Adult↗
PubMed1985

[Free-vision refraction determination].

A refraction process is called free vision if the patient's visual field is not restricted at all, or at most by the same amount as when using normal spectacles. Free-vision refraction measurement is performed with the help of virtual lenses, which are real optical images of material lenses. In certain circumstances virtual lenses act as normal optical lenses. The advantage of free-vision refraction measurement lies above all in the fact that remote refraction measurement can also be performed from a distance of less than five meters. Moreover, it permits over-refraction, which enables the duration of the measuring procedure to be shortened considerably.

Eyeglasses↗
PubMed1983

[Comparative vision tests using objective and subjective testing methods in amblyopia].

In 20 amblyopic eyes without reading ability a comparison was made between the visual acuity found by subjective tests and with the Catford Visual Acuity Apparatus, Kotowski's Visumeter and Lotmar's Moiré Visometer. These instruments all work on the basis of different physiological functions. The Kotowski Visumeter seems to be the best instrument for an expertise on the visual acuity of an amblyopic eye. With the test pattern moving from nasal to temporal the results corresponded to the patients reading ability in 16 cases (80%); 4 patients had poorer vision. With the checkerboard pattern moving temporonasally the average results were better than the patients' actual vision. The Catford apparatus gave results corresponding to the subjective reading test only in 12 cases (60%). Apparatus with interferometric scales are not suitable for objective visual testing of amblyopic subjects; the results they give are always much better than the actual vision of the patient.

Adolescent↗
PubMed1981

[Visually evoked cortical potentials (VECP) in patients with doubtful impairment of central vision (author's transl)].

Visual evoked cortical potential (VECP) to non-structured, brightness (luminance) stimuli do not provide an appropriate means for assessing the degree of impaired central vision. In comparison, visually evoked cortical potentials to structured (patterned) stimuli presented by pattern reversal of equal mean luminance are highly susceptible to visual changes caused by reduced central vision. Employing different check sizes, the use of checkerboard pattern reversal VECPs permits, independently of the patient, to assess the impairment of central vision.

Accommodation, Ocular↗
PubMed1981

[Trial and evaluation of a new test to examine color vision (author's transl)].

With the new Rodenstock color test disk it is possible to distinguish with 99% accuracy between deuteranopia and protanopia. In addition, the diagnosis is quantitatively correct (anomaly or anopia) in 92% of deuteranopia and 98% of protanopia cases. A special scheme for evaluation is presented. Special emphasis was placed on describing exactly the function of this new method of examining inherited color vision deficiencies. Only persons who were already known to have defective color vision were tested. Therefore, no conclusions can be drawn regarding the efficiency of detection of color vision deficiencies.

Color Perception Tests↗
PubMed1985

Tactual perception of embossed Morse code and braille: the alliance of vision and touch.

In three experiments observers made visual matches to tangible embossed patterns. Stained glass was used to blur vision and thus allow the effect of visual guidance of tactual exploration on the accuracy of symbol recognition to be evaluated. Stained glass rendered the embossed code invisible, but allowed sight of the hand. In the first experiment subjects identified patterns made up of dots and dashes drawn from Morse code; in the second and third experiments they studied braille. The results show that subjects are more accurate in 'reading' tangible codes when provided with visual guidance. Performance was higher for braille than for Morse code. Vision aided touch through the provision of a frame of reference and through sight of scanning movements. Naive sighted observers were able to identify invisible braille dots by watching other individuals touch the symbols, suggesting the importance of vision of kinesthetic patterns.

Female↗