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At least 1,621 records · Page 90Linked to original sources

PubMed2002

[The vision of welders in France].

PURPOSE: A study was conducted to measure the impact of welding on the vision of welders. METHODOLOGY: This study was conducted in France by the occupational medicine staff of large companies on 1.131 people, namely 850 welders and 281 control subjects. This investigation included two examinations at the beginning and the end of a year. The investigative procedure examined the different welding processes, the percentage of working time spent on welding activity, the length of exposure in years, as well as the medical variables: the optical correction type and history of ocular traumatology. The Visiotest or the Ergovision were used for the visual examination, equipment in common use by occupational medicine departments. RESULTS: The welders were comparatively young (59.53% of them were less than 45 years old). Moreover, for 69.75% of the welders, more than 75% of their activity was devoted to welding. All currently used welding processes were represented, including the modern PLASMA-TIG welding process. No excessive blood alcohol levels were observed in all subjects, but welders did smoke slightly more than the control subjects (40% vs 33%). Self-medication was rather less frequent among the welders, except as regards the use of eye drops, where the proportions were clearly inverted. Optical correction for hyperopia was similar between the two groups; however, as regards myopia, the welders were corrected less often. Lastly, contact lens use was exceptional among the welders. Nearsightedness varied logically with age, but also, inexplicably, with the welding processes. Vision recovery time after exposure to glare was much longer among the welders, except for the PLASMA-TIG processes. No difference was observed in the other parameters of the study. No change in the visual functions studied was noted between the two examinations. DISCUSSION: The examination techniques used showed no impairment of the studied visual functions, probably because companies use protective and preventive eye care methods. Moreover this study is the first to examine the type of welding used by workers and particularly the modern PLASMA-TIG process. The vision recovery time after exposure to glare seems better for the PLASMA-TIG process may be the result of the lower luminous intensity of this process. CONCLUSION: This study was conducted for preventive purposes to contribute to better monitoring of safety and comfort for welding workers and has shown no alteration of the visual function among welders in general.

Adaptation, Ocular↗

PubMed2004

Insertion of green fluorescent protein into nonstructural protein 5A allows direct visualization of functional hepatitis C virus replication complexes.

Hepatitis C virus (HCV) replicates its genome in a membrane-associated replication complex, composed of viral proteins, replicating RNA and altered cellular membranes. We describe here HCV replicons that allow the direct visualization of functional HCV replication complexes. Viable replicons selected from a library of Tn7-mediated random insertions in the coding sequence of nonstructural protein 5A (NS5A) allowed the identification of two sites near the NS5A C terminus that tolerated insertion of heterologous sequences. Replicons encoding green fluorescent protein (GFP) at these locations were only moderately impaired for HCV RNA replication. Expression of the NS5A-GFP fusion protein could be demonstrated by immunoblot, indicating that the GFP was retained during RNA replication and did not interfere with HCV polyprotein processing. More importantly, expression levels were robust enough to allow direct visualization of the fusion protein by fluorescence microscopy. NS5A-GFP appeared as brightly fluorescing dot-like structures in the cytoplasm. By confocal laser scanning microscopy, NS5A-GFP colocalized with other HCV nonstructural proteins and nascent viral RNA, indicating that the dot-like structures, identified as membranous webs by electron microscopy, represent functional HCV replication complexes. These findings reveal an unexpected flexibility of the C-terminal domain of NS5A and provide tools for studying the formation and turnover of HCV replication complexes in living cells.

Amino Acid Sequence↗

PubMed1992

[Vision disorders in children with acquired severe brain damage].

27 children with severe brain injuries were examined by an ophthalmologist and had several paediatric examinations during an eight or ten weeks' course of rehabilitation. With highly reduced levels of consciousness they had hardly any cortical visual function but frequently had brainstem controlled reactions of eyelids, pupils and eyeballs. The development of these reactions was followed up and correlated to the recovering visual functions. Some of the palpebral reflexes seemed to be of prognostic significance to the reappearance of cortical visual functions.

Adolescent↗

PubMed2003

Horizontal rectus tenotomy in patients with congenital nystagmus: results in 10 adults.

OBJECTIVE: We wished to determine the effectiveness of horizontal rectus tenotomy in changing the nystagmus of patients with congenital nystagmus and, secondarily, how their visual function changed. DESIGN: This was a prospective, noncomparative, interventional case series. PARTICIPANTS: Ten adult patients with varied associated sensory defects and oculographic subtypes of congenital nystagmus (including asymmetric periodic or aperiodic alternating nystagmus) and no nystagmus treatment options. METHODS: By using standard surgical techniques, simple tenotomy of all four horizontal recti with reattachment at the original insertion was accomplished. Search-coil eye movement recordings and clinical examinations were performed before and 1, 6, 24, and 52 weeks after surgery. MAIN OUTCOME MEASURES: The primary outcome measure was the expanded nystagmus acuity function, obtained in "masked" fashion directly from ocular motility recordings. Secondary outcomes included breadth of null zones, preoperative and postoperative masked measures of visual acuity (Early Treatment Diabetic Retinopathy Study [ETDRS] chart), and the National Eye Institute Visual Function Questionnaire (NEI-VFQ-25). RESULTS: At 1 year after tenotomy and under binocular conditions, 9 of 10 patients had persistent, significant postoperative increases in the expanded nystagmus acuity function of their fixing (preferred) eye; 1 remained high, and 1 was not tested under the same conditions. Average foveation times increased in all 9 fixing (preferred) eyes. Binocular visual acuity measured with the ETDRS chart increased in 5 patients and was unaffected in five, whereas the NEI-VFQ-25 showed an improvement in vision-specific mental health in 9 patients. There were no adverse events. Tenotomy also radically changed the periodicity of one patient's asymmetric periodic or aperiodic alternating nystagmus. CONCLUSIONS: In 9 of 10 adult patients with clinical and oculographic variations in their congenital nystagmus, tenotomy resulted in significant improvements in a nystagmus measure and subjective visual functions.

Adult↗

PubMed1997

Objective morphological assessment of macular hole surgery by scanning laser tomography.

AIM: To assess the morphological change in retinal topography using a scanning laser tomographer following macular hole surgery. To compare the results of scanning laser tomography with clinical evaluation and visual function assessment. METHODS: The sample for this pilot study comprised four eyes exhibiting different stages of macular hole formation preoperatively. Subjects were assessed preoperatively and at 1 and 3 months postoperatively. Each assessment included visual acuity, letter contrast sensitivity, clinical examination (including automated static perimetry), and scanning laser tomography. The Heidelberg retina tomograph (HRT) was used to acquire digitised scanning laser tomography images of the macula (10 degrees and 20 degrees fields). Surgery essentially comprised vitrectomy, peeling of the posterior hyaloid face, if still attached, and intraocular gas tamponade. The magnitude and significance of topographic change were determined postoperatively using the HRT topographic difference facility. RESULTS: Topographic difference analysis of the right and left eyes of case 1 showed a significant reduction in the height of the retina postoperatively. Topographic difference analysis of case 2 showed no significant change in topography. Topographic difference analysis of case 3 showed a significant increase in the height of the retina postoperatively. Scanning laser tomography agreed with clinical assessment based upon fundus biomicroscopy in three of the four eyes studied; the postoperative closure of the stage 2 macular hole (as noted by clinical assessment) proved to be too small to reach statistical significance. Scanning laser tomography agreed with the assessment of visual function in two eyes; the agreement between scanning laser tomography and visual function depends, in part, on the stage of development of the macular hole. CONCLUSION: Scanning laser tomography provides an objective evaluation of the outcome of macular hole surgery. Studies employing larger sample sizes are required to fully determine the clinical worth of the technique.

Adult↗

PubMed2006

A new way for multidimensional medical data management: volume of interest (VOI)-based retrieval of medical images with visual and functional features.

The advances in digital medical imaging and storage in integrated databases are resulting in growing demands for efficient image retrieval and management. Content-based image retrieval (CBIR) refers to the retrieval of images from a database, using the visual features derived from the information in the image, and has become an attractive approach to managing large medical image archives. In conventional CBIR systems for medical images, images are often segmented into regions which are used to derive two-dimensional visual features for region-based queries. Although such approach has the advantage of including only relevant regions in the formulation of a query, medical images that are inherently multidimensional can potentially benefit from the multidimensional feature extraction which could open up new opportunities in visual feature extraction and retrieval. In this study, we present a volume of interest (VOI) based content-based retrieval of four-dimensional (three spatial and one temporal) dynamic PET images. By segmenting the images into VOIs consisting of functionally similar voxels (e.g., a tumor structure), multidimensional visual and functional features were extracted and used as region-based query features. A prototype VOI-based functional image retrieval system (VOI-FIRS) has been designed to demonstrate the proposed multidimensional feature extraction and retrieval. Experimental results show that the proposed system allows for the retrieval of related images that constitute similar visual and functional VOI features, and can find potential applications in medical data management, such as to aid in education, diagnosis, and statistical analysis.

Algorithms↗

PubMed2006

[The influence of IOL implantation on visual acuity, contrast sensitivity and colour vision 2 and 4 months after cataract surgery].

PURPOSE: To assess the change in visual acuity, contrast sensitivity and colour vision in relation to the time after cataract surgery and to the type of implanted IOL, and to compare visual functions by patients with one and two pseudophakic eyes. METHODS: 45 cataract patients were examined before and then 2 and 4 month after the cataract surgery. Visual acuity (VA) was tested on logMAR optotype chart with Landolt rings, contrast sensitivity (CS) was tested on the Pelli-Robson chart and the SWCT chart. For colour vision (CV) testing, the standard Farnsworth D-15 test and the desaturated Lanthony D-15 test were used. The patients were divided into two groups--a group with one pseudophakic eye and a group with two pseudophakic eyes, and also according to the type of IOL--PMMA or hydrophobic acrylate that had been implanted. Control group was composed of phakic subjects with no ocular pathology. RESULTS: After the cataract surgery, in both groups there was a significant improvement in monocular and binocular VA (p < 0.05), in monocular and binocular CS using both types of charts--Pelli-Robson (p < 0.05) and SWCT in all the spatial frequencies (p < 0.05). Also, a significant decrease in the number of minor errors in the standard Farnsworth D-15 test (p < 0.05) as well as a substantial decrease in the number of minor and major errors in the desaturated Lanthony D-15 test (p < 0.05) and an overall improvement of CV (p < 0.05) were detected. There was no difference between the results 2 and 4 month after the surgery, except for CS in 12 c/deg (p < 0.05). The patients with two pseudophakic eyes had postoperatively better binocular VA and CS in the spatial frequencies of 12 c/deg and 18 c/deg and attained postoperative values comparable to those of control subjects. No significant difference in VA, CS or CV was found between the PMMA and hydrophobic acrylate intraocular lenses. CONCLUSION: After the cataract surgery, the visual functions tested by means of psychophysical methods of VA, CS and CV significantly improve and are stable 2 month after the surgery. The second eye surgery improves binocular visual functions the level of which doesn't differ from that of normal phakic subjects. There was no influence of the type of IOL on final state of VA, CS or CV.

Aged↗

PubMed2006

Views of glaucoma patients on aspects of their treatment: an assessment of patient preference by conjoint analysis.

PURPOSE: To determine by conjoint analysis which factors in the management and treatment of glaucoma were of most importance to patients and to relate these factors to the patient's clinical glaucoma condition. METHODS: An interview-based study was performed. Demographic and visual function data are recorded. Participants completed the Visual Function Questionnaire-25 and ranked 10 hypothetical patient scenarios that contained different risks of moderate visual loss, postoperative complications, long-term blindness, use of topical medication, and glaucoma surgery. Conjoint analysis was performed to determine the relative importance of these factors for individuals and the group as a whole. RESULTS: Eighty-two patients were interviewed from two consultants' outpatient clinics. Forty-five were male and 37 female. Seventy-nine were white. The most important factors to patients with glaucoma were the risk of moderate visual impairment and the risk of blindness, with an importance of 38% and 27%, respectively. The use of topical medication had an importance of 11%. Proceeding to surgical intervention (trabeculectomy) had an importance of 15%, and the small risk of visual deterioration after surgery (trabeculectomy) had an importance of 9%. CONCLUSIONS: To patients, the most important factors regarding glaucoma and its treatment are the risks of moderate visual loss (the ability to continue to drive) and long-term blindness. The treatment methods used are of much less importance.

Adult↗

PubMed1979

Striate cortex and visual acuity functions in the cat.

Using a two-choice visual discrimination paradigm, thresholds for size (gratings), parallelness (parallel vs. non-parallel lines), contour alignment (vernier offset), and angularity (polygon figures) were behaviorally determined in cats before and after ablations of portions of the geniculo-cortical system. Animals with a total loss of cortical area 17, and with a loss, in some cases, of up to 90% of areas 18 (with and without infringement into area 19), showed about a 30% reduction in grating acuity, a three-fold increase in parallelness and angularity thresholds, and a total loss of contour alignment ability. Control animals with ablations sparing area 17 showed no significant threshold changes. All animals were able to learn classic form discriminations postoperatively, but those with area 17-18 lesions at a somewhat slower than normal rate. Control procedures indicated that all tested discrimination capabilities did not depend on luminance differences between targets, local flux cues within the targets, or on the animals' use of residual portions of area 17 representing the peripheral visual field. Since the cat has multiple thalamo-cortical visual pathways, the results of the present study are consistent with the hypothesis that pathways parallel to the geniculo-striate system are capable of processing spatial information of considerable detail. The results also suggest, however, that the geniculo-striate system is uniquely necessary for the processing of the finest attributes of spatial contours.

Animals↗

PubMed1987

The stimulus-response functions of visual systems.

Two commonly used forms of presenting photoreceptor functions are compared: the incident light function, which represents photoresponses as a function of the total light intensity (stimulus plus background), and the increment stimulus function, which represents photoresponses as a function of light increments. The changes in these two functions with increasing background light are analyzed. If the receptor adapts to light according to Weber's law, the changes are very similar. The increment stimulus functions are often adequate in studies of excitation and adaptation mechanisms, while the incident light functions are more explicit when interest is focused on contrast sensitivity.

Adaptation, Ocular↗

PubMed2003

Enhancement of declarative memory by emotional arousal and visual memory function in Alzheimer's disease.

The specific effects of visual and verbal memory on the ability of emotional arousal to enhance declarative memory were examined by using multiple linear regression analysis on data from a sample of 56 patients with probable Alzheimer's disease (AD). The enhancing effect of emotion on memory was evaluated by an illustrated story paradigm, and the visual and verbal memory by a standard memory test. In AD, memory enhancement by emotion was significantly correlated with visual memory but not with verbal memory, regardless of age, sex, educational attainment, and severity of dementia, suggesting a close association between memory enhancement by emotion and visual memory.

Aged↗

PubMed2000

[The development of a computer-based visual field analyzer].

Visual field is one of the important visual functions; it is the extent of the visual field defect that can be employed in judging whether the visual function is impaired. The rapid achievements in computer technologies do provide an impulse for improvement of visual field detection, making possible the automatic, rapid, accurate, detailed and large-scaled visual field detection. This paper gives a thorough description about development of the visual field analyzer, model TEC-2A, which is based on PC windows platform, Visual Basic software developing tool, ISA peripheral circuits, standard Goldmann visual field half-ball and standard stimulus.

Adolescent↗

PubMed2000

Amblyopia: is visual loss permanent?

AIM: To ascertain whether recovery of visual function in amblyopic eyes is likely to occur when the fellow eye is lost as a result of age related macular degeneration. METHODS: The records of 465 patients with an established diagnosis of age related macular degeneration who had attended a specialist macular clinic between 1990 and 1998 were scrutinised. A full clinical examination and standardised refraction had been carried out in 189 of these cases on a minimum of two occasions. Cases were looked for where an improvement of one or more lines of either distance or near acuity was recorded in the eye unaffected by macular disease. In each one of these cases the improvement in visual acuity could not be attributed to treatment of other existing pathology. RESULTS: 12 such cases were detected. In nine of these the eye showing improvement of acuity had a history of amblyopia. The mean improvement in distance and near acuity in amblyopic eyes by 12 months was 3.3 and 1.9 lines logMAR respectively. The improvement in acuity generally occurred between 1 and 12 months from baseline and remained stable over the period of follow up. CONCLUSIONS: Older people with a history of amblyopia who develop visual loss in the previously normal eye can experience recovery of visual function in the amblyopic eye over a period of time. This recovery in visual function occurs in the wake of visual loss in the fellow eye and the improvement appears to be sustained.

Amblyopia↗

PubMed1998

Assessment of stereopsis in college baseball pitchers and batters.

BACKGROUND/PURPOSE: In baseball pitching is a much less visually demanding task than hitting is. We sought to find a stronger relationship between visual function (as measured by stereopsis) and hitting a baseball than between stereopsis and pitching skill. METHODS: Multiple parameters including near and distance stereopsis (as a measure of visual function) were measured in 23 returning college baseball players (with a prior year's record). Their level of stereopsis (measured at distance with use of the B-VAT II BVS Binocular Vision Testing System) was compared with their batting statistics (in the case of the 14 position players) or their pitching statistics (for the 9 pitchers). Batting average and slugging percentage were used as measures of hitting skill, and earned run average, "out percentage" (1.000--Opposing players' batting average) and "strike-out percentage" (frequency of batters struck out) were used as pitching parameters. RESULTS: As a group, visual parameters were excellent in these college athletes. Although the newer test of distance stereopsis correlated with the standard near stereo test (Spearman coefficients), there was no correlation between distance stereopsis and any of the pitching or hitting performance parameters. CONCLUSIONS: The nature of the visual demands required of successful baseball hitters may have yet to be determined or are difficult to identify among a population homogeneous for excellent visual function, true for most groups of competitive athletes. In addition, simpler parameters such as plain visual acuity may be the most important factor(s).

Baseball↗

PubMed2001

[Ocular hemodynamics and visual field in glaucoma treated with dorzolamide].

OBJECTIVE: It has been shown that oral carbonic anhydrase inhibitors improve visual function in glaucoma. Furthermore topical dorzolamide might improve ocular hemodynamics, as was demonstrated previously. This study was undertaken to evaluate whether topical dorzolamide affects visual function and ocular hemodynamics in glaucoma. METHODS: In a retrospective, open clinical trial, dorzolamide eye drops were administered to 28 patients with confirmed primary open angle glaucoma (POAG) in both eyes, 3 times daily for a mean follow up of 9 months. One eye was randomly chosen for evaluation. IOP, blood pressure, heart rate, pulsatile ocular blood flow (POBF) and Humphrey 30-2 visual fields were measured at baseline and after the start of the therapy. POBF was determined by pneumotonography. For statistical analysis the Wilcoxon-matched-paired test and the Bonferoni-Holm adjustment were used. RESULTS: In dorzolamide-treated patients the IOP dropped from 18 mmHg to 15.5 mmHg after 9 months therapy (p < 0.01) and the visual field improved significantly by 18% (p < 0.05). A statistically significant change was found for POBF from 543 microliters/min to 675 microliters/min (p < 0.05). CONCLUSIONS: The results showed the expected drop in intraocular pressure. Visual function and pulsatile ocular blood flow improved significantly which might be explained by an analogous, vasodilatory effect as was observed in orally applied carbonic anhydrase inhibitors.

Aged↗

PubMed1996

Is dietary docosahexaenoic acid essential for term infants?

There is a need to determine whether there is a dietary requirement for docosahexaenoic acid (DHA, 22:6 omega 3) by term infants to achieve their full developmental potential. Studies of brain fatty acid composition have demonstrated that infants who were breast fed have greater levels of cerebral cortex DHA than infants who were formula fed, suggesting that DHA in the cerebrum is dependent on a supply in the diet. Some physiological studies report that electrophysiological and behavioral assessments of visual function are improved in breast-fed infants relative to those fed formula, and that this is related to the level of DHA in their erythrocytes, whereas other studies demonstrate equivalent visual function between breast- and formula-fed infants. However, randomized studies of DHA supplementation of infant formula demonstrate that the visual function of formula-fed infants can be improved to breast-fed levels by adding DHA to formula. Further work is necessary to establish if there are long-term benefits of dietary DHA to the term infant.

Brain↗

PubMed2004

Attitudes towards and perceptions of visual loss and its causes among Hong Kong Chinese adults.

BACKGROUND: As part of a study of visual function among Hong Kong Chinese adults, their attitudes and perceptions related to visual loss were examined. These included fear of visual loss, negative functional impacts of visual loss, the relationship between ageing and visual loss and help-seeking behaviours related to visual loss. Demographic factors associated with these variables were also studied. METHODS: The study population were people aged 40 and above randomly selected from the Shatin district of Hong Kong. The participants underwent eye examinations that included visual acuity, intraocular pressure measurement, visual field, slit-lamp biomicroscopy and ophthalmoscopy. The primary cause of visual disability was recorded. The participants were also asked about their attitudes and perceptions regarding visual loss using a structured questionnaire. RESULTS: The prevalence of bilateral visual disability was 2.2% among adults aged 40 or above and 6.4% among adults aged 60 or above. Nearly 36% of the participants selected blindness as the most feared disabling medical condition, which was substantially higher than conditions such as dementia, loss of limbs, deafness or aphasia. Inability to take care of oneself (21.0%), inconvenience related to mobility (20.2%) and inability to work (14.8%) were the three most commonly mentioned 'worst impact' effects of visual loss. Fully 68% of the participants believed that loss of vision is related to ageing. A majority of participants would seek help and advice from family members in case of visual loss. CONCLUSIONS: Visual function is perceived to be very important by Hong Kong Chinese adults. The fear of visual loss is widespread and particularly affects self-care and functional abilities. Visual loss is commonly seen as related to ageing. Attitudes and perceptions in this population may be modified by educational and outreach efforts in order to take advantage of preventive measures.

Adult↗

PubMed1996

AFNI: software for analysis and visualization of functional magnetic resonance neuroimages.

A package of computer programs for analysis and visualization of three-dimensional human brain functional magnetic resonance imaging (FMRI) results is described. The software can color overlay neural activation maps onto higher resolution anatomical scans. Slices in each cardinal plane can be viewed simultaneously. Manual placement of markers on anatomical landmarks allows transformation of anatomical and functional scans into stereotaxic (Talairach-Tournoux) coordinates. The techniques for automatically generating transformed functional data sets from manually labeled anatomical data sets are described. Facilities are provided for several types of statistical analyses of multiple 3D functional data sets. The programs are written in ANSI C and Motif 1.2 to run on Unix workstations.

Brain↗