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Results for “Visual function”

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At least 1,441 records · Page 80Linked to original sources

PubMed1998

Increased excitability of the human corticospinal system with hyperventilation.

OBJECTIVES: Hyperventilation is effective in inducing generalized spike-wave discharges in patients with absence seizures and improves visual function and normalizes visual function in patients with multiple sclerosis. Hyperventilation increases the excitability of cutaneous and motor axons. In experimental animals, hyperventilation increases excitability of hippocampal neurons. There is however no direct evidence of a hyperventilation-induced increase in neuronal excitability within the central nervous system in humans. In this study we determined the effects of hyperventilation on the human corticospinal system. METHODS: We studied the effects of hyperventilation on (1) motor evoked potentials (MEPs) induced by transcranial magnetic pulse stimulation of the motor cortex and (2) F-wave responses. Six subjects were studied. RESULTS: Hyperventilation resulting in an end-tidal pCO2 of 15 mm Hg or less enhanced the amplitude of the MEP and resulted in a shortened onset latency. F-wave amplitudes were enhanced without any change in onset latency. CONCLUSIONS: These findings indicate that hyperventilation increases the excitability of the human corticospinal system. A hyperventilation-induced increase in excitability within the central nervous system may account for clinical phenomena such as facilitation of spike-wave discharges.

Adult↗

PubMed2003

Visual factors should be assessed in older people presenting with falls or hip fracture.

Visual impairment, although not routinely assessed, is an important risk factor for falls and hip fracture in older people. Impaired vision is highly prevalent and commonly unreported in the elderly population particularly in women and those living in nursing homes. Measurement of visual functions such as visual acuity, contrast sensitivity and depth perception may identify older people at risk of falls and hip fracture. Visual loss in older people is correctable in most cases. Intervention strategies, for example, change of glasses or cataract extraction may have the potential of improving visual function and preventing falls in older people.

Accidental Falls↗

PubMed2001

The Collaborative Initial Glaucoma Treatment Study: interim quality of life findings after initial medical or surgical treatment of glaucoma.

OBJECTIVE: To present interim quality of life (QOL) findings in the Collaborative Initial Glaucoma Treatment Study (CIGTS) using all available follow-up through 5 years from treatment initiation. DESIGN: Randomized controlled clinical trial. PARTICIPANTS: Six hundred seven newly diagnosed patients with open-angle glaucoma from 14 clinical centers. INTERVENTION: Patients were randomly assigned to either initial medical therapy or initial trabeculectomy. After treatment initiation and early follow-up, patients received clinical and QOL evaluations at 6-month intervals. QOL assessments were administered by telephone at a centralized interviewing center. MAIN OUTCOME MEASURES: The CIGTS collected comprehensive QOL information that included both generic and vision-specific QOL measures. This article focuses on initial treatment group differences related to symptom reporting, as measured by a Symptom and Health Problem Checklist, and changes in daily visual functioning, as measured by the Visual Activities Questionnaire (VAQ). RESULTS: Across both treatment groups, there was an overall decline in the percent of participants reporting symptoms over time. Of 43 possible symptoms, 12 symptoms were reported with greater frequency by the surgically treated group and 7 symptoms more frequently by the medically-treated group. The surgical patients reported more total Symptom Impact Glaucoma (P = 0.005) and, in particular, more bother related to local eye symptoms. Very few treatment group differences were noted in visual functioning, although surgical patients reported more problems with activities related to their visual acuity (P = 0.024). The percentage of patients across treatment groups reporting worry about blindness was 50% at baseline but declined to approximately 25% over time. CONCLUSIONS: Overall, the QOL impact reported by the two treatment groups as measured by instruments used in this study is remarkably similar, with relatively few significant study group differences observed after up to 5 years of follow-up in the CIGTS. When significant differences in visual function have been detected using the VAQ, they are consistent with the clinical outcomes. To date, the most persistent QOL finding is the increased impact of local eye symptoms reported by the surgical group compared with the medical group. Although no changes are recommended in the treatment of newly diagnosed glaucoma patients at the time of this interim report, further follow-up will allow for more definitive answers to the QOL impact of these two treatment approaches.

Adrenergic beta-Antagonists↗

PubMed2003

Loss of cone function in age-related maculopathy.

PURPOSE: To evaluate cone visual function of subjects with age-related maculopathy (ARM). METHODS: Cone thresholds in 16 patients with ARM and 14 age-matched control subjects were compared. All subjects had visual acuity of 6/12 or better in the studied eye. A range of contrast thresholds were measured to evaluate diverse aspects of cone visual function under steady state conditions (spatiotemporal, color and luminance, and photopic sensitivity) or after bleaching (adaptation dynamics). RESULTS: ARM produced a diffuse loss across all cone steady state visual functions in 31% to 44% of subjects. The adaptation time constant of cone recovery was significantly prolonged in most (69%) ARM eyes. A cross-correlational analysis found adaptational kinetics to be independent of other steady state losses, with cone photopigment regeneration being the most affected visual function in ARM (chi(2) = 4.03, P < 0.05). CONCLUSIONS: The results show that cone-adaptational kinetics are affected in ARM more so than are steady state thresholds. Given that cone recovery is easy to examine in a clinical setting, this test may provide a useful index of photopic function in patients with ARM.

Adaptation, Ocular↗

PubMed2006

Benefit to patients of bilateral same-day cataract extraction: Randomized clinical study.

PURPOSE: To compare patients' self-assessed visual function after bilateral surgery performed on the same day with visual function after surgery in 1 eye at a time. SETTING: Department of Ophthalmology, Blekinge Hospital, Karlskrona, Sweden. METHODS: Patients with bilateral cataract were assigned randomly to 2 groups, patients having bilateral surgery on the same day and patients with 2 surgeries done 2 months apart. Both groups were examined before and 2 months and 4 months after surgery. All patients completed the Catquest questionnaire at each ophthalmic examination. RESULTS: Until both eyes were operated on, patients having surgery in 1 eye had significantly more difficulties performing daily life activities (P<.001) and a worse binocular contrast sensitivity (P<.01) than patients who had bilateral surgery on the same day. Four months after surgery of both eyes in both groups, there was no difference in visual function. CONCLUSIONS: Bilateral cataract surgery on the same day allowed rapid rehabilitation of the patient and helped avoid suboptimal visual function in daily life while waiting for second-eye surgery. However, there was no extra long-term benefit of self-assessed visual function compared with cataract surgery in 1 eye at a time.

Activities of Daily Living↗

PubMed1993

Visual evoked potential characteristics and early diagnosis of Pelizaeus-Merzbacher disease.

OBJECTIVE: Early diagnosis of Pelizaeus-Merzbacher disease; assessment of disease progression. DESIGN: Pediatric neuro-ophthalmology evaluation of visual function with pattern and luminance visual evoked potentials; behavioral state assessment; electrophysiological diagnostic test; baseline estimates at the age of 11 weeks; 1-year follow-up. SETTING: University hospital electrodiagnostic vision research laboratory. PATIENTS CASE STUDY: X-linked Pelizaeus-Merzbacher disease; leukodystrophy; patient tested at the age of 11 weeks and at the age of 58 weeks for follow-up; five age-matched normal controls. INTERVENTIONS: Physical therapy, medication, evaluation. MAIN OUTCOME: Early diagnosis; diagnostic confirmation; objective monitor of disease progression. RESULTS: Abnormal spatial and temporal vision and abnormal visual pathway maturation; visual evoked potentials of proband with Pelizaeus-Merzbacher disease were grossly abnormal, reflecting myelination disorder. CONCLUSIONS: Visual evoked potential pediatric electrodiagnosis yields reliable measures of visual function and visual system maturation in leukodystrophy.

Behavior↗

PubMed2000

A fully functional rod visual pigment in a blind mammal. A case for adaptive functional reorganization?

In the blind subterranean mole rat Spalax ehrenbergi superspecies complete ablation of the visual image-forming capability has been accompanied by an expansion of the bilateral projection from the retina to the suprachiasmatic nucleus. We have cloned the open reading frame of a visual pigment from Spalax that shows >90% homology with mammalian rod pigments. Baculovirus expression yields a membrane protein with all functional characteristics of a rod visual pigment (lambda(max) = 497 +/- 2 nm; pK(a) of meta I/meta II equilibrium = 6.5; rapid activation of transducin in the light). We not only provide evidence that this Spalax rod pigment is fully functional in vitro but also show that all requirements for a functional pigment are present in vivo. The physiological consequences of this unexpected finding are discussed. One attractive option is that during adaptation to a subterranean lifestyle, the visual system of this mammal has undergone mosaic reorganization, and the visual pigments have adapted to a function in circadian photoreception.

Amino Acid Sequence↗

PubMed1993

Ophthalmic results in patients with macroprolactinomas treated with a new prolactin inhibitor CV 205-502.

Macroprolactinomas are pituitary tumours which have been effectively treated medically since the introduction of bromocriptine. The visual function of 13 patients treated with a new prolactin (PRL) inhibitor CV 205-502 (Sandoz Basle), a potent and selective dopamine D2 receptor agonist, was evaluated. This is the first detailed ophthalmic report of the use of this drug in macroprolactinomas. Patients were enrolled from June 1988 to July 1990 (mean follow up 30 months). Visual function including visual acuity, ocular pressure, and visual fields was regularly controlled. Visual fields (VF) were tested with Goldmann and automatic static perimetry (Vision Monitor). Treatment was globally effective. No modifications of the visual function were observed in nine patients (six normal, three previous VF losses after surgery). In four other patients, visual function dramatically improved (regression of a III paresis, one case; disappearance of a chiasmatic syndrome, three cases). A pituitary necrosis was observed in one case and successfully cured. CV 205-502 seems to be an effective and well tolerated treatment of macroprolactinomas.

Adult↗

PubMed1998

Visual behaviours of neurologically impaired children with cerebral visual impairment: an ethological study.

BACKGROUND/AIMS: Visual functions of neurologically impaired children with permanent cerebral visual impairment (CVI) can be difficult to determine. This study investigated the behavioural profile of CVI children by means of ethological observations in order to gain a better understanding of their visual functions. METHODS: Video registrations of nine subjects who were unable to undergo more orthodox methods of visual function testing were observed and analysed by an ethologist. RESULTS: A series of behaviours (direct signs) and supportive or confirming behavioural elements (indirect signs) indicating some visual perception in the children were found. CONCLUSION: Detailed ethological observations of visual behaviour were shown to be useful for analysing visual functions of children with permanent CVI.

Blinking↗

PubMed2002

Variation in visual acuity within pigmented, and between pigmented and albino rat strains.

Many researchers assume that laboratory rats have poor vision, and accordingly, that they need not consider differences in the visual function of rats as a consequence of strain or experience. Currently, it is not specifically known whether rat domestication has negatively affected the visual function of laboratory rat strains, what the effects of strain albinism are on rat visual function, or whether there are strain differences in the visual function of laboratory rats that are independent of pigmentation. In order to address these questions, we measured psychophysically the vertical grating acuity of three pigmented (Dark Agouti, Fisher-Norway, Long-Evans) and three albino (Fisher-344, Sprague-Dawley, Wistar) strains of laboratory rats, and compared their acuity with that of wild rats. The grating thresholds of Dark Agouti, Long-Evans and wild strains clustered around 1.0 cycle/degree (c/d) and did not significantly differ from one another. Fisher-Norway rats, however, had a significantly higher threshold of 1.5 c/d. The grating thresholds of Fisher-344, Sprague-Dawley, and Wistar strains, which were clustered around 0.5 c/d, were significantly lower than those of the pigmented strains. These data demonstrate that there is significant strain variability in the visual function of laboratory rats. Domestication of Long-Evans and Dark Agouti strains does not appear to have compromised visual acuity, but in the case of Fisher-Norway rats, selective breeding may have enhanced their acuity. Strain selection associated with albinism, however, appears to have consistently impaired visual acuity. Therefore, a consideration of strain differences in visual function should accompany the selection of a rat model for behavioral tasks that involve vision, or when comparing visuo-behavioral measurements across rat strains.

Albinism↗

PubMed1982

A model of the early stages of the human visual system: functional and topological transformations performed in the peripheral visual field.

A model of the early stages of the visual system is presented, with particular reference to the region of the visual field outside the fovea and to the class of retinal and lateral geniculate nucleus cells which are most active in the processing of patter information (X-cells). The main neuroanatomical and neurophysiological properties taken into account are: the linear increase of the receptive fields diameter with eccentricity, the constancy of the overlap factor and the topological transformation operated upon the retinal image by the retino-cortical connection. The type of filtering taking place between the retina and the visual cortex is analyzed and some simulations are presented. It is shown that such a filtering is of a bandpass space variant type, with center frequencies that decrease from the center (i.e. the fovea) toward the periphery of the visual field. This processing is "form invariant" under linear scaling of the input. Moreover, considering the properties of the retino-cortical connection, it is shown that the "cortical images" undergo simple shifts whenever the retinal images are scaled or rotated.

Humans↗

PubMed1999

The prevalence of optometric anomalies and symptoms in children receiving special tuition.

A case-control study was performed where 9 pupils receiving special tuition (ST-group) were compared with 36 controls. Six (66.7%) of the pupils in the ST-group were diagnosed as dyslexic. No significant correlation was revealed between receiving special tuition and having reduced visual function, nor between reduced visual function and number of visually related symptoms. Although the number of symptoms was not significantly greater in the ST-group, some of the symptoms were significantly more common in the ST-group, and none were significantly more common in the control group.

Adolescent↗

PubMed2004

[Evaluation of subjective complaints of patients with a visual acuity of 20/30 to 20/20 before and after cataract surgery].

PURPOSE: To quantify patient's functional visual complaints in early cataract and after cataract surgery. PATIENTS AND METHODS: Forty-nine patients scheduled for cataract surgery with a visual acuity of 20/30 or better on Snellen optotypes at the time of patient selection and no other ocular pathology were evaluated subjectively for visual functions preoperatively and 12 months postoperatively. Subjective visual functions were evaluated using a questionnaire that evaluated patient's visual functions by assessing the degree of difficulty they experience in performing tasks involving distance vision, near vision, mesopic vision and glare conditions. RESULTS: The questionnaire scores were correlated with visual performance both before cataract surgery and thereafter. Significant improvement of subjective visual performance was described postoperatively. CONCLUSION: Questionnaire should be considered as adjuncts to visual acuity and constrast sensitivity testing in evaluation of early cataract.

Adult↗

PubMed2002

Visual perceptual functions predict instrumental activities of daily living in patients with dementia.

OBJECTIVE: To assess relations between discrete visual perceptual functions commonly affected in patients with neurodegenerative dementia and the performance of instrumental activities of daily living (IADL). BACKGROUND: Neuropsychologic measures are often used to predict IADL performances in dementia patients. Prior studies have focused on the contribution of higher-level memory and executive deficits to IADL. The relation between visuoperceptual dysfunction and IADL has not been studied systematically. METHODS: Thirty-five elderly patients with neurodegenerative disorders, most diagnosed with probable Alzheimer disease, participated. Patients completed tasks tapping visual perceptual functions believed to be mediated by occipital lobe structures (shape discrimination), posterior inferotemporal regions (face, object form, and written word discrimination), and the dorsolateral parietal lobe (spatial localization). A knowledgeable caregiver rated IADL performance. RESULTS: Object form discrimination, but not other visual perceptual functions, correlated significantly ( = 0.60) with performances of visually based IADL (e.g., misjudging distances, driving, and recognizing familiar people), but not with other IADL, when the variance attributable to dementia severity, language disturbance, and other visual perceptual abilities was controlled. CONCLUSIONS: In contrast to prior investigations that have focused primarily on relations of memory and executive control deficits with IADL in neurologically impaired patients, the results of this study highlight the important contribution of bilateral inferotemporal visual perceptual systems for the performance of IADL in elderly patients with neurodegenerative dementia.

Activities of Daily Living↗

PubMed1991

Visual/cognitive correlates of vehicle accidents in older drivers.

Older drivers have more accidents per miles driven than any other age group and tend to have significant impairments in their visual function, which could interfere with driving. Previous research has largely failed to document a link between vision and driving in the elderly. We have taken a comprehensive approach by examining how accident frequency in older drivers relates to the visual/cognitive system at a number of levels: ophthalmological disease, visual function, visual attention, and cognitive function. The best predictor of accident frequency as recorded by the state was a model incorporating measures of early visual attention and mental status, which together accounted for 20% of the variance, a much stronger model than in earlier studies. Those older drivers with a visual attentional disorder or with poor scores on a mental status test had 3-4 times more accidents (of any type) and 15 times more intersection accidents than those without these problems.

Accidents, Traffic↗

PubMed1989

Effects of very low birth weight (VLBW) on visual development during the first year after term.

Behavioural visual functions were assessed in 155 very low birth weight (VLBW) infants during the first 12 months after expected term. Visual development was examined (mainly cross-sectionally) at 6 weeks, 3, 6, 9, and 12 months of corrected age by assessment of visual acuity, visual fields, optokinetic nystagmus and visual threat response. Many VLBW infants showed visual impairments (54.2%). No single visual function appeared to be specifically susceptible to impairments, deficits were often apparent across a range of functions. Visual impairments were observed at all test ages, and could already be assessed at 6 weeks of corrected age. The highest incidence of visual impairments was scored at 6 months corrected age. Beyond 6 months, less deficits were observed, suggesting in many infants a delayed rather than a permanently impaired visual development. In some infants deficits became evident at a later stage, after an apparently normal initial development. The results suggest that VLBW infants are at risk for impaired visual development.

Humans↗

PubMed1985

Cataract surgery. Outcome assessments and epidemiologic aspects.

Part one defines the topics and study purposes. The 12 studies reviewed in this survey focuses on following 3 topics of which the current knowledge is very limited: Assessment of outcome of cataract surgery (effectiveness studies). Pre-operative prediction of outcome of cataract surgery. Epidemiologic aspects of cataract surgery. These three topics were chosen as study objectives because more accurate knowledge of these points is necessary to assure a better cataract treatment in future, and as a basis for securing sufficient resource allocation to cataract surgery in the public health care. Each topic will be treated separately in the following 3 parts. Part two concerns the effectiveness studies on cataract surgery (publ. I-VI). Primary, a visual functioning index is presented and evaluated. The index is meant as a new supplementary tool for evaluation of the rehabilitation effect. This index, together with visual acuity and other outcome evaluators, was then used for assessment of the effectiveness of cataract extraction generally and in different sub-groups, supplemented with quantitative assessment of rehabilitation problems and analysis of outcome predictors. In a consecutive series of patients, in which intraocular lenses were not used, it was found, that 82% of the patients obtained a final visual acuity of 0.5 or better and 74% of the patients had normal or near normal basic visual functioning at one year follow-up. In spite of these good results, the rehabilitation of these aphakics were difficult. The difference between the two figures above represents some of the 'aphakic vision cripples' with severe difficulties of adaptation to aphakic spectacles. 26% of cataract extracted patients in a normal consecutive group were found to be dissatisfied with the outcome. Two main reasons for dissatisfaction were found: macular disease and low quality of vision with aphakic spectacles, especially in monaphakics, of which 75% had complaints about vision. Although monaphakics nearly reach the same level in basic functioning as the biaphakics, the latter are much more satisfied. It seems likely that basic visual functioning is gained by first eye surgery and more delicate visual functioning and a subjective 'visual comfort' is obtained by second eye surgery. Adaptation to aphakic spectacles seem to be far less difficult for the biaphakics. In series of patients rehabilitated with intraocular lenses or extended-wear contact lenses, the monaphakics appear to have a generally better visual functioning and they are much more satisfied with outcome than spectacles corrected monaphakics.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

PubMed1985

Multiple sclerosis: abnormalities in luminance, chromatic, and temporal function at multiple retinal sites.

Visual function was assessed in a group of patients with multiple sclerosis (MS) and in a group of matched normal controls. In these patients the disease was relatively mild. For each subject, measures of a range of psychophysical visual functions were carried out at multiple sites in each eye. Previous reports have only included some of these functions. Here, luminance threshold, two-flash resolution, perceptual latency, luminance critical flicker frequency (CFF), and chromatic CFF were all measured. Variabilities of these functions and correlation between chromatic and luminance CFFs were also evaluated. For both the MS group and the normal control group, the correlations between pairs of visual parameters were not overall significantly greater than chance level. The MS group did give a significantly reduced value relative to the normal group for luminance CFF and for the gradient of the plot of chromatic CFF against luminance CFF. This group was then subdivided according to history of visual involvement. The subgroup with previous visual symptoms had significant impairment for luminance threshold, variability of luminance threshold, luminance CFF, variability of two-flash resolution, and for the gradient of the plot of chromatic CFF against luminance CFF. The subgroup without previous visual symptoms showed no significant impairment for any individual parameter, although the gradient of the plot of chromatic CFF against luminance CFF was lower than normal.

Adult↗