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Results for “Visual function”

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

PubMed1990

Effect of levodopa on contrast sensitivity and scotomas in human amblyopia.

The neurotransmitter dopamine (DA) is involved in several visual functions. Visual deprivation decreases retinal DA concentration in chickens and monkeys. In animals with deprivation amblyopia, several studies suggest that neurotransmitters are involved in visual-cortical plasticity and can restore partial visual acuity in adult cats. We investigated in a cross-over, double-masked study the influence of levodopa on contrast sensitivity and binocular suppression in human adult strabismic and amblyopic patients. After one single administration of levodopa, a significant increase in contrast sensitivity and decrease of the size of the fixation point scotoma was found. No changes could be detected after placebo administration. Levodopa did not induce changes in contrast sensitivity in the dominant eyes of the patients or in normal subjects. In conclusion, we found a short-term effect of levodopa on contrast sensitivity and fixation point scotomas in amblyopic eyes of adult patients.

Adult↗

PubMed1989

The measurement of visual efficiency standards for pilots in the United States Air Force.

Military aviation requires a high degree of visual skill and efficiency. The current visual standards for flying status in the United States Air Force employ static tests of visual function. Visual factors utilized in flight are continually changing to meet the demands of the situation. This study evaluates the performance of two carefully matched samples of people on a test of dynamic visual change, i.e., vergence facility. We compared the ability of a sample of military pilots to make rapid fusional movements in a base-in and base-out direction with a group of nonpilots matched for other normal visual characteristics. The number of times each subject could reestablish fusion while viewing an anaglyph target through alternating 16 delta base-out and 4 delta base-in prism lenses was recorded over a 1-minute time interval. We found the pilot's ability to initiate and sustain fusional vergence movements to be similar to that of their nonrated military counterparts. Our work does not indicate that this test of visual efficiency would discriminate between the pilots and nonpilots in our sample if it were included in a test battery to identify individuals with exceptional visual proficiency.

Adult↗

PubMedDate not supplied

[The effect of refractive abnormalities in young people on their success in sharpshooting].

The visual functions (visual acuity, binocular vision, color tests and visual field) have been examined in three homogenous group of subjects aging 23-28 years involving 101 subjects, and their success in the basic shooting ability has been followed up. Specially selected psychologic tests relevant to shooting have been followed up paralelly. The first group consisted of subjects with hypermetropia, complex or simple hypermetropic astigmatism of the eye used in shooting with the corresponding optical correction achieved the mean mark of 4.30 of the maximum of 5 marks. The second group consisted of subjects with myopia, myopic complex or simple astigmatism with the corresponding optical correction achieved the mean mark of 4.67. The third or control group consisted of subjects without refractory anomalies (emetropics) achieved the mean mark of 4.96. It has been concluded that for evaluation of the shooting ability of a greater importance is the visual acuity achieved by the optical appliances than the degree and types of eye refraction.

Adult↗

PubMed1989

[Late results of transscleral hypotensive low-energy laser therapy of glaucoma].

The paper discusses remote observations (within 5 years) over 64 patients (94 eyes) with open-angle glaucoma after transscleral hypotensive low-energy laser therapy. Before treatment, intraocular pressure was moderately increased in 63 eyes (67%), high--in 31 (33%). In 27 eyes with minimum, moderately expressed dystrophic changes in the anterior segment of the eye, a course of transscleral hypotensive low-energy laser therapy, 1-2 sessions, resulted in normalization of intraocular pressure and improvement of hydrodynamics, remaining stable within the whole period of observation. In 49 eyes with moderately expressed dystrophic changes in the anterior segment of the eye, a course of 3-5 sessions brought about normalization of intraocular pressure, remaining stable within 6-12 months, on the average. In 18 eyes with strongly expressed dystrophic changes in the anterior segment of the eye, a partial hypotensive effect was achieved and the patients were operated a month later. In patients with a normalized intraocular pressure, stabilization of visual functions (visual acuity and visual field) within the whole period of observation is also recorded.

Follow-Up Studies↗

PubMedDate not supplied

[Anterior ischemic optic neuropathy. The experience of 71 cases].

The purpose of the study is to point out the characteristic clinical, therapeutical and evolutive features in the acute ischaemic suffering of the optic nerve's preliminary portion. A retrospective study has been performed, on the patients with anterior ischaemic optic neuropathy (AION), hospitalized in the Ophthalmologic Clinic from Cluj-Napoca, between 1986-1994: 71 cases. The main functional (visual field, visual acuity) and ophthalmoscopic aspects are analyzed, as their evolution after treatment. Results are significantly better if corticosteroids are systemically used (43.3% improvement of the visual field) than in their absence (17.07% improvement of the visual field). The high percentage of failures (70%) proves the absence of a therapeutical method to cure or bring a significant visual function's improvement in AOIN.

Acute Disease↗

PubMed1994

Tank crew vision.

Army optometrists stationed at The Armor Center, Fort Knox, identify the vision conservation needs and the functional visual requirements of each member of the tank crew. This article contains recommendations for vision conservation and for enhancement of visual function of the tank crewmen.

Humans↗

PubMed1996

Clinical assessment of Holo-Or trifocal diffractive contact lens.

PURPOSE: To evaluate the objective and subjective performance of the Holo-Or multifocal contact lens, a new rigid gas permeable (RGP) trifocal diffractive contact lens. METHODS: Eleven experienced and two non-experienced RGP contact lens wearers participated in the study. Eleven patients were presbyopic (age range: 40-57 years) and two were aphakic (ages: 12 and 14 years). Each patient was evaluated by comparing best spectacle correction to Holo-Or multifocal contact lens correction, using the following tests of visual function: visual acuity at 6 m, 80 cm, and 40 cm; contrast sensitivity at near and distance; and depth of focus. RESULTS: No significant differences were found between best spectacle correction and the Holo-Or contact lenses. When using the contact lenses, there was an improvement in depth of focus and a small reduction in contrast sensitivity compared with best spectacle correction. Overall satisfaction and comfort was good to excellent in ten of thirteen patients. CONCLUSIONS: Holo-Or trifocal diffractive contact lenses are a satisfactory means of optical correction for patients with presbyopia or accommodative problems.

Adult↗

PubMed2005

Thinking about visual behavior; learning about photoreceptor function.

Visual behavioral assays in Drosophila melanogaster were initially developed to explore the genetic control of behavior, but have a rich history of providing conceptual openings into diverse questions in cell and developmental biology. Here, we briefly summarize the early efforts to employ three of these behaviors: phototaxis, the UV-visible light choice, and the optomotor response. We then discuss how each of these assays has expanded our understanding of neuronal connection specificity and synaptic function. All of these studies have contributed to the development of sophisticated tools for manipulating gene expression, assessing cell fate specification, and visualizing neuronal development. With these tools in hand, the field is now poised to return to the original goal of understanding visual behavior using genetic approaches.

Animals↗

PubMed2006

Functional degradation of visual cortical cells in old cats.

Visual function declines with age. Using extracellular single-unit in vivo recordings, we compared the function of primary visual cortical (area 17) cells in young and old paralyzed, anesthetized cats. The results reveal that cortical neurons in old cats exhibit higher visually evoked responses, higher spontaneous activities, lower signal-to-noise ratios, and weaker orientation and direction selectivity than do cells in young adult cats. These findings are consistent with previously reported age related declines in cortical function in senescent macaque monkeys. Thus, similar declines in cortical function accompany old age in different mammalian species with well developed cortices.

Action Potentials↗

PubMed2002

Language-specific tuning of visual cortex? Functional properties of the Visual Word Form Area.

The first steps in the process of reading a printed word belong to the domain of visual object perception. They culminate in a representation of letter strings as an ordered set of abstract letter identities, a representation known as the Visual Word Form (VWF). Brain lesions in patients with pure alexia and functional imaging data suggest that the VWF is subtended by a restricted patch of left-hemispheric fusiform cortex, which is reproducibly activated during reading. In order to determine whether the operation of this Visual Word Form Area (VWFA) depends exclusively on the visual features of stimuli, or is influenced by language-dependent parameters, brain activations induced by words, consonant strings and chequerboards were compared in normal subjects using functional MRI (fMRI). Stimuli were presented in the left or right visual hemifield. The VWFA was identified in both a blocked-design experiment and an event-related experiment as a left-hemispheric inferotemporal area showing a stronger activation to alphabetic strings than to chequerboards, and invariant for the spatial location of stimuli. In both experiments, stronger activations of the VWFA to words than to strings of consonants were observed. Considering that the VWFA is equally activated by real words and by readable pseudowords, this result demonstrates that the VWFA is initially plastic and becomes attuned to the orthographic regularities that constrain letter combination during the acquisition of literacy. Additionally, the use of split-field stimulation shed some light on the cerebral bases of the classical right visual field (RVF) advantage in reading. A left occipital extrastriate area was found to be activated by RVF letter strings more than by chequerboards, while no symmetrical region was observed in the right hemisphere. Moreover, activations in the precuneus and the left thalamus were observed when subjects were reading RVF versus left visual field (LVF) words, and are likely to reflect the attentional component of the RVF advantage.

Adult↗

PubMed2005

Effect of cataract surgery on cognitive function in older adults.

OBJECTIVES: To assess whether cataract surgery has an effect on cognitive function in older adults. DESIGN: Longitudinal. SETTING: Assessment of patients seen in eye clinics. PARTICIPANTS: Patients with no cataract (n=92), patients with cataract who elected surgery (n=122), and patients with cataract who declined surgery (n=87). MEASUREMENTS: At baseline and 1-year follow-up visits, the following information was obtained: demographic, health behavior, general health status, medication use, depressive symptoms, cognitive function, and visual function information. This information was compared within and between groups at baseline and follow-up visits. RESULTS: Mattis Organic Mental Syndrome Screening Examination scores at baseline and follow-up varied across the three groups, with the cataract/no surgery group having the highest scores (more cognitive impairment) and the no-cataract group having the lowest scores (less cognitive impairment). For the within-group analysis, at follow-up, the cataract/no surgery group and the cataract/surgery group had significantly less cognitive impairment (P<.001), whereas the no-cataract group experienced no change. For those with cataract, there were no associations between changes in visual function and cognitive function. CONCLUSION: Improvement in cognitive function may occur after cataract surgery but cannot be attributed to the cataract surgery per se or to improved visual function. Clinicians may find this information useful when discussing the nonvisual outcomes of cataract surgery with patients.

Aged↗

PubMed1999

Functional magnetic resonance imaging identifies abnormal visual cortical function in patients with occipital lobe epilepsy.

PURPOSE: To determine whether functional magnetic resonance imaging (fMRI) can reliably identify lateralized cortical dysfunction in patients with suspected occipital lobe epilepsy. METHODS: We compared visual cortical function of 10 patients with intractable occipital lobe epilepsy with nine control subjects' fMRI. Visual stimulation by using an alternating checkerboard pattern results in transient increases in the intensity of the proton magnetic resonance signal of water in the occipital lobes during echo-planar imaging. We used these stimulus-dependent changes in signal intensity to construct functional activation maps, which we registered onto anatomic images. RESULTS: After full-field stimulation, none of the patients with occipital lobe epilepsy had normal activation patterns, whereas eight of the nine control subjects had normal patterns (p = 0.001). Abnormalities consisted of either a markedly asymmetric activation pattern in six of 10 patients (p = 0.04), or a complete absence of activation in four of 10 patients (p = 0.05). The abnormal side of activation was concordant with the side of seizure onset in all six patients with asymmetric activation maps. Half-field stimulation produced less reliable results. Although more patients had abnormal activation maps than did controls with half-field stimulation (p = 0.04), the abnormal side was discordant with the side of seizure onset in three of the five patients who had markedly asymmetric activation patterns. CONCLUSIONS: These results suggest that fMRI with full-field stimulation is a reliable, noninvasive method for identifying areas of abnormal visual cortical function ipsilateral to the epileptogenic region in patients with occipital lobe epilepsy.

Adolescent↗

PubMed2005

[A new method of visual exploration analysis].

The term visual field corresponds to the angular field of view that is seen by the eyes when they are fixed on a point straight-ahead. In neurological patients--e.g. stroke, trauma, or tumour patients--visual field function can be restricted, depending on lesion site and size. In contrast, the term "functional visual field" describes the area of visual field responsiveness under more ordinary viewing conditions. The visual exploration, i.e. the capacity to explore and analyze our visual world, is dependent on the integrity of the visual system and the oculomotor system which has to move the fovea from one object of interest to the next. In this paper, we present a new method to assess the functional visual field, conceptualized as the area that a patient actively scans with eye movements to detect predefined targets placed on everyday scenes. This method allows us to compare three levels of visual field function: (a) the spatial distribution of successful search (hits, i.e. which targets did the patient find?), (b) the spatial distribution of fixations (i.e. where did the patient preferentially search for targets?), and (c) the retinotopic level (i.e. the visual field assessed by perimetry). By integrating these three levels, one can evaluate functional outcomes of visual field disorders. Of particular importance is the question of how a patient compensates for a visual field loss with appropriate eye movements. A further clinical application of this method is the comparison of pre- with post-treatment data. Patients with visual field disorders usually undergo specific exploration trainings, aimed at enhancing the number and amplitude of saccades towards the region of the visual field deficit. The first experiences and clinical application with this method are presented here.

Eye Movements↗

PubMed2006

Retinotopic organization of primary visual cortex in glaucoma: Comparing fMRI measurements of cortical function with visual field loss.

Primary open angle glaucoma (POAG) is a progressive optic neuropathy characterized by retinal ganglion cell loss. Experimental primate glaucoma indicates neuronal degeneration of the lateral geniculate nucleus (LGN) and activity changes in the visual cortex (V1). Neuronal degeneration has also been shown in a post-mortem human study of the optic nerve, LGN and visual cortex. Functional magnetic resonance imaging (fMRI), a non-invasive means of inferring function-specific neuronal activity, provides an opportunity to evaluate glaucomatous changes in neuronal activity throughout the visual pathway in vivo. The purpose of this study is to demonstrate that the relationship between visual field loss in human POAG and the functional organization of V1 can be measured using novel fMRI analysis methods. Visual field defects were measured using standard automated perimetry (SAP). A retinotopic map of visual space was obtained for V1, and the retinotopy data was fit with a template. The template was used to project regions within the visual field onto a flattened representation of V1. Viewing through the glaucomatous vs. fellow eye was compared by alternately presenting each eye with a scotoma-mapping stimulus. The resulting blood oxygen level dependent (BOLD) fMRI response was compared to interocular differences in thresholds for corresponding regions of the visual field. The spatial pattern of activity observed in the flattened representation agreed with the pattern of visual field loss. Furthermore, the amplitude of the BOLD response was correlated on a pointwise basis with the difference in sensitivity thresholds between the glaucomatous and fellow eyes (r = 0.53, p < 0.0001). The BOLD signal in human V1 is altered for POAG patients in a manner consistent with the loss of visual function. FMRI of visual brain areas is a potential means for quantifying glaucomatous changes in neuronal activity. This should enhance our understanding of glaucoma, and could lead to new diagnostic techniques and therapies.

Animals↗

PubMedDate not supplied

Multicenter clinical trial for evaluating methylprednisolone pulse treatment of idiopathic optic neuritis in Japan. Optic Neuritis Treatment Trial Multicenter Cooperative Research Group (ONMRG).

BACKGROUND: A randomized, controlled clinical trial was conducted in 1991 to compare an intravenous megadose of methylprednisolone with a control drug (mecobalamin) for treating acute idiopathic optic neuritis. CASES: Sixty-six cases from 22 clinical centers throughout Japan were examined to evaluate the treatment on visual function parameters, such as visual acuity, visual field, color vision, contrast sensitivity, and critical flicker frequency. OBSERVATIONS: The methylprednisolone pulse treatment group showed faster recovery of visual function, particularly the visual acuity at 1 week (P<.05), Humphrey field analyzer mean deviation at 3 weeks (P<.05), and color vision at 1 week (P<.05). Recovery of contrast sensitivity at several different spatial frequencies was significant in the pulse treatment group at 1 (P<.01), 2 (P<.05), and 4 weeks (P<.05) after the start of treatment. Visual function test results at 12 weeks and 1 year were essentially the same in the two treatment groups. Side effects appeared more frequently in the pulse treatment group than in the control (P<.05). CONCLUSIONS: Pulse treatment does not appear effective for idiopathic optic neuritis even though visual function in the pulse treatment group of this trial recovered more quickly during the initial phase compared to the controls. More effective and specific treatment should be established for optic neuritis.

Adolescent↗

PubMed1995

Image processing of computerised visual field data.

BACKGROUND: Computerised perimetry is of fundamental importance in assessing visual function. However, visual fields are subject to patient response variability which limits the detection of true visual loss. METHODS: A method of improving the repeatability of visual field data was demonstrated by applying techniques used in image processing. An illustrative sample of nine normals and nine patients with field loss was used. Two successive Humphrey fields were selected for each subject. Repeatability was defined as the standard deviation of the pointwise differences between sensitivity values of the reference field and repeat field. The field data were then separately subjected to Gaussian and median image processing filters and the repeatability was compared with the unprocessed field results. RESULTS: Improvement in repeatability, by a factor of approximately 2, was demonstrated by both processes. CONCLUSION: These techniques may improve the reliable detection of loss of visual function using computerised perimetry.

Adult↗

PubMed1995

The function of visual search and memory in sequential looking tasks.

UNLABELLED: Eye and head movements were recorded as unrestrained subjects tapped or only looked at nearby targets. Scanning patterns were the same in both tasks: subjects looked at each target before tapping it; visual search had similar speeds and gaze-shift accuracies. Looking, however, took longer and, unlike tapping, benefitted little from practice. Looking speeded up more than tapping when memory load was reduced: memory was more efficient during tapping. CONCLUSION: eye movements made when only looking are different from those made when tapping. Visual search functions as a separate process, incorporated into both tasks: it can be used to improve performance when memory load is heavy.

Eye Movements↗

PubMed1991

Low-dose cyclosporine therapy of granulomatous optic neuropathy and orbitopathy.

Four patients with granulomatous disease of the anterior visual pathway presented with optic neuropathy between July 1986 and February 1987, secondary to an orbital pseudotumor (n = 1) and sarcoidosis (n = 3). All but one became resistant to corticosteroid therapy, and all were subsequently treated for 1 to 2 years with low-dose cyclosporine alone or in combination with tapering doses of prednisone. Two patients experienced pronounced recovery of visual function, and visual function was stabilized in the other two; in one of these, magnetic resonance imaging showed substantial regression of intracranial lesions. Steroid-induced complications of uncontrolled hyperglycemia (n = 2) and obesity (n = 4) were controlled with cyclosporine. The authors conclude that low-dose cyclosporine is a safe and effective therapeutic alternative in ocular granulomatous diseases.

Adult↗