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Results for “Visual function”

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At least 217 records · Page 12Linked to original sources

PubMed1985

Orthoptic effects on accommodation and related visual functions in an adult alternating esotrope.

Orthoptic therapy was instituted in an adult, alternating esotrope with asthenopia who exhibited inaccurate static accommodative responses with adequate, clinically determined, accommodative facility. During and following therapy the patient showed considerable improvement in accommodative accuracy and related visual functions, such as contrast sensitivity, in the absence of any change in strabismic deviation. This case provides the first laboratory documentation of orthoptic effects on accommodation in an adult strabismic.

Accommodation, Ocular↗

PubMedDate not supplied

Video display units and visual function.

The widespread use of visual display units (VDU) in the workplace has engendered visual complaints and concern for workers' health and safety. The detectable levels of radiation emitted from VDUs have been well below safety levels and exposure to VDUs does not appear to cause any organic damage to the eye. However, visual disturbance and eye discomfort affects many workers using VDUs, and these symptoms may be alleviated by a number of measures, including proper diagnosis of pre-existing ocular problems, use of special eyeglasses, and correct arrangement of lighting and furniture in the work area.

Cataract↗

PubMed1992

In situ measurements of lens fluorescence and its interference with visual function.

Irradiation of the primate lens by near-ultraviolet wavelengths results in a blue fluorescence, which can be an intraocular source of veiling glare. This study quantitated the fluorescence intensity as a function of exciting intensity and wavelength. As the exciting wavelength was increased from 360 to 430 nm, the decreasing fluorescence intensity (for equal radiant exposures) was partially offset by a shift in the fluorescence spectrum to wavelengths of greater luminous efficiency so the luminance of the lens fluorescence remained approximately constant. The measured luminance of the lens fluorescence was high enough to imply degradation of visual function as a result of reduced contrast of the retinal image. To obtain an objective measure of visual deficit associated with the fluorescent glare, the visual evoked potential (VEP) elicited by counterphased sine-wave gratings was recorded while the subject eye was continuously exposed to the 413 nm emission from a krypton laser. The VEP amplitude was reduced in the presence of the exciting laser even at levels defined as "safe" (ie, where exposure levels are insufficient to induce an acute ocular lesion). Because the direct glare effect of the exciting radiation was negligible in this experiment, the VEP response loss is attributed to the effect of the lens fluorescent glare.

Animals↗

PubMed1976

Monitoring of visual function during parasellar surgery.

Damage to the visual system is an unfortunate complication of surgery in the area of the optic chiasm. It is now possible tomonitor the functional status of the visual system intreoperatively at regulat intervals. This is accomplished by recording the Visual Evoked Response to flashes of light from light-emitting-eiodes. These diodes are embedded in a special plastic shell which inserts under the eye lids of each eye. Since the light comes from the diodes in the plastic shell, there is no need to disturb the surgical procedure when a test run is desired. A record is obtained by averaging 100 three-per-second flashes.

Adenoma, Acidophil↗

PubMed1987

Vision for coloured pictures at different acuities: the Sonksen picture guide to visual function.

The vision 70 normal-sighted children was tested for both Snellen letters and life-size colour pictures of everyday objects. All the children wore spectacles for the tests: 60 were fitted with lenses which would induce a refractive error, the remainder had glassless frames only. Compared with acuity measures based on the Snellen letters, the pictures needed to be brought much closer than might be expected before the children with induced minor visual errors could recognise them. This highlights the importance of detecting and correcting refractive errors in preschool children who learn from such material, and suggests that the pictures may be a useful tool for detecting children with such errors. 18 pictures, comprising the Sonksen Picture Guide to Visual Function, have now been selected for this purpose.

Child↗

PubMedDate not supplied

Contrast sensitivity letter charts as a test of visual function in amblyopia.

Anisometropic and strabismic amblyopes were studied using the Regan Contrast Sensitivity Charts. At all levels of contrast, the amblyopic eyes of both the strabismic and anisometropic patients scored significantly lower than did their fellow normal eyes, which were used as controls. In comparing the differences between the normal and amblyopic eyes of both groups, we noted a normalization of the visual function of strabismic amblyopes at low contrast. This feature was not observed in the anisometropic amblyopes who consistently scored poorly when viewing either the high or low contrast chart.

Adolescent↗

PubMedDate not supplied

Effect of photorefractive keratectomy on visual functioning and quality of life.

The authors present the results of the psychosocial outcomes of 45 patients undergoing excimer laser photorefractive keratectomy (PRK). The patients were evaluated by means of self-report questionnaires preoperatively and 6 months after surgery to determine the effect of uncorrected vision change on the patients quality of life. The measurements include the following variables: clinical end points (spherical equivalent refraction); visual function (night driving, day driving, near vision, far vision, glare disability); functional status (physical, social, and role functioning, mental status); general well-being (health perceptions, personal well-being, overall quality of life); and satisfaction with surgery (expectations, satisfaction with medical staff, postoperative pain, satisfaction with treatment outcomes). Preliminary results indicate that changes of uncorrected vision after PRK are reflected by improvement in each of the quality-of-life functions.

Activities of Daily Living↗

PubMed1995

[Personal computer used in visual function screening].

BACKGROUND: The number of medical screenings is increasing. This fact is specially pronounced in the field of occupational health. Due to restricted financial resources and limitations in time there is a need for rationalisation in medical screenings. MATERIALS AND METHODS: Possible uses of personal computers (PC) enabling organisational and financial benefits in medical screenings are suggested. By means of a test for colour-blindness it is shown how unfavourable technical conditions may be by-passed. RESULTS AND DISCUSSION: Rationalisation in medical screenings can be achieved when using the PC as a multi-functional screening-device as well as an expert system, measuring apparatus and as a communication-device. Due to a lack of literature it is difficult to discuss possible effects of technical differences between PC-based screenings of visual functions and screenings where "traditional". Reliability, sensitivity and validity is insufficiently investigated for many of the commercial available screening-devices based on a PC.

Color Perception Tests↗

PubMed1992

ORG 2766 fails to improve visual functions in rats with occipital lesions.

Adult rats were trained on a white versus black card discrimination in a circular water tank. Three independent variables were manipulated: lesion (sham, lateral occipital, medial occipital), dose of ORG 2766 administered (0 or 25 micrograms in saline on alternate days for 18 days), and time of administration (during the post-surgical recovery interval or during post-operative testing). Both visual cortical lesions produced a prominent retention deficit and defective pattern vision. Neither post-surgical nor concurrent administration of ORG 2766 improved visual functions. These results, along with a growing body of evidence, challenge the generality of the positive influences of ORG 2766 upon behavioral recovery observed in animals with limbic lesions.

Adrenocorticotropic Hormone↗

PubMed1994

[Development of visual function in infants and children].

The development of P1 component of VEP was studied in 150 normal infants and children between the age of 2 weeks and 9 years. The results indicates that the VEP consists of simple positive waves within 8 weeks following birth, the latencies of P1 components shorten dramatically from 2 to 4 months, the development of the latencies of low, medium and high spatial frequencies of P1 components reaches adult levels in infants and children of 4 months, 4 years and 9 years, respectively and the VEP amplitudes of infants and children are significantly higher than those of adults. Based on the results of our research, the development of visual function can be divided into 3 phases: the first, within 4 months following birth; the second, 5 months to 4 years and the third, 5 to 9 years.

Child↗

PubMed1994

Improved visual function and attenuation of declines in health-related quality of life after cataract extraction.

OBJECTIVE: To measure the effect of cataract extraction and lens implantation on elderly persons' health-related quality of life and on their ability to perform visual activities. DESIGN: Evaluations of health status were conducted preoperatively and at 3 and 12 months after surgery on patients scheduled for cataract extraction. SETTING: Patients were enrolled from the General Eye Service of the Massachusetts Eye and Ear Infirmary and 33 Boston practices. PATIENTS: The cohort consisted of 464 patients aged 65 years or older who were identified from the surgical schedule of the Massachusetts Eye and Ear Infirmary. At 3 to 12 months after surgery, 458 (99%) of the participants were successfully contacted. Health-related quality of life data were available for 419 (90%) to assess changes after surgery. MAIN OUTCOME MEASURES: Ophthalmologic examinations were performed preoperatively and during the follow-up period. The Activities of Daily Vision Scale (ADVS) and the Medical Outcomes Study 36-item short from (SF-36) were administered before surgery and at 3 and 12 months postoperatively to assess changes in health status. RESULTS: At 12 months after surgery, 95% of patients had improved Snellen visual acuity, 80% had improved ADVS scores, but only 36% had improved SF-36 physical functioning. Average scores on seven of eight SF-36 subscales worsened at 12 months. Patients with improved ADVS scores had significantly smaller declines across all SF-36 dimensions except for role limitations due to emotional problems. CONCLUSION: Improved visual function after cataract surgery was associated with better health-related quality of life, suggesting that age-related declines in health may be attenuated by improvements in visual function.

Activities of Daily Living↗

PubMed1984

Retinal boundaries and visual function in gyrate atrophy.

Three patients with gyrate atrophy of the retina and choroid underwent fundus photoperimetry, the combination of fundus photography and visual field analysis within the same instrument, to examine the correspondence between the funduscopically observed, scalloped margin of remaining retina and the functional limit of the peripheral visual field. The results suggest that near the border between remaining retina and atrophic areas, visual sensitivity falls off quite rapidly, producing perimetric isopters that conform closely to the scalloped retinal margin. In some instances, visual function can be demonstrated in islands of remaining retina that are totally surrounded by atrophic areas. This study demonstrates the usefulness of fundus photoperimetry in following the course of degenerative retinal diseases.

Adult↗

PubMed1995

Visual function in Rett syndrome.

The authors examined refractive error, pattern onset visual evoked potentials, ocular posture and they performed internal and external eye examinations in 11 subjects with Rett syndrome (aged between four and 24 years) and 18 normal controls (aged between six and 20 years). Substantial refractive errors were common in the Rett syndrome group. Spectacle correction had never previously been worn and glasses were provided where appropriate. No subjects had nystagmus or optic nerve pallor and only one was strabismic. All subjects had recognisable and reproducible pattern-onset VEPs and latencies and amplitudes did not differ significantly from those of the controls. All demonstrated VEP thresholds of at least 24'. In contrast to other populations with profound disabilities, people with Rett syndrome have good function of the afferent visual pathways and, in view of their substantial refractive errors, are likely to benefit from spectacle correction.

Adolescent↗

PubMed1976

[Several biochemical signs of loss and restoration of visual function].

With the aid of cytophotometry the author studied the cellular chemistry of neurons (according to the activity of glutamate dehydrogenase) in the III, IV and V layers of the visual cortex in rats during the period of rehabilitation of specific functions following long-term light deprivation. It was demonstrated that a 2-week stay of deprivated animals in conditions of usual light is accompanied by visible normalization of the glutamate dehydrogenase activity in the cortical neurons. However, a complete rehabilitation of the control level was not attained. The study demonstrated differences in the reactions of identical neurons in the IV and V layers to the rehabilitation of specific functions. It is being assumed that the rehabilitation of the visual function may be due to biochemical reconstructions in the monomodel and certain parts of the polymodal neurons in the visual cortex.

Animals↗

PubMed1988

Altering body position affects intraocular pressure and visual function.

Intraocular pressure (IOP) can be altered by changing body position. This report describes two experiments evaluating variations in IOP, as well as neural functioning of the retina and visual cortex (as measured by pattern-reversal electroretinogram and visual evoked potential), associated with whole-body, head-down tilt. The subjects, ten per experiment, were visually normal with IOP less than 19. In the first experiment, IOP elevations were induced by varying the angle of tilt in discrete steps between +90 degrees (upright) and -90 degrees (inverted). In each position IOP was measured and significant elevations (up to 3x baseline) were noted. These elevations were maintained for 1 min during which simultaneous retinal and cortical biopotentials were measured. In the second experiment, 6 degrees head-down tilt was maintained for 2 hr during which time the IOP and both biopotentials were measured repeatedly. Our findings confirm the effect of body position of IOP, while also revealing that head-down tilt produces significant reductions in neurophysiological function at both the retinal and cortical levels. The neural effect is maximized when 6 degrees head-down tilt is maintained for 20 min.

Adult↗

PubMed1989

Prediction of visual function behind cataract using displacement threshold hyperacuity.

Visual acuity and displacement threshold hyperacuity were measured in a group of patients awaiting cataract extraction, and this was repeated several weeks subsequent to surgery. In addition, measurements were made on a group of patients with various ocular pathologies but without the presence of cataract. Displacement thresholds in the cataract group increased only slightly with the severity of the opacity. On the other hand, displacement thresholds for the pathology group showed a marked dependence upon visual acuity--the worse the acuity, the higher the threshold. This results in a clear distinction between vision loss due to optical factors (cataract) and retinal/neural factors. There was a good correlation between pre- and post-operative displacement thresholds in the cataract group, with post-operative thresholds being slightly better than pre-operative thresholds. The results suggest that this technique may offer patients a good indication of the likely quality of vision achieved following cataract extraction.

Aged↗

PubMed1993

Contrast detection in noise: a new method for assessing the visual function in cataract.

The detectability of a signal decreases in the presence of externally added visual noise. A linear relation exists between the energy of a signal at threshold and the spectral density of the added visual noise. This relation, represented by contrast detection in noise function, allows a given loss in contrast sensitivity (CS) to be attributed to an increase in the internal intrinsic noise and/or a decrease in the detection efficiency of the observer. Intrinsic noise gives a measure of the random background noise within the visual system, whereas detection efficiency is a measure of how effectively the observer utilizes the available stimulus information. Recent work shows that neural dysfunction produces a decrease in the detection efficiency, whereas optical deficits produce a change in the intrinsic noise only. We investigated whether the CS loss in cataract can be attributed to either a change in intrinsic noise, in detection efficiency, or both. Contrast detection in noise functions was measured for 10 uniocular cataract patients. Comparison between the two eyes showed no significant difference in detection efficiency, although the intrinsic noise increased significantly in the cataractous eye. The data suggest that detection efficiency may provide a measure of neural visual function behind a cataract and, conversely, that intrinsic noise provides a measure of the visual effect of the cataract itself. We discuss the implications of intrinsic noise as a measure of cataract for both clinical assessment and research.

Aged↗

PubMed1978

Modification of visual functions of the parietal lobe at early age in the monkey.

In addition to the visual pathway ending in the visual cortex, visual information is also processed in the associative areas of the cortex. We have studied the posterior parietal association area (Brodmann's area 7), and in our sample about 40% of the neurons were influenced by visual stimulation or ocular movements. The visually activated neurons in this region in normal adult monkeys have large, binocular receptive fields and they respond well to all moving visual stimuli near the animal. They do not differentiate between different patterns of visual stimuli but respond well to objects of interest, such as food, drinks, new objects, etc. Many visual neurons also respond to somatic stimulation. Preliminary experiments on two young monkeys suggest that the visual input into area 7 is strongly modified by early visual deprivation. In one monkey monocular deprivation lead to total absence of any influence from the deprived eye to area 7. No deprivation effect was observed in the lateral geniculate nucleus of the thalamus and the effect in area 7 was stronger than in the visual cortex (area 17). One monkey raised with bilateral eye closure was behaviourally blind after the opening of the eyes and remained so for the observation period of one month. In area 7 of this monkey the proportion of recording sites responsive to visual stimulation was sharply reduced. In kittens binocular deprivation is known to effect the function of the visual cortex much less than monocular deprivation. It seems possible that at early age inputs representing different sensory systems compete for influence in the associative cortical areas in the same way as there is competition between inputs from the two eyes to the visual cortex.

Age Factors↗