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Results for “Visual function”

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At least 181 records · Page 10Linked to original sources

PubMed1992

Visual function and the subsequent development of exudative age-related macular degeneration.

The eyes of 47 subjects with exudative age-related macular degeneration in the fellow eye were tested with a battery of visual function tests at baseline and followed for at least 18 mo. Fundus photographs also were obtained at baseline. These photographs were used to verify the absence of exudative lesions in the 47 eyes tested. Functional and funduscopic baseline data each were compared against outcome data obtained typically at 18 mo. The baseline data were analyzed for their ability to distinguish eyes that had developed detectable exudative age-related macular degeneration from eyes that had not. Eyes with relatively slow foveal dark adaptation rates despite low foveal quantum absorption capabilities (as inferred from the effects of test area on the Rayleigh color match) were especially likely to develop subretinal neovascularization. The resulting sensitivity/specificity and odds ratios were comparable to those of the most effective funduscopic risk indicators. Low S (blue) cone-mediated sensitivity also was associated with an exudative outcome.

Aged↗

PubMed1990

The prism dissociation test in detecting unilateral functional visual loss.

The prism dissociation test is useful in quantifying visual acuity in an eye with functional unilateral visual loss, whether severe or mild in degree. A small vertical prism is used to induce diplopia of a 20/20 or larger size projected Snellen letter, and the patient is asked to comment on the quality of each image seen. The acknowledgement of diplopia and comments on the clarity of the dissociated images serve as testimony to the actual level of visual acuity in each eye. In one case, a patient feigned 20/50 visual acuity in one eye after trauma. The prism dissociation test confirmed visual acuity of 20/20 in that eye, as well as excluding an abnormality of contrast sensitivity. In another case, an amblyopic eye previously noted to have 20/30 visual acuity, which allegedly had acute severe visual loss, was documented to have 20/30 visual acuity by the prism dissociation test.

Diplopia↗

PubMed1989

[Physiologic principles of studying visual functions].

The retinal coding system for visual information comprises three important steps: 1) hyper- and depolarization of the sensory cells as the active basis for perception of light and dark; 2) reaction solely to changes in the bipolar cell on/off system, as a consequence of the action of the horizontal cells with the receptive fields, as a basis for adaptation to brightness and glare; and 3), under the influence of the amacrine cells, important time-space functions as a basis for visual perception of movement. The signal form, which changes over from analog to digital in the ganglion cell system, also results from this last step. therefore, both latencies and amplitudes (VEP) are important criteria for long signal response paths. Taking the examples of "statistical perimetry", visual acuity testing, and examination of contrast sensitivity, clinically relevant methodological problems from signal detection theory are illustrated: there are no "certain" measured values. This uncertainty and the age-dependence of normal values make it difficult to identify pathologic conditions, though trend analyses can help. As the sizes of the retinal areas examined by these methods differ so widely, correlations between the various examination methods are theoretically possible; but one method can never be substituted by another. In routine practice, to detect pathology early, one will sometimes deviate from the prescribed examination method (vision tests with low contrast for visual acuity).

Dark Adaptation↗

PubMed1980

Gyrate atrophy of the choroid and retina: improved visual function following reduction of plasma ornithine by diet.

In a patient with gyrate atrophy of the choroid and retina, an arginine-deficient diet has reduced plasma ornithine concentration fivefold during the past 20 months. Subjective improvement in her visual function was noted approximately 15 months after institution of her diet. This has been documented by improvements in the electroretinogram, dark-adaptation, and color vision. The improvement involves rod and, to a lesser extent, cone function. The results, although preliminary and limited to a single patient, suggest that reduction of plasma ornithine with a low arginine diet is beneficial in this disease.

Adult↗

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↗

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↗