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Biomedical subjects

U Schiefer

Publications and source records attributed to U Schiefer.

At least 37 records · Page 2Linked to original sources
PubMed2001

[Comparison of local differential luminance sensitivity (dls) between Oculus Twinfield Perimeter and Humphrey Field Analyzer 630 (HFA I) in normal volunteers of varying ages].

PURPOSE: Purpose of this study was to compare age-corrected normal values of differential luminance sensitivity (dls) of the Oculus Twinfield Perimeter with those of the Humphrey Field Analyzer 630 (HFA I). Furthermore, naso-temporal and superior-inferior asymmetries in the central visual field were analyzed. METHODS: 72 ophthalmologically normal volunteers, 12 per decade, were examined with both perimeters using a 4-2 dB bracketing strategy with two reversals for threshold estimation. A biometric model, which fits a hill of vision to the data, was developed. The age-related hills, created by the model, were compared between the instruments and analyzed for asymmetries. RESULTS: The normal dls values for the Twinfield perimeter were about 1.5 dB above those of the HFA I. The shape of the hill in regard to slope in corresponding locations did not differ substantially. The decline of local differential luminance sensitivity showed a nonlinear correlation to age: it remained almost constant up to the 4th decade, with a steeper decline beyond that age. A naso-temporal as well as a superior-inferior asymmetry was found. Along the vertical meridian, the slope of the hill was steeper in the superior part than in the inferior. At an excentricity of 20 degrees we found a superior-inferior difference of 2.1 dB for the HFA and of 1.8 dB for the Twinfield perimeter benefitting the inferior meridian. Along the horizontal meridian there was a distinct difference in regard to the shape of the hill. The sensitivity was greater in the temporal half of the visual field than in the nasal. At an excentricity of 30 degrees, the difference was about 2.75 dB for the HFA and 2.5 dB for the Twinfield perimeter. These asymmetries seem to appear in all age groups. Unfortunately, the exact influence of age on the appearing asymmetries cannot be quantified by the used model. CONCLUSION: The normal dls values benefit the Twinfield for about 1.5 dB compared to the HFA. There seems to be a critical age of about 40 - 50 years, beyond which a decline of dls becomes manifest.

Adolescent↗
PubMed2000

[Perimetry findings and driving performance. "How much visual field" does a motorist need?].

OBJECTIVE: On 01-01-99 the new driving licence regulations came into force. Are the visual field criteria mentioned there sufficient for an adequate evaluation of driving fitness? METHODS: Typical (binocular) visual field defects were digitally superimposed onto photographs of traffic scenes to show the influence of such scotomata on visual perception. RESULTS: Exemplary cases clearly show that evaluation of visual field borders alone is not sufficient for evaluating driving fitness. They also prove that binocular scotomata affecting the (para-)central region of the visual field are of special importance to driving performance. The actual guidelines given by the traffic commission of the German Ophthalmological Society (DOG) and the legally defined limits will be critically discussed. CONCLUSION: From the ophthalmological point of view the actual visual field criteria of the new driving licence regulations do not seem to be sufficient for the evaluation of driving fitness: An additional consideration of (para-)central scotoma is mandatory. This publication provides recommendations for execution and interpretation of perimetric examinations for traffic ophthalmological purposes.

Automobile Driver Examination↗
PubMed2000

[Hereditary motor and sensory neuropathy type I associated with a unilateral incomplete external oculomotor paralysis. A case report].

HMSN is a hereditary symmetric ascending neuropathy of the peripheral nerves. Several cases of HMSN with motility disorders of both eyes have been reported in the literature. We describe a patient with HMSN type 1 and an incomplete peripheral 3rd nerve palsy of the right eye. To the best of our knowledge, this is the first report of developed unilateral oculomotor disorder in a patient with HMSN.

Adult↗
PubMed2000

[Are cross-eyed persons worse drivers? The effect of stereoscopic disparity on driving skills].

BACKGROUND: The motorist obtains about 90% of the information required to drive a vehicle from the sense of vision. In road traffic, various situations with respect to size, distance, and position have to be evaluated at different speeds. Does depth perception based on disparity play an essential role in these situations? METHODS: Each of ten subjects with defective stereopsis due to strabismus was compared with an age matched healthy control, who was also matched in yearly mileage, type of vehicle and duration of driving experience. After ophthalmological examination including stereotests for both distance and near, all subjects performed the following driving tests: (1) Stopping as close as possible in front of an obstacle, (2) reversing into a parking position, (3) driving a slalom parcours at the speed of 40 km/h, (4) estimating the relative position of two cars within a limited time while approaching them with 40 km/h. All tests were performed both under monocular (the non-leading eye covered) and binocular conditions. The sequence of the tests was randomized in order to minimize training effects. RESULTS: Comparing the driving performance of both groups, the controls performed significantly better (p < 0.01; ANOVA) only in the "slalom task". In "estimation of position" the controls performed significantly worse (p < 0.01; ANOVA) compared to their counterparts with defective stereopsis. A significant difference between the monocular and binocular performance was found only in the "stopping task", exclusively for the group of normals, benefitting from the binocular performance (p < 0.05; ANOVA). CONCLUSION: Stereopsis improves the driving performance only in dynamic situations at intermediate distances.

Adult↗
PubMed1999

[White-noise field campimetry in HIV+ patients].

PURPOSE: The first morphological changes in eyes with HIV infection are microvascular disease of the retina with cotton-wool spots and microaneurysms. The study was performed to find out if evidence of disturbances of ocular microcirculation can be established by non-invasive methods. PATIENTS AND METHODS: Twenty-seven patients with HIV infection and without opportunistic infections underwent thorough ophthalmologic examination with threshold-oriented, suprathreshold perimetry (TAP 2000 ct, Oculus) and white-noise field campimetry (TEC, Oculus). RESULTS: Visual field examination was normal in 23 out of 27 patients (85%), whereas 4 patients showed relative field defects in at least one eye. In white-noise field campimetry 13 out of 23 perimetrically unaffected patients (56%) perceived scotomas in one or both eyes. These scotomas were not stable. Three of 4 patients with relative scotomas in the visual field had cotton-wool spots in the retina and showed a stable scotoma in campimetry. Visual acuity, IOP, and cup/disc ratio were within normal ranges. CONCLUSION: White-noise field campimetry complements the standard examination of patients with HIV and might be capable of indicating disturbances of ocular microcirculation by a non-invasive method before morphological changes in the retina can be seen.

Adult↗
PubMed1999

[Age-dependent error rates in automatic screen campimetry with bright and dark stimuli].

PURPOSE: To assess patient reliability and compliance, most perimeters check for false-positive and -negative answers. In this study the results of catch trials were obtained with video campimetry with respect to age-related changes and differences for tests using increment and decrement stimuli. METHODS: Sixty-one ophthalmologically normal persons (aged 20-80 years) were tested with automated campimetry on a computer screen. Examination strategy included bright and dark 1 degree-stimuli at 69 test locations within the central 30 degrees of the visual field (presented on a computer screen). Four percent of all stimulus presentations were used for testing false-positive answers, 4% for false-negative answers. RESULTS: The rate of false-positive answers was not significantly age-related and there was no difference for tests with dark and bright stimuli. Concerning false-negative answers, no difference between dark and bright stimuli was found. There was also no strong correlation with age. CONCLUSION: In this study rates of false-positive and -negative answers were low at a comparable level for either stimulus type (bright/dark) or age of the tested persons.

Adult↗
PubMed1999

Development of brightness matching and colour vision deficits in juvenile diabetics.

We studied hue discrimination and brightness matching throughout the spectrum in ten juvenile patients suffering from diabetes mellitus (Type I) with no (eight patients) or mild (two patients) retinopathy. In addition, the FM 100-Hue test was performed. The data were collected once every year over 5 years. Over the 5 years, the diabetics show a continual change in the shape of their brightness matching function. Wavelength discrimination ability remains quite stable with time at the long end of the spectrum but is variable at short wavelengths. FM-100 error scores remain similar over the period tested, at a level slightly higher than that of a control group. Additional experiments show that the sensitivity of the S-cone in the diabetic group is similar to that of controls. The results can be explained by an early relative reduction in the sensitivity of post-receptoral processes in juvenile diabetics.

Adolescent↗
PubMed1999

Models for the description of angioscotomas.

To describe small scotomas in visual field examinations several statistical models are proposed and applied to the evaluation of angioscotoma in 13 ophthalmologically normal subjects. A special perimetric grid is used where thresholds can be estimated along a line of narrow-spaced test points which crosses the predicted location of the retinal vessel. A two-stage analysis employs single estimations to fit a threshold curve by means of a special parametric description of the luminance difference sensitivity threshold as a function of stimulus position. An alternative model incorporates the threshold as a function of position into the probabilistic description of the binary response (stimulus seen/not seen).

Adult↗
PubMed1999

Angioscotoma detection with fundus-oriented perimetry. A study with dark and bright stimuli of different sizes.

Fundus-oriented perimetry (FOP) was used to evaluate the effectiveness of different-sized bright and dark stimuli in detecting and quantitatively measuring angioscotoma. The foveolas and optic disks of digitized fundus images were aligned with their psychophysical counterparts to construct individual grids of perimetric stimuli. Each grid included a linear set of test point locations crossing a retinal vessel. Angioscotomas immediately became visible in nine of 13 healthy normal volunteers tested with FOP. Additional mathematical processing of local loss of differential light sensitivity (dls) disclosed an angioscotoma for at least one stimulus condition in all persons tested. The angioscomas were usually deeper for small (12) targets than for large (32') ones. On the other hand, the overall noise at dls thresholds was generally higher for small than for large stimuli regardless of whether the stimuli were bright or dark. No noteworthy differences were found in detection rates or signal-to-noise ratios under different stimulus conditions (dark/bright/small/large). FOP permits the individual arrangement of stimuli for specific morphological conditions and is thus capable of detecting even minute visual field defects such as angioscotomas.

Adult↗
PubMed1999

Preretinopic changes in the colour vision of juvenile diabetics.

AIMS: To examine the colour vision of juvenile patients suffering from diabetes mellitus without retinopathy in relation to metabolic and ophthalmic state. METHODS: Metameric matches, both Rayleigh (red/green) and Moreland (blue/green) were used to test the colour vision yearly of 10 juvenile patients. The patients were monitored over 4 years, and during the final year, their blood glucose level was determined directly after testing colour vision. An ophthalmic examination was performed on the day of colour vision testing and blood and urine were analysed regularly throughout the 4 years. Their results are compared with an aged matched control group of 20 subjects, seven of whom were retested after 9-16 months. RESULTS: After 4 years, the colour vision results show an enlarged matching range for the Moreland match, as well as a smaller increase in the matching range for the Rayleigh match. No significant correlation was found between blood glucose at the time of testing and any of the variables measured. CONCLUSION: The pattern of colour vision deficits in metameric matching shown by juvenile diabetics is consistent with postreceptoral alterations of the inner retina, at this preretinopic stage of disease. Duration of diabetes is correlated with both colour vision changes and morphological alteration of the retina.

Adolescent↗
PubMed1999

Detection and follow-up of homonymous visual field defects - perimetric essentials for evaluation of spontaneous recovery.

Clinical detection and follow-up of homonymous visual field defects require appropriate perimetric procedures: since postgeniculate lesions are usually characterised by absolute scotomata, time consuming threshold methods can be replaced by supraliminal strategies with comparatively high stimulus densities. Compared with equidistant rectangular grids, a centripetal stimulus condensation represents the physiological conditions more adequately and thus is more effective. It allows one to differentiate central changes of the visual field, like macular sparing or splitting, which also interfere with reading performance. This procedure requires test points to be located to either side of the vertical meridian, rather than directly on it. Multimodal assessment of visual subfunctions (using static, kinetic or colour test points, random dot patterns or optokinetic stimulation) specifies the effect of the lesion in different channels or regions of the visual pathways. Automation of perimetric procedures and continuous monitoring of fixation are important tools, enhancing the quality of examination and follow-up. The above mentioned psychophysical techniques for detection of functional defects and documentation of eventual recovery, as well as matching neuroimaging findings, are demonstrated by illustrative cases.

Journal Article↗
PubMed1998

Lesion location influences perception of homonymous scotomata during flickering random dot pattern stimulation.

An attempt was made to clarify whether the site of postchiasmal lesions affects subjective perception of homonymous visual field defects during stimulation with flickering random dot patterns (white noise-field). Out of 56 patients with homonymous hemianopia, 38 (68%) perceived scotomata in this situation, but 18 (32%) discerned none at all. Neuroradiologic superposition of cerebral lesions detected by computed tomography (CT) or magnetic resonance imaging (MRI) showed that nearly all patients who perceived their scotomata had lesions involving the primary visual cortex or the perigeniculate region, whereas those who received no scotoma had lesions centered within the optic radiation. Functional MRI of six normal subjects during stimulation with flickering random dot patterns indicated predominant activation of the primary visual cortex. Since noise-field defects were most frequently perceived by patients whose lesion involved the primary visual cortex, it appears that the sensitivity of noise-field campimetry depends on the site of damage in the visual pathway. The explanation for this may be that damage to long-range horizontal connections impairs filling-in processes.

Adolescent↗
PubMed1998

[Objective assessment of visual field defects using multifocal electroretinography].

BACKGROUND: Multifocal electroretinography allows simultaneous recording of 61 focal electroretinographic signals from the retina of the posterior pole. The function of the outer retinal layers can be mapped for a visual field of 30.5 degrees radius. We herein describe the topography of such potentials in patients with hemianopic and concentric visual field defects. SUBJECTS AND METHODS: Six patients with visual field defects caused by chorioretinal and central visual pathways diseases were examined using multifocal ERG. RESULTS: In 30 normal volunteers in the entire 30 degrees visual field clear signals were obtained. In the patients with visual field defects caused by retinal diseases in areas with reduced light sensitivity diminished electroretinographical activity was found. In contrast, in patients with bitemporal hemianopsia due to a chiasmal lesion no correlation between visual field and magnitude of focal ERGs was seen. CONCLUSIONS: In retinal disorders defects in multifocal ERG presented the similar pattern as scotomata in perimetry. The patient with visual field defects due to disturbances in the chiasma exhibited a normal ERG-topography. In patients with visual field defects multifocal ERG supported differentiation of the location of the lesion.

Adult↗
PubMed1996

[Noise field screening. Results of a television field study for detection of visual field defects].

White noise field campimetry is able to transform usually negative scotomas immediately into perceivable visual field defects. As this method needs a monitor, the obvious solution was to evaluate the suitability of the noise field stimulus broadcasted to home TV sets. Therefore, in cooperation with the "Süddeutscher Rundfunk" (SDR) as well as several health insurance companies ("AOK Baden-Württemberg" and other "RVO-Kassen"), approximately 300,000 viewers were invited to take this test after receiving brief information and instruction. There were 531 calls for questionnaires to document the subjects' findings and the results of a subsequent ophthalmological examination. In most cases this clarified the perceived noise field defect. Out of 127 evaluable questionnaires, 78 cases did not show any relevant ophthalmological pathology; this held true especially for lesions of the visual pathway. However, in 49 persons the ophthalmologists detected pathological findings; in 20 of these, the scotomas were previously unknown to the physicians. Glaucomatous optic neuropathy and macular degeneration were most frequently diagnosed as causing the white noise field defects. Finally, some preliminary estimates of the costs and benefit of this study are presented.

Adolescent↗