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Biomedical subjects

E Zrenner

Publications and source records attributed to E Zrenner.

At least 91 records · Page 5Linked to original sources
PubMed1998

[Diagnostic error in Leber's optic neuropathy. Value of clinical and molecular genetic studies].

BACKGROUND: Leber's hereditary optic neuropathy is associated with point mutations in the mitochondrial DNA (mtDNA) that appear to be pathogenic for this disease. These mutations affect nucleotide positions 3460, 11,778 and 14,484. MATERIALS AND METHODS: We reviewed the clinical and molecular genetic characteristics of 29 visually symptomatic patients with the clinical diagnosis of LHON. RESULTS: Nine patients really suffered from LHON, but in 20 patients other ocular diseases could be proven. Degeneration of the retina and choroid was most common (seven patients), followed by vascular optic disease (six patients). Three patients suffered from tobacco-alcohol amblyopia, two from optic neuritis and two from autosomal dominant optic neuropathy. CONCLUSIONS: The clinical diagnosis of LHON is strengthened by a proven maternal inheritance and clinical signs such as a severe decrease in visual acuity, central or centrocecal scotomas in the perimetry and pseudoedema of the optic disc, followed by optic atrophy. Pathognomonic clinical signs of LHON are twisted vessels and ectatic capillaries in the fundus of these patients and their relatives of the maternal line, i.e., peripapillary microangiopathy. A careful analysis of the patients' pedigrees, anamnesis and the functional and morphological results of the clinical examinations helps to avoid misdiagnosis of the disease. However, the expensive and time-consuming molecular genetic analysis is always necessary to confirm or exclude the diagnosis of LHON.

Adult↗
PubMed1998

A computer-controlled system for measuring dark adaptation and other psychophysical functions.

BACKGROUND: Psychophysical thresholds, including dark-adaptation functions and increment threshold sensitivities, are useful for the early detection and diagnosis of visual pathologies. However, few instruments have been designed or adapted for their routine clinical measurement. METHODS: Here we describe an instrument prototype designed to meet this need, which we refer to as the PULS (Programmier-barer Universeller Licht-Stimulator). The instrument is computer-controlled and fully automated. It allows direct control over target location, luminance, size, duration and temporal profile and over background luminance and spectral composition. It also incorporates an efficient and statistically rigorous strategy for determining threshold. RESULTS: We present examples of psychophysical functions-dark-adaptation curves, increment threshold sensitivities, estimates of temporal summation in the dark and during the time course of dark adaptation-which have been measured by the PULS prototype in normal observers and clinical patients. CONCLUSIONS: The PULS instrument provides an automatic and efficient means of measuring dark adaptation and other psychophysical functions. It determines threshold by a more rigorous and faster method than is conventionally employed in clinical adaptometry.

Adolescent↗
PubMed1998

Prognostic value of the pattern electroretinogram in cases of tumors affecting the optic pathway.

BACKGROUND: Tumors compressing the optic pathway may lead to irreversible loss of vision which may be detected by the pattern electroretinogram (PERG) because of its relation to ganglion cell function. METHODS: Eyes of 19 patients were tested shortly before and 5-10 days after tumor surgery. Visual acuity, the 30-deg visual field and the transient and steady-state pattern reversal ERG were measured. RESULTS: Using patterns of 1.5 x 1.2 deg there was a good correlation between the change of pre- and post-surgical visual performance and most of the pattern ERG amplitudes. For all variables tested--P50, N95- and steady-state amplitude--there was a critical value beyond which the visual outcome could be bad or favorable, whereas patients showing higher amplitudes always remained stable or improved after surgery. CONCLUSION: The positive correlation between pattern ERG amplitudes and the post-surgical outcome in the case of tumors affecting the optic pathway may be helpful in predicting the outcome for these patients.

Adolescent↗
PubMed1998

Ocular symptoms in association with antiphospholipid antibodies.

OBJECTIVE: To describe the clinical and serologic findings of 50 antiphospholipid antibody (APA)-positive patients within a retrospective study. METHODS: Measurement of visual acuity, slit-lamp biomicroscopy, tonometry, fundus examination and perimetry. Laboratory tests were performed for detection of APA against thromboplastin and cardiolipin. Antinuclear antibodies (ANA), antibodies to dsDNA, antithyroidal and antiparietal antibodies were also tested. RESULTS: A combination of both transient and permanent visual disturbances was noticed in more than half of the patients. Transient visual disturbances included transient blurred vision, partial defects of the visual fields and amaurosis fugax. The most frequent permanent abnormalities were optic atrophy in 20 patients, due to AION in 9 cases, and disturbances of the choroidal circulation in 17 patients. Fourty-six patients had positive levels of thromboplastin APA; cardiolipin APA were found to be increased in 36 patients. CONCLUSIONS: We did not find a clear correlation between APA activity or the immunoglobulin classes in the individual and the severity of the ocular disease. The benefit from a therapy with the antiplatelet agent acetylsalicylic acid was evident in a reduction of the patients' transient visual disturbances and, in most cases, no further progression of permanent visual field defects was observed.

Adolescent↗
PubMed1998

Multifocal electroretinography in retinitis pigmentosa.

PURPOSE: To investigate the diagnostic potential of multifocal electroretinography for the evaluation of retinal affection by retinitis pigmentosa in a clinical setting. METHODS: For this prospective study, multifocal electroretinograms were obtained from 38 patients who matched the inclusion criteria of either a detectable photopic Ganzfeld response or visual fields of 10 degrees or more, and from 30 normal volunteers. Recordings were performed with the visual evoked response imaging system, using a resolution of 61 hexagonal elements within a 30-degree visual field. The results of the left eye of each patient and control subject were used for statistical evaluation by the Mann-Whitney U test. RESULTS: The 38 eligible patients included those with Usher syndrome types I and II (one patient and six patients, respectively) and those with autosomal-recessive (18), X-recessive (two), and autosomal-dominant (11) forms of retinitis pigmentosa. In 27 (71%) of these 38 patients, at least a central response of the multifocal electroretinogram was detectable. Loss of multifocal electroretinogram response density in patients with retinitis pigmentosa was significant (P < .00001) in all five eccentricity groups (concentric rings), with a progression from center to periphery. Implicit time was significantly elevated in the third eccentricity group (P < .0038) and increased further toward the periphery (P < .00001). The results did not differ notably between retinitis pigmentosa subgroups. CONCLUSIONS: Because the multifocal electroretinogram differentiates between affected and nonaffected retinal areas, eccentricity-dependent changes in both amplitude and implicit time were found. It can therefore add to the diagnostic information of many patients with retinitis pigmentosa.

Adolescent↗
PubMed1998

Colour vision in normal subjects tested by the colour arrangement test 'Roth 28-hue desaturated'.

The aim of the study was to obtain normal values for the colour-arrangement test, Roth 28-hue desaturated. In 146 healthy non-smokers colour vision was tested monocularly. The subjects were divided into four age groups: 0-19, 20-39, 40-59, and 60-79 years. The overall error score for all groups was 54 +/- 24 (median +/- mean absolute deviation). The values for the 20-39 year group were significantly lower than those for the other groups (Kruskal-Wallis: P < 0.0001 with subsequent multiple Mann-Whitney test). An increasing predominance of errors along the blue-yellow-axis was observed with increasing age. The error scores of normal subjects tested by the Roth 28-hue desaturated were comparable with those on the well-known Farnsworth-Munsell 100-hue (FM-100). Because the Roth 28-hue desaturated is shorter and simpler to administer, it is an alternative to the FM-100 in situations that need to assess colour discrimination and error axis quantitatively and quickly.

Adolescent↗
PubMed1998

Flicker cone electroretinogram in dichromats and trichromats.

To measure cone signal strengths in the flicker electroretinogram (ERG) of dichromats and trichromats, we developed a set of flickering stimuli (30 Hz), which excite the middle-wavelength-sensitive (M-) and long-wavelength-sensitive (L-) cones independently. ERG responses to eight different ratios of L- to M-cone contrasts were recorded from each subject. The short-wavelength-sensitive (S-) cone contrast was 0% in all measurements. The recordings were Fourier analyzed to determine the amplitude of the fundamental component. ERG threshold values for each subject resulted in ellipses when plotted in an L-/M-cone contrast space. As expected, the orientations of the threshold ellipses of the protanopes (N = 2) were parallel to the L-cone axis, whereas those of the deuteranopes (N = 2) were parallel to the M-cone axis. For the trichromats (N = 5), there was considerable interindividual variation in ellipse orientation.

Adult↗
PubMed1998

Multifocal ERG reveals long distance effects of a local bleach in the retina.

To examine the distribution of ERG-activity in the central visual field after local bleaching of the fovea, multifocal electroretinograms were recorded in eight normal volunteers before, during and after recurrent light exposure. During bleaching (90% bleached pigment), the response density (scalar product) of the foveal area (0-2 degrees eccentricity) decreased from 10.7 +/- 3.5 to 4.1 +/- 1.9 nV/degree2 (P < 0.001). The average activity in the extrafoveal macular area was unchanged, while the amplitudes were frequently (in 53 of 54 areas) enhanced at 5-30.5 degrees eccentricity. Here the average response density changed from 3.1 +/- 0.9 to 3.5 +/- 1.0 nV/degree2 (P < 0.001). A fast recovery of foveal responses after cessation of bleaching occurred. Besides a strong decrease of response in the directly bleached area, local bleaching led to enhanced activity mainly 3-27 degrees distant from the bleached area.

Adaptation, Ocular↗
PubMed1998

Response phase of the flicker electroretinogram (ERG) is influenced by cone excitation strength.

We measured electroretinogram (ERG) response phases at different cone contrasts in trichromats and dichromats to investigate the dynamics of the long-wavelength-sensitive (L-) and middle-wavelength-sensitive (M-) cone pathways. ERG responses to stimuli, temporally modulated at 30 Hz, were recorded. The stimuli were generated on a computer controlled colour monitor. Thirty-two different combinations of L- and M-cone excitation strength, expressed as cone contrasts, were presented. The short-wavelength-sensitive (S-) cones were not stimulated (S-cone contrast = 0%). The response phase of the fundamental stimulus component was obtained from Fourier analysis. The ERG response phase lags decreased with increasing cone contrast. This was observed in all subjects with a normal appearing fundus. In dichromats and trichromats at low and intermediate contrasts, the phase lags to M-cone isolating conditions were smaller than those to L-cone isolating stimuli. In one dichromat with extreme myopia and cupping of the optic disc, the ERG phase lags increased with increasing cone contrast. The ERG response phase may be potentially useful for detecting retinal abnormalities.

Color Vision Defects↗
PubMed1998

Spatial cone activity distribution in diseases of the posterior pole determined by multifocal electroretinography.

Thirty patients with a reduced central vision due to diseases of the posterior pole were examined with the VERIS system developed by Sutter and Tran (Vis Res 1992;32:433-446) to characterize the topography of electroretinographic (ERG) changes in comparison to the results in 30 normal volunteers. Diagnoses included Stargardt's macular dystrophy (SMD, n = 10), age-related macular degeneration (AMD, n = 5), cone dystrophy (CD, n = 5), central retinal vein occlusion (CRVO, n = 5), and autosomal dominant optic atrophy (ADOA, n = 5). The 61 local responses obtained from each subjects were grouped by eccentricity to form five concentric rings. The foveal ERG, originating from a central area of 2 degrees radius, was non-recordable or markedly diminished in all patients except those with optic atrophy, where amplitudes were found to be in the normal range. In patients with advanced stages of SMD, functional defects were larger and involved more peripheral areas than in patients with early stages of SMD or with AMD. A reduction of response amplitude even in the most peripheral ring (17-30.5 degrees eccentricity) was found in cone dystrophies and--moderately--in patients with advanced SMD and central retinal vein occlusion only. Prolonged implicit times were found in all but the patients in early stages of SMD and they were maximal in patients with CRVO. This study shows that the multifocal ERG (MFERG) can contribute to differential diagnosis of retinal diseases of the posterior pole especially in cases with a normal photopic Ganzfeld ERG.

Adult↗
PubMed1998

Total colourblindness is caused by mutations in the gene encoding the alpha-subunit of the cone photoreceptor cGMP-gated cation channel.

Total colourblindness (OMIM 216900), also referred to as rod monochromacy (RM) or complete achromatopsia, is a rare, autosomal recessive inherited and congenital disorder characterized by photophobia, reduced visual acuity, nystagmus and the complete inability to discriminate between colours. Electroretinographic recordings show that in RM, rod photoreceptor function is normal, whereas cone photoreceptor responses are absent. The locus for RM has been mapped to chromosome 2q11 (ref. 2), however the gene underlying RM has not yet been identified. Recently, a suitable candidate gene, CNGA3, encoding the alpha-subunit of the cone photoreceptor cGMP-gated cation channel, a key component of the phototransduction pathway, has been cloned and assigned to human chromosome 2q11 (refs 3,4). We report the identification of missense mutations in CNGA3 in five families with RM. Homozygous mutations are present in two families, whereas the remaining families show compound heterozygous mutations. In all cases, the segregation pattern of the mutations is consistent with the autosomal recessive inheritance of the disease and all mutations affect amino acids that are highly conserved among cyclic nucleotide gated channels (CNG) in various species. This is the first report of a colour vision disorder caused by defects other than mutations in the cone pigment genes, and implies at least in this instance a common genetic basis for phototransduction in the three different cone photoreceptors of the human retina.

Base Sequence↗
PubMed1998

An L-type calcium-channel gene mutated in incomplete X-linked congenital stationary night blindness.

The locus for the incomplete form of X-linked congenital stationary night blindness (CSNB2) maps to a 1.1-Mb region in Xp11.23 between markers DXS722 and DXS255. We identified a retina-specific calcium channel alpha1-subunit gene (CACNA1F) in this region, consisting of 48 exons encoding 1966 amino acids and showing high homology to L-type calcium channel alpha1-subunits. Mutation analysis in 13 families with CSNB2 revealed nine different mutations in 10 families, including three nonsense and one frameshift mutation. These data indicate that aberrations in a voltage-gated calcium channel, presumably causing a decrease in neurotransmitter release from photoreceptor presynaptic terminals, are a frequent cause of CSNB2.

Amino Acid Sequence↗
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↗
PubMed1998

[Multifocal electroretinography in acquired macular dysfunction].

BACKGROUND: Multifocal electroretinography allows physiological mapping of the central retina. The purpose of this study was to describe the spatial distribution of ERG-activity in patients with impairment of macular function which usually do not exhibit a pathologic Ganzfeld-ERG. SUBJECTS AND METHODS: 6 patients with macular lesions due to uveitis (4), retinitis centralis serosa (1), and contusio bulbi (1) were examined using the multifocal ERG technique. RESULTS: In normal volunteers the response density of the multifocal ERG decreased with eccentricity according to cone density distribution. In eyes with impaired central vision the foveal and macular responses were markedly diminished while surrounding signals were of normal or moderately decreased amplitudes. CONCLUSIONS: With the multifocal ERG disturbances of macular function due to oedema and secondary structural changes were detected in the presented cases and the extension of the central lesions was estimated.

Adolescent↗
PubMed1998

Multifocal electroretinography in patients with Stargardt's macular dystrophy.

AIMS: To describe the topography of multifocal electroretinograms (ERGs) and to explore its diagnostic value in patients with Stargardt's macular dystrophy (SMD). METHODS: 51 patients with SMD were examined by means of the m-sequence technique to characterise the topography of electroretinographic responses in the central visual field. The results were compared with data from 30 normal volunteers. RESULTS: In 49 of 51 patients with SMD, macular electroretinographic activity was markedly diminished or non-detectable. Towards more peripheral areas, ERG responses of the SMD patients approached those of normals. Implicit times were not markedly delayed at any eccentricity. CONCLUSION: In contrast with Ganzfeld electroretinography, multifocal electroretinography is useful to detect foveal dysfunction in SMD. Areas of dysfunction were found to be usually larger than expected from psychophysical measurements and morphological alteration. In early stages of the disease it was possible to detect foveal dysfunction, even in patients lacking morphological fundus changes and with good visual acuity.

Adolescent↗
PubMed1998

The role of the peripherin/RDS gene in retinal dystrophies.

Peripherin/RDS is a transmembrane glycoprotein expressed in vertebrate photoreceptors. It is located at the rim of the disc membranes of the photoreceptor outer segments, where it is thought to play an important role in folding and stacking of the discs. Initially, the identification of a mutation in the rds mouse model defined the role of this gene in hereditary retinal dystrophies. To date over 60 different mutations have been reported in human retinal diseases, with most being restricted to single families. A characteristic of mutations in the peripherin/RDS gene is the broad phenotypic spectrum in patients, and the variability in clinical expression, even within families. Thus, genotype-phenotype correlations are difficult and only reliable for a minority of mutations.

Animals↗
PubMed1998

Implicit time topography of multifocal electroretinograms.

PURPOSE: To describe the implicit time topography of multifocal electroretinograms in normal subjects and to examine the change in this topography in patients affected by retinitis pigmentosa. METHODS: Thirty normal subjects and 38 patients with retinitis pigmentosa were examined with the Visual Evoked Response Imaging System using 61 hexagonal elements within a visual field of 30 degrees radius. The peak implicit times of the 61 first-order kernels (which are analogues of the photopic electroretinogram [ERG]) were measured to determine their distribution across the retina. RESULTS: Implicit times had a low interindividual variability in the normal group. High implicit times were found at the blind spot, the upper and lower borders of the stimulated field, and the macula. Low values were present in the area encircling the macula and were most prominent in the temporal retina. In the group with retinitis pigmentosa, implicit times were unchanged in the central region but were prolonged in the peripheral regions. CONCLUSIONS: The spatial distribution of multifocal ERG implicit times in a normal population follows a specific topographical pattern across the retina. This pattern has to be taken into account when interpreting results in patients. Deviations in retinitis pigmentosa were found, and they show the potential for diagnostic use.

Adolescent↗