Search PubMed⌕ Search

Biomedical subjects

E Zrenner

Publications and source records attributed to E Zrenner.

At least 55 records · Page 3Linked to original sources
PubMed2000

L- and M-cone driven ERGs are differently altered in Best's macular dystrophy.

To study the L- and M-cone pathways and their interactions in patients with Best's macular dystrophy (BMD), ERG response thresholds were measured to stimuli which modulated exclusively the L- or the M-cones, or both in various combinations. The ERG threshold data could be described with a vector addition model. Compared with normals, BMD patients showed generally larger amplitudes of the L-cone driven ERGs. However, the M-cone driven ERGs were similar in amplitude but significantly phase advanced. The data confirm our previous observations that L- and M-cone pathways can be affected differently by retinal degeneration, despite their large physiological and biochemical similarities.

Adolescent↗
PubMed2000

Continuous monitoring of the stimulated area in multifocal ERG.

INTRODUCTION: Multifocal electroretinography (MF-ERG) is widely used in the detection of local retinal dysfunction. However, the position of the stimulus on the retina and the stability of fixation are usually not directly accessible. Thus, devices have been designed for a continuous fundus visualization during recording. METHODS: MF-ERGs were recorded with a RetiScan system connected to two different Scanning-laser ophthalmoscopes (SLOs) that use either a red (633 nm) or green (415 nm) laser for stimulation, and a VERIS 4 system connected to a piggyback stimulator prototype that added the stimulus to the optical pathway of the SLO by means of a wavelength-sensitive mirror. Fundus visualization was achieved with the infrared lasers of the SLOs (780 and 835 nm). RESULTS: The most extensive study so far with a green laser stimulus in a cat model of retinal degeneration demonstrated the capability of the device to detect retinal landmarks and the different stages of degeneration. Also, the advantages of exactly reproducible stimulus positioning for averaging within and comparison between disease groups became apparent. The results with the same setup in transgenic mice suggest a pure cone origin of the responses. In humans, recordings show that fixation is sufficiently good in most subjects. It is not clear yet whether red or green laser stimulation (or both) is preferable. The results with the prototype were very similar to the MF-ERGs obtained with a standard CRT screen. CONCLUSIONS: All three devices allowed us to record MF-ERGs with continuous fundus monitoring. Although further refinements are necessary, it is obvious that fundus controlled methods will improve the reliability of MF-ERG in future research on glaucoma, transplantation studies, and evaluation of gene therapy.

Journal Article↗
PubMed2000

Clinical applications of multifocal electroretinography.

The multifocal ERG using the m-sequence stimulation technique allows the derivation of 61 - 241 local ERG signals in a central visual field of about 60 degree diameter in a short time between 4 and 16 min. A recording in a light adapted state offers local information comparable to cone responses in the full-field ERG. Retinal functional losses due to regional disorders in outer retinal layers can be described in detail with this technique. In maculopathies decreased or absent central ERGs are found surrounded by normal ERG. The extent of the central lesion can be estimated. In diseases of the outer retina the pattern of distribution of multifocal ERG activity is similar to the the pattern of the visual field defect. In addition to decreased ERG amplitudes a delay of implicit time may be an important sign of pathology, i.e. the pronounced delay of implicit times in the periphery in retinitis pigmentosa and the implicit time delays in regions associated with retinal edema like CRVO and cystoid macula edema in intermediate uveitis. No simple correlation of the first order kernel multifocal ERG and field defects could be found in disorders of the ganglion cell layer. The multifocal ERG is therefore useful in the differential diagnosis of retinal and optic nerve diseases.

Diabetic Retinopathy↗
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↗
PubMed2000

[Carcinoma-associated retinopathy: a review with clinical examples].

Cancer-associated retinopathy (CAR) is a rare paraneoplastic syndrome. In this survey we report about two further patients with CAR, who were referred to the University Eye Hospital of Tuebingen within a few months. The most common primary tumor associated with CAR is small cell carcinoma of the lung. Case reports about rhabdomyosarcoma, carcinoma of the endometrium, prostate and mamma were also described. The exact pathogenesis of CAR is still unknown. Specific autoantibodies were found against the photoreceptor protein recovering (23-kd retinal CAR antigen). However, this reaction is not present in all patients, and probably other antigens are also involved. Most of the patients experience symptoms of CAR before the primary tumor is detected. Besides glare sensitivity and flashing lights, a rapidly progressive, often asymmetric visual loss may occur. Although paracentral and mid-peripheral scotomas can be found frequently, visual field defects are often quite heterogeneous. Typically, the responses in the electroretinogram (ERG) are markedly reduced, but normal ERGs were also described. The fundus picture in CAR shows sheathing of the retinal vessels, narrowing of the arterioles and clumbing of the retinal pigment epithelium. The prognosis is poor. Frequently there is progression to bilateral loss of vision within a few months. Treatment of the primary tumor does not seem to alter the ocular prognosis. Systemic corticosteroids may be helpful in some patients. Nevertheless, no proven therapeutic regimen is currently available.

Aged↗
PubMed2000

[Cost effectiveness of mass orthoptic screening in kindergarten for early detection of developmental vision disorders].

PURPOSE: Orthoptic screening in the kindergarten is one option to improve early detection of amblyopia in children aged 3 years. The purpose of this study was to analyse the cost-effectiveness of such a screening programme in Germany. METHODS: Based on data from the literature and own experience gained from orthoptic screening in kindergarten a decision-analytic model was developed. According to the model, all children in kindergarten, aged 3 years, who had not been treated for amblyopia before, were subjected to an orthoptic examination. Non-cooperative children were reexamined in kindergarten after one year. Children with positive test results were examined by an ophthalmologist for diagnosis. Effects were measured by the number of newly diagnosed cases of amblyopia, non-obvious strabismus and amblyogenic refractive errors. Direct costs were estimated from a third-party payer perspective. The influence of uncertain model parameters was tested by sensitivity analysis. RESULTS: In the base analysis the cost per orthoptic screening test was DM 15.39. Examination by an ophthalmologist cost DM 71.20. The total cost of the screening programme in all German kindergartens was DM 6.1 million. With a 1.5% age-specific prevalence of undiagnosed cases, a sensitivity of 95% and a specificity of 98%, a total of 4,261 new cases would be detected. The cost-effectiveness ratio was DM 1,421 per case detected. Sensitivity analysis showed considerable influence of prevalence and specificity on the cost-effectiveness ratio. It was more cost-effective to re-screen non-cooperative children in kindergarten than to have them examined by an ophthalmologist straight-away. CONCLUSIONS: The decision-analytic model showed stable results which may serve as a basis for discussion on the implementation of orthoptic screening and for planning a field study.

Amblyopia↗
PubMed2000

Pupil perimetry using M-sequence stimulation technique.

PURPOSE: M-sequence stimulation technique allows mapping of the retinal function by multifocal electroretinographic (ERG) recordings. However, the information provided about visual field is limited to retinal function. Optic nerve diseases and diseases of the higher visual pathways usually show normal multifocal ERGs. Using pupillary responses instead of the electrical retinal responses might enhance the diagnostic possibilities of this system. The problems of local ERG recordings are very similar to those encountered in pupil perimetry: Local stimuli have to be dim to avoid or at least reduce stray-light responses. Dim stimuli, close to the absolute threshold, elicit only subtle pupillomotor responses. Therefore, techniques that are able to detect small focal responses are promising. METHODS: Pupillography was done by means of an infrared video camera and real time image processing (50 Hz) using a custom-designed videoboard in a personal computer (486). Recording conditions: The stimulus was presented on a monitor (75 Hz) in 26 cm distance from the patient's eyes. It contained 37 hexagons in a 25 degrees visual field. Each element changed between black (1.6 cd/m2) and white (160 cd/m2) after a binary M-sequence independently from other elements. Four thousand ninety six different stimulus pictures of 120-msec duration were shown during a single pupillogram recording. Thirty-seven local pupillograms were calculated in a cross-correlation of stimulus sequence and the pupil diameter. RESULTS: The pupillomotor fields in normals showed a shape and sensitivity distribution as known from conventional pupil perimetry techniques. Artificial paracentral scotomas (5 degrees) created by masking different locations could be demonstrated convincingly. Even in patients with optic nerve lesions it was possible to demonstrate visual field defects. CONCLUSIONS: Pupil perimetry using the M-sequence technique is a promising method of objective perimetry that may find its entrance into clinical application.

Adult↗
PubMed2000

Multifocal oscillatory potentials in type 1 diabetes without retinopathy.

PURPOSE: To study multifocal recordings of oscillatory potentials (m-OPs) in diabetic (Type 1) eyes that have no visible fundus alterations, to ascertain whether topographical changes in sensitivity are evident when compared with recordings from control subjects. METHODS: The Visual Evoked Response Imaging System (VERIS; EDI, San Diego, CA) system was used to elicit m-OPs from 61 independent areas, subtending the central 30 degrees of the retina, from 24 eyes of 12 patients with diabetes without retinopathy and from 26 eyes of 14 control subjects. For each group of subjects, the mean first- and second-order (first slice) kernel components of the responses for one eye, randomly chosen from each subject, were analyzed and compared for a retinal ring analysis and for an analysis of retinal quadrants. RESULTS: Both first- and second-order kernel responses of the diabetic group show significant delays in the implicit times of some of the m-OPs, compared with those of the control group. No significant changes in amplitude were found. For the first-order component, significant differences are found for both potentials between 5 degrees and 22 degrees eccentricity, for the nasal retina, and for one of the potentials for the remaining retinal areas. In the second-order kernel responses, the differences are significant for two of the three potentials in the midperiphery between 5 degrees and 13 degrees eccentricity, with the central potential being significantly delayed in all rings and quadrants. CONCLUSIONS: Patients with diabetes without retinopathy show prolonged latencies in m-OP recordings. This indicates an alteration in inner retinal sensitivity that can be explained by an impaired rod-cone interaction.

Adolescent↗
PubMed2000

Cost-effectiveness of orthoptic screening in kindergarten: a decision-analytic model.

PURPOSE: The purpose of this study was to analyze the cost-effectiveness of orthoptic screening for amblyopia in kindergarten. METHODS: A decision-analytic model was used. In this model all kindergarten children in Germany aged 3 years were examined by an orthoptist. Children with positive screening results were referred to an ophthalmologist for diagnosis. The number of newly diagnosed cases of amblyopia, amblyogenic non-obvious strabismus and amblyogenic refractive errors was used as the measure of effectiveness. Direct costs were measured form a third-party payer perspective. Data for model parameters were obtained from the literature and from own measurements in kindergartens. A base analysis was performed using median parameter values. The influence of uncertain parameters was tested in sensitivity analyses. RESULTS: According to the base analysis, the cost of one orthoptic screening test was 7.87 euro. One ophthalmologic examination cost 36.40 euro. The total cost of the screening program in all kindergartens was 3.1 million euro. A total of 4,261 new cases would be detected. The cost-effectiveness ratio was 727 euro per case detected. Sensitivity analysis showed considerable influence of the prevalence rate of target conditions and of the specificity of the orthopic examination on the cost-effectiveness ratio. CONCLUSIONS: This analysis provides information which is useful for discussion about the implementation of orthoptic screening and for planning a field study.

Amblyopia↗
PubMed2000

Genetics and phenotypes of RPE65 mutations in inherited retinal degeneration.

PURPOSE: To characterize the spectrum of RPE65 mutations present in 453 patients with retinal dystrophy with an interest in understanding the range of functional deficits attributable to sequence variants in this gene. METHODS: The 14 exons of RPE65 were amplified by polymerase chain reaction (PCR) from patients' DNA and analyzed for sequence changes by single-strand conformation polymorphism (SSCP) and direct sequencing. Haplotype analysis was performed using RPE65 intragenic polymorphisms. Patients were examined clinically and with visual function tests. RESULTS: Twenty-one different disease-associated DNA sequence changes predicting missense or nonsense point mutations, insertions, deletions, and splice site defects in RPE65 were identified in 20 patients in homozygous or compound heterozygous form. In one patient, paternal uniparental isodisomy (UPD) of chromosome 1 resulted in homozygosity for a probable functional null allele. Eight of the disease-associated mutations (Y79H, E95Q, E102X, D167Y, 669delCA, IVS7+4a-->g, G436V, and G528V) and one mutation likely to be associated with disease (IVS6+5g-->a) have not been reported previously. The most commonly occurring sequence variant identified in the patients studied was the IVS1+5g-->a mutation, accounting for 9 of 40 (22.5%) total disease alleles. This splice site mutation, as well as R91W, the most common missense mutation, exists on at least two different genetic backgrounds. The phenotype resulting from RPE65 mutations appears to be relatively uniform and independent of mutation class, suggesting that most missense mutations (15 of 40 disease alleles [37.5%]) result in loss of function. At young ages, this group of patients has somewhat better subjective visual capacity than is typically associated with Leber congenital amaurosis (LCA) type I, with a number of patients retaining some useful visual function beyond the second decade of life. CONCLUSIONS: RPE65 mutations account for a significant percentage (11.4%) of disease alleles in patients with early-onset retinal degeneration. The identification and characterization of patients with RPE65 mutations is likely to represent an important resource for future trials of rational therapies for retinal degeneration.

Adolescent↗
PubMed2000

Continuous monitoring of the stimulated area in multifocal ERG.

INTRODUCTION: Multifocal electroretinography (MF-ERG) is widely used in the detection of local retinal dysfunction. However, the position of the stimulus on the retina and the stability of fixation are usually not directly accessible. Thus, devices have been designed for a continuous fundus visualization during recording. METHODS: MF-ERGs were recorded with a RetiScan system connected to two different Scanning-laser ophthalmoscopes (SLOs) that use either a red (633 nm) or green (415 nm) laser for stimulation, and a VERIS 4 system connected to a piggyback stimulator prototype that added the stimulus to the optical pathway of the SLO by means of a wavelength-sensitive mirror. Fundus visualization was achieved with the infrared lasers of the SLOs (780 and 835 nm). RESULTS: The most extensive study so far with a green laser stimulus in a cat model of retinal degeneration demonstrated the capability of the device to detect retinal landmarks and the different stages of degeneration. Also, the advantages of exactly reproducible stimulus positioning for averaging within and comparison between disease groups became apparent. The results with the same setup in transgenic mice suggest a pure cone origin of the responses. In humans, recordings show that fixation is sufficiently good in most subjects. It is not clear yet whether red or green laser stimulation (or both) is preferable. The results with the prototype were very similar to the MF-ERGs obtained with a standard CRT screen. CONCLUSIONS: All three devices allowed us to record MF-ERGs with continuous fundus monitoring. Although further refinements are necessary, it is obvious that fundus controlled methods will improve the reliability of MF-ERG in future research on glaucoma, transplantation studies, and evaluation of gene therapy.

Animals↗
PubMed1999

Selective loss of cone function in mice lacking the cyclic nucleotide-gated channel CNG3.

Two types of photoreceptors, rods and cones, coexist in the vertebrate retina. An in-depth analysis of the retinal circuitry that transmits rod and cone signals has been hampered by the presence of intimate physical and functional connections between rod and cone pathways. By deleting the cyclic nucleotide-gated channel CNG3 we have generated a mouse lacking any cone-mediated photoresponse. In contrast, the rod pathway is completely intact in CNG3-deficient mice. The functional loss of cone function correlates with a progressive degeneration of cone photoreceptors but not of other retinal cell types. CNG3-deficient mice provide an animal model to dissect unequivocally the contribution of rod and cone pathways for normal retinal function.

Animals↗
PubMed1999

Twelve novel myosin VIIA mutations in 34 patients with Usher syndrome type I: confirmation of genetic heterogeneity.

Usher syndrome is a heterogeneous autosomal recessive trait and the most common cause of hereditary deaf-blindness. Usher syndrome type I (USH1) is characterised by profound congenital sensorineural hearing loss, vestibular dysfunction, and prepubertal onset of retinitis pigmentosa. Of the at least six different loci for USH1, USH1B maps on chromosome 11q13, and the MYO7A gene has been shown to be defective in USH1B. MYO7A encodes myosin VIIA, an unconventional myosin, and it consists of 48 coding exons. In this study, MYO7A was analysed in 34 unrelated Usher type I patients by single-strand conformation polymorphism analysis and direct sequencing. We identified a total of 12 novel and unique mutations, all single base changes. In addition, we found a previously reported nonsense mutation (C31X) on nine alleles of a total of six patients from Denmark.

Chromosome Mapping↗
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

Evaluation of the Night Vision Spectacles on patients with impaired night vision.

BACKGROUND: The Night Vision Spectacles (NiViS) were developed by a consortium of European companies to assist individuals who suffer from impaired night vision. They consist of a head-mounted video camera (input) and binocular displays (output) connected to a portable computer processor, which uses an algorithm to enhance the luminance and contrast of the video image. METHODS: Eighteen patients with impaired night vision were tested, including those with retinitis pigmentosa (7), Usher syndrome (2), fundus albipunctatus (1) and complete (4) and incomplete (4) congenital stationary night blindness. Normal trichromats (3) and typical, complete achromats (2) acted as controls. A battery of tests assessed: visual acuity at 5 m (projection unit) and 1 m (chart) and at high and low contrasts; contrast sensitivity; absolute and increment threshold; the influence of glare; contrast motion detection; and hand-eye performance. The tests were performed, with and without the NiViS, at three adaptation levels: low scotopic (10(-3) cd/m2), high scotopic (10(-2) cd/m2) and mesopic (10(-1) cd/m2). RESULTS: At the low and high scotopic levels, the majority of patients showed improved performance on the visual acuity, contrast sensitivity and motion contrast tests with the NiViS. At the mesopic level, the advantage with the NiViS was greatly reduced, but still present for contrast sensitivity. CONCLUSION: Patients with impaired night vision can benefit from the NiViS when performing tasks involving contrast and motion perception. Those with normal visual fields and retaining good photopic vision will benefit more than those with constricted visual fields and impaired cone vision. Recommendations regarding desirable improvements of the NiViS and suitability for the individual patient are given.

Adolescent↗
PubMed1999

Comparative study of visual, auditory, and olfactory function in Usher syndrome.

BACKGROUND: Usher syndrome is a genotypically and phenotypically heterogeneous group of autosomal recessive diseases featuring retinitis pigmentosa (RP) and sensorineural hearing loss. A general ciliary dysfunction has been suspected following reports of a mutated cytoskeletal protein (myosin VIIA) in type IB, and preliminary data has suggested an olfactory deficit. The purpose of this study was to quantitatively assess olfactory function in Usher syndrome patients and to search for a correlation between the degree of impairment of the three sensory systems as indication of an underlying ciliary defect. METHODS: 39 patients with Usher syndrome (8 type I, 31 type II) were examined. The ophthalmologic protocol included patient history, visual acuity, eye morphology, Goldmann perimetry, and electroretinography. The ENT protocol included a thorough examination, speech-recognition test, pure-tone audiometry and an olfactory function test. RESULTS: In both groups, visual acuity was typically 20/40, the remaining visual field area was small, and the ERG responses were low to non-detectable. Average hearing loss was 100% in type I and 40% in type II. Olfactory thresholds were normal [median 9.7 (I) and 8.5 (II) vs. 8.5 in the control group]. There were multiple significant correlations between parameters of the same organ, but no relationship between parameters of different sensory systems. CONCLUSION: Almost all Usher syndrome patients in this study had an advanced form of RP. In contrast, auditory function differed considerably between type I and type II. An impairment of the olfactory system could not be detected, and there was no correlation between parameters representing visual function, hearing ability, and olfactory sense.

Adult↗