Beat-to-beat variability of nystagmus. A clinical study.
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Adult↗
Biomedical subjects
M Juhola
Publications and source records attributed to M Juhola.
An identification technique for the spike artefact of saccadic eye movements.
Many subjects have a negative spike in the beginning of a saccade in electro-oculographic signals. The amplitude of the spike depends on the location of the electrodes. The spike distorts the saccades and causes errors in the parameters. The saccade spike can assist in the identification of small saccades. A syntactic technique based on formal languages and parsing is presented which looks for spikes from the electro-oculographic signal. For calculation of the algorithm, saccades from the photoelectric signal have been concurrently recorded and compared with the electro-oculographic signal.
Algorithms↗
Effect of sampling frequencies on the velocity of slow and fast phases of nystagmus.
A computer analysis of slow and fast phase of velocity of nystagmus is presented. Several methodological factors are known to affect the computation of velocities, such as sampling frequencies, cutoff frequencies of the differentiation method, and resolution in bits of analog-digital conversion. A simulated signal without noise was first applied in nystagmus data in order to study maximum velocities at the theoretical level. Electro-oculographic postrotational nystagmus movements were then examined to test theoretical results. It was shown that the sampling frequency ought to be 400 Hz at least, the cutoff frequency about 70 Hz, and the resolution of analog-digital conversion 12 bits or higher.
Diagnosis, Computer-Assisted↗
The effect of digital lowpass filters on the maximum velocity of saccadic eye movements.
The present paper is a study of how the inaccuracy of coefficients of digital lowpass filters may distort the maximum angular velocities of saccadic eye movements. Maximum velocity is one of the most important parameters of saccades. There are several diseases which decrease the maximum velocities of saccades. It was investigated how a fourth order Butterworth lowpass filter can affect maximum velocities. The lowpass filter has been tested by simulation as well as real eye movement data recorded electro-oculographically and photoelectrically. The coefficients of digital lowpass filters should be computed and applied with sufficient accuracy to prevent filters from altering the maximum velocities a phenomenon which might lead to erroneous diagnosis.
Computer Simulation↗
Analysis of saccadic eye movements with a microcomputer.
This analysis of saccadic eye movements has found use in clinical diagnosis. Saccades are induced by a microcomputer-controlled TV stimulator and are recorded by electro-oculography. The analysis algorithm detects saccades by the velocity profile of eye position and then computes the principal saccadic parameters, peak velocity and amplitude. In addition, the saccades are presented on the VDU screen, together with the computed results of the analysis; they may be edited if necessary. The programs have been implemented in Pascal and Assembler languages.
Computers↗
Visual stimulator for eye movement studies based on a microcomputer system.
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Child↗
Detection of saccadic eye movements using a non-recursive adaptive digital filter.
Saccadic eye movements provide important information about the neuron system at several levels. In recent years computer analysis of saccades has been adapted for use in clinical work. The most common detection methods do not always function without the user's control and aid. In the present paper a digital filter is described for the detection of saccades. This non-recursive filter unscrambles saccade data which has been collected during the execution of an algorithm. The method is suitable for use with microcomputers. The filter is adaptive. Two concise experiments using the method are described.
Biometry↗
Intra-individual variation in oculomotor performance in man.
Peak velocity of saccade, maximum velocity of smooth pursuit, and peak velocity of slow phase of vestibular and optovestibular nystagmus were measured three times daily on three separate days in 6 healthy subjects in order to estimate the intra-individual variation of the results of oculomotor tests. Analysis of variance revealed that the oculomotor performance of the individual subjects varied systematically, depending on whether the tests were performed in the morning, at noon, or late in the afternoon. In particular, the velocity of saccade displayed lowest values in the afternoon. The present results indicate that oculomotor performance may depend on the individual biological rhythm of fatigue; however, it is also possible that eye motor behaviour is coupled to an independent rhythm of motor activity. Circadian rhythmicity of oculomotor performance should be considered in follow-up studies and in examination of patients with reduced vigilance.
Adult↗
Effect of filtering in the computer analysis of saccades.
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Computers↗
On automatic diagnosis of pathological saccadic eye movements.
A syntactic technique is described for the recognition of saccadic eye movements to distinguish normal saccades from those distorted by brain stem lesions. A digitalized eye movement signal is transformed into a sequence of symbols. Eye movements are then found from this sequence by using a parser. This recognition method appropriately enlarged could be applied as a classifier of saccades to aid in diagnosis.
Algorithms↗
A syntactic method for analysis of nystagmus and smooth pursuit eye movement.
Eye movements are studied in neurophysiology, neurology, ophthalmology, and otology both clinically and in research. In this article, a syntactic method for recognition of horizontal nystagmus and smooth pursuit eye movements is presented. Eye movement signals, which are recorded, for example, electro-oculographically, are transformed into symbol strings of context free grammars. These symbol strings are fed to an LR(k) parser, which detects eye movements as sentences of the formal languages produced by these LR(k) grammars. Since LR(k) grammars have been used, the time required by the whole recognition method is directly proportional to the number of symbols in an input string.
Algorithms↗
Motorized head impulse stimulator to determine angular horizontal vestibulo-ocular reflex.
The objective of the current study was to develop a computer-controlled mechanical system for the generation of impulsive head rotations to measure eye movements induced by angular horizontal vestibulo-ocular reflex. This is a clinical eye movement test recently introduced for the usage of otoneurological balance laboratories. We built the system and modified our prior computer software developed for other types of eye movement tests. Motor controlled stimulation has fulfilled the requirement of more uniform and constant acceleration stimulation than obtained with manually administrated impulses. After having executed preliminary experiments at our balance laboratory we found the system to be efficient, reliable and secure.
Acceleration↗
Decision tree induction in the diagnosis of otoneurological diseases.
Expert systems have been applied in medicine as diagnostic aids and education tools. The construction of a knowledge base for an expert system may be a difficult task; to automate this task several machine learning methods have been developed. These methods can be also used in the refinement of knowledge bases for removing inconsistencies and redundancies, and for simplifying decision rules. In this study, decision tree induction was employed to acquire diagnostic knowledge for otoneurological diseases and to extract relevant parameters from the database of an otoneurological expert system ONE. The records of patients with benign positional vertigo, Meniere's disease, sudden deafness, traumatic vertigo, vestibular neuritis and vestibular schwannoma were retrieved from the database of ONE, and for each disease, decision trees were constructed. The study shows that decision tree induction is a useful technique for acquiring diagnostic knowledge for otoneurological diseases and for extracting relevant parameters from a large set of parameters.
Algorithms↗
Clinical evaluation of dysrhythmia of postrotatory nystagmus.
Postrotatory responses of nystagmus were analysed in an exponential model by utilizing linear regression analysis. Four nystagmus qualities (velocity and duration of slow and fast phases) were studied in 10 patients with vestibular peripheral lesions, 10 patients with frontal lobe lesions and 10 patients with brain-stem lesions, together with 10 control subjects. In addition, pauses during the responses were quantified. Patients with frontal lobe lesions differed from other groups by scoring higher values of slow phase velocity and by exhibiting more pauses. The time constant was significantly shorter in patients with brain-stem lesion than in any other group. As regards other qualities, e.g. slow phase duration and fast phase velocity, or duration, no differences were observed. The pathological dysrhythmia may therefore be presented as changes in the gain and time constant of slow phase velocity as well as in pauses during nystagmus. Since all these changes may be encountered in normal subjects, one should be cautious in interpreting these changes as being pathological in each individual case.
Adult↗
An expert system for the computer-aided diagnosis of dizziness and vertigo.
We have developed an expert system to assist in the diagnostic work-up of otoneurological cases. Our otoneurological expert system ONE takes advantage of both patient history and clinical measurement data in order to supply all possible information about the patient's symptoms and other findings. This paper presents ONE after its initial stage of development, which included tests with numerous patients.
Adult↗
An essay on power of expert systems versus human expertise.
In connection with several recent studies of medical informatics, the usefulness and use of expert systems have been both criticized and defended. We have examined the issue of the inference power of expert systems compared to that of human experts. At an abstract level we have shown that there is no doubt that expert systems could successfully complement human experts within strictly limited and well-defined specialties, and actually be of reasonable aid in diagnosis, provided that the expert systems have been correctly and effectively elaborated. Also practical experiments were conducted with our recently implemented expert system.
Brain Diseases↗
Interpretation guidelines of DNA histograms from tissue sections of breast cancer.
BACKGROUND: Evaluation of nuclear DNA staining intensity from histological breast cancer sections has not always been accepted, because of the difficulties in interpreting the histograms. One reason for this is the lack of evidence based interpretation guidelines. MATERIALS AND METHODS: The DNA staining intensity of 140 breast cancer samples was measured with flow cytometry (FCM) and image cytometry (ICM). The methods were compared by using grading efficiency (GE). RESULT: First, the ICM histograms were evaluated with a computer assisted image cytometry system using different cut off points for aneuploidy. The GE results varied from 67.9-76.4%. Subjective interpretation and evaluation according two previously published interpretation methods did not improve the GE. Secondly, we excluded histograms which showed clearly different cell clones in FCM and ICM. The GE of remaining histograms was 77.9%. Comparison of these histograms allowed formulation of interpretation guidelines which improved the GE to 85.3%. CONCLUSIONS: This study suggests that efficient interpretation guidelines of section-based DNA histograms can be created.
Aneuploidy↗