1,720,961 research outputs found
Spectral Analysis of Pendular Waveforms in Congenital Nystagmus
No full textWe analyzed quantitatively electronystagmographic recordings of pendular waveforms via spectral analysis methods. We found (1) symmetrical pendular oscillations in orbital positions spanning a range as wide as 40°, with frequencies between 2 and 8 Hz; (2) stable and small pendular oscillations in patients without a null zone and unstable and large pendular oscillations in patients with a neutral zone; (3) a non-decreasing relationship between the amplitude and the frequency of the eye oscillations, and (4) pendular components in orbital positions at the two sides of a neutral zone. It is argued that pendular nystagmus can be generated independently of normal (jerk) nystagmus in the same orbital position
Computer-analysis of Eng Spectral Features From Patients With Congenital Nystagmus
No full textPower spectral estimation,from electronystagmographic recording of eye position is proposed as a simple digital processing method to quantify both the amplitude and the frequency features of eye motion in patients affected by the oculomotor disorder of congenital nystagmus (CN). Di$erent basic wave shapes clinically identified and studied in the literature are shown to have slightly different power .spectra, which ran be used to characterize the CN disorder from nystagmus waveforms. This
treatment, statistical in nature, does not depend strongly on the detailed structure of each recorded wave shape, thus emphasizing that accurate descriptive analysis of all patient’s waveforms characteristics adds little to the comprehension of CN. We show that the power spectral estimation also represents a useful tool in modelling both the CN defect and the non-defective oculomotor
Jystem, and in assessing the effect of the surgical treatment of CN through the differences in the power spectra before and after surgery
On the Variations of the Time Constant of the Slow-Phase Eye Movements Produced by Surgical Therapy of Congenital Nystagmus: A Preliminary Report
No full textAmount of Surgery in Congenital Nystagmus
No full textBy analyzing the clinical data on the amount of surgery on the extraocular muscles and resulting angular shift of the null zone in 24 patients with congenital nystagmus, a linear dependence was found to exist between these two variables. Hence, the amount of surgery can be confidently established in advance of treatment in order to obtain the shift of the null zone. Many cases of partial surgical successes are discussed and explained a posteriori by a lack of a proper amount of surgical rotation
Association of ataxia-telangiectasia and progressive muscular dystrophy. Clinico-biological study of a case.
No full textFrequency distribution of the time interval between quick phase nystagmic eye movements
No full textWe measured the frequency distribution of the time interval between quick phases of nystagmic eye movements in 8 patients with congenital nystagmus. For each patient we recorded a 3- to 4-second long electro-oculographic (EOG) signal, repeating each session 22 times. The period of the nystagmic cycles was computed for each record, by evaluating the peak frequency of the nystagmic oscillations via spectral analysis of the EOGs. This period is a measure of the time interval between quick phases. Its distribution ranged between 100 and 600 ms and peaked at about 240 +/- 50 ms, with a gaussian shape for values less than about 300 ms. Our measurements were considered as providing the distribution of intersaccadic latencies in normal humans
Spectral-analysis of Dual Jerk Wave-forms In Congenital Nystagmus
No full textCongenital nystagmus (CN) is a disorder of the ocular motility characterized by oscillatory eye movements preventing the correct fixation of a target. Many typical waveforms of eye position recordings have been recognized and classified in the literature: in jerk CN a slow phase eye movement is followed by a fast phase, giving rise to a typical saw-tooth waveform, while in pendular CN the eyes exhibit a periodic motion, giving rise to an approximately sinusoidal waveform. Dual jerk waveforms seemed to show small, rapid oscillations superimposed on a jerk-like waveform, thus being originary classified as a mixture of jerk and pendular CN. On the contrary, a theoretical model of CN has appeared recently, which suggests a possible interpretation of the small amplitude oscillations in dual jerk waveforms as consecutive pieces of growing and decaying exponentials.
By spectral analysis of dual jerk waveforms in a number of patients with CN, we show that the oscillations are truly sinusoidal in nature, thus suggesting the possibility of a different explanation of dual jerk waveforms in CN
Quantitative photoacoustic spectroscopy of cataractous human lenses
No full textQuantitativephotoacoustic spectra of the nuclei of cataractoushumanlenses with various degrees of colouration and opacification were measured in the spectral range 250 – 600 nm. The lens nuclei were obtained from 20 cataractous patients through extracapsular cataract extraction. These measurements yield the light loss per unit path length in the nucleus of cataractouslenses
Electro-oculographic measurement of the time constant of slow phase eye movements in congenital nystagmus
No full textA recent model of the defective oculomotor system producing congenital nystagmus emphasizes that the time constant of the slow-phase eye movements of jerk nystagmus represents a useful parameter in the quantification of the effects of the surgical therapy, since it is directly related to the patient's potential for good visual acuity. The authors analyzed preoperative and postoperative electrooculographic records from five patients with congenital nystagmus and estimated the average time constant of the slow-phase eye movements over seven gaze angles for each patient. This model's parameter was shown experimentally to be a valid tool in monitoring the surgical effects, validating the theoretical indication
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