Biomedical subjects
Publications and source records attributed to L A Novikova.
The authors analyze the results of vision acuity estimation with the use of visual evoked potentials (VEP) and Ye. M. Orlova's table in infants with amblyopia due to strabismus or impaired refraction. The results of electrophysiologic and clinical examinations correlated in 80 percent of cases, this proving the desirability of the VEP method for assessment of the vision acuity in infants.
Visual evoked potentials to reversed chess patterns have been examined in children with dysbinocular and refraction amblyopia of varying severity before and after pleoptic treatment. This method appears to be helpful for the prediction of the visual results and for monitoring the vision acuity restoration during the treatment of amblyopia in children.
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For the analysis of plastic rearrangements in the visual system under the influence of different conditions of adaptation and early deprivation of objective vision, VEPs to checkerboard patterns with various check sizes were studied in subjects with normal vision and with amblyopia resulting from a congenital cataract. Sensitivity of P 180-230 component to the check sizes was revealed as well as a shift of its optimum toward bigger sizes following a transition from the light to the dark adaptation. In amblyopic subjects, in response to the checkerboard patterns the amplitude of P 80-120 component significantly increased, whereas that of P 180-230 decreased, with a shift of its optimum toward bigger check sizes. Informational significance of VEP waves and possible mechanisms of amblyopia are discussed.
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EPs elicited by diffuse light flashes and check patterns, were studied in children and juveniles with congenital and traumatic cataract, during different periods and various durations of deprivation, as well as in a control group of children and juveniles with normal vision. Specific age characteristics were found in the EPs to check patterns in seven years-old children. In children with congenital cataracts significant changes in the shape and amplitude-temporal EP parameters were recorded. In children with traumatic cataracts, presumably developed after the end of the sensitive period, the changes in EPs were much less pronounced. The obtained data are discussed from the point of view of the duration of the sensitive period of the formation of the visual function in humans and of informative value of different EP components.
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The human visual system is the most sensitive to the deprivation of the object vision up to the age of 7, when the amblyopia produced by congenital or traumatic cataract develops in all cases and is "relatively" sensitive during the period from 7 to 15 years, when probability of amblyopia development and its degree are determined by the age of cataract appearance and duration of its existence. Visual deprivation taking place after 15 years does not lead to ambliopy. The data on visual evoked potentials (VEP) obtained during stimulation of the ambyopic and the second, intact eye are used in discussion of the neurophysiological mechanisms of the unilateral visual deprivation and of informative importance of VEP.
Auditory evoked potentials (AEP) elicited by acoustic stimuli of various frequencies and intensities were studied in children aged from three to sixteen years. With age, peak latencies of the AEP components decrease on the average (taking into account the differences of such changes depending on the frequency and intensity of the stimuli presented) by 67.6 +/- +/- 13; 82.0 +/- 7.5; 65.6 +/- 7.2; 32.3 +/- 6.7 ms for components P1, N1, P2, N2 respectively. In 90% of the cases the thresholds of auditory sensations coincided with AEP thresholds; in 10% of the cases the thresholds of electrocortical reactions were by 5 dB lower than those of the auditory sensations. Enhancement of the stimulus to 80 dB lead to an increase of the AEP amplitude, while further augmentation of stimulus intensity in most cases resulted in a decrease of the AEP amplitude which was accompanied by unpleasant sensations or preceded their appearance. The frequency of this phenomenon drops with the age from 90% in 3-4 years old children, down to 30% in juveniles 15-16 years old.
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A study was made of EP recorded in the visual projection area of the cerebral cortex in children with normal sight and in those with disturbed refraction when presented with blank and checkered patterns, the dimensions of the chess squares equalling 10, 20, 40, 60 and 120 angular minutes. In children with normal sight the patterns were defocussed by eyeglass lenses of --1 to +/- 6 dioptries. The investigation revealed a different EP configuration on the presentation of blank and checkered patterns. There was a similarity between the EP change when a blank pattern was replaced by a checkered one, and when the checkered pattern was made sharper. It is assumed that these EP changes results from enhanced lateral inhibition due to the contrast boundaries of the checkered pattern, The experiments carried out on children with disturbed refraction indicated that the maximal EP amplitude corresponded to the optimal optic correction, which shows that theuse of EP is a promising cue in determing vision acuity.