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T Kau

Publications and source records attributed to T Kau.

4 recordsLinked to original sources
PubMed1991

[Normal and disordered visual development with preferential looking].

Normal and disturbed development of grating acuity in preverbal infants has been studied using the Teller acuity card procedure. The results of 195 normal and 34 premature children are in good accordance with those reported in the literature. In more than 86% no interocular differences of grating acuity could be detected in these groups. On the other hand the incidence of interocular acuity differences reached 30% in 37 cases showing monolateral convergent squint. This is much higher than has been reported in current literature and may indicate that grating and Snellen acuity correlate better than expected in infants' squint amblyopia. As to the problem of monitoring early amblyopia therapy by PL, four longitudinal cases are presented.

Amblyopia↗
PubMed1990

[Normal and defective development of visual stimulus processing: psychophysical and electrophysiologic test results].

Two methods were developed for the assessment of normal and disturbed visual development in infancy and early childhood: the preferential looking procedure (PL) as a psychophysical method and measurement of visual evoked potentials (VEP) as an electrophysiological principle. Both methods test visual functions, but on different levels of the visual system. Proper interpretation of the methods requires direct comparison. This was accomplished over a 12-months period in infants and young children with normal and disturbed visual development in the first year of life. For normal infants older than 4 weeks we found accurately configurated VEP responses and rapidly increasing visual accuity, ranging from 0.4 cpd (age 2.5 weeks) to 10 cpd (36 weeks) and better. There was a close agreement between the VEP and PL results, possibly due to our conservative interpretation of VEP acuity, which was not extrapolated from the VEP amplitude versus spatial frequency function, but defined by the relationship to the simultaneously registered noise level of the responses. The last response that could be differentiated from this noise level was defined as VEP acuity in analogy to the acuity definition of the Teller acuity cards. In visually impaired children there was a delay in visual development. Visual deficits in congenital cataract were much more marked than in congenital squint. Infants with congenital cataract showed a nearly newborn stage when tested shortly after lensectomy. With our preliminary results is was not possible to determine any statistical relationship among the psychophysical, electrophysiological and clinical findings.(ABSTRACT TRUNCATED AT 250 WORDS)

Attention↗
PubMed1989

[Recording of visual evoked potentials in infants: characteristics and optimization of the method].

As the capacities for concentration and fixation are limited in infants and young children it is necessary to adapt the method of VEP measurement. An appropriate stimulus presentation is the appearance, disappearance mode with sequentially presented gratings of different spatial frequencies. Variation in the conditions such as fixation, attention or electrode properties, during a recording session affects all cortical responses equally. The duration of VEP examination is shortened by using rapid sequences of stimuli. The purpose of our study was to improve the presentation of the stimuli. We used a small bright monitor (9 x 9 cm) for stimulation; the test distance was 60 cm, and the mean luminance 60 cd/m2. Stimuli were achromatic gratings. These parameters were chosen in order to compare the results of our method with psychophysical measurements, such as preferential looking (PL) with Teller acuity cards. The gratings with increasing spatial frequencies were presented in a sequence of 7 steps. In order to control the influence of artefacts and the variability of the responses summation/subtraction curve of the responses, was displayed simultaneously with the VEP on the control monitor. By increasing the temporal stimulus frequency in steps from 2.5 Hz (transient stimulus) to higher values we got excellent responses from on/off-stimuli at 5 Hz frequency. Thus the signal-to-noise-ratio was improved without alteration of the spatial transfer function which is found when using higher frequencies due to the Brücke-Bartley-effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Child, Preschool↗