Potential sources of error when applying a corneal reflex eye-monitoring technique to infant subjects

The early development of visual attention and its implications for social and cognitive development

Looking behavior plays a crucial role in the daily life of an infant and forms the basis for cognitive and social development. The infant's visual attentional systems undergo rapid development during the first few months of life. During the last decennia, the study of visual attentional development in infants has received increasing interest. Several reliable measures to investigate the early development of attentional processes have been developed, and currently a number of new methods are giving fresh impetus to the field. Research on overt and covert as well as exogenously and endogenously controlled attention shifts is presented. The development of gaze shifts to peripheral targets, covert attention, and visual scanning behavior is treated. Whereas most attentional mechanisms in very young infants are thought to be mediated mainly by subcortical structures, cortical mechanisms become increasingly more functional throughout the first months. Different accounts of the neurophysiological underpinnings of attentional processes and their developmental changes are discussed. Finally, a number of studies investigating the implications of attentional development for early cognitive and social development are presented.

Quantitative assessment of the static properties of the oculo-motor system by the photo-oculographic technique

The paper addresses the problems raised by the application of the photo-oculographic technique to the quantification of static orientations of the eye in ophthalmology. Eye orientations are determined from the relative positions of corneal reflex and pupil images. The relationship between the positions of these images and the angular rotations of the eye is studied with an optical model of the anterior chamber of the eye. This model is used to analyse the influence of technical and physiological variables and to evaluate the accuracy of different calibration procedures applicable to clinics.

The accurate calibration of infants' scanning records

The visual scanning characteristics of 10 infants were assessed repeatedly over the 2- to 14-week age period, using a bright-pupil/corneal reflection technique. The present report focuses on the calibration process--a procedure by which stimulus figures are mapped onto the raw scanning data. It is concluded that the major calibration parameters vary significantly among infants, and therefore separate calibration data must be collected on each infant if errors on the order of several degrees of visual angle are to be avoided. Moreover, it was found that infants' saccades often are not directed accurately toward the attracting stimulus, and hence repeated calibration trials are required for the precise determination of parameter values. After about 6 weeks of age, the parameter values established for a given infant remained largely invariant. During the initial weeks of life, however, parameter values occasionally changed, apparently because very young infants sometimes will center the image of an attracting stimulus about some extrafoveal location. This raises an additional complexity when interpreting the scanning records of very young infants.