The visual evoked potential to flash stimulation has been studied in premature infants for many years. There have been no studies of the response to pattern reversal stimuli during the pre-term period, however. Twenty babies all born prematurely between 32 and 35 weeks post menstrual age had pattern reversal visual evoked potentials recorded on at least two occasions between the ages of 32.5 and 52 weeks post menstrual age with the first recording prior to reaching 40 weeks post menstrual age. The stimulator consisted of a small hand-held television with a 55 โข 40mm screen, and responses were averaged by a Cadwell 5200 averager. The check size was 7 โข 7 mm and the contrast was 78%. The stimulator was held at a distance of 20cm from the eyes. The angular subtense of the TV screen was 15.3 ~ โข 11.31 ~ On each occasion flash visual evoked potentials were obtained for comparison, as were flash electroretinograms recorded with a DTL electrode. The infants were randomly assigned to receive breast milk substitute with or without taurine.
Pattern reversal responses consisted of a positive component with a mean latency of 320 msec at 32.5 weeks post menstrual age. The negative relationship between age at recording and the latency of the major positive component of the pattern reversal visual evoked potential was significant at p < 0.0001. There was no apparent difference in the visual responses of the two groups.