The study of optokinetic 'look' nystagmus in children: our experience.

Seventy health children underwent an OKN trial. The authors have chosen to perform only four tests (slow and fast clockwise and counterclockwise OKN) taking into account (in agreement with several international studies) four parameters: sTAP, fTAP, sTSAP, fTSAP (where s and f indicate the velocity of the shifting target slow or fast, TAP is total asymmetry percentage of the SSC--speed of slow components--and TSAP is total asymmetry percentage of saccades). They carried out the statistical analysis of the results, which did not show peculiar difference between child and adult OKN. The result of the test was independent of the side first tested and of sex. The authors have tried to identify the normal range of values more suitable to the study of child OKN; on the basis of the calculation of the 95% percentile the normality range was wider than the range assumed for adults. The authors have also tried to subdivided the results for three different groups of age (I = 3-7 years; II = 8-11 years; III = 12-14 years) in order to observe the degree of OKN maturation with age. From the results obtained the maturation of OKN pathways seems to occur in the 7th year of age for the slow movements; the findings related to the fast movements are more doubtful and need further analysis. Finally, although the number of saccades interposed to the tracings depends on enormous variations unrelated to age, sex and first side tested, our data show their higher incidence during the slow test.