NEW TECHNIQUES FOR ASSESSING VISION IN INFANTS AND YOUNG CHILDREN

Summary A range of methods has been developed, which can be used both to investigate the course of normal visual development and to assess clinical vision problems in infants. The behavioural 'preferential looking' method has been used to test acuity and contrast sensitivity in infants aged between 1–6 months and shows a rapid improvement in acuity (from 6/180 to 6/60) between I and 3 months. We have made monocular assessments and found, in most infants, similar acuity for each eye but somewhat better binocular acuity. A tracking test is under development for measurements in older infants and we have used an operant procedure with 3-year-olds which shows adult acuity at this age, These results have been extended to the newborn by measuring the amplitude of visual evoked potentials to patterned stimuli, indicating an acuity of approximately 6/180. The infants' refractive state has been studied by means of 'photorefraction'. Many infants under 1 year are astigmatic but this has decreased to adult levels of incidence by 2 years. Infants of 6 months and older accurately accommodate over the adult range; younger infants accommodate appropriately for distances closer than 75 cm. Neural development rather than accommodative error appears to be the principal factor in limiting infants' acuity. A development of this technique may provide an effective means of refractive screening in young infants.