The development of visual pursuit during the first months of life

Background: Then are few previous investigations of smooth pursuit in infants. The aim of our study was to quantify visual pursuit in infants between 1 day and 16 weeks of age. Methods:Eye movements of 97 healthy infants between 1 day and 16 weeks of age were recorded one to seven times with infrared photo-oculography. For stimulation of visual pursuit a square of 9.4 deg of visual angle with vertical gratings moved horizontally at a constant velocity of 7.5 deg/s. Results: In the first 2 weeks of life, segments of smooth pursuit were measured with a maximum velocity of 7.93 deg/s, with a maximum gain of 1.06 and a maximal duration of 3.16 s. In sequential recordings no significant increases of velocity, gain or duration were found. However, the total time the subjects followed the stimulus with smooth plus saccadic pursuit increased significantly with age (from a median of 39.0% to a median of 61.5% of examination time). Conclusion: This study clearly demonstrates that smooth pursuit is already present in the first week of life. We found no significant increase in velocity, gain and duration of smooth pursuit segments in the first 16 weeks of life with our recording technique. However, the total pursuit time, reflecting attention, increased with age. The ocular machinery to drive pursuit appears to be in place at birth and seems not to be influenced by increased attention in the first months of life.