Little is known about the development of the ocular motor system in children. We hypothesize that quantitative analysis of "at risk" infants eye movement systems can detect abnormalities that precede and predict the onset of strabismus. We will collect data on the eye movements of a group of infants born between 36 and 44 weeks of post-conceptual age. These infants are enrolled between 4 and 24 weeks after birth and followed at 4 week (+/-5 days) intervals until 28 weeks of age and then yearly until 3 years after birth. After study enrollment infants will undergo a complete ophthalmic evaluation and ocular motor analysis at all study visits. The ocular motor analysis will include evaluation of ocular following, saccadic, pursuit and vergence eye movements using stimulus paradigms that have been specially developed for use in children. Children will be followed on an annual basis after 28 weeks of age until age 3 years to monitor the development of ocular alignment and to detect other visual system abnormalities. Study endpoints for each subject are at 28 weeks of age (ocular motor recordings completed) and 3 years of age (ophthalmic examinations completed). This will provide basic knowledge regarding the etiology of both normal and abnormal binocular alignment in infants in the first 28 weeks of life.