The "severe visual impairment" group is defined as the BCVA of at least one eye outside the 99% referenced range or worse than light perception with structural abnormalities or other examination results.

For the "likely healthy" group, the visual acuity of both eyes is in the 95% referenced range with no structural abnormalities.

The referenced range could be found in the following publication:

Mayer, DL., et al. Monocular acuity norms for the Teller Acuity Cards between ages one month and four years. Investigative Ophthalmology & Visual Science. 36(3):671 (1995)

The "mild visual impairment" group is defined as the BCVA in the 99% referenced range in both eyes with abnormalities of structure or other examination results.

A domenstic apparatus, scenario, and procedure is applied to record all the behavioral phenotypes.

For each standardized procedure, the guardian sits in the chair, holding the infant facing the mobile phone screen. Each infant is given a few minutes to adapt to the surroundings and to be calm before recording. No hints or simulations are permitted during the entire process. The recording process lasted for about 3 minutes to ensure that behavioral phenotypes could be completely recorded.

Normal or abnormal behavioral dynamics of infants are recorded by mobile phones. Five experienced ophthalmologists identify the occurence of abnormal behaviors independently, and 2 professors with over 10 years of experience in pediatric ophthalmology department are consulted in cases of disagreement. The AUC of model based on analyzing the behavioral dynamics will be calculated.