Review Question - QID 213477

A 2-month-old baby girl is brought to the clinic by her parents for a wellness check-up. She was born vaginally at home via a midwife, at 38 weeks of gestational age without any complications. The mother denies any fevers, changes in feeding, or excessive crying. She is concerned that her baby doesn’t smile much like her previous child. A physical examination demonstrates a well-developed baby who is following her growth curve appropriately. Findings of the eye examination are shown in Figure A. Which of the following is the most likely to be deficient or abnormal in this patient?