What behavior observed in a fatigued 2-year-old may indicate strabismus?

When assessing for strabismus in a child, particularly in a fatigued 2-year-old, observing one eye moving inwards is a significant indicator. Strabismus, or misalignment of the eyes, can manifest in various forms, including esotropia, where one eye turns inward towards the nose. This misalignment may become more noticeable when the child is tired, as fatigue can exacerbate the difficulty in maintaining proper eye alignment.

In young children, the ability to coordinate visual tracking and focus can diminish with tiredness, leading to a more pronounced misalignment. Thus, noticing one eye moving inward would suggest an issue with muscle control and coordination between the eyes, characteristic of strabismus.

While the other behaviors mentioned can be associated with eye strain or other visual issues, they are less specific indicators of strabismus. Eye redness can occur due to various reasons, including allergies, irritation, or infections, frequent blinking might indicate general discomfort or fatigue but does not point directly to misalignment, and loss of balance is typically more indicative of vestibular issues rather than problems strictly related to eye alignment. Therefore, observing one eye moving inwards is the most direct and telling sign of potential strabismus in this context.