Some common signs to look for include:

1. One or both eyes appear misaligned or do not track together
2. Turning or tilting the head to see things
3. Squinting, closing one eye, or blinking excessively
4. Poor hand-eye coordination or excessive clumsiness
5. Frequent headaches or strained eyes
6. Frequent nausea or dizziness
7. Holding things very close to their face

Trouble signs that require immediate attention include:

1. A white pupil
2. Swelling or droopy eyelid
3. Excessive redness, tearing, or discharge
4. Double vision