Samsung UA40ES6200R E-Manual page 255

Active Glasses and rest.
ΠWatching 3D images for an extended
period of time may cause eye strain.
If you feel eye strain, stop viewing
3D TV; remove your 3D Active
Glasses and rest.
ΠA responsible adult should frequently
check on children who are using the
3D function. If there are any reports
of tired eyes, headaches, dizziness, or
nausea, have the child stop viewing