Facial muscle imbalance – One side of the face may be more active or tighter than the other. Sleeping on one side – Constant pressure on one side can affect eye shape over time. Eye strain or screen time – Overuse of one eye can cause temporary drooping or fatigue. Poor blood circulation or lymph blockage – Leads to puffiness or heaviness on one side. Posture imbalance – Neck or shoulder tightness can affect facial nerves and muscles. Eyebrow or eyelid muscle weakness – Causes one eye to appear