Sometimes hard... "tired" eyes can have a variety of differing sensations. Tired eyes most often come from problems with focus or eye alignment. What is confusing is some visual tasks such as reading make dry eye worse. The usual complaint with dry eyes is redness, foreign body sensation usually under the upper lids, intermittently blurred vision. Try tears and see what happens first.
Can be same thing. The feeling of tired eyes can be related to dry eye. Dryness typically feels like something is in the eye, irritation, redness, scratchiness, blurred vision, tired eyes due to eye strain typically causes headaches, blurred vision, fatigue. Many other issues can cause similar symptoms..
Sometime same. Your eyes can be tired from moving your eyes or focusing for too long. However, most tired eyes are prob from overuse causing dry eyes. Dry eyes on the other hand, can cause you to have symptoms of tiredness. So many times, they are one and the same.