Why is my right eye still blurry 3 weeks after laser eye surgery?

It is still early in your healing process, so the blur may be due to dryness. I would use preservative free tears every two hours. If there's no improvement, I recommend returning to your doctor to ensure normal healing. There could be a chance that there is under correction, but it is too early to know at this point. 

 There are several possibilities of why your vision is still blurry three weeks after Lasik.  Temporary dryness in the center of the cornea is the most common cause blurry vision. The exact correction maybe close but not perfect and you might need a touch-up procedure. You should return to your doctor's office and have an evaluation.

The vision can vary between eyes and between patients. Dryness is a common issue.Although most problems clear quickly, it's better to be checked early as some things are best treated early.See you surgeon soon.