how come salt hurts your eyes but they are already filled with salt to stop freezeing

Question: how come salt hurts your eyes but they are already filled with salt to stop freezeing
- Keywords:
  eye,
  hurt,
  salt,
  salty,
  stop,
  tears,
  water
Asked by bowser to Alan, Caspar, Murray, Sarah on 24 Mar 2011.
- Sarah Thomas answered on 24 Mar 2011:
  
  Tears are really salty, so if you get sea water in them, it surprisingly does not hurt! However it can irritate your eyes if there are particles of grit or sand in the water.

Question: how come salt hurts your eyes but they are already filled with salt to stop freezeing