Sold scratched glasses

I bought glasses on the 9th April 2016,I was told they were polarized ,and they told me i must check them of which i never do it properly since i never saw any scratch at that time and make me sign , i could not drive in the sun with these glasses so after 7days I returned them back since I had 30 days to change,when I got to the shop the following weekend,I was told that my glasses had scratches of which I could not even see since i never saw them on the purchase date so it means they sold me glasses with a scratches