As a full time glasses wearer I have prescription sunglasses as well as glasses and often when driving they are on and off and thrown to 1 side. For such expensive accessories I think glasses can be treated pretty roughly.
I have created a case which is padded and has a fastening at the top opening which is just simple and effective.
It's been designed to be large enough for sunglasses, but the padding and top fastener keeps smaller frames secure.
These are available in lots of fabrics, these cases are very handily machine washable and fully lined.
Cick on the box below to see all the available designs. Do let me know in the comments below which is your favourite!