Companies will frequently provide safety glasses for employees and little or no cost. The catch is the side shields are "permanently" attached the glasses. No problem if you only intend to use the glasses when you need safety glasses. If you want to be able to use the glasses without the side shields it will take a few minutes of work.
The picture above shows the side shields held with a horseshoe shaped piece of metal attached to the arm on glasses with a special screw. The screw breaks off when the side shields are installed, preventing the screws from being removed.
To remove the "permanent" side shields the lens should be covered to prevent damage. Then use a Demel or similar rotary grinding tool to cut a groove as shown the lower picture. After the groove has been cut a small screw drive can be used to spread the open end of the horseshoe and free it from the arm of the glasses.
The side shields can easily be slipped of or back on again if you want.
This modification allows you use your glasses at times you would not use them if they had the shields. I use my safety glasses as back up glasses and frequently use them around the house in the evening or the weekend.