As a person who wears prescription glasses all the time, I had tried a few different solutions for solutions for sunglasses in the past. I started with clip-ons that were made for my frames which were ok, but somewhat heavy and unflattering. Then I got a pair of sunglasses and has prescription lenses put into them. This was ok, but it meant carrying around an extra pair of glasses everywhere. Next, I tried Transitions lenses that get dark outside when exposed to UV rays. Those were ok, but they didn't work in the car, and also when you go inside, it would take a while for them to go back to normal.
So finally, I was without any eye protection and still wearing my regular glasses. I wanted some kind of sunglass solution, mainly for driving when there is a lot of reflection from the sun on the cars in front of you. I thought about getting prescription lenses put into my sunglasses again, but the cost would be over $100. Then I looked up clip-on option again. I found that Walgreens was selling a variety of these for $15. This is reasonable so I went to check them out.
At Walgreens, I found the display of Solar Shield clip-ons. They had a lot of different styles and sizes. What's nice is the cases snap open so you can take them out to try on to see if they fit your frames. I tried a bunch of different sizes until I found one that fit the best. Of course it wasn't perfect, but for $15 you can't complain. They are adjustable by way of a spring in the middle that lets you stretch them out and let them retract. They are also available online at sites like Amazon.
On the package it says they are polarized, scratch resistant, and block 100% of UV rays. I really wanted the polarized because that is suppose to block the glare. Once outsize I tried them out. They didn't really block the glare that much which was disappointing, but overall it did provide a shield from the sun.
The build quality of the frames is ok, but they are not that strong. I would recommend being very careful with them. I could see them breaking if you sat on them or something.
Since my clip-ons were a little big, I tried to modify them a bit. I got this clear adhesive rubber and attached little strips to the inside of the little hooks on the edges of the clip-ons. I secured them with some thread. Now they fit very well.
The Solar Shields come with a clear plastic case that you can use. I opted to use an old flexible clip-on case that I had from a previous pair of glasses.
Overall if you wear prescription glasses and are looking for an economical way to block the sun, I would recommend trying out Solar Shield clip-on sunglasses.
Update 4-6-15 3 years later, I still have the Solar Shield Clip Ons and they are still working well. They are a little scratched up do to normal wear and tear but overall they are still good. I would buy another set if these ever wear out too much.