After wearing broken and taped glasses for most of my life, I decided to see how difficult it would be to make my own frames. 3D Printing seemed to be the best approach, but in order to design my frames, I needed to reference the shape of my lens.
I used Autodesk's 123D Catch, which is free 3D scanning software that makes 3D models from photos. It's available here http://www.123dapp.com/catch for PC or iphone/ipad.
You can see how I designed my frames around my lens here: https://www.instructables.com/id/How-to-design-3d-printed-glasses/
Step 1: Masking Tape
Start by covering the front surface of your lens with masking tape. 3D Scanners have trouble recognizing shiny, black and especially clear materials.
Step 2: Trimming
Carefully trim the excess tape as close as possible to the edge of your lens. Be very careful not to scratch it!
Step 3: Sharpening Details
Use a hard surface to gently crease the tape over the edge. I used an allen wrench. This is important to capture the exact outer edge of your lens.
Step 4: Take Photos
Take 20-30 photos a complete 360 degrees around your lens. It helps to try to keep a consistent distance and angle for each shot and have it well lit.
Having your lens on a textured surface might also help. I'm not sure exactly how the software works, but I think the wood grain and knot on my desk helped with registration of the photos.
Upload your photos into 123D Catch and wait for it to work its magic! The quality and resolution of my scan was perfect for a 3D reference.
I've attached my 123D catch file for you to use as a reference.