Importing transparent Png and render order

First let’s assign a Lens Material to the lens, Import a transparent Png to the lens, the process to import any texture jpeg or png is the same.

Once our texture is loaded let’s tick transparent and keep it at 1.

We can now add extra color effects to the lens, adjust the reflectivity, the transmission amount.
As well as the standard material parameters such as Emissive Roughness, Metalness and Occlusion.

For any of these you can add a map. 

When working with transparent materials, it's important to set the correct render order to avoid issues where objects that are in the back are rendered incorrectly.

For example you can set the lens render order to 1 and keep the frame and temples at 0. 

Under eyewear tab you can click widget tryon, and check your model under different lighting conditions while editing it in realtime.