Various implementations disclosed herein include devices, systems, and methods that use a marking on a transparent surface (e.g., a prescription lens insert for an HMD) to identify information (e.g., prescription parameters) about the transparent surface. In some implementations, the markings do not interfere with eye tracking through the transparent surface or using the transparent surface to view virtual content or a physical environment. In some implementations, image data is obtained from an image sensor of an electronic device, the image data corresponding to a transparent surface attached to the electronic device. Then, a code is identified in the image data, wherein the code is detectable on the transparent surface by the image sensor without interfering with a function of the electronic device involving the transparent surface. In some implementations, content is provided at the electronic device based on the identified code, wherein the content is viewable through the transparent surface.