February 2023 Resources

IOT Free-Form Insights Part 33

Historically, producing optically viable high-wrap eyewear was limited and required specialty labs (especially for progressive lenses). Conventional manufacturing methods were only capable of generating a sphere or torus on the back surface of the lens. Therefore, only a narrow range of prescriptions could be produced in high-wrap frames. Labs that dealt in high-wrap eyewear used formulas to calculate and compensate for the power error and oblique astigmatism caused by the angle formed between the visual axis and the lens optical axis in the primary gaze position. They also added equal and opposite prism to cancel the induced prism. Later came aspheric designs that improved peripheral optics when they fit correctly but still had room for improvement.
January 2023 Resources

IOT Free-Form Insights Part 32

Digital free-form lenses have existed since 2000, yet the terms used to define concepts related to these highly technical lenses still confuse us. For example, opticians use the terms personalization and compensation interchangeably, but they are different yet often related concepts.