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.