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High Definition Digital Occupational Lenses
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Focimeter Measuring a Lens | The drawing on the left shows a typical setup for measuring lens power with a lensometer. Notice that the lens surface is placed perpendicular to the ray beam of the instrument. Conventional lenses have been developed to yield the correct power when being measured like this. This type of calculation method is known as nominal power calculation. It assumes that the same design is good for every prescription, what we could call a “static” design. |
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User Power vs Lens Meter Ray Paths | But, the eye's optical system is very different from the optical system used to measure a lens, as you can see on the left. The eye rotates around its center, and the light follows an oblique trajectory that affects the power experienced by the wearer. |
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Oblique errors in a conventional lens | The drawing on the left illustrates the effect described above. This example shows the power experienced by the wearer of a conventional Single Vision lens when looking through various areas of the lens. The difference between power experienced and that actually prescribed can be more than 0.5D for a lateral gaze angle of 30º. This effect is known as oblique aberration, and is the main optical aberration that cannot be resolved by conventional surfacing techniques. |
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Digital Ray Path Performance | This last drawing shows the effect of a lens with the same prescription, calculated with Digital Ray-Path, ground with Free-form equipment. The Power experienced by the wearer is stable on the whole lens, providing perfect vision for every direction of sight. |