Why compensate lenses? Free-form lens design and surfacing technology compensate the lens surface, making the effective power perceived by the patient in the primary gaze position match the prescribed power given by the refracting doctor. Why are they not the same? Short answer: The trial lenses used to refract the patient are flat and sit perpendicular to the patient’s visual axis in the primary gaze position, but when the lens is worn, it forms an oblique angle to the visual axis, inducing oblique aberration, changing the effective power perceived.
My sister-in-law called, worried about her husband. He was having headaches and neck and shoulder pain, and she didn’t know why. My optical instincts kicked in, and I asked when he had his last eye exam. It was about four years ago. He is 65, working from home on digital devices, and wearing the readers he got at his last exam. I told her his complaints were consistent with digital eye strain, that he needed an eye exam, and most likely progressive lenses. “But they’re so expensive!” she replied. I did my best to convince her that the investment was well worth it. It worked.
In Part 11, we learned about IOT’s foundational technology, Digital Ray-Path®. This technology minimizes oblique aberrations in customized free-form lenses. We learned that “The value of the merit function is given by a weighted sum of the optical aberrations of the lens system. To achieve the best lens performance optimization of the optical system means finding the values of the free parameters that make the value of the merit function minimal.” (Dr. Jose Alonso et al)
When it comes to free-form personalized lenses, we hear “Trust the Computer,” which we do, because our proof is in the patient’s response; they love them. Still, we want a rudimentary understanding of how free-form technology works. In this article, we will pull back the curtain and learn about the process behind IOT’s Digital Ray-Path® foundational free-form personalization technology. The upcoming Part 12 will delve into how IOT Digital Ray-Path 2 builds on the classic theory of oblique power error minimization.
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