Recently, progressive lens designers have begun paying closer attention to high-order aberrations and in some cases, even patenting progressive lens designs with reduced high-order aberrations, such as coma.
Unfortunately, you cannot eliminate the high-order aberrations produced by a progressive lens surface, just as you cannot eliminate unwanted surface astigmatism. In fact, for modern progressive lens designs at least, average levels of high-order aberrations calculated globally over the central lens surface are often similar in magnitude.
Nevertheless, both the low- and high-order aberrations in a progressive lens can be managed.
Although higher-order aberrations may result in a reduction in image quality and a loss of contrast, low-order aberrations generally account for the greatest impact on the quality of vision in progressive lenses. In particular, unwanted astigmatism dominates much of the lens surface. Further, in contrast to the case of low-order aberrations, clinical research has demonstrated that the high-order aberrations in progressive lenses are seldom any greater in magnitude than the inherent high-order aberrations of a typical eye.
Research has also demonstrated that the impact of high-order aberrations on visual acuity in the progressive corridor, where these aberrations are often highest, is negligible. Additionally, the caustic focus produced in the presence of small amounts of high-order aberrations may improve the wearer's depth-of-focus and tolerance to the blur caused by the second-order aberrations of the lens. In fact, aberration coupling between the high-order aberrations of the progressive lens and the high-order aberrations of the eye can sometimes yield better visual acuity than in the naked eye.
Nevertheless, the high-order aberrations produced by a progressive lens will have some impact on the wearer's vision and therefore, represent a meaningful quantity to evaluate during the optical design process.
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