{"id":5,"date":"2016-12-13T11:44:08","date_gmt":"2016-12-13T19:44:08","guid":{"rendered":"http:\/\/www.formulens.com\/?p=1"},"modified":"2023-05-15T04:11:21","modified_gmt":"2023-05-15T04:11:21","slug":"progressive-lens-anatomy","status":"publish","type":"post","link":"https:\/\/www.formulens.com\/index.php\/2016\/12\/13\/progressive-lens-anatomy\/","title":{"rendered":"Progressive Addition Lens Anatomy"},"content":{"rendered":"<p>With digital lens surfacing (a.k.a freeform) one or both surfaces of a lens can be completely specified by the Lens Design System (LDS). For example the LDS can provide a <em>height map<\/em>, giving points on a grid of some chosen spacing. This surface will be produced with very high accuracy by the generator.<\/p>\n<p>The optical performance of a freeform lens when used in spectacles, is difficult to predict. Either the lens must be manufactured and analyzed with a complex apparatus that can measure optical properties for a range of realistic view directions, or the lens must be simulated computationally using sophisticated ray-tracing algorithms.<\/p>\n<p><!--more--><\/p>\n<p>FormuLens utilizes our <a href=\"https:\/\/www.formulens.com\/index.php\/2010\/09\/19\/simulens\/\">SimuLens<\/a> ray-tracing program to perform this measurement.<\/p>\n<p>For example the following are simulated sphere and cylinder maps from a realistic Progressive Addition Lens (PAL) with plano Rx:<\/p>\n<p><img decoding=\"async\" loading=\"lazy\" class=\"alignnone size-full wp-image-51\" src=\"https:\/\/www.formulens.com\/wp-content\/uploads\/2017\/05\/powermaps_unlabeled.jpg\" alt=\"\" width=\"1901\" height=\"800\" \/><\/p>\n<p>PAL&#8217;s have certain common requirements, based on the optical performance when the patient&#8217;s view utilizes different regions of the lens while worn:<\/p>\n<ul>\n<li>A large distance viewing region (a.k.a Far Zone) which provides clear vision at the patient Rx.<\/li>\n<li>A reading region (a.k.a. Near Zone) which has more sphere power, or Add, in addition to the patient&#8217;s Rx power.<\/li>\n<li>A progressive channel (a.k.a. corridor) of smoothly varying power, increasing from the patient&#8217;s Rx at the Far Zone, to the Add power at the Near Zone.<\/li>\n<\/ul>\n<p>These regions are indicated in the plano PAL simulation below:<\/p>\n<p><img decoding=\"async\" loading=\"lazy\" class=\"alignnone size-full wp-image-52\" src=\"https:\/\/www.formulens.com\/wp-content\/uploads\/2017\/05\/powermaps_labeled.jpg\" alt=\"\" width=\"1892\" height=\"912\" \/><\/p>\n<p>Also indicated in the simulation above are &#8220;Swim Zones&#8221;, to the sides of the Near Zone, which are unavoidable side-effects of progressive lenses. These regions contain large amounts of astigmatism (hence the high Cylinder value there), as well as other unwanted properties such as visual distortion (the &#8220;Swim&#8221;). A key goal of PAL design is the minimization\/mitigation of these effects.<\/p>\n<p>Overall, PAL design requires a number of trade-offs, such as controlling the value of Swim which achieving desirable sizes for the clear zones and the channel.<\/p>\n<p><img decoding=\"async\" loading=\"lazy\" class=\"alignnone wp-image-54\" src=\"https:\/\/www.formulens.com\/wp-content\/uploads\/2017\/05\/pal_zones_crop.png\" alt=\"\" width=\"459\" height=\"434\" \/><\/p>\n<p>FormuLens uses our <a href=\"https:\/\/www.formulens.com\/index.php\/2010\/09\/19\/simulens\/\">SimuLens<\/a> ray-tracing program, coupled with advanced numerical algorithms, to optimize each design for any possible design requirements, potentially in real-time, to create completely customized designs.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>With digital lens surfacing (a.k.a freeform) one or both surfaces of a lens can be completely specified by the Lens Design System (LDS). For example the LDS can provide a height map, giving points on a grid of some chosen<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2],"tags":[],"_links":{"self":[{"href":"https:\/\/www.formulens.com\/index.php\/wp-json\/wp\/v2\/posts\/5"}],"collection":[{"href":"https:\/\/www.formulens.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.formulens.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.formulens.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.formulens.com\/index.php\/wp-json\/wp\/v2\/comments?post=5"}],"version-history":[{"count":2,"href":"https:\/\/www.formulens.com\/index.php\/wp-json\/wp\/v2\/posts\/5\/revisions"}],"predecessor-version":[{"id":135,"href":"https:\/\/www.formulens.com\/index.php\/wp-json\/wp\/v2\/posts\/5\/revisions\/135"}],"wp:attachment":[{"href":"https:\/\/www.formulens.com\/index.php\/wp-json\/wp\/v2\/media?parent=5"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.formulens.com\/index.php\/wp-json\/wp\/v2\/categories?post=5"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.formulens.com\/index.php\/wp-json\/wp\/v2\/tags?post=5"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}