{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,4]],"date-time":"2026-09-04T16:44:47Z","timestamp":1788540287252,"version":"build-2803163510"},"reference-count":37,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2026,6,22]],"date-time":"2026-06-22T00:00:00Z","timestamp":1782086400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Diagnostics"],"abstract":"<jats:p>Background\/Objectives: To derive and validate a simplified modification of the Haigis intraocular lens (IOL) power calculation formula by reducing the three-constant effective lens position (ELP) model to a single constant while introducing an optimized keratometer index and axial length correction. Methods: In this retrospective study, a large multicentric dataset (Dataset 1; 22,466 eyes, 113 IOL models) was used to optimize the Haigis constant triplet and keratometer index using nonlinear programming with Cooke\u2019s axial length correction. A second independent dataset (Dataset 2; 3181 eyes, six IOL models) was used for cross-validation. Three approaches were compared: classical Haigis, modified triplet, and two single-constant models acting on IOL power (H1) or ELP (H2). Results: The optimized keratometer index (1.3296 \u00b1 0.0003) was significantly lower than the classical value, indicating systematic overestimation of corneal power. Modified triplet and single-constant approaches achieved comparable or slightly lower prediction errors than the classical formula. The H1 approach showed marginally superior performance. Bootstrapping confirmed parameter stability. Conclusions: A single-constant modification of the Haigis formula incorporating an optimized keratometer index and axial length correction maintains prediction accuracy while simplifying clinical implementation.<\/jats:p>","DOI":"10.3390\/diagnostics16121938","type":"journal-article","created":{"date-parts":[[2026,6,23]],"date-time":"2026-06-23T06:13:37Z","timestamp":1782195217000},"page":"1938","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Simplification of a Three-Constant Intraocular Lens Calculation Formula to a Single-Constant Approach: The Haigis Formula"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-9175-6177","authenticated-orcid":false,"given":"Achim","family":"Langenbucher","sequence":"first","affiliation":[{"name":"Department of Experimental Ophthalmology, Saarland University, 66424 Homburg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"N\u00f3ra","family":"Szentm\u00e1ry","sequence":"additional","affiliation":[{"name":"Department of Experimental Ophthalmology, Saarland University, 66424 Homburg, Germany"},{"name":"Department of Ophthalmology, Semmelweis University, 1085 Budapest, Hungary"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0779-7449","authenticated-orcid":false,"given":"Alan","family":"Cayless","sequence":"additional","affiliation":[{"name":"School of Physical Sciences, The Open University, Milton Keynes MK7 6AA, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4228-6073","authenticated-orcid":false,"given":"Benjamin","family":"Fassbind","sequence":"additional","affiliation":[{"name":"Department of Experimental Ophthalmology, Saarland University, 66424 Homburg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Iwan","family":"Bolzern","sequence":"additional","affiliation":[{"name":"Department of Experimental Ophthalmology, Saarland University, 66424 Homburg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Peter","family":"Hoffmann","sequence":"additional","affiliation":[{"name":"Augen- und Laserklinik Castrop-Rauxel, 44575 Castrop-Rauxel, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4145-2559","authenticated-orcid":false,"given":"Jascha Armin","family":"Wendelstein","sequence":"additional","affiliation":[{"name":"Department of Experimental Ophthalmology, Saarland University, 66424 Homburg, Germany"},{"name":"Department of Ophthalmology, Ludwig-Maximilians-University, 80539 Munich, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,6,22]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"333","DOI":"10.1016\/S0886-3350(13)80705-5","article-title":"Development of the SRK\/T intraocular lens implant power calculation formula","volume":"16","author":"Retzlaff","year":"1990","journal-title":"J. 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