Miguel Faria-Ribeiro1, Daniela Lopes-Ferreira2, Norberto López-Gil3, Jorge Jorge2, José Manuel González-Méijome2. 1. Clinical & Experimental Optometry Research Lab, School of Sciences (Optometry), University of Minho, Braga, Portugal. Electronic address: mig.afr@gmail.com. 2. Clinical & Experimental Optometry Research Lab, School of Sciences (Optometry), University of Minho, Braga, Portugal. 3. Ciencias de la Visión, Facultad de Óptica y Optometría, Universidad de Murcia, Murcia, Spain.
Abstract
PURPOSE: To evaluate the error in the estimation of axial length (AL) with the IOLMaster partial coherence interferometry (PCI) biometer and obtain a correction factor that varies as a function of AL and crystalline lens thickness (LT). METHODS: Optical simulations were produced for theoretical eyes using Zemax-EE software. Thirty-three combinations including eleven different AL (from 20mm to 30mm in 1mm steps) and three different LT (3.6mm, 4.2mm and 4.8mm) were used. Errors were obtained comparing the AL measured for a constant equivalent refractive index of 1.3549 and for the actual combinations of indices and intra-ocular dimensions of LT and AL in each model eye. RESULTS: In the range from 20mm to 30mm AL and 3.6-4.8mm LT, the instrument measurements yielded an error between -0.043mm and +0.089mm. Regression analyses for the three LT condition were combined in order to derive a correction factor as a function of the instrument measured AL for each combination of AL and LT in the theoretical eye. CONCLUSIONS: The assumption of a single "average" refractive index in the estimation of AL by the IOLMaster PCI biometer only induces very small errors in a wide range of combinations of ocular dimensions. Even so, the accurate estimation of those errors may help to improve accuracy of intra-ocular lens calculations through exact ray tracing, particularly in longer eyes and eyes with thicker or thinner crystalline lenses.
PURPOSE: To evaluate the error in the estimation of axial length (AL) with the IOLMaster partial coherence interferometry (PCI) biometer and obtain a correction factor that varies as a function of AL and crystalline lens thickness (LT). METHODS: Optical simulations were produced for theoretical eyes using Zemax-EE software. Thirty-three combinations including eleven different AL (from 20mm to 30mm in 1mm steps) and three different LT (3.6mm, 4.2mm and 4.8mm) were used. Errors were obtained comparing the AL measured for a constant equivalent refractive index of 1.3549 and for the actual combinations of indices and intra-ocular dimensions of LT and AL in each model eye. RESULTS: In the range from 20mm to 30mm AL and 3.6-4.8mm LT, the instrument measurements yielded an error between -0.043mm and +0.089mm. Regression analyses for the three LT condition were combined in order to derive a correction factor as a function of the instrument measured AL for each combination of AL and LT in the theoretical eye. CONCLUSIONS: The assumption of a single "average" refractive index in the estimation of AL by the IOLMaster PCI biometer only induces very small errors in a wide range of combinations of ocular dimensions. Even so, the accurate estimation of those errors may help to improve accuracy of intra-ocular lens calculations through exact ray tracing, particularly in longer eyes and eyes with thicker or thinner crystalline lenses.
Keywords:
Axial length measurement; Cálculo de LIO; Cálculo de lentes intra-oculares; IOL calculation; Intra-ocular lens calculation; Medición de la longitud axial
Authors: David A Atchison; Emma L Markwell; Sanjeev Kasthurirangan; James M Pope; George Smith; Peter G Swann Journal: J Vis Date: 2008-04-28 Impact factor: 2.240
Authors: David P Piñero; Vicente J Camps; María L Ramón; Verónica Mateo; Rafael J Pérez-Cambrodí Journal: Int J Ophthalmol Date: 2015-06-18 Impact factor: 1.779
Authors: Yu-Cherng Chang; Keke Liu; Carolina de Freitas; Alex Pham; Florence Cabot; Siobhan Williams; Ethan Adre; Giovanni Gregori; Marco Ruggeri; Sonia H Yoo; Arthur Ho; Jean-Marie Parel; Fabrice Manns Journal: Biomed Opt Express Date: 2017-04-26 Impact factor: 3.732
Authors: Gerd U Auffarth; Tadas Naujokaitis; Louise Blöck; Anna Daghbashyan; Jan Meis; Victor A Augustin; Ramin Khoramnia; Timur M Yildirim Journal: Diagnostics (Basel) Date: 2022-01-11