A simple confocal fibre-optic laser method for intraocular lens power measurement

Abstract

Purpose: To develop novel confocal fibre-optic laser method (CFOLM) for accurate and objective measuring of the dioptric power of both positive and negative intraocular lenses (IOLs). Methods: The CFOLM principle of operation is based on a simple apertureless single-mode fibre laser confocal design. The key element is a single-mode fibre coupler that serves simultaneously as a point light source (3-5μm fibre diameter) used for the formation of a collimated Gaussian beam, and as a confocal point receiver that is highly sensitive to spatial displacements of the focused backreflectance laser emission. The basic CFOLM systems include IOL testing set-ups for the measurement of both positive and negative IOLs. Results: The CFOLM designs provide high accuracy (≤1μm) in spatially locating the IOL focal point and in measuring the focal length in a broad range of both positive and negative powers including high-magnification IOLs with power greater than ±20D. We have tested various IOL samples with both positive (+5 to +30D) and negative (-5 to -20D) powers and we have obtained high levels of power testing repeatability estimated by a SD in the interval of 0.004-0.06/ 0.003-0.013D and a relative error in the interval of 0.015-0.3/ 0.02-0.16%, for positive/negative IOLs, respectively. Conclusions: The presented IOL power testing method offers a simple, accurate, objective, quick, and relatively inexpensive approach for dioptric power measurement of positive and negative IOLs. It provides an independent source of IOL power measurement data and information for evaluating the effectiveness and safety of novel IOL products.