Intra-Observer and Inter-Observer Variability of Intraocular Lens Measurements Using an Interferometry Metrology Device.

The NIMO TEMPO (Lambda-X, Nivelles, Belgium) is a novel, user-friendly and compact device designed for in vitro optical analysis of refractive and diffractive intraocular lenses (IOLs). This device analyzes the IOL wavefront and generates a synthetic eye model for numerical computation. The objective of this study was to evaluate the precision of this innovative device. Intra- and inter-observer variability were calculated using a two-way analysis of variance (ANOVA) after conducting ten measurements of eight different IOL models, with each measurement being repeated by three distinct operators (resulting in a total of 30 measurements for each IOL). The device demonstrated satisfactory intra- and inter-observer variability in evaluating IOL power and modulation transfer function (MTF) profiles, with values of 0.066 and 0.078 diopters for IOL power and 0.018 and 0.019 for MTF measurements, respectively. Furthermore, this hybrid optical and numerical in vitro IOL wavefront analyzer appears to have several advantages over conventional optical bench devices. It reduces the need for operator manipulation, and allows for numerical modeling of various optical environments, including cornea models and apertures. In conclusion, this novel metrology device designed for refractive and diffractive IOLs appears to provide a satisfactory precision, making it a promising tool in the field of IOL metrology.

Optical deflection tomography with the phase-shifting schlieren.

We present a new optical deflection tomography method that takes advantage of the phase-shifting schlieren. The reconstruction algorithm is based on filtered backprojection. The instrument is well adapted for three-dimensional imaging of spatially sparse objects exhibiting large refractive index variations. It achieves a 35 µm resolution with a 3 mm depth of field. Its performance is illustrated with a bundle of fibers immersed in a matching index solution.

The reproducibility of a new power mapping instrument based on the phase shifting schlieren method for the measurement of spherical and toric contact lenses.

PURPOSE: To assess a new method of power measurement of soft and rigid contact lenses. The method is the phase shifting schlieren method, as embodied in the Nimo TR1504 instrument. MATERIALS AND METHODS: Three Nimo TR1504 instruments were used to measure the power related dimensions of: (a) a range of custom toric rigid lenses; (b) a range of commercially available spherical hydrogel lenses; and (c) a commercially available range of toric silicone hydrogel lenses. The measurements were carried out using a standard ISO ring test protocol where independent tests were carried out under conditions of reproducibility. The analysis of the measurements was carried out using ISO methods which enabled the reproducibility standard deviation, SR, of the method to be calculated. RESULTS: The results show that this new method has SR of 0.048D for spherical soft (hydrogel) lenses. This means the back vertex power of spherical soft lenses having a power in the range +/-10.0D can be determined to current ISO product tolerances with a single measurement. The method has SR of 0.059D for sphere power and 0.093D for cylinder power for toric soft lenses having powers in the range +/-10.0D and cylinder powers in the range +/-2.0D. A single measurement will determine sphere power to current ISO tolerance limits with 95% confidence while two measurements are required to determine the cylinder power to the same confidence level.

Phase-shifting schlieren: high-resolution quantitative schlieren that uses the phase-shifting technique principle.

A quantitative autocalibrated high-resolution schlieren technique for quantitative measurement of reflective surface shape is proposed. It combines the schlieren principle with the phase-shifting technique that is generally used in interferometry. With an appropriate schlieren filter and appropriately tailored setup, some schlieren fringes are generated. After application of the phase-shift technique, the schlieren phase is calculated and converted into beam deviation values. Theoretical and experimental demonstrations are given. The technique is validated on a reference target, and then its application in a fluid physics experiment is demonstrated. These two examples show the potential of the phase-shifting schlieren technique that in some situations can become competitive with interferometry but with a much better dynamic range and with variable sensitivity. The technique can also be used to measure refractive-index gradients in transparent media.