Astigmatic Refraction Using Peaks of the Interferogram Fourier Transform for a Talbot Moiré Interferometer

Abstract

PURPOSE: To calculate the spectacle correction from a Talbot Moiré wavefront sensor using the location of peaks in the Fourier transform of the interferogram image. METHODS: A relationship was developed between the spectacle correction for an ocular wavefront and the location of Fourier transform peaks in the aberrated interferogram. These spectral peaks were located to subpixel accuracy using a two-dimensional polynomial fit. A Talbot Moiré wavefront system was developed to collect examination images from an astigmatic model eye and human eyes. The authors' Fourier transform calculation procedure was applied to captured interferogram and results were tabulated. RESULTS: Five examinations were made of the astigmatic model eye. The mean sphere and cylinder were -4.26 D (SD = 0.004) and -2.90 D (SD = 0.008), respectively. The axis for all measurements was 92°. These values were consistent with the model eye design parameters. The patient was a 46-year-old man with best spectacle-corrected visual acuity of 20/20. Ten examinations were made of the patient's eye. The mean sphere and cylinder were -0.09 D (SD = 0.11) and -1.45 D (SD = 0.14) , respectively. The mean axis was 69.1° (SD = 1.29°). The calculation time was 46 ms per image running on a 3.6-GHz PC using 512x512 fast Fourier transforms. This processing time is fast enough for real-time acquisition and display of a patient's refractive state. CONCLUSIONS: The Fourier transform calculations provided a fast and simple method of determining the spectacle correction in an aberrated ocular wavefront imaged by a Talbot Moir? wavefront sensor. [J Refract Surg. 2007;23:972-977.]

Effect of intraoperative aberrometry on the rate of postoperative enhancement: Retrospective study

“…The device has found applications in the construction and enhancement of peripheral corneal relaxing incisions and accurate rotational placement of toric IOLs. The system uses Talbot moiré technology, 15,16 which has a more robust measurement capability than Hartmann-Shack or Tscherning aberrometry.…”

“…The aberrometer uses Talbot moiré interferometry, 15,16 which is based on 2 transmission grids spaced a specific distance apart and rotated relative to each other. The spectacle correction in an aberrated ocular wavefront is determined using Fourier transform calculation and is represented in the resulting interferogram.…”

Intraoperative aberrometry: an update on applications and outcomes

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Design and validity of a miniaturized open-field aberrometer

“…The one commercially available device, the secondgeneration ORange (Wavetec Vision), uses Talbot moir e interferometry, which is based on 2 transmission grids spaced a specific distance apart and rotated relative to each other to assess the wavefront. 10 This device appears to have limited availability, and the resolution is undisclosed, although the first generation correlated moderately well with a standard aberrometer. 11 Moreover, it can take only static measurements over 2 to 5 seconds each 12 and a web-based program is necessary for analysis of the wavefront images.…”