Comparison of double-pass estimates of the retinal-image quality obtained with green and near-infrared light.
We compared retinal point-spread functions obtained by the double-pass method with two different wave-lengths, green (543 nm) and near-infrared (780 nm), in both cases under the best conditions of focus. The best refractive state at each wavelength was determined with two procedures: subjective refraction and analysis of the recorded double-pass images as a function of focus. Since the refraction results agree quite well, we assume that in both cases, green and near-infrared light, most of the light of the central core in the double-pass images comes from a layer close to that of the photoreceptors. The central spread of the double-pass images was also quite similar for the two wavelengths: a width of approximately 2-3 arcmin at half-intensity relative to the peak. However, larger differences were found in the tails of the images, with the infrared images presenting a larger scattering halo, probably as a result of a more important contribution of retinal and choroidal scattering for that wavelength. By using the central core in the double-pass images and ignoring the tails, we can use the near-infrared data to predict the modulation transfer function measured with the use of green light. These results raise the possibility of using near-infrared illumination the double-pass method to estimate the optical performance of the human eye.
López-Gil
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Departamento de Física, Universidad de Murcia, Spain.
Artal
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D000328:Adult; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007259:Infrared Rays; D008027:Light; D008297:Male; D012160:Retina / Q000502:physiology*; D014785:Vision, Ocular / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology