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D. De Brouwere, H. S. Ginis, T. J. T. P. van den Berg, I. G. Pallikaris; Comparative Study of Optical and Psychophysical Measurements for Intraocular Scatter Using Calibrated Scattering Contact Lenses. Invest. Ophthalmol. Vis. Sci. 2007;48(13):6006.
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© ARVO (1962-2015); The Authors (2016-present)
Ocular scatter is often seen as an important parameter in the degradation of visual function. Therefore several approaches to estimate ocular scatter have been proposed in the last decade. In this paper, we developed contact lenses with varying amounts of scatter in order to compare the functionality of a single pass scatter instrument, a double pass scatter intstrument and a psychophysical instrument.
Plano contact lenses (Menicon) have been manufactured in 4 different concentrations of microspheres (Jaygo Inc.) with diameter varying from 1 to 20 microns. A fifth lens without microspheres was used as control. We measured scatter in a single pass method the image of a homogeneous illuminated half field object on a CCD camera through the contact lenses incorporated in the camera lens. The angular scatter profile and scattering density was estimated quantifying the image quality on the camera. After the single pass lens characterization, we measured the intraocular scatter in a group of 6 eyes wearing all 5 different contact lenses using an optical scatter measurement and pshychophysical analysis. For the optical meausurement, we modified a Tscherning aberrometer (WaveLight WaveFront Analyzer) by changing the mask to measure ocular scatter with a double pass technique. A psychophysical instrument based on the compensation method ( C-Quant straylight meter) was used. In the single pass and the double pass measures, we calculated ballistic ratio (BR) as the ratio of non-scattered light to the light passing the scattering medium. In the straylight meter, a straylight parameter (s) is retrieved from compensation treshold luminance value of the flickering target.
The single pass setup gives a BR for the contact lenses ranging lineary from 0.95 to 1 according to the different concentrations of scatterers. We could quantify a qualitive degradation of the double pass images with increasing amounts of scatter in the contact. The log(s) straylight parameter increased with the concentration of microspheres from 0.85 for clear lenses to 1.3 for the most dense scattering lenses.
We validated the use of glass microspheres in contact lenses to simulate increased corneal scatter with values comparible to data observed in clinical practice. The contact lenses can be used for calibration and comparison of devices for measuring ocular scatter using either optical or psychophysical techniques.
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