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D. H. Corregidor Carrio, Sr., P. Barrionuevo, M. Jaen, L. Issolio, E. Colombo; Determination of a Scattering Index for Filters That Simulate Cataracts by an Integrative Method. Authentication With the Compensation Comparison Method. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1835. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
In order to find an optimal optical characterization of different diffusers that are used to simulate cataracts we determined the scattering index S (S= PSF. θ2) with an angular scatter-meter between 0° and 90°. These measurements showed that the function S(θ) did not remaind constant in the interval for most of the measured filters. Then, the most appropriate way for calculating a characteristic index would be to consider the integration of the S function in the range of interest and to obtain a mean value for S(θ1,θ2)
To authenticate the proposed method a C-Quant device was used with different ophthalmic lens (-2 to +4 diopters) what allowed to vary the area of the glare ring. In order to calculate for the selected filters,S(θ1,θ2)function was integrated over glare ring area which grows with lens focus increasing. On the other hand S value was measured by indirect and direct methods according to those proposed by de Wit et al (2006) and van den Berg (2009) using the C-Quant and results were compared.
In general, as the glare disk increasing, S values decreases with the three methods but direct and indirect methods gave higher values than integrative method in most of the cases. As the divergence was within measurement uncertainties the correlation between the proposed method and the direct or indirect methods is in general good, obtaining R2 ≥0.95 for a straight line of unitary slope and null ordinate fitting in both cases. As control correlation between data obtained with direct and indirect methods was calculated and R2 = 0.996 was obtained.
These results confirm our hypothesis that the proposed method is more general and could be adapted mainly for non homogeneous or very difusive filters which is important as it could be in correspondence with advanced cataracts.
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