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Mihai State, Robert Rosen, Patricia A Piers; Preclinical evaluation of IOL associated dysphotopsia footprint. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2722.
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© ARVO (1962-2015); The Authors (2016-present)
Generally described as spurious bright images or shadows occurring after the implantation of a capsular bag intraocular lens (IOL), dyphotopsia was previously theoretically evaluated and several rationales were proposed to explain its origin, clinical detectability and visual impact. The current study describes dysphotopsia assessment through a theoretical model, the development of a preclinical measurement method including figures of merit, and comparative results for different IOLs. Such a method would enable the quantitative evaluation of the dysphotopsia footprint characteristic to a given IOL platform design.
For the theoretical in-vitro evaluation, a non-sequential ray tracing model eye with an anatomically average cornea was used. The IOL geometry was described as a 3D CAD object. For a discrete series of object angles and clinical conditions, the irradiance was mapped on the entire image plane. Analogously, the measurements were performed by means of an off-axis MTF bench with a 12-bit CCD camera. For each object angle, the main image, glares and interlaced frames were processed off-line by the means of a Matlab script. The figures of merit were area under the intensity curves, glares contrast and their angular position with respect to the main image. Several monofocal aspheric IOLs were evaluated.
The measured photic footprint (see Fig. 1) bears a close similarity to the simulated one (see Fig. 2). To account for the edge glare relative intensity, the edge frosting effect was retro-fitted by a Lambertian scattering surface. For the IOL models and object angles evaluated, the angular offset of the cornea glare with respect to the main image was on average 3.7 degrees with a standard deviation of 0.39 degrees. For the same glare, as expected, the contrast increases as a function of object angle and for 60 degrees a factor two difference was recorded between various models.
A method enabling the preclinical evaluation of dysphotopsia was developed. Its results can be integrated at the IOL design stage and used for the quantification of the IOLs photic footprint in clinically representative conditions.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
Fig. 1 Negative dysphotopsia (ND) measurement results (60 degrees): MI – main image, upper row - raw frames, lower row - intensity plots.
Fig. 2 Intensity profiles comparison (60 degrees): black - theoretical, coloured - measurements.
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