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Peripheral 2D Image Quality Metrics of Different Types of Multifocal Contact Lens

Purpose: To evaluate the impact of different designs of multifocal contact lenses on the peripheral image quality metrics.

Methods: Series of Hartmann-Shack images were recorded by using an open-view high-resolution peripheral wave-front sensor (VPR, Voptica SL, Murcia, Spain) in 13 young myopic subjects (mean spherical equivalent error: -3.25D; range: -0.75 to -6.50D). For each eye, horizontal scans covering 40° of visual field were obtained at five different vertical fixations (0°, +10°, +20°, -10°, -20°). Measurements were taken while subjects were wearing: 1) no lens 2) a multifocal center-distance (MFCD) or 3) a multifocal center-near (MFCN) soft contact lens (Xtensa by mark’ennovy; distance Rx: -0.25DS). At each peripheral angle, the point spread function (PSF) was calculated and used to convolve the “Lena” image. After this, the convolved images passed a low pass filter to remove the spatial frequencies that where above the cutoff spatial frequency for the corresponding eccentricity. Subsequently, the filtered images were cropped and compared with the original image, to obtain 2-D cross-correlation values as an image quality metrics.

This was used to determine 2D significance maps, based on the cross-correlation values for all the subjects and conditions. Additionally, one significance map was defined by using the theoretical spatial frequency limit. The differences (root mean square errors: RMSE) between the 2-D significance maps and the cut-off map were used to quantify the overall differences produced by each condition for each subject.

Results: While analyzing the full visual field, the naked eye condition (1) obtained the highest similarity to the ideal image quality (RMSE=0.2315). In contrast, the MFCN design significantly degraded the overall quality metric (RMSE= 0.2897; p=0.0166), while the MFCD did not (RMSE=0.2720, p=0.3552).

Conclusions: The amount of blur on the retina can be modified by optical treatments such as contact lenses. A better understanding of the image quality with different optical treatments can shed some light on the efficacy of different solutions for myopia management.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 – May 2, 2019.

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