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Aiswaryah Radhakrishnan, Carlos Dorronsoro, Lucie Sawides, Michael Webster, Eli Peli, Susana Marcos; Internal code for blur: Interocular effects. Invest. Ophthalmol. Vis. Sci. 2014;55(13):5970.
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© ARVO (1962-2015); The Authors (2016-present)
To assess the relationship between the internal code for blur and the differences in ocular optical quality between eyes.
A custom adaptive optics system with a psychophysical channel was used to measure the ocular aberrations and to perform blur adaptation tests under fully-corrected aberrations. Blur magnitude was characterized by the Strehl Ratio (SR), and blur orientation by the point spread function’s (PSF) major axis. Interocular differences were defined as 30% discrepancy in SR (blur) and/or 20-deg axis (orientation) between eyes. Subjects showed either same blur magnitude and orientation in both eyes (n=4); same blur magnitude but different orientation (n=2); or different blur magnitude and orientation between eyes (n=4). All tests were monocular, and performed in both eyes. Best perceived focus (BPF) was measured using a QUEST 2AFC psychophysical paradigm, in which subjects were presented with 128 images blurred with different SR and the best perceived image identified. Additionally, the directional internal code for blur (ICB) for each subject and eye was obtained using a pattern classification technique (Sawides PLOS One 2013) in which 500 pairs of images with similar magnitude of blur (same SR) but different blur orientations are presented, the subjects selecting the best image from the pair. The ICB was obtained by averaging and weighting of the positive responses, and its orientation determined. The BPF and ICB were compared between eyes and correlated with the ocular PSFs.
The average discrepancy in ocular image quality (SR) between eyes was 24.47%. Despite the differences in ocular SR, the BPF measured in right and left eye was similar in most subjects (8.47% average discrepancy in SR; r=0.98, p<0.0001). The BPF correlated highly with the least aberrated eye’SR (r=0.787, p<0.0001) or the average SR of both eyes, (r=0.677, p<0.0001), and less with the more aberrated eye (r=0.52, p=0.026). In all subjects, the estimated ICB was highly correlated between left and right eyes (mean r=0.996, p<0.0001). In all subjects with different interocular PSF orientaton, ICB axis matched the PSF axis of the least aberrated eyes (within 8.78 deg on average).
The internal code for blur is similar between eyes despite interocular differences in magnitude and orientation of blur. In most of the subjects the internal code for blur is driven by the eye with better optical quality.
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