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Joung Yoon Kim, Aixa Alarcon, Geunyoung Yoon; Improving binocular through focus visual performance by inducing different interocular orientation of astigmatism.. Invest. Ophthalmol. Vis. Sci. 2014;55(13):5972.
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© ARVO (1962-2015); The Authors (2016-present)
Our previous study found that the human binocular system is capable of selecting the sharper parts of the monocular retinal images to yield a higher binocularly perceived image quality. The goal of this study is to investigate whether this capability is effective for extending depth of focus binocularly when orthogonal orientations of astigmatism are induced to the two eyes.
Binocular through focus high contrast visual acuity (VA) from far to near (0D to 2D in 0.5D increment) was measured using the tumbling E letter in 4 cyclopleged subjects for a 4mm pupil under three conditions: aberration free, same horizontal orientation (0°) of astigmatisms (0.5D) and orthogonal orientations (0° and 90°) of astigmatisms (±0.5D) to each of the two eyes. Binocular adaptive optics vision simulator was used to correct subject’s native aberrations in both eyes, and induce the proper amounts of astigmatism and defocus to simulate different vergences
Astigmatism reduced VA at distance, -0.27±0.02 LogMAR VA for no astigmatism, -0.15±0.03 LogMAR VA for same orientation and -0.18±0.03 LogMAR VA for orthogonal orientation. However, at all of the defocus points measured, through-focus VA showed a significant improvement (p<0.05 for all distances, Student t-test). On average the VA improvement was 0.08±0.01 LogMAR for same orientation of astigmatism and 0.09±0.01 LogMAR for orthogonal orientation of astigmatisms. All subjects showed better VA for orthogonal than for same orientation of astigmatism by 0.027±0.015 LogMAR on average across the defocus points. This improvement was only statistically significant for 2D (p<0.05).
Astigmatisms significantly improves binocular through focus visual performance. More interestingly, it was found from all of 4 subjects that visual acuity of orthogonal orientation of astigmatism at distance and 2D was better than the same orientation of astigmatism. These findings suggest that use of orthogonal orientation of astigmatism can be another binocular approach to overcome presbyopia.
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