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Guillaume Van Der Meer, Pierre-Jean Pisella, Richard Legras; Binocular through-focus image quality with various combinations of modified monovision. Invest. Ophthalmol. Vis. Sci. 2013;54(15):827.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the binocular through-focus (TF) subjective vision with various combinations of modified monovision (ie different profile of spherical (SA4) and secondary spherical (SA6) aberration on each eye).
We used a numerical eye model to calculate the appearance of an image (ie three 0.4 logMAR size high contrast letters) viewed thought an eye taking into account of the variation of pupil size as a function of proximity (ie 4.7mm at distance vision to 3.3mm at near vision). Images were calculated for various combinations of SA4 and SA6 (ie SA4-0.4μm, SA4+0.4μm, SA4-0.4μm and SA6+0.2μm, SA4+0.4μm and SA6-0.2μm) and for all proximities from -5-D to 5-D with a 0.125-D step. A 3D-NVIDIA video device was used to simulated binocular vision by projecting a different image on each eye with a 120Hz frequency. TF subjective vision was evaluated by using a grading scale (ITU-R 500 recommendation) by three subjects under monocular and binocular condition for each tested conditions (ie various combination of the five multifocal profiles).
Binocular TF curves followed the best monocular curve but there was no binocular summation of quality of vision. Binocular inhibition was greater when the difference in subjective vision between each eye was important. Ocular dominance affected the level of inhibition. We calculated area under the binocular curve (AUC) to evaluate subjective quality of vision and depth-of-focus. AUC increased when adding spherical aberrations and can even be doubled, compared to naked eye, with reverse profile of SA4 and SA6 between each eye (ie SA4-0.4μm and SA6+0.2μm on one eye and SA4+0.4μm and SA6-0.2μm on the other eye). Pupil diameter variations had to be taken into account when using simulated images. The decrease of pupil size in near vision led to a better TF subjective vision especially with combination of SA4 and SA6. Although we distinguished two different optical performance profiles (ie (i) good distance vision/acceptable intermediate vision/poor near vision, and (ii) good distance vision/poor intermediate vision/good near vision) there was a good correlation (r2=0.89) between AUC and mean quality of vision at distance/intermediate and near vision.
There is no binocular summation of quality of vision. However the use of different SA profiles on each eye especially reverse profile of SA4 and SA6 profile involved a better binocular TF subjective vision.
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