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Richard Legras, David Rio, ; Tolerance to blur and visual activities and vision quality questionnaire. Invest. Ophthalmol. Vis. Sci. 2014;55(13):776.
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To determine if tolerance to blur is linked to everyday visual activities and/or vision quality. It has been observed that a relationship exists (r2= 0.21) between tolerance to blur and personality. How we use our vision and the feeling we have on its quality could influence tolerance to blur.
Tolerance to blur was defined as the range of proximities for which the quality of vision was still judged acceptable (objectionable blur) and was measured three times on three 20/50 high-contrast letters. Sixty-six young normally sighted subjects (median age of 21 years), viewed displayed images through a 3 mm artificial pupil to limit the impact of their own aberrations. Simulated images were calculated for various defocuses (i.e. step of 0.055 D) and for a 5 mm pupil diameter, using a numerical eye model. Prior to these measures, subjects filled in a questionnaire composed of the VAQ (i.e. 36 questions) and 20 additional questions detailing/quantifying their visual activities (sport, TV, computer, reading….).
The average intra-individual standard deviation (0.053 D) was comparable to the step of measurement, involving a good repeatability. Blur tolerance ranged from 0.67 to 1.55 D. The highest correlation obtained with one questionnaire item was r2 = 0.35. When taking into account 7 questions, the correlation level (r2) rise to 0.48 (p < 0.001). These items mainly concern near vision activities and difficulties, difficulties in localization of static or moving objects. Moreover, blur tolerance was not correlated to higher order native aberrations (r2 = 0.005) and to spherical error (r2 = 0.03).
Tolerance to blur seems driven by some vision issues encountered in every day life. Such a questionnaire could be helpful to predict the acceptability of degraded image qualities like with multifocal optics. When developing customized optics, the designers should take into account these parameters.
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