Abstract
Background: Despite the growing body of evidence demonstrating that perceptual learning (Chung and Susana, 2011; Levi et al., 2009; Polat et al., 2012; Tan & Fong, 2008) and eye-training (Horwood et al., 2014; Kang et al., 2016) can improve visual functions, it is still controversial whether those improvements are practically significant enough to treat maladies such as myopia and presbyopia (Allen, et al., 2009; Deveau & Seitz, 2014). We devised a novel training task where participants discriminated the sharpness of a grating stimulus and measured the effects of training for presbyopia. Methods: Three female participants (age: 70, 51 and 50 years) completed pre-tests, 20-day training, and post-tests. In pre- and post-tests, participants’ visual acuity, comfortable viewing distance, and motion sensitivity were measured. In training, a grating stimulus with sine/square wave (orientation randomized) was alternately presented on a far (280 cm) or near-screen (2–70 cm). The spatial-frequency of the far-screen stimulus and the viewing distance of the near-screen changed adaptively depending on participant’s performance. Participants reported the grating’s sharpness (i.e. sine or square wave) by pressing a sharp-edged/a blunt-edged button within 5 seconds after the stimulus onset (stimulus duration:1 second). Participants ran 800 trials per day for about 35 minutes. Results: Participants’ performances in both near and far-screen tasks gradually improved over 20 days of training. Mean comfortable viewing distance for near-screen decreased from 27.0 cm to 8.8 cm. Spatial frequency threshold for far-screen stimulus increased from 8.6 cycle/degree to 20.7 cycle/degree. In post-test participants’ VA (pre-test=0.9; post-test=1.07, p=0.04) and comfortable viewing distance (pre-test=28.83 cm; post-test=6.63 cm, p=0.04) improved significantly. However, motion sensitivity (large-sized stimuli: p=0.12; small-sized stimuli: p=0.09) didn’t improve significantly. Conclusions: Results suggest that sharpness discrimination can be an effective training task for presbyopia, although additional experiments with control conditions are necessary to clarify the effects of the task.