Simulated image doubling and visual acuity: effects of doubling magnitude, orientation, and ghost image intensity

Abstract

Purpose The effects of image doubling on logarithmic progression chart visual acuity were investigated by simulating diplopia on a computer monitor. Methods Ten participants (6M, 4F) aged 21–28 years (mean 22.4 ± 2.3) were assessed viewing with their left eye while wearing their best correction. Stimuli were eight rows of five Sloan letters, from 0.4 to −0.3 logMAR (6/15 to 6/3) arranged in logarithmic progression format, generated on an HD monitor. Stimuli were generated with different magnitudes of doubling, different directions of doubling, and different intensity ratios between the ghost image and main images. Results When the ghost image had the same intensity as the main image, there was a significant effect of doubling magnitude on visual acuity, with the mean acuity being −0.11 logMAR (6/4.7) for no doubling. Acuity thresholds (logMAR) increased when doubling exceeded 1 min of arc, reaching a level of 0.12 logMAR (6/7.9) for doubling of 16 min of arc. There were no significant effects of orientation on acuity, nor were there significant orientation‐doubling magnitude interaction effects of visual acuity. Image doubling magnitude level affected visual acuity differently for different ghost image intensities, with the highest acuity elevation occurring when ghost and main images were equal or nearly equal. For faint ghost image intensities (10% and 20%) image doubling did not significantly affect visual acuity. Conclusions Image doubling will degrade visual acuity if doubling is greater than 1 min of arc, and ghost images are sufficiently intense. However, even with very obvious visually‐disturbing image doubling, visual acuity remains only slightly reduced.

Understanding the Impact of Individual Perceived Image Quality Features on Visual Performance

“…The findings in this study can be generalized to the normal population in studies where acuity is impacted by contrast, 24 , 36 blur, 24 , 37 and/or ghosting. 38 For example, the relationship between visual quality and visual acuity fails when ghosting is introduced (based on simulation). 21 …”

“…The findings in this study can be generalized to the normal population in studies where acuity is impacted by contrast, 24,36 blur, 24,37 and/or ghosting. 38 For example, the relationship between visual quality and visual acuity fails when ghosting is introduced (based on simulation). 21 It should be noted that the sample from which the wavefront aberrations were obtained and used to answer our research question relating perceived image quality and performance was a sample of convenience from an ongoing project and not critical to this simulation study.…”