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Simulated image doubling and visual acuity: effects of doubling magnitude, orientation, and ghost image intensity
Author(s) -
Carkeet Andrew,
Chang YuChong Anderson,
Chang TeYuan,
Chen PoYen Mike,
Gu Ming,
Lin Vincent,
Ng Jia Hao
Publication year - 2019
Publication title -
ophthalmic and physiological optics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.147
H-Index - 66
eISSN - 1475-1313
pISSN - 0275-5408
DOI - 10.1111/opo.12605
Subject(s) - magnitude (astronomy) , orientation (vector space) , intensity (physics) , visual acuity , optics , image (mathematics) , physics , artificial intelligence , mathematics , computer science , geometry , astronomy
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 log MAR (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 log MAR (6/4.7) for no doubling. Acuity thresholds (log MAR ) increased when doubling exceeded 1 min of arc, reaching a level of 0.12 log MAR (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.