Impact of higher-order aberrations on depth-of-field

It is well known that depth-of-focus (DOF) is influenced by optical factors (such as pupil size & monochromatic aberrations). However, neural factors such as blur sensitivity and defocus adaptation that may play an important role on the extent of DOF. A series of experiments were conducted to study if optical or neural factors are most pertinent in explaining the variability of DOF across subjects. An adaptive optics system with a B/W target, a 3.8-mm artificial pupil, and a subjective criterion (based on objectionable blur) were used to measure depth-of-field (DOFi, i.e. DOF computed in the object space) in eleven participants, after at least 6 minutes of adaptation. This was done under 3 conditions: 1) with their own higher-order aberrations (HOA); 2) after correction of their monochromatic HOA; and, 3) after altering the HOA pattern for some participants to reflect the HOA pattern measured for a different participant. Natural DOFi and DOFi after HOA correction were positively correlated (R² = 0.461), but a significant decrease in DOFi (21% on average) was found after HOA correction (p = 0.042). Effect of HOA on the inter-subject variability of DOFi was 3.9 times smaller than the effect of the image neural processing. This study shows that DOFi depends on both optical and neural factors, but the latter can even play a more important role than the former.