Abstract
Purpose :
Image convolutions are often used to simulate the effects of ocular aberrations on image quality.We studied potential discrepancies in the image degradation/visual performance using convolved images(viewed through corrected optics)or the real aberrations,in both monochromatic & white light(WL)
Methods :
On bench & visual acuity measurements in patients were obtained using a custom polychromatic Adaptive Optics(AO).The system allows measurement (Hartman-Shack,HASO)& correction/induction(deformable mirror,DM,MIRAO,Imagine Eyes) of high order aberrations(HOAs).Stimuli were displayed in a Digital Micro-Mirror Device(DMD),illuminated with 450,555,670nm,& WL.Image convolutions of a stimulus (20/100 black E-letter,25cd/m2) were obtained with standard Fourier Optics(Matlab) using subject's HOAs(diffraction limit (DL)control).An artificial eye was used to image the original stimulus through real HOAs (mapped on DM)or the convolved(conv) stimulus(AO).In subjects(4 young cyclopleged)Visual Acuity(VA,tumbling high contrast E-letter,8AFC+QUEST)was measured under natural HOAs & with conv images under AO,for the 3λ & WL(6mm pupil)
Results :
Subject's Visual Strehl ranged from 0.17-0.33.On bench, the stimulus contrast through diffracted/aberrated optics & the conv image with a DL/subject PSF differed on avg by 0.40/0.50(450),0.34/0.58(555),0.30/0.58(670) & 0.43/0.53(WL),with conv images overestimating image degradation.Computer simulations revealed that the second-pass(DL/residual aberration) was only responsible of 11/12%loss in contrast.In subjects,logMAR VA was on avg,0.10±0.01,-0.08±0.03,0.03±0.02 &-0.03±0.04 with natural aberrations & 0.27±0.03,0.10±0.05,0.18±0.02 & 0.14±0.04(450,555,670&WL)using conv stimulus.Measured VA is correlated with native optical quality in 555nm with natural optics(r2=0.98,p=0.01)but not in WL(r2=0.45,p=0.30).Differences(Natural-Conv)ranged btw -0.07 to-0.29(avg across λ for each subject).There was not a consistent larger difference in monochromatic vs WL
Conclusions :
The use of convolved stimuli underestimates the measured VA(comparison with high contrast stimuli & natural optics).Discrepancies must occur in part from optical grounds,as are also found on bench.Although the magnitude of the native optical aberrations & chromatic effects appear to play some role,they do not fully responsible for the effect,likely associated to approximations in the convolution representation of the images
This is a 2021 ARVO Annual Meeting abstract.