Abstract
Purpose :
Ocular resolution due to diffraction becomes better with increasing pupil size, but that due to aberrations becomes worse. When imaging the retina, optimum pupil sizes can provide improved image quality in less expensive instruments, without adaptive optics. Here we study optimum pupils as a function of age and in a larger data set than previously considered.
Methods :
Individual phase plate eye models were implemented in Code V (optical design software) using measured ocular higher order aberrations (HOAs) for 1219 individuals from 20-70 years specified at 550 nm. Image quality with increasing pupil size was analysed for each eye, and results were stratified by age group. The spot size corresponding to 50% encircled energy (EE) specified lateral resolution. The optimum pupil size gave the smallest 50% EE. An average optimum pupil size was identified for each age group. Regression was carried out between optimum pupil size, age and higher order root mean squared (HORMS) wavefront error. Optimal pupil size for the oldest group was also specified for 830 nm by applying a chromatic correction from the literature to the HOAs at 550 nm.
Results :
As expected, on average at a given pupil size, image quality decreased with age, consistent with HOAs increasing with age. Optimum pupil sizes significantly deceased (p < 0.02) and corresponding best lateral resolution significantly worsened (p < 0.04) with age. The optimum pupil size for ages 58-70, was 2.7 ± 0.4 mm, providing a lateral resolution of 4.5 ± 0.6 μm. For ages, 20-32, optimum pupil size was 3.1 ± 0.5 mm, providing a lateral resolution of 4.0 ± 0.6 μm. The optimal pupil size for the oldest group at 830 nm was 3.1 ± 0.5 mm with a lateral resolution of 5.9 ± 0.8 μm, larger than at 550 nm. A significant (R2 > 0.7; p < 10-85) exponential fit of optimum pupil size to HORMS wavefront error accurately predicted an individual’s optimum pupil size. Thus, for best resolution in retinal imaging, average optimum pupil sizes can be defined for each age group. If values for HORMS wavefront error are available, optimal pupil sizes can be accurately predicted for each individual.
Conclusions :
When designing and/or using instruments for retinal imaging, optimum pupil sizes for best lateral resolution decrease significantly with the age of the group being imaged. HORMS wavefront error accurately predicts the optimum pupil size which gives best image quality for each individual.
This is a 2021 Imaging in the Eye Conference abstract.