Telecentric model eye for correction of image distortion in adaptive optics ophthalmoscopes

Here, we demonstrate a telecentric model eye for measuring scanning, sampling, and optical distortion in AO ophthalmoscopes across a 10-diopter focus range, seeking to improve the reproducibility of adaptive optics (AO) ophthalmoscopy biomarkers. The model eye lens provides diffraction-limited performance when imaging with 800 nm light over circular 2.0, 3.0, 4.6, and 9.2° fields of view through 8, 6, 4, and 2 mm diameter aperture stops, respectively. Measurements of double-pass wavefront aberrations using both model and real retinas show that the use of opal glass model retinas, rough model retina surfaces, and wavefront sensing beacon scanning mitigate first-pass aberrations. This is particularly important, as first-pass aberrations are often assumed but not always achieved in AO ophthalmoscopes. Using the model eye with custom distortion estimation algorithms, we recorded 0.06% non-isotropic scaling repeatability, 0.02° shear repeatability, 0.5% reproducibility for both metrics and a root-mean-square residual distortion of 0.1 pixels across the field of view and focus range.