Theoretical versus empirical measures of retinal magnification for scaling AOSLO images

The adaptive optics scanning light ophthalmoscope (AOSLO) allows cellular resolution imaging of the living retina. The accuracy of many quantitative measurements made from these images requires accurate estimates of the lateral scale of the images. Here, we used trial lenses, which are known to affect the relative magnification of the retinal image, to compare empirical measures of image scale with theoretical estimates from a four-surface optical model. The theoretical optical model overestimated the empirically determined change in image scale in 70% of the subjects examined, albeit to varying degrees. While the origin for the differences between subjects is not known, residual accommodation during imaging likely contributes to this variability in retinal magnification. These data provide an opportunity to derive improved lateral scaling error estimates for structural metrics extracted from AOSLO retinal images.