Improving adaptive optics image quality in high powered eyes

Adaptive optics (AO) retinal imaging has been widely used for high resolution in vivo imaging studies in the human eye over the last two decades. More recently, this technology has been applied to image the retina of small animals such as rodents. Small animal eyes offer many advantages for the scientific study of retinal diseases, and theoretically have potential for superior image quality compared to human eyes. Unfortunately, to date AO image quality in practice is inferior to state-of-the-art image quality obtained from the human eye, and the cause of these limitations has not been fully understood. This work aimed to investigate and address the limitations to AO image quality in rodent eyes, and explore novel techniques in adaptive optics correction and image processing to overcome these limitations. The first experiment used optical modelling to test several commonly made assumptions in human AO imaging. These assumptions were found to be inappropriate for extrapolation to rodent eyes, due to their very high power and dioptric thickness of the retina. Specifically, results showed that AO image quality for the human eye is robust against positioning errors of the AO corrector and to differences in imaging depth and wavelength compared to the wavefront beacon. On the other hand, image quality for the rat eye declined sharply with each of these manipulations. The second experiment used a purpose-built flood-illumination AO ophthalmoscope designed for rat eyes to validate the modelling results from the first experiment, using physical model eyes of varying optical power. It was found that in general, AO image quality from the lower powered (60 D) model eye was much less susceptible to manipulations similar to those described in the first experiment, compared to the higher powered (220 D) model eye, thus confirming the optical modelling results. The same optical system was then used to account for these limitations as much as possible, while imaging adult pigmented