Adaptive Optics Flood-illuminated Camera for High Speed Retinal Imaging

Abstract

Abstract: : Purpose: Current adaptive optics (AO) flood-illuminated retina cameras operate at very low frame rates, acquiring retinal images below 1/10th Hz and deterring their deployment in a clinical setting. To this end, we have developed a novel CCD-based AO camera that achieves significantly higher acquisition rates. The accrued benefit for quick focusing and surveying the microscopic retina was examined. Methods: A flood-illuminated retina camera equipped with AO was developed for imaging microscopic structures in the living human retina. The AO system consisted of a Shack-Hartmann wavefront sensor and 37-actuator Xinetics mirror, which provided dynamic correction of the eye’s wave aberrations. A multimode optical fiber system coupled to a superluminescent diode (SLD) provided uniform illumination of a 1 deg patch of retina. A back-illuminated scientific-grade CCD captured aerial images of the retina whose acquisition was synchronized to the strobing fiber light source. Results: Cone photoreceptors at the fovea were observed in several subjects. The AO system was found to reduce the wavefront error across a 6 mm pupil to about 0.1 microns RMS in several subjects and provided up to 22 wavefront corrections per second. A continuous frame rate exceeding four retinal images per second was achieved, a factor of at least 40 higher than current AO flood-illuminated cameras. Short four-image bursts were successfully collected at rates exceeding 500 per second and revealed temporal dynamics of the microscopic retina. The inherent parallel nature of the CCD precluded intra-image registration that is required for scanning retina cameras to offset retina motion artifacts. Conclusions: An AO retina camera employing a flood-illuminated light source achieved rapid image collection. This was found to permit easier focusing and exploration of the living retina at the cellular level.

Keywords: physiological optics • microscopy: light/fluorescence/immunohistochem • retina