Surpassing the diffraction limit for improved lateral resolution in adaptive optics optical coherence tomography of the living human eye.

Advances in adaptive optics optical coherence tomography (AOOCT) have facilitated the three-dimensional assessment of structural and functional properties of individual retinal cells in the living human eye. However, even with diffraction-limited AOOCT systems, some cells in the living human retina can be difficult to resolve, especially when using near-infrared wavelengths of light (~1000 nm). We demonstrate that modifying the traditional AOOCT instrument design to enable annular illumination and sub-Airy disk detection results in improved imaging resolution beyond fundamental limits imposed by diffraction. We successfully applied this approach to in vivo human retinal imaging, achieving on average 36% improvement in lateral resolution beyond conventional imaging conditions, enabling improved visualization of the foveal cone and rod photoreceptor mosaics using AOOCT. These results demonstrate an effective strategy for improving lateral resolution in point-scanning AOOCT in a manner that is compatible with new and existing instruments.