Pancorrection and Ultrahigh Resolution Optical Coherence Tomography: Unveiling the Three-Dimensional Architecture of the Cone Mosaic in the Living Human Retina

Abstract

Purpose:: To increase transverse and axial resolution in ophthalmic 3D ultrahigh resolution optical coherence tomography (UHR OCT) by using pancorrection. This novel technique allows simultaneous compensation of monochromatic and chromatic ocular aberrations. When combined with UHR OCT it enables to resolve single retinal cells in vivo.

Methods:: An adaptive optics system was interfaced to a frequency domain UHR OCT set-up. The correcting system used a new magnetic force enabled deformable mirror (MIRAO52) and a Hartmann-Shack wavefront sensor (HASO32). The apparatus incorporated a lens specifically designed to correct chromatic aberration covering the entire spectral range of interest for OCT (700 to 900nm). The UHR OCT system used an ultrabroad bandwidth spectral source, emitting a continuous, Gaussian shaped spectrum, centred at 800nm and 140nm full width at half maximum.

Results:: Near isotropic resolution in the living retina (~2x2x2µm) was demonstrated by using pancorrection and UHR OCT. Correction of chromatic aberration allowed the entire set of spectral components emitted by the source to be focused on the same retinal plane. The deformable mirror corrected high order monochromatic aberrations with a record amplitude of 100µm. 3D images of the human photoreceptors’ structure were obtained in vivo.

Conclusions:: Full correction of ocular aberrations allowed ultrabroad bandwidth spectral sources to be efficiently focused onto the retina, increasing transverse and axial resolution in OCT. The 3D structure of the photoreceptors in the living retina was shown. Other intraretinal morphological features of unknown nature were also resolved. Their significance and interpretation is to be unveiled in subsequent studies.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • retina • photoreceptors