Adaptive Optics Ultrahigh Resolution Optical Coherence Tomography

Abstract

Abstract: : Purpose: To demonstrate for the first time the combination of ultrahigh resolution optical coherence tomography (UHR OCT) and adaptive optics (AO) for high axial and transverse resolution in vivo retinal imaging. Methods: A compact (30 x 30 cm) closed–loop adaptive optics system, based on a real–time Hartmann–Shack wave–front sensor at 30 Hz and a 37 element low–cost micromachined membrane deformable mirror (OKO Tech, Holland), was interfaced to an UHR OCT system, based on a commercially available OCT 1 (Carl Zeiss Meditec Inc., CA, Dublin) instrument, employing a compact Titanium:sapphire laser with 130 nm optical bandwidth centered at 800 nm. Results: Adaptive optics ultrahigh resolution OCT enabled unprecedented identification of intraretinal layers in vivo with 3 µm axial resolution. Closed–loop correction of ocular aberrations was accomplished with a residual uncorrected wave–front of 0.1 µm for a 3.68 mm pupil diameter. Strehl ratio improvements of a factor of 10 or more were achieved. A significant UHR OCT signal to noise ratio improvement of up to 9 dB using AO, as compared to uncorrected ocular aberrations, was obtained. AO UHR OCT enabled a transverse resolution of 5–10 µm. This is a 2–3 time improvement as compared to UHR OCT systems used so far, that employed a 1 mm beam diameter without AO. Preliminary results on healthy normal subjects as well as selected patients are presented and further potential technical improvements are discussed. Conclusions: Adaptive optics and ultrahigh resolution OCT has been combined, according to our knowledge, for the first time, demonstrating the potential to increase sensitivity and to enable retinal imaging with 3 µm axial and up to 5 µm transverse resolution. Further technical improvements might enable the three dimensional visualization of retinal features like photoreceptors or capillaries.

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