Ultrahigh-Speed Retinal Imaging at 236,000 Axial Scans Per Second Using Swept Source/Fourier Domain OCT

Abstract

Purpose:: This investigation demonstrates new technology for ultrahigh-speed optical coherence tomography (OCT) imaging at 236,000 axial scans per second (236 kilohertz) using swept source/Fourier domain OCT. Ultrahigh-speed retinal imaging promises to enable rapid, high-definition volumetric imaging of retinal microstructure and physiology. Conventional spectral/Fourier domain OCT achieves imaging speeds of ~25,000 axial scans per second, enabling three-dimensional (3D) OCT. However, speeds are not high enough to eliminate eye motion artifacts and sampling density remains limited. A new generation of OCT technology with higher speeds would improve performance, enabling denser sampling with reduced motion artifacts.

Methods:: Recent advances in spectral/Fourier domain OCT using spectrometers have enabled high-speed retinal imaging and improved sensitivity compared with time domain OCT. Swept source/Fourier domain OCT, which uses wavelength swept lasers, has similar capabilities, but can scale to higher imaging speeds. A wavelength swept laser and prototype OCT instrument were developed in the 1050 nm wavelength range. The full tuning range was 63 nm, enabling an axial resolution of ~11 microns in tissue.

Results:: OCT imaging of the retina and optic nerve head were performed at 1050 nm and 236,000 axial scans per second. 1050 nm wavelengths enable imaging deeper in the choroid compared with 800 nm. OCT images with 500 transverse pixels are acquired at 470 images per second. A 3D data set consisting of 350 images is acquired in ~0.8 seconds. This is ~500 times faster than conventional time domain OCT and almost 10 times faster than conventional spectral/Fourier domain OCT. Therefore, motion artifacts were dramatically reduced.

Conclusions:: Ultrahigh-speed retinal imaging was demonstrated at 236,000 axial scans per second using swept source/Fourier domain OCT. These unprecedented speeds enable rapid acquisition of three-dimensional data sets. High sampling densities are possible in both transverse dimensions, enabling en face OCT fundus imaging. Single OCT images may be acquired in milliseconds, and measurements with temporal resolutions on the microsecond time scale are possible. Ultrahigh-speed, swept source/Fourier domain OCT improves retinal imaging performance compared previous technologies, and promises to enable novel protocols for measuring retinal structure and function.

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