Ultrahigh Speed and Multiscale Volumetric 1050nm Ophthalmic OCT Imaging at 100,000-400,000 Axial Scans per Second

Abstract

Purpose: : OCT acquisition speed limitations of 25,000 to 52,000 axial scans per second in commercial instruments allow only a single, sparsely sampled 3D volume to be acquired due to blinking and eye movement. This investigation demonstrates imaging at 100,000 to 400,000 axial scans per second (10X faster than commercial instruments) using new short cavity swept laser technology. High scan rates enable acquisition of 3D volumes at multiple scales, providing multiresolution large area and small feature correlated data sets of retinal and anterior eye features.

Methods: : A reconfigurable, 1050nm swept source/Fourier domain prototype OCT instrument with 100kHz-200kHz (single beam) and 400kHz (dual beam) axial scan rate, 5.5-6um axial resolution in tissue with 3.8mm (retinal) to 7.5mm (anterior) imaging range was developed. Dense 3D volumes consisting of 500x500 to 1100x1100 axial scans over 700umx700um to 12mmx12mm were acquired of the retina. Anterior segment imaging was performed with 500x500 to 800x800 axial scans over 3.5mmx3.5mm to 17mmx17mm. Multiple volumes with orthogonal scan directions were registered using custom algorithms to correct for eye movement.

Results: : Large area retinal volumes show contiguous morphological data spanning the macula and optic disc, while small area correlated volumes enable visualizing individual cone photoreceptors. Large volumes of the anterior segment show the cornea, iris, and anterior lens in a single acquisition, while small volumes show small outflow features, such as Schlemm’s canal. 3D data registration reduces motion artifacts and improves signal to noise.

Conclusions: : Image acquisition at multiple scales is enabled by ultrahigh speed OCT. Large features spanning ~10mm (e.g. retinal nerve fiber bundle pathways and the complete anterior ocular surface) are complimented by correlated data sets showing individual features on the order of 10um (e.g. cone photoreceptors and Schlemm’s canal). Ultrahigh speed OCT, 3D data registration, and multiscale OCT imaging promise to provide additional insights into possible disease related correlated changes occurring at multiple spatial scales within the eye.

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