High Three-Dimensional Resolution and Long Imaging Range Retinal Optical Frequency Domain Imaging using Dual-Axicon Lens Illumination

Abstract

Purpose: In order to investigate the microstructures of retina with high three-dimensional (3-D) resolution and long imaging range, we developed an optical frequency domain imaging system, also known as swept-source optical coherence tomography (SS-OCT) system, using dual-axicon lenses (DA-OFDI). The Bessel beam illumination created by imaging optics with dual-axicon lenses provide small transverse focal spot over a long depth of focus, resulting in high 3-D resolution imaging in combination with high axial-resolution OFDI system. This study aims to evaluate clinical utility of DA-OFDI in retinal imaging.

Methods: Six eyes of 6 volunteers were imaged using the DA-OFDI and conventional OFDI. With the use of dual-axicon lenses, a ring-shaped Bessel beam was illuminated at an eye while circular beam was used with the conventional system. En face images of different retinal layers were reconstructed from 3-D data to compare the lateral resolution of the DA-OFDI and the conventional OFDI system. In addition, the lateral resolution of DA-OFDI system was theoretically analyzed using ray-tracing Zemax software with a human eye model.

Results: DA-OFDI system enhanced the visualization of retinal and choroidal capillaries. The lateral resolution of each retinal en face image was improved and the depth of focus was extended, compared with those of conventional OFDI. The lateral resolution of the DA-OFDI system was measured to be ~ 6 um, which is compatible with the results of Zemax simulation and much better than the 15 um of the convention system.

Conclusions: DA-OFDI can noninvasively detect the microstructures of the retina and choroid with high 3-D resolution and long imaging range. The results imply that DA-OFDI can be used for imaging the minimal changes of pathologies in early stages of ocular diseases. In addition, DA-OFDI provides imaging with reduced spherical aberration which is another advantage of using the Bessel beam illumination.

Keywords: 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • 688 retina • 452 choroid