Human retinal imaging using visible-light optical coherence tomography guided by scanning laser ophthalmoscopy

Abstract

We achieved human retinal imaging using visible-light optical coherence tomography (vis-OCT) guided by an integrated scanning laser ophthalmoscopy (SLO). We adapted a spectral domain OCT configuration and used a supercontinuum laser as the illumating source. The center wavelength was 564 nm and the bandwidth was 115 nm, which provided a 0.97 µm axial resolution measured in air. We characterized the sensitivity to be 86 dB with 226 µW incidence power on the pupil. We also integrated an SLO that shared the same optical path of the vis-OCT sample arm for alignment purposes. We demonstrated the retinal imaging from both systems centered at the fovea and optic nerve head with 20° × 20° and 10° × 10° field of view. We observed similar anatomical structures in vis-OCT and NIR-OCT. The contrast appeared different from vis-OCT to NIR-OCT, including slightly weaker signal from intra-retinal layers, and increased visibility and contrast of anatomical layers in the outer retina.

Keywords: (110.4190) Multiple imaging; (170.0110) Imaging systems; (170.4470) Ophthalmology; (170.4500) Optical coherence tomography.

Fig. 1

(a) Schematic of the vis-OCT system for humans; (b) photograph of the system. SC: Supercontinuum laser source; SF: Single-mode fiber; SM: Spectrometer; Ref: Reference arm; FM: Motorized flip mirror; MS: Motorized beam stop; GM: Galvometer mirror; MF: Multimode fiber; APD: Avalanche photodiode; MR: Mirror; ND: Neutral density filter. In (a), the ND and MR were placed at the position of eye ball to characterize the system performance. In (b), a blue arrow points to the three-dimensional translational chin rest for adjusting eye position; a yellow arrow points to the stational optics board.

Fig. 2

System characterization. (a) Normalized spectrum measured by the spectrometer; (b) The relative standard deviation over 1,000 spectra acquired subsequently; (c) Measurements of axial resolution, system sensitivity, and sensitivity roll off.

Fig. 3

SLO and vis-OCT images centered at the fovea. (a-b) En face images of SLO and vis-OCT; (c-d) Contrast-adjusted images from the squared area in (a) and (b); (e) Cross-sectional vis-OCT image from the position highlighted in (b) with all anatomical structures labeled. ILM: Inner-limiting membrane; NFL: Neural fiber layer; GCL: Ganglion cell layer; IPL: Inner plexiform layer; INL: Inner nuclear layer; OPL: Outer plexiform layer; ONL: Outer nuclear layer; IS/OS: Inner/outer segment junction; OS: Outer segment of photoreceptor; RPE: Retinal pigmented epithelium; BM: Bruch’s membrane. (f) Single cross-sectional image using a commercial NIR-OCT system. (g) Averaged vis-OCT image from eight consecutive B-scans. The motion artifact was removed by aligning the adjacent B-scans.

Fig. 4

SLO and vis-OCT images centered at ONH. (a-b) En face images from SLO and vis-OCT; (c-d) Contrast-adjusted images from the squared area in (a) and (b); (e) Cross-sectional vis-OCT image from the location highlighted in (b); Arrows points to the signal from blood within major retinal vessels.

Fig. 5

(a) Cross-sectional vis-OCT image around ONH. The inset at the botton-right corner shows the en face vis-OCT image where the B-scan is taken from. (b-c) Magnified images from the squared areas in (a). Arrow points to the signal from the choriocapillaris immediately beneath Bruch’s membrane. The anatomical structures in the outer retina are labeled in (b).

Fig. 6

Original 10° × 10° field of view images. (a-d) original images for Fig. 3(c), 3(d) and Fig. 4(c), 4(d).

Fig. 7

Magnified images of RPE/BM structures from vis-OCT and NIR OCT. (a-b) Replots of Fig. 3(e) and 3(f). (c-d) 4x magnified images from the squared areas in (a) and (b).