Long working distance OCT with a compact 2f retinal scanning configuration for pediatric imaging

Abstract

Young and/or autistic children cannot be imaged with tabletop or handheld optical coherence tomography (OCT) because of their lack of attention and fear of large objects close to their face. We demonstrate a prototype retinal swept-source OCT system with a long working distance (from the last optical element to the subject's eye) to facilitate pediatric imaging. To reduce the number of optical elements and axial length compared to the traditional 4f telescope, we employ a compact 2f retinal scanning configuration and achieve a working distance of 350 mm with a 16° OCT field of view. We test our prototype system on pediatric and adult subjects.

Figures

Fig 1

Comparison of 4f afocal relays (a) and 2f relays (b) for OCT retinal imaging. The 2f system can achieve the same working distance as the 4f system but with ⅓ the relay axial length (distance from scanner to last optical element) and fewer number of required optical elements. ΘSM: scan angle.

Fig 2

Schematic of a novel 2f retinal OCT scanner design enabled by delivering converging light into a single 2f refractive relay.

Fig 3

Optical design of the 2f sample arm. (a) Complete optical design with defined parameters and distances. (b-c) Detailed lens design of L1 (b) and L2 (before cost optimization) (c).

Fig 4

Simulated optical performance at the plane conjugate to the scanners without the schematic eye model and before cost optimization. The ray fan plots show the angular deviation of the rays from paraxial collimation. Deg: degree; mr: milliradian. SR: Strehl ratio. Red: 1010 nm, green: 1100 nm, blue: 1060nm.

Fig 5

Simulated optical performance at the retinal plane of a schematic eye before (a) and after (b) cost optimization of L2. The polychromatic geometric spots are shown for the extrema of the FOV The black circles show the Airy disk, and the Airy radii (AR) are in microns. Scale bars: 10 μm. Red: 1010 nm, green: 1100 nm, blue: 1060nm

Fig. 6

Representative images acquired from adult and pediatric subjects with the long working distance OCT system. (a-b) Custom optomechanical design (a) and photograph of in vivo use with iris camera frame in the top right (b). (c-d) Averaged (20 frames) B-scans centered on the fovea (c) and optic nerve (d) of a healthy adult. (e-f) Single-frame foveal B-scans acquired before (e) and after (f) refraction error correction. (g) Retinal volume acquired from a healthy adult. (h-i) Foveal B-scans acquired from patients with macular pathology. Red arrow denotes subretinal fluid in (h) and foveomacular vitelliform dystrophy in (i). (j-k) Averaged (20 frames) B-scans of the optic nerve (j) and fovea (k) of a healthy 6-year-old child.