Truly simultaneous OCT of the anterior and posterior eye with full anterior chamber depth and 30° retinal field of view

Abstract

Purpose : Conventional OCT systems image only the anterior or posterior eye, not both. Newer OCT systems begin to do both but with compromises such as only imaging the fovea with the anterior segment or rapidly switching between the anterior and posterior eye. We describe here the development of an OCT system with truly simultaneous imaging of both the front and back of the eye capable of imaging the full anterior chamber depth and 30° on the retina (macula + optic nerve).

Methods : A swept source (λ₀=1045nm, Δλ=100nm, 200 kHz A-scan rate; Axsun, Inc.) OCT system with a polarization encoded, dual channel sample arm was designed to simultaneously image both the anterior and posterior eye with the requisite fields of view (Fig. A). The posterior eye pathlength was matched to the reference arm pathlength while the anterior eye pathlength was offset by one laser cavity length to take advantage of coherence revival [1]. A subject was consented under an IRB approved protocol. Repeated B-scans (1200 A-scans; 4128 samples per A-scan or 11.1mm of depth) were taken such that the fovea, optic nerve head, and anterior chamber were observed within each B-scan. The retina was encoded into the first 3mm of the scan with the anterior chamber occupying the remainder.
[1] A Dhalla, et al. Opt. Lett.37, 1883-1885 (2012)

Results : Figure B and C show 50 repeated and averaged B-scans acquired simultaneously from a healthy subject. The subject was wearing a contact and the corneal epithelial layer can be visualized (Fig. B). In the simultaneously acquired posterior scan, the retinal nerve fiber layer, outer plexiform layer, and the photoreceptor segment layer are visualized (Fig. C).

Conclusions : We have demonstrated an OCT system capable of truly simultaneous imaging of the both the anterior and posterior eye with sufficient field of view to see the full anterior chamber depth and the macula and optic nerve within one acquisition. This has important implications for clinical use of OCT to image the eye and for biometric applications.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

 

A) Simultaneous ocular anterior and posterior segment SSOCT imaging system schematic B) Anterior chamber of normal subject from 50 registered and averaged B-scans. There is a contact lens on the cornea and the corneal epithelial boundary is visible. C) Retina image acquired simultaneously with the anterior chamber scan in B (same 50 B-scans).