Speckle Noise Reduction in Visible-Light OCT

Abstract

Purpose : Visible-light optical coherence tomography (vis-OCT) is a novel ocular imaging modality with anatomical and functional imaging capabilities. Speckle noise can make it challenging to detect fine details, complicating the interpretation of vis-OCT images. The purpose of this study was to demonstrate vis-OCT image optimization using our novel speckle noise reduction (SR) approach.

Methods : Six healthy volunteers were scanned using a vis-OCT device (Opticent, Evanston, IL). We used two scanning modes: a) normal raster, in which 8 subsequent A-scans are averaged, and b) SR protocol, in which 8 A-scans oriented orthogonal to the y and z-axes are averaged. This SR strategy averages scans sufficiently spaced to capture a tissue’s unique features, but near enough to reduce distortion caused by inadvertently capturing adjacent tissues. This is an ideal method to apply to layered retina tissue, in which the scale of morphological tissue structure change is greater in the lateral compared to axial direction.

Results : Visual comparison reveals improved visualization and clarity of retinal layers and reduced noise in the SR images compared to the normal scans (Figure 1). In all six SR images there was consistent improvement in border definition with improved contrast of all intraretinal layers, especially the border between the ganglion cell and inner plexiform layers. The texture within each layer retained a grainy appearance, unlike frame averaged images with an eye-tracking system, which tend to present a smeared texture. Around the retinal pigment epithelium, 5 highly reflective layers became clearly visible with less fuzziness at the inner and outer borders of each layer, which made the apparent layer thickness thinner in SR images.

Conclusions : We demonstrated that our SR methodology subjectively improved vis-OCT images without the need for frame averaging, which requires a longer scanning time. SR in vis-OCT augments fine details within target structures, which has potential to improve the clinical application of this technology.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

 

Figure 1. Each row corresponds to one eye before (left) and after (right) SR. Improvements in retinal pigment epithelium layers (red boxes in (a) and (b)) and ganglion cell-inner plexiform layers (red boxes in (c) and (d)) can be visualized.