Enface Thickness Mapping and Reflectance Imaging of Retinal Layers in Diabetic Retinopathy

Abstract

PurposeTo present a method for image segmentation and generation of enface thickness maps and reflectance images of retinal layers in healthy and diabetic retinopathy (DR) subjects.MethodsHigh density spectral domain optical coherence tomography (SDOCT) images were acquired in 10 healthy and 4 DR subjects. Customized image analysis software identified 5 retinal cell layer interfaces and generated thickness maps and reflectance images of the total retina (TR), inner retina (IR), outer retina (OR), and the inner segment ellipsoid (ISe) band. Thickness maps in DR subjects were compared to those of healthy subjects by generating deviation maps which displayed retinal locations with thickness below, within, and above the normal 95% confidence interval.ResultsIn healthy subjects, TR and IR thickness maps displayed the foveal depression and increased thickness in the parafoveal region. OR and ISe thickness maps showed increased thickness at the fovea, consistent with normal retinal anatomy. In DR subjects, thickening and thinning in localized regions were demonstrated on TR, IR, OR, and ISe thickness maps, corresponding to retinal edema and atrophy, respectively. TR and OR reflectance images showed reduced reflectivity in regions of increased thickness. Hard exudates appeared as hyper-reflective spots in IR reflectance images and casted shadows on the deeper OR and ISe reflectance images. The ISe reflectance image clearly showed the presence of focal laser scars.ConclusionsEnface thickness mapping and reflectance imaging of retinal layers is a potentially useful method for quantifying the spatial and axial extent of pathologies due to DR.

Alterations in Retinal Layer Thickness and Reflectance at Different Stages of Diabetic Retinopathy by En Face Optical Coherence Tomography

“…This finding is consistent with that in a previous study that reported the presence of hyper-reflective spots in inner retinal layers of NPDR subjects, particularly the INL, which had the largest number of spots among inner retinal layers. 37 As previously reported, 38 alterations of en face retinal layer reflectance indicate pathological changes, including intraretinal fluid and hard exudates. For example, intraretinal fluid resulted in decreased layer reflectance, while hard exudates appeared as localized areas of hyperreflectivity.…”

Deep longitudinal transfer learning-based automatic segmentation of photoreceptor ellipsoid zone defects on optical coherence tomography images of macular telangiectasia type 2

“…EZ defects are also observed in other retinal diseases such as age-related macular degeneration (AMD) [ 22 ], macular edema (ME) [ 10 ], and diabetic retinopathy (DR) [ 11 ]. Semi-automatic EZ defects analysis has also been performed in these diseases [ 10 , 12 , 29 ].…”

Enhanced Visualization of Subtle Outer Retinal Pathology by En Face Optical Coherence Tomography and Correlation with Multi-Modal Imaging

“…In the last 2 decades, optical coherence tomography (OCT) has become an indispensable retinal imaging modality because it captures a three-dimensional image of the retina [3]. However, direct comparison between the en face images obtained from NIR, FAF, FA, SLO and the cross-sectional OCT images is not possible because these imaging planes are orthogonal [4]. Such limitation can be overcome by alignment of consecutive OCT scans, volume reconstruction and retinal layer segmentation to generate an en face image of each layer of the retina [5–18].…”

“…Such limitation can be overcome by alignment of consecutive OCT scans, volume reconstruction and retinal layer segmentation to generate an en face image of each layer of the retina [5–18]. Various terminologies have been used to describe this method of OCT images visualization, including C-scan [4], OCT fundus image [11], projection OCT fundus [14] and en face OCT [19]. In this paper, the term “ en face OCT” will be used to encompass all these concepts.…”

“…The increased scattering and reflection of the infrared light from OCT at the level of the retinal nerve fiber layer, inner and outer plexiform layers and the four outer retinal bands (external limiting membrane, ellipsoid zone, interdigitation zone and retina pigment epithelium-Bruch’s membrane complex) have been used to generate en face OCT images to detect subclinical disease. En face OCT images have been correlated with fundus photography [10,14,20–22], SLO [4], fluorescein angiography [10,14], fundus autofluorescence [19,23] and functional measures [19,24]. However, the ability to reconstruct en face view from OCT scans in diseased retina is limited by frequent segmentation error in the identification of the retinal pigment epithelium and Bruch’s membrane.…”