Abstract
Photoreceptor ellipsoid zone (EZ) defects visible on optical coherence tomography (OCT) are important imaging biomarkers for the onset and progression of macular diseases. As such, accurate quantification of EZ defects is paramount to monitor disease progression and treatment efficacy over time. We developed and trained a novel deep learning-based method called Deep OCT Atrophy Detection (DOCTAD) to automatically segment EZ defect areas by classifying 3-dimensional A-scan clusters as normal or defective. Furthermore, we introduce a longitudinal transfer learning paradigm in which the algorithm learns from segmentation errors on images obtained at one time point to segment subsequent images with higher accuracy. We evaluated the performance of this method on 134 eyes of 67 subjects enrolled in a clinical trial of a novel macular telangiectasia type 2 (MacTel2) therapeutic agent. Our method compared favorably to other deep learning-based and non-deep learning-based methods in matching expert manual segmentations. To the best of our knowledge, this is the first automatic segmentation method developed for EZ defects on OCT images of MacTel2.
Highlights
Macular telangiectasia type 2 (MacTel2) is a progressive retinal disease of unknown cause which affects with varying severity the juxtafoveolar region of both eyes
We compared Deep OCT Atrophy Detection (DOCTAD) to the alternative method whereby the layer boundaries were first segmented, and the ellipsoid zone (EZ) thicknesses projected onto an en face image where EZ defects could be identified
We have developed DOCTAD, a novel deep learning-based method to automatically segment EZ defects on spectral domain (SD)-optical coherence tomography (OCT) images from eyes with MacTel2
Summary
Macular telangiectasia type 2 (MacTel2) is a progressive retinal disease of unknown cause which affects with varying severity the juxtafoveolar region of both eyes. Signs of MacTel visible on OCT include hypo-reflective spaces in the inner and outer retina, thinning and defects of the retina temporal to the foveal center, and atrophy of the hyper-reflective layer or band that is located external to the external limiting membrane (ELM) and internal to a band thought to represent cone photoreceptor tips [2,3,4,5, 8, 9]. Recent publications [10,11,12,13,14,15,16], including that from a consensus International Nomenclature group [17], refer to this band as the ellipsoid zone (EZ) as it is thought to represent the ellipsoid region of the photoreceptor inner segments which have densely-packed mitochondria that are likely hyper-reflective on OCT [18]. Without making a judgment about the true nature of this band, we have used the EZ terminology, as it is more commonly used in the recent MacTel clinical trial literature [13, 23,24,25]
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