Automated segmentation and quantification of calcified drusen in 3D swept source OCT imaging

Abstract

Qualitative and quantitative assessments of calcified drusen are clinically important for determining the risk of disease progression in age-related macular degeneration (AMD). This paper reports the development of an automated algorithm to segment and quantify calcified drusen on swept-source optical coherence tomography (SS-OCT) images. The algorithm leverages the higher scattering property of calcified drusen compared with soft drusen. Calcified drusen have a higher optical attenuation coefficient (OAC), which results in a choroidal hypotransmission defect (hypoTD) below the calcified drusen. We show that it is possible to automatically segment calcified drusen from 3D SS-OCT scans by combining the OAC within drusen and the hypoTDs under drusen. We also propose a correction method for the segmentation of the retina pigment epithelium (RPE) overlying calcified drusen by automatically correcting the RPE by an amount of the OAC peak width along each A-line, leading to more accurate segmentation and quantification of drusen in general, and the calcified drusen in particular. A total of 29 eyes with nonexudative AMD and calcified drusen imaged with SS-OCT using the 6 × 6 mm2 scanning pattern were used in this study to test the performance of the proposed automated method. We demonstrated that the method achieved good agreement with the human expert graders in identifying the area of calcified drusen (Dice similarity coefficient: 68.27 ± 11.09%, correlation coefficient of the area measurements: r = 0.9422, the mean bias of the area measurements = 0.04781 mm2).

Choriocapillaris Impairment, Visual Function, and Distance to Fovea in Aging and Age-Related Macular Degeneration: ALSTAR2 Baseline

“…In the same study, we demonstrated that reduced flow signal was not confined to areas under drusen and that the mean difference in FD% when including drusen vs excluding drusen was negligible. Drusen, especially if calcified, may reduce FD% detectability, 62 , 63 a pertinent concern for AMD eyes at more severe stages of intermediate AMD than those included in ALSTAR2.…”

Non-Neovascular Age-Related Macular Degeneration Assessment: Focus on Optical Coherence Tomography Biomarkers

“…The development of sophisticated image processing algorithms has enhanced the accuracy of automatic RPE-drusen complex calculations [100][101][102]. The automated quantification of drusen as well as other retinal abnormalities is useful in monitoring AMD progression.…”

Calcified Drusen Prevent the Detection of Underlying Choriocapillaris Using Swept-Source Optical Coherence Tomography Angiography

“…31 , 32 Consequently, the calcified deposits impede the OCT light from penetrating into the choroid, resulting in hypoTDs in the choroidal layer. 29 This process is similar to the one caused by increased pigmentation within the retina, known as hyperreflective foci, or along the RPE border. 9 , 33 However, although we observed complete hypoTDs in the CC layer and deeper choroidal layers beneath hyperpigmentation, CaD resulted in a complete hypoTD specifically within the deeper choroidal layers (e.g., subRPE slab) but not in the CC layer.…”

“…The presence of CaD, also known as refractile drusen on color fundus imaging or drusen with either hyperreflective or hyporeflective cores on OCT imaging, has been shown to be a biomarker for disease progression. [28][29][30] CaD contain calcium phosphate spherules, 6 leading to increased optical absorption and light scattering. 31,32 Consequently, the calcified deposits impede the OCT light from penetrating into the choroid, resulting in hypoTDs in the choroidal layer.…”