Abstract
Glaucoma is a group of eye diseases which can cause vision loss by damaging the optic nerve. Early glaucoma detection is key to preventing vision loss yet there is a lack of noticeable early symptoms. Colour fundus photography allows the optic disc (OD) to be examined to diagnose glaucoma. Typically, this is done by measuring the vertical cup-to-disc ratio (CDR); however, glaucoma is characterised by thinning of the rim asymmetrically in the inferior-superior-temporal-nasal regions in increasing order. Automatic delineation of the OD features has potential to improve glaucoma management by allowing for this asymmetry to be considered in the measurements. Here, we propose a new deep-learning-based method to segment the OD and optic cup (OC). The core of the proposed method is DenseNet with a fully-convolutional network, whose symmetric U-shaped architecture allows pixel-wise classification. The predicted OD and OC boundaries are then used to estimate the CDR on two axes for glaucoma diagnosis. We assess the proposed method’s performance using a large retinal colour fundus dataset, outperforming state-of-the-art segmentation methods. Furthermore, we generalise our method to segment four fundus datasets from different devices without further training, outperforming the state-of-the-art on two and achieving comparable results on the remaining two.
Highlights
Glaucoma is the collective name of a group of eye conditions that results in damage to the optic nerve at the back of the eye, which can cause vision loss
For the optic disc (OD) and optic cup (OC) segmentation task, our proposed deep learning based approach shown in Figure 2 comprises three main steps: (i) Pre-processing: the image data is prepared for training with different pre-processing schemes considering the green channel only from colour
The performance of the proposed method for segmenting the OD and OC when compared with the ground truth was evaluated using many evaluation metrics such as Dice coefficient (F-Measurement), Jaccard, accuracy, sensitivity, and specificity which can be defined as follows: Dice( DC ) =
Summary
Glaucoma is the collective name of a group of eye conditions that results in damage to the optic nerve at the back of the eye, which can cause vision loss. Glaucoma is known as the “silent thief of vision” since, in the early phases of the disease, patients do not have any noticeable pain or symptoms of vision loss. It is only when the disease progresses to a significant loss of peripheral vision that the symptoms potentially leading to total blindness may be noticed. It is believed that IOP can cause irreversible damage to the optic nerve head, or optic disc (OD). Since the cornea is transparent, the optic disc can be imaged by Symmetry 2018, 10, 87; doi:10.3390/sym10040087 www.mdpi.com/journal/symmetry
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