A Convolutional Autoencoder Approach for Boosting the Specificity of Retinal Blood Vessels Segmentation  
[PERSON]  
1 Computer Engineering and Informatics Department, University of Patras, 26504 Patras, Greece 1  
[PERSON]  
1 Computer Engineering and Informatics Department, University of Patras, 26504 Patras, Greece 12 Computer Technology Institute and Press \"Diophantus\", 26504 Patras, Greece 2  
[PERSON]  
1 Computer Engineering and Informatics Department, University of Patras, 26504 Patras, Greece 12 Computer Technology Institute and Press \"Diophantus\", 26504 Patras, Greece 2  
[PERSON]  
1 Computer Engineering and Informatics Department, University of Patras, 26504 Patras, Greece 1  
[PERSON]  
3 Institute of Data Science and Digital Technologies, Vilnius University, 01513 Vilnius, Lithuan 3  
[PERSON]  
1 Computer Engineering and Informatics Department, University of Patras, 26504 Patras, Greece 1  
Footnote 1: email: {natalia.povilas. vessels of the retina, as it occurs mainly in diabetic patients. Diabetic retinopathy caused by elevated blood sugar levels, is a complication of diabetes in which retinal blood vessels leak into the retina, accompanied by the swelling of the retinal vessels [3]. Diabetic retinopathy can cause the growth of new blood vessels [4]. Another disease that sthe visualisation of the retina can detect is a stroke, which is a condition where the blood supply stops in a part of the brain. As a result, the brain cells do not receive oxygen and die. Scientists have discovered the vessels of the 'eye's retina can help diagnose and treat stroke. In addition, many pathological changes in the retinal vessels constitute direct reflections of the fundus disease. An indicative example is glaucoma and age-related macular degeneration, a condition of macular degeneration that can cause the progressive loss of central vision. Lastly, glaucoma is caused by the high pressure of fluids in the interior of the eyes, causing gradual destruction of the human optic nerve and, as a result, the absence of the peripheral and the end of the 'patient's total vision. Thus, by analysing the length, width and branch structure of retinal vessels, doctors can detect the above diseases early and provide a proper cure for them. The visualisation of the retina is now done with the help of fundus cameras. [PERSON] developed back in 1910 the notable fundus camera, which is the main concept still used today for image the retina [5]. With these cameras, there is a direct representation of the condition of the retina and therefore documented diagnostic access to the most common or rare diseases of the retina. Fundus cameras create a two-dimensional image from the three-dimensional surface of the eyes using a system that contains a low-energy microscope to which a CCD camera fits. The general procedure is as follows. First, the patient should sit with the chin supported and the forehead positioned properly towards a bar. At the same time, the device operator focuses and positions the camera correctly before pressing the button and activating the photo flash. The resulting photo is mainly an upright, enlarged photo of the retina with standard 30\({}^{\circ}\), 45\({}^{\circ}\), or even 60\({}^{\circ}\) imaging angles and magnification up to 2.5 times, depending on the system settings [6]. The resulting image of a fundus camera is illustrated in Figure 1.  
The retinal imaging procedure takes a digital picture of the back of the human eye. A detailed representation of the back of the human eye helps ophthalmologists detect many diseases, such as hypertension, diabetes, stroke and many other cardiovascular diseases. The fundus camera is the most widely used tool for photographing the eye's retina. Retina vessel segmentation is the primary step for the early detection and treatment of various  
Figure 1: The original image (**right**), the corresponding ground-truth segmentation masks (**middle**), and the corresponding field-of-view masks (**left**). Example cases from the DRIVE (**top**) and from the STARE (**bottom**).