# Diabetic Macular Edema Characterization and Visualization Using Optical Coherence Tomography Images
## 1 Introduction  
Currently, due to the consumption habits in the developed countries, diabetes-related diseases have been increasing in prevalence [1]. Diabetes mellitus is characterized by a defective use or lack of insulin in the body, resulting in an increase in sugar levels in blood. This causes a progressive damage in different parts of the human body, specially in its most sensible structures like the retinal and choroidal vascularity [2; 3]. Among the most common consequences of this pathology, we can find the Diabetic Retinopathy [4] and the Diabetic Macular Edema (DME). In particular, the latter is characterized by fluid accumulations in between the retinal layers, producing the progressive vision deterioration that may result in severe blindness [5; 6]. Given that the pathology only causes vision impairment in advanced stages (where the damage may be irreversible), an early detection is critical [7]. Additionally, the more the pathology advances, the more drastic and severe the treatment has to be for a successful management of the pathology. Currently, to study these pathologies, eye care practitioners commonly use Optical Coherence Tomography (OCT) images [8; 9; 10]. These images correspond to cross-sectional cuts of the retina, allowing to perceive its histological organization and internal characteristics. Using the OCT images as reference, [PERSON] et al. [11] established three different types of DME. An accumulation of fluid with cystic properties, an accumulation in the external layers of the retina causing a detachment of the photoreceptor layer and a sponge-like retinal thickening. This DME classification became the reference in the clinical field after being expanded by [PERSON] et al. [12] defining these fluid accumulations as Diffuse Retinal Thickening (DRT), Cystoid Macular Edema (CME) and Serous Retinal Detachment (SRD) with more precise limits, subcategories and including an study on the status of the innermost retinal layers (also called _epiretinal traction_). These three main retinal fluid accumulations are represented in Figure 1:  
DRT is characterized by a sponge-like texture, formed by the accumulation and mixture of normal retinal tissues and the retinal fluid leakages. These leakages cause a sensible swelling in the retina, but without noticeable fluid accumulations and reduced visual capabilities of the patient. On the other hand, CME consists of a sensible fluid accumulation causing cystoid spaces that are formed in the retinal layers. These cysts may have defined cell barriers and, depending on its location and size, may cause minor to severe visual impairment. Finally, SRD consists in a subretinal dome-like fluid accumulation [13]. The more these fluid accumulations are closer to the fovea, the more severe the vision impairment (as this type of accumulation directly affects the photoreceptor layer of the retina). The characterization of the different types of edema previously described is a crucial task during the diagnosis. Each type represents a different stage and complication of the pathology, as different types of fluid accumulations can affect different regions of the field of view with different levels of intensity. In addition, different types of edemas also require different types of treatment; ranging from  
Figure 1: OCT image with the 3 different clinically defined types of DME as well as an example of healthy region. monitoring and changing the habits of the patient, pharmacological treatment or, in more severe or refractory cases, surgery. While DRT can be easily reabsorbed, the other types of fluid accumulations represent a greater difficulty depending on the extent of the accumulated damage and possibility of scar tissue formation. Given the complexity and differences among each of the DME types and the relevance of the DME disease, several automated methodologies have arisen trying to offer a quantitative analysis of these pathological fluid accumulations.