Abstract

Deep learning (DL) enables the creation of computational models comprising multiple processing layers that learn data representations at multiple levels of abstraction. In the recent past, the use of deep learning has been proliferating, yielding promising results in applications across a growing number of fields, most notably in image processing, medical image analysis, data analysis, and bioinformatics. DL algorithms have also had a significant positive impact through yielding improvements in screening, recognition, segmentation, prediction, and classification applications across different domains of healthcare, such as those concerning the abdomen, cardiac, pathology, and retina. Given the extensive body of recent scientific contributions in this discipline, a comprehensive review of deep learning developments in the domain of diabetic retinopathy (DR) analysis, viz., screening, segmentation, prediction, classification, and validation, is presented here. A critical analysis of the relevant reported techniques is carried out, and the associated advantages and limitations highlighted, culminating in the identification of research gaps and future challenges that help to inform the research community to develop more efficient, robust, and accurate DL models for the various challenges in the monitoring and diagnosis of DR.
keyword: Dataset of retinal images, CNN



Introduction
Diabetes is a long-term blood sugar disorder that impairs an individual/s body's capacity to use blood sugar efficiently . This is primarily due to a decrease in insulin synthesis in the body. When the cells stop responding to insulin, too much
blood sugar is present in the person's bloodstream. This further causes health issues such as cardiovascular disease, loss of eyesight, and renal disease. Hence, the early detection of diabetes is crucial as medical intervention can avert significant repercussions. Diabetes is classified into Type 1, Type 2 and "Gestational diabetes" . Diabetes type 1: Children and teens are most typically diagnosed with type 1 diabetes. When an individual has diabetes type 1, their immune system targets the pancreatic cells that produce insulin.
Diabetes type 2: Type 2 diabetes is caused when an individual's body stops reacting to the insulin produced by the pancreas. The pancreas eventually quits making enough insulin. It's usually caused by a mix of hereditary and
environmental factors.

Diabetes is a long-term blood sugar disorder that impairs an individual/s body's capacity to use blood sugar efficiently. This is primarily due to a decrease in insulin synthesis in the body. When the cells stop responding to insulin, too much blood sugar is present in the person's bloodstream. This further causes health issues such as cardiovascular disease, loss of eyesight, and renal disease. Hence, the early detection of diabetes is crucial as medical intervention can avert significant repercussions. Diabetes is classified into Type 1, Type 2 and "Gestational diabetes".
Diabetes type 1: Children and teens are most typically diagnosed with type 1 diabetes. When an individual has diabetes type 1, their immune system targets the pancreatic cells that produce insulin.
Diabetes type 2:Type 2 diabetes is caused when an individual's body stops reacting to the insulin produced by the pancreas. The pancreas eventually
Gestational Diabetes: also known as Diabetes that is caused during pregnancy. This kind of diabetes is caused by hormonal changes that occur during pregnancy.
Placental hormones can reduce the body's sensitivity to insulin. This can lead to elevated blood sugar levels during pregnancy.


Individuals with diabetes are prone to Diabetic retinopathy, which is an eye disorder . When this happens, elevated blood sugar levels harm the retina's blood vessels. They have the potential to expand and leak. Alternatively, they could close, preventing blood flow. On the retina, abnormally new blood vessels can occasionally form. These various changes can adversely affect the eyesight of the person. Refer Figure 1 for a visual understanding.
Early stages of Diabetic Retinopathy show no significant symptoms. Some individuals, however, experience changes in vision. During the later stages of DR, the retinal blood vessels start to leak into the vitreous, which is a gel-like fluid that fills an eye, this leads to the development of cobweb like black streaks which is mainly caused due to blood clots and other blood fluids. It is important to seek medical help immediately as if left untreated, it might cause scarring in the eye . Furthermore, the leaking of these blood vessels might worsen. Early detection of the disease can slow down its impact of the disease and the development of DR into a more advanced eyesight-threatening form can be prevented. quits making enough insulin. It's usually caused by a mix of hereditary and environmental factors.