An Approach for Automatic Detection and Grading of Macular Edema

Introduction

The retina is a light sensitive tissue found at the back of the eye. It perceives light signal passed through the lens and accumulates at the center of retina called macula. The perceived signal is then send to the brain through optic nerve, where it is translated to the picture we see. The legitimate functioning of retina depends on constant supply of oxygen carried through blood vessel (BV)s (Diabetes Care, 2004; Diabetes Care, 2003;NHS Choices, 2014). Inadequate supply of oxygen gradually ceases the functionality of retina leading to vision complexities. There are various aspects causing impairment of the retina such as, hypertension, diabetes, old age, heart diseases etc. Various complexities of the retina is commonly known as ‘Retinopathy’. Retinopathy begins with blockage of BV leading to blood leak over the retina. With gradual progression of the disease blood constituents like lipids and fatty materials also get deposited over retina. With deposition of such materials, the vision becomes blur. We may visualize it as being looking into an object through these depositions as shown Figure 1. As shown in second image of Figure 1 we observe the image as blur, because blood is not clear as water and the black region in the image represents the fatty material depositions over retina.

Figure 1.

Normal vision vs. Vision with Retinopathy

The macula (Cataract and Laser Institute, 2012) of the retina consists of large number of cone cells located at the posterior pole of the eye, between the superior and inferior temporal arteries and is responsible for the central and sharp vision, for example, reading, watching television, writing, recognizing objects, colors etc. During progression of retinopathy, if depositions include macula or neighborhood of macula it is known as maculopathy. During maculopathy the vision severely gets effected and if not taken care at early stage, it may lead to vision loss. Various symptoms of maculopathy (Patient, 2014) includes, gradual loss of central vision causing obstruction or blurred patch as shown in Figure 2, distortion of image size and shape etc. As shown in the figure, the patient is able to see the clock but not the time.

Figure 2.

Effect of maculopathy in vision