Is there any segmentation technique which can be used to segment regions which has no fixed shape,size, edge, position?

I am working on retinal images and I want to segment the cotton wool spots (soft exudates) from the image. They appear as cloudy patterns and the colour is similar like the optic disk. The cotton wool spots appear with different shape and size in different images. They dont have any specific edge. Also their position is not fix. It may occur at any position in the image. I am attaching a retinal image having cotton wool spots. Could you please suggest me a good image segmentation technique for this purpose. I would be very thankful for that.