How to remove glare from image

edit

I am trying to detect circular object in image. I am not using hough circles as it gives many false outputs as well. I am converting the image into binary after applying median blur. For conversion into binary, I have used simple thresholding which works fine with me because the circular object is usually of white or some other color and it is placed on a black background. The only problem I face is that due to some liquid put on the black background, it reflects light which disturbs the thresh image and hence causes problem in the detection of circular object. Is there anyway I can remove the glare effect from my images ? I have attached a sample image for reference. Thanks