Finding the center of eye pupil

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I want to find the center of eye pupil. Here are the steps that I followed:

1- Obtained eye image from the extracted face image:

2- Thresholding the grayscale eye image with the following settings: Max value: 255 Threshold: 60 Threshold Type: CV_THRESH_BINARY

3- I can't find the contour of the eye pupil from the image above. So I applied dilatation first opencv_imgproc.cvDilate(left_eye, left_eye, null, 3);

4- Need to rescale it: opencv_imgproc.cvErode(left_eye, left_eye, null, 6);

Now the problem is to find eye center as fast as possible. How can I achieve such a goal?