How do I remove objects not in focus?

I have an image of droplets and some of them are out of focus. What should I do to remove them. Am attaching the image along with this. I am using MATLAB R2017b.

[Image Analyst]

Which ones are out of focus, and why do you want/need to remove them? They seem like less of a problem than the partial droplets.

[Edin Michael]

My ultimate aim is to find out the droplet sizes in the plane of focus.

If i include the droplets which are not focused they will give wrong results and it seems there are lot of them.

The first image that i have attached here is back ground subtracted one.

I then selected a band from it which is shown in the second image.

The third one shows an example of unfocused droplet (droplet whose edges would be blurry, the gradient across the border would be less).

Yesterday I used deghosting which did kind of remove them (Fig.4). But as you said the presence of partial droplets also need to be attended to. Would like help in that too.

I am also attaching the code that I am using.