Just a suggestion:
When you are doing the meditation, you can try placing the focus of your ocular attention on your Ajna chakra, as a preparation for then changing your focus to the object of your meditation. When people ask what to do with their eyes during meditation, I tell them to focus them towards the Ajna chakra, and leave them there. It's a loose focus though. You don't want to meditate cross-eyed or anything.
Just sit them in the area, to where when you are aware of your eyes, you think of the Ajna chakra and not the physical eyes.
When trying to imagine an object in your mind and hold it steady, the physical eyes "want to look at it" too, even though they cannot. That is, the body is trained to relate pictures of objects with ocular activity. So naturally, when you go to focus on an object in your mind, the physical eyes may strain themselves trying to view the object.
If you turn your attention to the Ajna chakra however, it is a way of letting your body know, "Hey, we are looking at this with the 'mind's eye', not the physical eye." This alone can help your physical eyes move to a natural, resting position, and help get over the hump of physical interference while practice inner workings.
Like I said, it's just a suggestion, an idea. It's something that worked for me, and may possibly work for others.