Imagine that you can already see everything clearly, and that the reason you are perceiving blur is because you are not looking at small enough details. And looking at small enough details means imagining them, and it has to be done in a calm, deliberate, soft, effortless way.
So in this exercise, how well your eyes see is a non-issue, and you might find it’s easier to stop straining them once you adopt the mindset that there is nothing extra for them to do, other than pointing, with no wasted movement or an ounce of extra effort, to the location of the next detail you’re imagining, and the next.
Take all that energy you’ve been putting into trying to make your eyes focus and move it into visualizing the details. If you can’t see the detail, it doesn’t matter. If you can’t imagine any detail (it might not be the one you expect), you wait for a second to give it a chance, and then move on.