strain one's eyes

I strained my eyes to see them, but there was nothing to be seen.

The Doctor strained his eyes, but there was nothing to see.

Sam strained his eyes to see him, but he could not.

He strained his eyes in the direction from which they had come.

The girl strained her eyes into the night before them.

I strained my eyes, trying to see where she was.

I strained my eyes and at last the shape moved again.

I strained my eyes to make sense of what she was saying.

Everyone strained their eyes to see - but the window was too far up.

They strained their eyes, but it was too far away.