as far as the eye can see; as far as the eye can reach
A set phrase describing the entire visible area; often used in literary or descriptive contexts.
As far as the eye could see, a field of flowers stretched out.
From the mountaintop, we could see the blue sea as far as the eye could reach.
A set phrase composed of 目 (eye), 届く (to reach), and 限り (limit), literally 'as far as the eye reaches'.