As to Allan’s point, to the effect " how can trout see well if they disregard a hook point dangling below the water?"
To this, I point out the experience of fishing when trout are feeding selectively and will only take an imitation of that particular insect. Pretty decent vision, I would say.
Also, most who study the trout conclude that there are triggers which bring the trout to the fly. So, it seems trout look for positives and can overlook “negatives”. My theory, anyway.