Eyes are the strongest language of emotion: they can express reactions both subtly and as expressly as possible. It is not for nothing that in caricatures, comics and animation the eyes are always enlarged - they emphasize and sharpen the emotion and story being told. The viewer always looks at the eyes first and the direction where the character is looking: at the action being performed, the person or object, thus trying to understand the character's intentions.
If you want the meaning of the story you are telling to be fully understood by the audience, you need to indicate where to look - “invisible” lines (leading, for example, to the eyes of the hero) will help with this, especially if your shots are short enough in editing. Let’s see how this principle is used in cinema: both acting and animation. Below are examples where the lines come to the front of the eyes.
Pay attention to the last frame on the left: the rails and the base of the stairs point to both heads of the two-headed character (Terry and Terry Parry) at once, Pixar uses this trick very often.
Concentrating and at the same time pointing designs in Star Wars create a majestic image of the main villain, it could only be made cooler if you shoot from a lower angle.
Usually, to demonstrate the thoughts of a character, the method of panning the camera to the hero is used, but, as you can see in the examples below, the lines, even in a static frame, perform the same function and take us into the inner world of characters just as well.
See how the lines help to create connections between the eyes of two or more people, thereby indicating contact between the characters.
Here, a huge number of lines create a concentration on a specific object, such compositions are suitable for moments of crisis or climax in a story.
In these examples, the lines do not point to the hero's eyes, but help to tell the story with the composition. These scenes are nice to watch and can remain completely static for quite some time, which is especially useful in pauses that follow active incidents.
Surely, you can always say that the line accidentally caught the eye and there is nothing super cool about it. But check the footage from Prometheus: the line almost passes through the eyes of the characters, and this "almost" could be made sharper and stronger.
Of course, you can go on without leading lines, but if you want to control the eye of the audience, this simple but very powerful principle is in your hands.