Trout depend heavily on their vision. They use eyesight to catch prey as well as detect danger. In order to catch trout the angler must be aware of the color and action of the lure they present as well as the effect of their own presence.
A trout's vision does extend beyond the surface of the water and they can see in color.
Trout can see, to some extent, above the surface of the water. There is a circular window from which trout view the terrestrial world. The width of this window depends on the depth of the trout. The Freshwater Angler’s Complete Guide to Catching Trout states that the diameter of the window is a little more than twice the depth of the trout. Thus, a trout located three feet below the surface of the water will have a window about six to seven feet wide to view the world above the surface.
In addition, items located at the edge of the window or lower on the trout’s horizon, such as a fisherman standing on the bank, will appear more distorted. Therefore, it is very important to keep a low profile when fishing for trout to avoid being seen. Fishing upstream will also help reduce the chances of the trout spotting you as they generally feed facing upstream.
Another aspect of trout sight that a fisherman should be aware of is the trout’s ability to see color. Trout do have color vision. This means a trout may be more or less likely to strike a lure depending on its color. The common thought on lure color selection is to use bright colors when the water is murky and to use duller shades when the water is clear. Its also probably better to use colors that resemble trout prey more during high visibility conditions. Whatever the expected conditions the best option is to bring an assortment of colors and experiment to determine what colors the trout are responding to.
Trout also have some night vision allowing them to detect prey at night but are more likely to depend on their lateral line to detect vibrations at night.
The basic fishing tactics concerning trout vision are to experiment with different colors and to keep a low profile and blend in with the surroundings, perhaps even wearing camoflage, when fishing shallow water.