To understand it, lets look at the eye itself. The eyes of a bass are positioned to either side of its head. This means that much of their sight is monocular. Monocular vision allows them to have a very wide field of view. In fact, their only blind spots are directly behind and below them. Subtle movements are noticed very easily by either eye. However, if only one eye is focused on the movement they will not be able to determine true size, shape, or distance of the object. To determine what and where the object is, the bass must orient its body to allow both eyes to see the object. This is binocular vision.
Once the bass focuses on the object with both eyes water color, clarity, and lure color play a much larger role in what the bass actually sees. The bass eye does possess a light sensitive pupil (although it slowly adjust). This means the eye has the ability to adjust to the environment and more specifically to the light in the water column. Light penetration in the water column is controlled by water color and clarity. Water color is dictated by many factors. Anything dissolved or suspended in water can contribute to color. Normally, the main contributor to water color is phytoplankton. This microscopic algae gives water its green coloration. Outside of phytoplankton, suspended soil particles can give water a grey to brown color depending on soil type. Certain chemicals can also manipulate water color.
Water clarity is dictated by the density of phytoplankton, soil particles, and other properties dissolved into the water. The lower the density of these properties (particles) the clearer the water, thus the further the bass can see. In extremely clear water, bass can see distances well over 25 ft. As particle density increases in the water, visibility is greatly reduced. With a low water clarity the distance a bass can see can easily decrease from feet to inches. This is why many anglers turn to vibration based lures in low visibility situations.
So, what does a bass see? Well the answer is everything to a degree. We can be certain that sight is the largemouth bass' greatest sense. Because they have no eye lids, they are always watching.
Thanks for reading and Happy Fishing!
Steven Bardin M.S.