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Definition of Fixation, Localization & Shift of Gaze in Vision Skills

You probably don't spend much time considering how you are able to see. Vision is possible due to a complex system of components in the eyes that all work together to transmit images to your brain. Vision involves several processes, including fixation, localization and shift of gaze. These vision activities take place every time you look at an object.

Eye Function
- Your eyes work in tandem with your brain to capture and interpret images. The human eye has three main functional layers ̵2; the transparent outer layer (cornea), the middle layer (the choroid and iris) and the inner layer (the retina) ̵2; and various other parts. Each part serves a specific function. The cornea refracts light, allowing the eye to focus. The choroid supplies blood to other parts with its network of vessels. The retina contains the rods and cones that the eye uses to determine colors and shapes.
Visual Fixation
- Visual fixation is the ability to maintain a gaze on one specific location. It is a function of the fovea, the part of the retina allowing humans and other animals to maintain sharp, centrally focused vision. As you read a book or watch television, your eyes are maintaining constant visual fixation. Optometrists often test visual fixation by having patients follow the doctor's finger as it moves slowly from right to left. During fixation, the eye may experience saccades, or brief, jerking and involuntary eye movements.
Visual Localization
- Visual localization is a process directly related to fixation. It is the ability to maintain a narrow focus on a object with minimal interruption caused by gaze shift or ocular tremor. Humans have a limited field of view, the extent to which they can see up, down, left, right and forward.Visual localization allows people to narrow the field of view enough to focus on specific objects at a distance. Tremors (rapid twitching of the eye muscles), saccades, blurred vision and other problems can interfere with visual localization.
Shift of Gaze
- Shift of gaze is the process of transferring visual fixation from one object to another, whether voluntary or involuntary. All sighted animals shift gaze naturally and frequently. However, involuntary shift of gaze is a biological phenomena during which a person's ability to fixate upon an image is interrupted and the gaze moves away from the intended object. When an eye doctor tests a patient's visual fixation ability, she is trying to observe this process. Shift of gaze often indicates a vision problem, such as a weak eye muscle or a damaged part of the eye.

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