Eye tracking involves measuring either where the eye is focused or the motion of the eye as an individual views a web page.

Purpose of Eye tracking

When your site visitors are connected to eye tracking software, you will be able to tell:

Where they are looking
How long they are looking
How their focus moves from item to item on your web page
What parts of the interface they miss
How they are navigating the length of the page
How size and placement of items on your existing site or on proposed designs effects attention

How it Works

As a participant looks at a webpage, the eye tracking device focuses on the pupil of the participants eye and determines the direction and concentration of their gaze. The software generates data about these actions in the form of heat maps and saccade pathways:

Heat maps

Heat maps represent where the visitor concentrated their gaze and how long they gazed at a given point. Generally, a color scale moving from blue to red indicates the duration of focus. Thus, a red spot over an area of your page might indicate that a participant, or group of participants, focused on this part of a page for a longer period of time.

Saccade pathways

Saccade pathways trace the eye’s movement between areas of focus. The movement is not unlike watching a hummingbird move between flowers. Periods of attention and then rapid movement. A red circle is the area of focus, while the red line indicates the flight.

Capabilities and Limitations of Eye Tracking

When deciding whether to undertake eye tracking on your site it is important to consider your goals and resources as well as the capabilities and limitations of the testing method. Equipment and software to perform eye tracking testing can be purchased through web and usability solutions vendors and can be quite costly.

Additionally, it is important to have knowledgeable usability specialists conduct and interpret the results of your eye tracking sessions. You may consider contracting eye tracking services through a usability consultancy if you do not have usability professionals in house.

When analyzing results, keep in mind the capabilities and limitations of eye tracking:

Tell you whether users are reading or scanning content.
Give you the relative intensity of a user’s attention to different parts of your web page.
Determine whether a user is searching for something. Pupil diameter appears to increase when users are not sure what words they are looking for. This can happen when users are on new sites or pages with groups of broad categories.
Allow you to compare different user groups’ scan patterns.

Cannot tell you for certainty that users saw something conscientiously. Users can aim their eyes at an area for a short period of time without any awareness.
Cannot tell you for a certainty that users did not see something, since eye tracking does not capture peripheral vision.
Cannot tell you why users are looking at something.
Cannot test everybody effectively. Problems have occurred when some users wore eyeglasses or hard contacts, had small pupils, a wandering eye or expressive face.

Best Practices

The Nielsen Norman Group has outlined considerations when conducting an eye tracking test. We have excerpted a number of them below to assist in planning and implementing a successful test.

Choose an office with good, but not overly bright lighting. Too much light could impact the eye tracker.
Seat the participant in a stationary chair without wheels, leaning or swivel capability.
Implement a pilot test to make sure you are comfortable with setting up, calibrating and testing well in advance of your participants’ arrival.
You will in all likelihood need to adjust the chair, monitor, and equipment to properly calibrate the eye tracker. Let the participant know this at the outset. Allowing time to do this properly is imperative to assure that you get good data out of the session.
This will have to be done each session so be sure to build this into your schedule.
You will need to do this right before testing – so make sure to have any consent forms or pre-session questions completed before you begin calibrating the equipment
Conduct a practice activity to get your participant comfortable with the equipment before you begin the actual tasks.
Remove distracting elements from the test area. They should not have to read or make note of anything during testing.
The moderator should sit next to and slightly behind the user so as not to encourage conversation
The moderator should watch the participant’s eye movement on a separate monitor out of the participant’s line of sight so as not to distract him/her.
To generate pure heat maps or Saccade paths, do not ask the participant to “think-aloud”
Be aware that when you initially present a task the participant may scan the screen to get familiar with the elements before they pursue the actual task, so take that into account when you begin your analysis.

Read more : http://www.usability.gov/how-to-and-tools/methods/eye-tracking.html

Heat maps represent where the visitor concentrated their gaze and how long they gazed at a given point.

Heat maps represent where the visitor concentrated their gaze and how long they gazed at a given point.

Saccade pathways trace the eye’s movement between areas of focus. The movement is not unlike watching a hummingbird move between flowers.

Saccade pathways trace the eye’s movement between areas of focus. The movement is not unlike watching a hummingbird move between flowers.

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