Which of the following is NOT an unintentional eye movement used to prevent the Troxler effect?

• A. Pursuits
• B. Microsaccades
• C. Tremors
• D. Drifts

Answer: (A)

The key idea here is that tiny, involuntary eye movements during fixation refresh the image on the retina to prevent fading of stationary details (the Troxler effect). Microsaccades, drifts, and tremors are follow-on movements that occur without conscious effort and continually shift the retinal image just enough to keep neurons from adapting to a constant stimulus. Pursuits, by contrast, are voluntary smooth tracking movements you make to follow a moving object. They’re not part of the automatic fixational repertoire used to counteract fading, because they involve deliberate motion rather than the ongoing, involuntary shifts that refresh the retinal input. So, pursuing a moving target isn’t one of the unintentional eye movements that prevent the Troxler effect.