UC Berkeley

Fixational eye movements’ (drift and tremor) utility has been long debated in the field of vision science. These small involuntary eye movements were traditionally thought to be artifacts of the visual system, but more recent research has revealed that adding a temporal aspect to vision through small changes in position over time may actually be beneficial in resolving fine detail. Using the adaptive optics scanning laser ophthalmoscope (AOSLO) to remove optical limits to acuity, we tested the most granular limits of human vision in various retinal motion conditions to help understand how drift and tremor reformat visual information at very fine spatial frequencies.

Chapter 1 provides an overview of the state of the literature in the field. This includes theories about why retinal motion is thought to be helpful to the perception of fine detail. Chapter 2 probes the time course over which these benefits accumulate. For movements to be useful, the eye and brain theoretically need to accrue changes in position over time. I show that this is indeed the case, and the utility of drift and tremor is dependent on stimulus duration. While retinal motion has been found to be beneficial, Chapter 3 introduces the notion that not all kinds of motion are useful to acuity. I show that this is also dependent on the characteristics of both the stimulus and retinal motion. Thus, eye movements can be detrimental to acuity if the stimulus features interact with eye movement magnitude and direction in a way that induces motion blur. In Chapter 4, I propose detailed methodology to probe the human contrast sensitivity function with and without eye movements to better understand the effect that eye movements have on visual perception. Chapter 5 provides a summary of this dissertation’s work and broader impact on the field.

By utilizing advanced imaging techniques and carefully designed experiments, this work sheds light on the complex interplay between retinal motion and stimulus characteristics, ultimately contributing to a deeper understanding of the mechanisms underlying human vision.