At the University of Melbourne’s Department of Optometry and Vision Sciences, Cassandra J. Brooks, who recently completed her PhD, is contributing to ongoing research aimed at better understanding how Visual Snow Syndrome (VSS) affects visual perception, how its symptoms present, and how future treatments might be evaluated.
In collaboration with researchers Joanne Fielding, Owen B. White, David R. Badcock, Yu Man Chan, and Allison M. McKendrick, the team is developing new tools to characterize visual symptoms and explore the neurological mechanisms underlying the condition.
Quantifying the Appearance of Visual Snow
In the study Improving Understanding of Visual Snow by Quantifying its Appearance and Effect on Vision, the research team examined visual snow.
Through a series of questionnaires and lab-based vision tasks, the researchers investigated:
- Visual snow dot size, brightness, flicker speed, and density
- The impact of visual snow in both bright and low-light conditions
- How visual snow affects perception of fine textures and patterns
The researchers created a customized matching task allowing individuals with VSS to match their personal experience of visual snow to a simulation. Findings revealed that while brightness and flicker speed of visual snow varied across individuals, the size of the dots remained remarkably consistent. Participants reported that visual snow became more noticeable in low-light settings, often interfering with reading, night driving, and general visibility.
Notably, individuals with VSS performed just as well as control participants on tasks involving pattern recognition—even when the patterns closely resembled their own visual snow. This suggests that people with VSS can separate their visual snow from external visual patterns, enabling those with VSS to maintain normal visual function in certain contexts.
Beyond advancing scientific understanding of visual snow, this study introduces a structured approach based on computerised vision testing that could serve as a foundation for developing outcome measures in future clinical trials.
Exploring Palinopsia in Visual Snow Syndrome
In a related study, Exploring the Phenotype and Possible Mechanisms of Palinopsia in Visual Snow Syndrome, the team examined palinopsia—a common symptom in people with VSS where afterimages or trailing effects linger in vision after the original object disappears.
The study involved:
- 31 participants with VSS
- 30 participants without VSS (control group)
- 25 participants with migraine but without VSS
Through a series of questionnaires and lab-based vision tasks, the researchers investigated:
- The typical presentation of palinopsia
- Whether it relates to how the visual system adjusts its sensitivity to contrast (the difference in brightness between an object and its background), known as contrast adaptation
- Whether it relates to standard laboratory measures of visual persistence
- How quickly the brain resolves visual changes over time
Results showed that approximately 80% of participants with VSS experienced afterimages, and about 45% reported trailing. These effects typically appeared as faint outlines and were triggered by everyday visual stimuli—not just bright lights.
The study also found that contrast adaptation remained intact, and participants did not exhibit signs of prolonged visual persistence. Interestingly, individuals with VSS demonstrated enhanced temporal resolution, meaning they were better able to distinguish between rapidly presented images than control participants.
These findings provide new insight into visual timing processes in VSS, offer a clearer picture of how palinopsia presents in VSS and suggest this symptom may reflect a difference in how the brain filters or processes low-level visual information.
