Some aspects of visual discomfort

2012

Certain visual stimuli evoke perceptions of discomfort in non-clinical populations. We investigated the impact of stimuli previously judged as uncomfortable by non-clinical populations on a visual search task. One stimulus that has been shown to affect discomfort judgments is noise that has been filtered to have particular statistical properties (Juricevic et al, 2010 Perception 39 884-899). A second type of stimulus associated with visual discomfort is striped patterns (Wilkins et al, 1984 Brain 107 989-1017). These stimuli were used as backgrounds in a visual search task, to determine their influence on search performance. Results showed that, while striped backgrounds did have an impact on visual search performance, this depended on the similarity between the target and background in orientation and spatial frequency. We found no evidence for a more generalised effect of discomfort on performance.

Journal of Vision, 2010

Images with excessive energy at medium spatial frequencies , or that have high color contrast and little or no luminance contrast (Wilkins et al 2008) appear uncomfortable or aversive and can induce headaches in hypersensitive observers. Such stimuli are uncharacteristic of natural images, and we examined whether visual discomfort more generally increases with deviations from the spatial and chromatic properties of natural scenes. Observers rated the level of discomfort or artistic merit in color images generated from noise or random overlapping rectangles (Mondrians). In one set, the slopes of the amplitude spectra for luminance or chromatic contrast were varied independently to create images ranging from strongly blurred to sharpened relative to a "natural" 1/f spectrum. Perceived blur was dominated by the luminance slopes, with discomfort rated lowest for ~1/f spectra. In a second set of focused Mondrians, color was varied along different axes in the LvsM vs. SvsLM chromatic plane. Discomfort ratings were lowest around bluish-yellowish axes that are again typical of natural outdoor scenes. A final set varied in the levels of both luminance and chromatic contrast. Discomfort increased with increasing color contrast or decreasing luminance contrast, and tended toward lower ratings for images with balanced levels of luminance and color contrast. Notably these ratings of discomfort were not related to judgments of artistic merit. Thus for both spatial and chromatic content the least aversive images corresponded to characteristic properties of the natural visual environment, and may reflect a normalization of visual coding to the natural world.

Visual discomfort occurs when the statistics of the retinal image depart from those of natural scenes, particularly in respect of an excess energy at spatial frequencies close to 3 cycles/degree. Computer models suggest that uncomfortable stimuli are processed with a larger and less sparse neural response. Uncomfortable stimuli usually evoke a relatively large oxygenation of the visual cortex of the brain, consistent with inefficient neural encoding. The discomfort may be homeostatic. The neural computation that sustains sight is therefore likely to be more complex when the visual scene is spatially periodic, when the colour contrast is high or when saccadic suppression is impaired by flicker that is too rapid to be seen.

Frontiers in Neuroscience

Much of the neural machinery of the early visual cortex, from the extraction of local orientations to contextual modulations through lateral interactions, is thought to have developed to provide a sparse encoding of contour in natural scenes, allowing the brain to process efficiently most of the visual scenes we are exposed to. Certain visual stimuli, however, cause visual stress, a set of adverse effects ranging from simple discomfort to migraine attacks, and epileptic seizures in the extreme, all phenomena linked with an excessive metabolic demand. The theory of efficient coding suggests a link between excessive metabolic demand and images that deviate from natural statistics. Yet, the mechanisms linking energy demand and image spatial content in discomfort remain elusive. Here, we used theories of visual coding that link image spatial structure and brain activation to characterize the response to images observers reported as uncomfortable in a biologically based neurodynamic mode...

Vision Research, 2011

Images created from noise filtered to have an approximately 1/f amplitude spectrum were altered by adding excess energy concentrated at various spatial frequencies. The effects of this manipulation on judgements of visual discomfort were studied. Visual noise with a 1/f amplitude spectrum (typical of natural images) was judged more comfortable than any image with a relative increase in contrast energy within a narrow spatial frequency band. A peak centred on 0.375-1.5 cycles/degree of spatial frequency was consistently judged as more uncomfortable than a peak at a higher spatial frequency. This finding was robust to slight differences in eccentricity, and when stimuli were matched for perceived contrast across spatial frequency. These findings are consistent with the idea that deviation from the statistics of natural images could cause discomfort because the visual system is optimised to encode images with the particular statistics typical of natural scenes.

Perception, 1998

Unpleasant somatic and perceptual side effects can be induced when viewing striped repetitive patterns, such as a square wave or a page of text. This sensitivity is greater in participants with higher scores on a scale of visual discomfort. In three experiments the effect that this sensitivity has on performance efficiency in a reading-like visual search task was investigated. In experiments 1 and 2, the ‘global’ structure of the patterns was manipulated to produce a square-wave, a checkerboard, and a plaid pattern. It was found that the group that suffered severe visual discomfort took significantly longer than other groups to perform the task, with interference greatest with presentation of the square-wave-like pattern. This supports the prediction of greatest distraction of visual attention from the local target elements with presentation of the pattern structure inducing greatest visual discomfort. In experiment 3, the internal pattern components were manipulated and task diffic...

2011

Certain visual stimuli, such as striped patterns and filtered noise, have been reported to be uncomfortable. Some filtered noise patterns judged as uncomfortable are those with a relative decrease in contrast amplitude at high spatial frequencies, compared with the statistics typical of natural images. Decreased amplitude at high spatial frequencies is a characteristic often associated with perceived blur. Additionally, the distribution of contrast across spatial frequencies also provides a cue for the accommodation (focusing) response. The purpose of this study was to investigate the relationship between excess low spatial frequency information, discomfort judgments and perceived blur. Results of these experiments show that a relative reduction in high spatial frequency contrast results in both increased discomfort and perceived blur. This is both in artificial and natural stimuli. A possible explanation for this relationship based on accommodation responses is proposed. Uncomfortable images Research using filtered noise patterns has shown that deviations from natural image statistics affect discomfort judgments. For example, Fernandez and Wilkins (2008) showed that filtered noise patterns with luminance amplitude falling with spatial frequency as 1/f 1 are judged as more comfortable than filtered noise patterns with a peak in the amplitude spectrum, i.e., images with an excess of spatial frequency information around 3 c/8. O'Hare and Hibbard (2011) asked observers to compare filtered noise patterns with peaks at a range of different spatial frequencies in the

Trends in Neurosciences, 1986

Ophthalmic and Physiological Optics, 2009

Although visual discomfort symptoms associated with near work have been correlated with clinical measures of accommodation, studies using objective recordings have not found corresponding deficits in accommodative function. One problem with previous studies is that accommodation measures have been too brief to assess accommodative fatigue. This study examined steady state accommodative responses among a college population with visual discomfort, over a 90-s time period. Thirty-one participants were grouped into high (n = 15) or low visual discomfort groups (n = 16) based on their scores on the Conlon Visual Discomfort Survey. Using the WAM-5500 autorefractor, accommodation responses were recorded at 5 Hz for two consecutive minutes at five viewing distances. The results showed a significant interaction between the high and low discomfort groups over time in accommodation response. The high discomfort group showed an increase in accommodative lag, whereas the low discomfort group had a stable response. Our study suggests that the high visual discomfort group is characterized by accommodative fatigue, with a higher lag of accommodation developing at a near viewing distance over time.

Brain, 1984

Certain patterns of stripes are judged to be unpleasant to look at. They induce illusions of colour, shape and motion that are sometimes perceived predominantly to one side of fixation. People who suffer frequent headaches tend to report more illusions, and if the pain consistently occurs on the same side of the head the illusions tend to be lateralized. The parameters of the patterns that induce illusions (including their shape, spatial frequency, duty cycle, contrast and cortical representation) closely resemble those that elicit epileptiform electroencephalographic abnormalities in patients with photosensitive epilepsy. The viewing conditions under which such abnormalities are likely to appear are also those under which more illusions are seen.