We are running a visual discrimination study in the peripheral vision of patients with partial cortical blindness that uses moving and static visual stimuli (real motion) in different orientations (vertical, horizontal). We are adjusting the stimulus contrast so that the stimulus is not "seen" in the blind visual field -- however the question arises whether we should probe the contrast with the moving stimulus, the static stimulus or both?? Take the average of vertical and horizontal stimuli, if different? Should we have separate contrasts for moving vs. static stimuli? Thanks in advance!
Hi
If I have understood your question correctly, you could modulate the contrast in the static image and vary the speed in the moving image with constant contrast at different level. As for your second part of the question, I am not completely sure of the type of stimuli. The visual system is known to have bias to specific orientation of the stimulus as well as the direction of motion. It would be worthwhile not to average these thresholds but report them individually. Or if possible use diagonally oriented stimuli so that this bias is avoided (that is if you are using gratings).
I am an internationally certified orientation and mobility specialist among the many hats that I wear. I have been working in this field for the past 25 years and have worked with all ages of cortical visual impairment and also cerebral visual impairment. I have learned much from each individual I worked with. I will tell you that there is a great difference in brains when the individual is training or retraining to interpret the visual target. I have learned that it is very important to using vision in these cases when the person is moving and the visual target is static and moving. I was taught this by a little seven year old boy. Do you use the three phases and ten ranges in the current body of knowledge about CVI that our field uses? These are invaluable in providing assessment and intervention. Kenalea Johnson, Ed.D.,COMS
In a nutshell as a 55 yrs experienced Optometrist, static field testing demands greater discrimination.
I also am a person who has experienced CVI after getting scotomas following laser surgeries. I have personally taken both types of testing and moving targets are very difficult at any time. But I can see that the comparison of both might lead to different results. But when the moving target gets to the scotoma area it disappears and the brain develops a latency that creates a wait for the brain to figure out why the target is gone.and then takes lag time to get the interpretation of the new target to find out if it is the some or a different one.. Hope this helps.
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