In the same way that your brain processes the colour and detail of what you are looking at, to create an accurate picture, it also processes any movement, and recreates it, to match any movement of what you are looking at, whether the scene is moving or you are.
This is another visual process in another part of your brain.
The area that processes movement, as we explained in Lesson 1d, is called MT/V5. The letters MT stands for Middle Temporal.
Movement is not just things that move around you, like cars passing and people walking past. Every time you move, not just walking or running, but even just moving your head to look up, you create movement, and the part of your brain that processes that movement is called MT/V5.
For everyone it is the case that when things move too fast they are not seen clearly.
When driving fast along a road, like in the above picture, the clarity, that is the detail of what you are looking at is reduced. Not just in relation to the sharpness, but also the colour. The visual information is moving too fast for your brain to keep up, so the visual information is of a reduced quality.
For some affected by CVI, the point where movement is too fast to clearly process may be much slower than for people who do not have CVI.
Where something is moving very fast, the clarity may be reduced to a point where it is no longer visible, just like the fast moving cars in the image below are no longer visible.
For someone with CVI, a car may only need to be travelling slowly, even the speed around a carpark, to be too fast for it to be seen. Then, when things do slow down enough, they can seem to pop-up out of nowhere, which can be very frightening.
The CVI where things that are moving too fast are not seen clearly is called dyskinetopsia.
This is another different CVI, and the approach will be different to the other CVI's. Here, the approach is to ensure movement is slow enough to be clearly visible.
A rarer CVI, where movement is not seen at all, so anything that is moving at any speed, slowly or fast, is not seen, and things are only visible when still, is called akinetopsia.
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