You could use vignette to some extent, but to have the best control I would use a custom blendable post-process material. You could use a circular gradient and turn the radius into a parameter, or you could implement your own eliptical gradient through math and use parameters to create the blink effect.
Probably the easiest though would be to use a linear gradient along with an offset parameter representing the top lid and just use the parameter to move this gradient down when blinking.