Wouldn’t it make sense to have partial vision all the time instead of a momentary black-out?
If you’re my yorkie you blink the left and then.. eventually.. the right. And that’s just one of the many ways we know she’s a slice short of a pie.
I have this, when I want to blink with my left eye- I can do it. But with my right eye, I have a lot of trouble – I have to close it with my hand first so that I could hold it closed after that. So blinking with two eyes at the same time doesn’t feel so bad for me.
When you use two eyes, your brain is stitching together information from two sources, pretty flawlessly, to give you a sense of depth perception. There is a lot of overlap in what each eye sees, and your brain needs to sort out how it all makes sense.
Blinking with one eye at a time (winking), would mean disrupting that balance, and your brain would need to adjust. In addition, you’d actually be spending longer with imperfect vision. Say, one eye closed for 2 seconds a minute compared to two eyes closed for one second. I’m guessing this trade-off wasn’t worth it biologically.