[0]: https://www.nytimes.com/2016/07/01/business/media/nielsen-su...
I'm not convinced they were wrong about chess either.
There is some evidence that myopia incidents(diagnoses?) have increased but I don't think there is proof that it is caused by our increased time spent looking at things close to us.
I also think it is harmful to have so much exposure especially because the most popular apps on smartphones are designed to grab our attention constantly and create this dependency on getting a notification.
Hopefully we see some great studies in the next 10-30 years that can properly map the effects the so-called "attention economy" has had on us
In my experience it is extremely consciousness-altering. And the effect sticks. It can become "reality" for a person.
In the meditation scene we have a technique for altering your consciousness through prolonged concentration. The Buddhists call it "Samatha". It is potent.