Seeing broadly

I recently re-read one of Heinlein’s old books and came across a concept which obviously had caught his attention at the time. It has to do with a technique of training a person to be more attentive their environment and Heinlein referred to it as “Renshawing” after the creator.
Obviously the technique is not in common usage now (at least not that I have ever heard) but out of curiosity I looked it up in Wikipedia. Few of the training methods can be applied without specialised equipment, but there was one which required nothing other than your own eyes. It has to do with consciously noticing things that occur at the edge of your vision – cars passing as you walk past and store displays being the examples given.
Apparently this not only increases your awareness of your surroundings but may have a positive effect on your vision generally. Being of a ‘certain age’ I have noticed significant deterioration of my vision in the last couple of years. So, although some of the benefits sound a little implausible, I thought that I may as well try it occasionally. Especially since increasing awareness is supposed to be a significant factor in ‘luckiness’.
Of course, introducing any new habit, means actually remembering to follow it occasionally – often easier said than done. Remembering to perform some action, at least for me and in this sort of context, triggers a round of thought processes about the purpose of the action and especially why it might be something worth doing: creating a mental model about what it happening and the underlying basis for it.
All of which is a round about way of getting to a series of thoughts about how eyes are used. Being an office worker I spend a lot of time in front of a computer. This requires focussing on a small area of my full range of vision (about 50cm – or probably less – in diameter). Much of the rest of the time my gaze is focussed on a small area – a book, a face or similar.
There are few situations in a city dweller’s my world where a wide view is necessary. And there are so many extraneous details that tight focus is often advantageous. This sets up a positive reinforcement to the extent that people walking in the streets don’t notice anything happening around them; and the bigger the town the worse the effect. (I live in a small town and work in the city.)
As it comes to the end of summer I realise that sunglasses also contribute. There is a great deal of my field of view which is NOT covered. But in general use I don’t tend to notice this – I only see what is in front of me and therefore what can be seen through the lenses.
Obviously this is all the absolute opposite of the technique described above. I wonder what the constant tight focus is doing to both our vision and to our view of the world around us.