I get these $1 wire-frame reading glasses from dollar stores. Easy to pop a lens out of its frame so there is one lens and one empty frame. I look at a nearby scene alternating right left eye open, seeing soft image as display and sharp image as reified as world. Self-learning :)
Ever taken impermanence of visual field as focus and just slam that for a while? Doing this for ~15 hours a day for a short retreat was really quite fascinating. I learnt this indirectly by hearing Shinzen talk tangentially about ‘subtle vanishings’ in visual experience.