If you plant a seed in sand, you can water it, give it all the sunlight in the world and even sing to it, and even though it will germinate and grow a tiny green stem and leaf, it will quickly die because it isn’t receiving the nutrients that it needs.
It can survive off of the seed for a short time, but it needs the constant nutrition that comes from soil to grow and progress.
Learning to see with stereopsis (3D vision) and fixing the visual system is the same way.
We can do all the right exercises and therapies and make some progress in fixing strabismus or a lazy eye, but in order for the brain to truly change, adapt and learn in order to form stereo images and 3D vision, it needs the right nutrients.
