The catalyst for this book was John discovering he had dry age-related macular degeneration and that his lifestyle and work choices have contributed to his low vision problems. 

(His choices aren't unique, and millions of others have made similar choices and experienced the same outcomes.)

John joined the IT industry in 1972. For the last fifty years, most of his working life involved regular daily interaction with a computer via a keyboard and screen. Keyboards aren't considered a threat to anyone's vision; however, screens don't enjoy that level of anonymity because of the blue light they emit. The digital screens on smartphones, laptops, tablets, and televisions also emit blue light, as does fluorescent and LED lighting.

However, the primary source of blue light is the sun. Exposure to the sun has been a problem for John as his primary recreation for nearly sixty years has involved regular visits to the beach to surf. And when riding a surfboard, you can't always take simple precautions like wearing a hat and sunglasses to protect your eyes.

A Harvard medical study states, "High Energy Visible (HEV) blue light has
been identified for years as the most dangerous light for the retina. After
chronic exposure, one can expect long-range growth in macular degeneration, glaucoma, and retinal degenerative diseases". 

The medical retinal specialist treating John's AMD attributes his 50+ years of constant exposure to blue light, via the sun and various computer screens, as one of the major causes of his AMD. 

John now uses a combination of diet and vitamin supplements to mitigate his AMD. He always wears a hat and polarised sunglasses, plus something from his collection of batik board shorts and vintage floral shirts when outdoors.