According to Kakusho Takasaki, who wrote “The lecture on Heart Sutra”. In that book he wrote as follows: “It is a story about during the WWII, some my friend unfortunately wounded and lost his eyesight. I went to see to encourage him. While conversation with my friend, I found that my friend is very well saying that “I appreciate your comfort words, of course when I lost my eyesight I was really pessimistic, I also lost my future too. but I could be able to open spiritual eyes instead of losing my physical eyes. Now I completely recover my mind so I am very calm and I am able to have brighter vision than before in my future. Thanks to the Heart Sutra, apparently I also feel like I understood the meaning of “色即是空” (form is emptiness; matter is void). I felt very shame on him after he heard my friend’s words that he could open his spiritual eyes instead of losing eyesight.
Most of the people are opening their physical eyes, but they are not opening the spiritual eyes. They are spiritually blind. “Opening eyes, but blind” so many people like that. They are always complaining, they don’t appreciate. Those people can be called “Opening eyes, but blind”. Hence, whether a life is dark or bright, happy or not, these are depending on whether you open spiritual eyes or not. I visited my friend with my comfort to him, but I returned my home felting so many complex emotions.”
That is very thinkable story, isn’t it? “To open spiritual (心) eyes” is to see invisible matters, invisible world, invisible existences then appreciate them with love and gratitude being given by them.