Thank you for your comments, French Claire.
When I wrote of the feeling of something missing, I was trying to describe the feeling in my right eye only. I actually noticed the phenomenon first, then tried to figure out what might be creating it.
I agree to some extent with your comments on 'white light'. The same thing happens, however, when anybody leads a meditation. They use the imagery that is meaningful to them to get you into 'state'. Whether it is light, warmth, muscle relaxation, etc. or a beach, a meadow, a stream, a mountaintop, etc. They also use mantras that are their favorites. And, many times, words they feel are more universally acceptable than 'God.' If you identify with the imagery that leader uses, you find his/her leadership very helpful.
But all of that is really only preliminary to the objective of the meditation. Its purpose is to get you into the open, receptive state in which you can receive the results offered by the focal part of the exercise - i.e. planning (or reviewing) my day, healing, centering, seeking inspiration, etc. I have found myself rebelling against the specific picture, or color, or words being used both at the beginning and at the end of led meditations. And this interferes with the effectiveness of the focal exercise.
So...I recommend finding a substitute that works for you, personally. For instance, my mantra is 'I am a child of God.' White works for my light, but sparkling seldom does. And I prefer to do progressive muscle relaxation from the top down rather than up one side and down the other. But just how you get into the meditative state is less important than what you do when you are there. Get 'centered' or 'into state' however it works for you. It is what you do while you are in the state that makes the difference in your life.
I wish you (and any other reader)the creation of a lovely day!
Margaret Ida