No TN here but I did recently experience that same white light and while not blindness I had blurriness and temp vision loss and severe eye pain and severe head pain. Mine however was from a zoster outbreak called Ramsay HUnt syndrome or a type of shingles. My vision loss is getting better.

Ask your husband if he has a feeling like the nerves in his head or eyes are like shaking or spasming or tremoring. Any facial droopiness?

Try to get him to a neuro-opthamologist as soon as possible.