photochromic sunglasses also called transition glasses. They can change the color when they are exposed to the UV rays directly. They are good for people who often switch from indoors and outdoors because it is very convenient to wear them as sunglasses outdoors and regular glasses indoors. As for care for your photochromic sunglasses, you should clean them in a proper way. Never use the window cleaner to clean your transition glasses. When you don't use them, you should keep them in the glasses cases.
The same as you keep other sunglasses, you shall clean them and store it in right place when you not wearing it.
In details, First of all, you shall clean them everyday. Wet a soft cloth to clean your sunglasses lenses. Please not use your T-shirt or dry cloth to wipe the lenses, or it may cause scratches on the lenses.
Second, you shall keep the photochromic sunglasses in cool and dry places. Because high temperature can destroy the lenses of the photochromic sunglasses lenses.
Third, put the sunglasses into cases when you not wearing them.