Light and memory
If you walked into a place you had never been before, what you see of it is what you will remember. If however there was total darkness when you got there, you would not see anything in the absence of light, thus you will not remember anything about that place.
Physical light will aid memory of what the eye can see. But light transcends the physical and we can describe it as that which brings understanding. I remember back in school there were certain subjects I never understood and so could never remember an answer when asked about it. Those who understood it on the other hand never forgot how to answer questions on it.
If you want to improve your memory on anything, then you need to get an understanding of it. You need the light to shine on that subject so you can clearly see all that pertains to it. There is nothing wrong with your ability to remember, it may just be that you do not have enough light to see what you need to know.