Retained eye cap, or injury?

So far my snake has been through a few sheds, and the blue dot in the center of my snake's eye is still there. According to the appearance of the skin, the eye caps did shed too.

What do you think? Did the snake sustain an injury, or could it been born with something that resulted in it eventually becoming blind? I've happened to just notice it one day. She wasn't brought like this. Initially I thought it was normal, but it's still here.

She was purchased as a sub-adult, and I've owned her for a few years now.

She's a Black Rat Snake.