I too have visual symptoms including afterimages, eye floaters, blurriness if I focus for too long, etc. . I noticed you said that these images last for "microseconds". Most people would not notice something that lasted for a microsecond. Hypervigilance is symptom of anxiety which basically means being acutely aware of sensory input. For others, this acute awareness causes them to startle easily, hear even the slightest noises, or respond very emotionally to seemingly reasonable situations.
It's like this: have you ever been really afraid at night? Perhaps this happened to you when you were a kid. You probably heard every little noise inside the house and outside of the house -the floor creaking, a door moving, the wind howling, etc.
The same thing is likely happening with you're vision. As an anxious person you are more likely aware of things in your vision. When you noticed what you thought was a visual disturbance you focused on it and begin looking online to see what it was. Then, you unconsciously started to look for it and, of course, you noticed it again and again. Then, because you were so focused on your eyes you began to notice other things.
Look into mindfulness/relaxation techniques. Google bellybreathing and give it a try. Your sympathetic nervous system is working in overdrive when you're anxious and you can alleviate many symptoms by calming that system down.
Also, as for the candy crush issue I would suggest this: Open the game and get a white piece of paper. Focus on the game for 5-10 seconds and then look at the paper. You will see afterimages of the game because of the bright lights. This is NOT a visual disturbance or evidence of some strange disease but rather a very normal experience.
Blessings to you!