I have decrease peripheral vision and a multi-colored fracture line in my right eye. much like a broken camera lens. what could a cause be?

Migraine possibility: A cracked glass appearing peripheral visual disturbance that typically shimmers, builds then disappears, is likely a visual aura of migraine. It may be accompanied by a headache, nausea, or even vomiting. Often after it resolves, you feel back to normal. I do recommend that you have your eyes examined to just reassure that it is not from a different problem, like a torn retina.

Duration?: If you are talking about transient loss of peripheral vision, migraine is on the top of the diagnostic list, but if this is a persistent loss of peripheral vision, you need to be evaluated by an ophthalmologist asap.