The cop had read a newspaper story about Lanza, and had a teenage son who was slowly going blind from a degenerative eye disease.
In this degenerative illness, patients lose the function of the left half of their brain.
I learned that he had a degenerative disease and might not live long enough even to finish his Ph.D. degree.
degenerative de·gen·er·a·tive (dĭ-jěn'ər-ə-tĭv)
Of, relating to, causing, or characterized by degeneration.