My Brother Had A Bright Light That Transversed From The

My brother had a bright light that transversed from the top to the bottom in the peripheral vision of the right eye. Episode was less than 30 minutes. Evaluation by ophthalmologist was negative for PVD/Retinal tear or detachment. By exclusion, the Dx was retinal migraine without HA. Since this problem is "rare" and occurred in a population outside the parameters of migraines (i.e., a 56 yoa M with no prior Hx of migraines nor a family Hx of migraines), is another differential Dx possible?