Cotton Wool Spots
These yellow-white spots are called cotton wool spots. They are caused by retinal nerve fiber layer microinfarcts. Exploded retinal ganglion cell axons extrude their axoplasm like toothpaste. Expect to find cotton wool spots arrayed around the optic disc and along the temporal vascular arcades.
Cotton wool spots have a myriad of causes. Any process that occludes small retinal arterioles will do this: hypertension, diabetes, HIV, severe anemia or thrombocytopenia, hypercoagulable states, connective tissue disorders, viruses, lues, Behçet's and many others.
To review the many other yellow-white things in the retina with which you could confuse cotton wool spots, check out Yellow-White Things in the Retina.