Good call on thorpe ~ Dorf, Dr Bill. The ops in hydropsy is the same as that in Odyssey's overseer, Cyclops, and is related to the eye, but in Greek it also meant 'face'. All from PIE *okw- 'to see' as are L occulus, German Auge, usw. Eyes and the face: there's also German Gesicht (lit. 'seen') and French visage.

http://www.bartleby.com/61/roots/IE360.html

OTOH, (o)edema is from the Gk oidema 'swelling' < oidein 'to swell', whence also Oedipus of the swollen feet, and from the same root *oid- 'to swell' comes Eng oat, German Eiter(beule) 'abcess, blain, boil, furuncle', and Sanskrit indra 'Indra'.