Jamieson, Fausset and Brown on 1 Samuel 11:2

2. thrust out all your right eyes--literally, "scoop" or "hollow out" the ball. This barbarous mutilation is the usual punishment of usurpers in the East, inflicted on chiefs; sometimes, also, even in modern history, on the whole male population of a town. Nahash meant to keep the Jabeshites useful as tributaries, whence he did not wish to render them wholly blind, but only to deprive them of their right eye, which would disqualify them for war. Besides, his object was, through the people of Jabesh-gilead, to insult the Israelitish nation.