It is accepted wisdom that predatory fish are triggered by, and focus on the eyes of their prey fish, and that to exaggerate these can result in very positive strikes.
Fish on either a floater or sink-tip line, with a leader of only 4 to 5 feet. Cast at an upstream angle, give the fly time to sink, then retrieve with very irregular strips and include slight rests, and vary the strip distance and speed…make it appear a wounded fish!
Oliver has used this pattern for many years; it has taken many good big browns (and huge Chubb!). These patterns are also effective on stillwater’s, particularly at ‘fry-bashing’ time.