With the Islanders' Josh Bailey off serving a double-minor for high-sticking, Gerbe put the Sabres ahead 3-2 when he buried a shot off a cross-ice pass from Tyler Ennis 1:48 into the third.
Myers made it 4-2 for Buffalo only 2 minutes later after New York turned it over in their own zone, lifting the Sabres to a split in their home-and-home series with the Islanders.
Ennis ended with a goal and an assist and Paul Gaustad and Jason Pominville also scored for the Sabres, who got 31 saves from Ryan Miller.
Matt Moulson scored twice and Jack Hillen added a marker for New York.
Rick DiPietro turned aside 18-of-22 shot in the Isles' loss.