An air bubble separator is provided for ophthalmic surgical systems, which includes a housing 102 having a diagonally-oriented flow channel 110 and a vertically-oriented flow channel 130 adjoining the diagonally oriented channel. The diagonally-oriented flow channel 110 has a downstream portion 112 disposed downstream of the vertically-oriented flow channel 130, and an upstream portion 118 disposed upstream of the vertically-oriented flow channel 130. The downstream portion 112 of the diagonally-oriented flow channel 110 has a cross-sectional area 114 that is greater than that of the upstream portion 118. The downstream portion's cross-sectional area 114 is greater than the upstream portion's cross-sectional area 124 by an amount or percentage that is sufficient to slow fluid flow through the diagonally-oriented flow channel 110, so as to cause air within the fluid to rise and flow into the vertically-oriented flow channel 130.