Plot3D[-4.53 + 2.67*x + 2.78*y - 1.09*x*y, {x, 1.8, 2.6}, {y, 1.8, 2.6},
        PlotRange -> {1.7, 2.6}, ColorFunction -> "GrayTones",
        Ticks -> {{1.8, 2., 2.2, 2.4, 2.6}, {1.8, 2., 2.2, 2.4, 2.6}, {1.8, 2., 2.2, 2.4, 2.6}},
        LabelStyle -> Opacity[0], BoxRatios -> {1, 1, 1}]