An inequality for the h-invariant in instanton Floer theory

Given a smooth, compact, oriented 4-manifold X with a homology sphere Y as boundary and b2+(X)=1, and given an embedded surface Σ⊂X of self-intersection 1, we prove an inequality relating h(Y), the genus of Σ, and a certain invariant of the orthogonal complement of [Σ] in the intersection form of X.