Wahl's conjecture on rational homology disk singularities

A rational homology disk singularity is a normal surface singularity whose link bounds a rational homology disk; a Wahl singularity is a cyclic quotient surface singularity of the form $\frac{1}{n^2}(1,na-1)$, where $n>a>0$ and $\gcd(n,a)=1$. Wahl's conjecture. Every rational homology disk singularity is a Wahl singularity. The conjecture predicts that all rational homology disk singularities belong to the cyclic quotient class introduced by Wahl. The supplied text gives no resolution status, so it remains open here.