  Let $\mu$ be a self-affine measure on $\mathbb{R}^{d}$ associated to a
self-affine IFS $\{\varphi_{\lambda}(x) = A_{\lambda}x +
v_{\lambda}\}_{\lambda\in\Lambda}$ and a probability vector
$p=(p_{\lambda})_{\lambda}>0$. Assume the strong separation condition holds.
Let $\gamma_{1}\ge...\ge\gamma_{d}$ and $D$ be the Lyapunov exponents and
dimension corresponding to $\{A_{\lambda}\}_{\lambda\in\Lambda}$ and
$p^{\mathbb{N}}$, and let $\mathbf{G}$ be the group generated by
$\{A_{\lambda}\}_{\lambda\in\Lambda}$. We show that if
$\gamma_{m+1}>\gamma_{m}=...=\gamma_{d}$, if $\mathbf{G}$ acts irreducibly on
the vector space of alternating $m$-forms, and if the Furstenberg measure
$\mu_{F}$ satisfies $\dim_{H}\mu_{F}+D>(m+1)(d-m)$, then $\mu$ is exact
dimensional with $\dim\mu=D$.
