In this Comment we discuss a recent analysis by Yu et al .
[ RAA 11 , 125 ( 2011 ) ] about constraints on the smoothness \alpha parameter and dark energy models using observational H ( z ) data .
It is argued here that their procedure is conceptually inconsistent with the basic assumptions underlying the adopted Dyer-Roeder approach .
In order to properly quantify the influence of the H ( z ) data on the smoothness \alpha parameter , a \chi ^ { 2 } -test involving a sample of SNe Ia and H ( z ) data in the context of a flat \Lambda CDM model is reanalyzed .
This result is confronted with an earlier approach discussed by Santos et al .
( 2008 ) without H ( z ) data .
In the ( \Omega _ { m } , \alpha ) plane , it is found that such parameters are now restricted on the intervals 0.66 \leq \alpha \leq 1.0 and 0.27 \leq \Omega _ { m } \leq 0.37 within 95.4 % confidence level ( 2 \sigma ) , and , therefore , fully compatible with the homogeneous case .
The basic conclusion is that a joint analysis involving H ( z ) data can indirectly improve our knowledge about the influence of the inhomogeneities .
However , this happens only because the H ( z ) data provide tighter constraints on the matter density parameter \Omega _ { m } .