The primary factor resulting in the noise of Hartmann-Shack wavefront sensors is the light reflected from corneas. A Hartmann-Shack apparatus with unequal entrance and exit pupil sizes are used to investigate two different ways of reducing noise, by measuring the signal-to-noise ratios in artificial eyes. Firstly, in the case of polarization beam splitters with inner reflection removed, the maximal signal-to-noise ratio is shown to be 11∶1, which is much higher than that got by using a traditional pellicle beam splitter. Secondly, the off-axial methods are used and the result is 200∶1. The results above and corresponding spots arrays are discussed and illustrated.