The aim of this study was to determine the effect of signal strength on mean retinal nerve fibre layer (RNFL) using spectralis optical coherence tomography (S-OCT). Thirty normal subjects were imaged with S-OCT using variably dense Bangerter foils to alter Q value (1 unit signal strength = 4 units Q). Results showed a statistically significant linear relationship between Q and RNFL (1 unit decrease Q = 0.181um mean RNFL increase). The authors also observed high interocular symmetry in RNFL thickness measurements with S-OCT, consistent with previous studies. Future studies are needed to further evaluate the effect of signal strength and / or media opacification on optic nerve head RNFL thickness measurements, particularly in cases of optic nerve pathology, as only normal eyes were used in this study.