The aim of the study is to determine whether dimethyl sulphoxide (DMSO), a common laboratory solvent, impacts retinal function. Long Evans rats (n = 17) were intravitreally injected with five different doses of DMSO representative of those reported in the literature and spanning over 3 log units of vitreal concentration (0.01-8%). Retinal function was evaluated 1 h after injection using electroretinograms, and the waveform was decomposed into outer (photoreceptor), middle (ON-bipolar cell) and inner retinal (amacrine and ganglion cell) components. DMSO induces a dose-dependent decrease in retinal function for concentrations of 0.6% or more which is retinal layer specific. The photoreceptors of the outer retina returned normal responses at all doses (P > 0.05), whereas the mid-retinal bipolar cell response showed dose-dependent losses ranging from 21 +/- 1 to 82 +/- 1% (0.6-8% DMSO; P < 0.05). In a similar dose-dependent fashion, the inner retinal response was also affected by DMSO (0.6-8%: 23 +/- 12 to 98 +/- 3% loss, P < 0.05). A single dose of DMSO < or =0.1% (2.96 x 10(-5) microM) may be safely used to dilute compounds injected into the vitreous of a rat eye. Higher doses produce short-term (at least 24 h) retinal dysfunction.