Cannabis is widely used, and over the last decade, this drug has been legalized in several jurisdictions. Many others are considering this change. While public information and road safety campaigns have consistently focused on alcohol, cannabis-related toxicity has been relatively neglected as a public health issue. Further, rigorous investigation of this drug is therefore timely and appropriate.
We read with interest the study by Schwitzer et al1 in which the pattern electroretinogram (PERG) was used as a measure of retinal ganglion cell function. They conclude that regular use of cannabis is associated with a delay in the PERG N95 component and infer this represents delayed transmission of action potentials from the retina to the visual cortex. However, shortcomings in the study design, methods, and data analysis, acknowledged in part by the authors, weaken their conclusions.
Lyons CJ, Robson AG. Retinal Ganglion Cell Dysfunction in Regular Cannabis UsersIs the Evidence Strong Enough to Consider an Association?. JAMA Ophthalmol. 2017;135(1):60-61. doi:10.1001/jamaophthalmol.2016.4780